Each type of foundation has its own purpose and scope, otherwise they would not be laid (built). Columnar is no exception, in which the load falls on pillars dug into the ground or erected in small pits. In appearance it looks like a pile system, but behind the superficial similarities lie deep differences. Which ones and in what way exactly, this is the topic of this article, as well as information on how to lay a columnar foundation with your own hands. In small individual construction (small-scale construction), this gives a lot of advantages, allowing you to save a huge amount of labor and up to 50% of the cost of the zero cycle, which, in turn, ranges from 20% to, for example, 50% of the total estimated cost of construction. In terms of money at today's prices, the figures come out to 6-7 digits.

Note: the entire cycle of work on the construction of the foundation of a building, from the first inspection of the site to its readiness for laying floors and erecting walls, is called laying the foundation. When studying materials on the topic, keep in mind that laying a foundation and burying it in the ground are two different things. Also, one should not confuse the work of laying the foundation with the amount of floor slabs, beams and lintels placed in the walls. In general, context, context and context again.

Unexpected quality

After Le Corbusier, the columnar foundation also attracted avant-garde architects with its ability to visually lighten the building or, conversely, give it monumentality, see fig. However, solutions of this kind are certainly applicable only on dense, well-bearing, low-water and low-heaving soils; Most houses of this design are built in the Mediterranean. In the Russian Federation, it is certainly possible to build similar ones in the black earth zone and further south, and after on-site surveys in accordance with existing conditions, no further north than the line approximately St. Petersburg - Nizhny Novgorod - Chelyabinsk - Omsk - Barnaul - Kyzyl - the border with the People's Republic of China.

The foundation on pillars and its pile counterpart are structured similarly, see figure: a support belt is placed on the pillars buried in the ground, distributing the load on them. It also forms the subfloor of the building and can also serve as a basement, for which it is equipped with vents. The pillars are placed according to certain rules according to the calculation (see below), and the spans between them are maintained within 1.5-2.5 m. More or less is not possible, or the load will fall unevenly and cause the same uneven settlement of the building, or the supports will interfere carry it to each other, with the same result.

A pillar is a pillar because it is capable of carrying only a concentrated constant load directed vertically from top to bottom. A pile is a pillar buried in the ground to a certain quite certain amount. This “certain” is the whole point, but we will return to the difference between a pile and a pillar below. For now, let’s see how they are similar: both do not themselves distribute the weight and climatic loads from the building over the supports; for this, a system of additional horizontal connections is needed. According to their structure and the nature of work in the structure, columnar foundations are divided into types, see figure:

Note: in all cases, the anti-heaving cushion is formed in a geotextile sleeve, and all parts of the foundation in contact with it and the ground are wrapped in waterproofing - 2 layers of roofing felt on bitumen mastic.

T. called.

This abbreviation in the last paragraph was not used in vain. The fact is that a columnar strip foundation does not exist from the point of view of structural mechanics and soil mechanics. Pile-tape is possible, but if you attach pillars to the tape as a load-bearing structure from below, then in terms of bearing the load they will end up in a kind of shadow and the tape will not help in any way. If soil saturated with moisture freezes quickly during freezing, it can cause damage due to uneven heaving in depth. It will be easier and cheaper to use excess concrete and earthworks to widen the belt or increase its depth, depending on local conditions. We will touch on this issue later.

Advantages and disadvantages

For a better understanding of the further, rather difficult, material, it would be more advisable to follow the example of Robinson Crusoe, who wrote down in 2 columns the sorrows and joys of a lonely life on a desert island. Here the pros and cons of a columnar foundation are summarized in the table:

pros	Minuses
Low cost and labor intensity as a result of the small volume of excavation work and required materials.	Low load-bearing capacity: on ordinary soils it is hardly possible to obtain more than 7 tf/column. The foundations of TISE (see below) are very promising, but the promises of 15 tf/support come not from the developers of this technology, but from its enthusiastic supporters.
For the same reason - speed of construction; a frame house on a columnar foundation can be built over the summer by two people.	As a consequence of the previous one, it is unsuitable for multi-storey construction: because You can’t move the pillars too close to each other (see above), then there simply won’t be enough space for them under a heavy building.
In most cases, no special equipment is required other than a concrete mixer; other types of work can be performed with hand tools.	For the same reason - poor use of the bearing capacity of the soil: let it carry 10 kg*sq. see, there is no point in building a brush of pillars in it, they will simply break like a domino and the house will slide to one side.
Simplicity of calculation as a consequence of the simple interaction of structural elements with each other and with the ground.	Impossibility of use on weak ones, bearing less than 1.7 kg*sq. cm, soils, in contrast to pile soil, see below.
For the same reason - suitability without special tricks for a wide variety of local conditions.	Sensitivity to horizontal loads: if there is a thin layer of heaving soil under the house, and under it a thick layer of dense non-heaving soil, then during a sharp cold spell after rains, tangential stresses can break the pillars.
All for the same reason - you don’t have to pay 30-100 thousand rubles. for a working project, but limit yourself to a sketch for 3-10 thousand rubles. or even pull a free one from the RuNet and calculate the pillars for it, as described below.	Unsuitability, for the same reason, for significantly heterogeneous soils: if the soil under humus on a building site is a patchwork quilt of dense loams and loose sandy loams, sands, gristly and gravelly pieces, you need to lay any foundation other than a columnar one.
Sufficient simplicity of legislative design, again for the same reasons. The municipal inspector may be persistent, irreconcilable, convinced and a hardened bribe-taker, but he is always an experienced builder. As for the columnar foundation, one glance at the project is enough for him to see whether the foundation will support the house or not. If there are no gross errors, then he will still approve or write comments/instructions where improvements need to be made; their payment is included in the state fee.	Unsuitable for heavily watered or littered soils and high groundwater levels, above approximately 2.5 m from the surface.
Laying a columnar foundation does not require high construction qualifications; even an amateur can do it.	It is impossible to arrange a basement.
No careful planning of the construction site is required; building a house on a columnar foundation on your own is possible on a slope of up to 15-20 degrees (!).	Vulnerability: when the house is already on the foundation, large-scale excavation work can be carried out no closer than double deepening of its pillars, and trenches must be dug very carefully.
Only 1 unqualified assistant is constantly needed for work; short-term episodic - 2-3 more of the same.	For the same reason, it is difficult to install additional communications.
An extremely cheap, lightweight and easy-to-make wooden columnar foundation under certain conditions (see below) can be more durable and reliable than concrete, brick or stone (!!).	The impossibility of constructing capital extensions is a consequence of the same circumstance.
The possibility in some cases of repairing the foundation on your own, see below. Repairing a foundation is a complex engineering and technical task, and a columnar foundation is the only one that sometimes allows its owner to repair itself.	As a consequence of all the above factors - a short service life; 50 years is the limit.

The hero Daniel Defoe has more minuses than pluses. We have them equally and for small-scale construction the advantages are generally more significant. Prejudices against laying columnar foundations for residential buildings come from Soviet SNiPs, oriented towards mass multi-storey construction, incl. and on collective farms/state farms, the gradual relocation of private owners to high-rise buildings and, in the bright communist future, the complete elimination of individual residential development. The current communists, by the way, who are still smart and understand the essence of their idea, now in the same future promise everyone their own home, like Khrushchev - each worker 3 (three) suits.

About bearing capacity

The soil is considered suitable for a columnar foundation if its load-bearing capacity is at least 1.7 kg*sq. see. Other soils are considered weak; as a rule, they can only be built on piles. Weak soils include:

1. Fine silty sand.
2. Plump clays and loams.
3. Loose sandy loams.
4. All soils of organic origin (silty, peaty), including chernozems over 1 m thick.

What's swelling

Frost heaving of the soil occurs due to the freezing of water in it. For a columnar foundation, which is light and compact in itself, in addition to increasing the volume of soil, the uniformity of heaving and freezing rate are also important. For which soils are unsuitable for construction on poles, see the disadvantages table. We'll talk about freezing speed below. And for further purposes, including calculations, we present the characteristics of soil heaving:

• Virtually no frizz – increase in volume up to 1%. These are hard clays, poorly saturated loose soils (gravelly, coarse and medium sands), rocky, boulder and pebble soils filled with coarse fragments of over 90%;. Dry silty sand can also be non-heaving if it contains less than 15% fractions by weight of fractions finer than 0.05 mm.
• Slightly heaving - increase in volume 1-3.5% The same as in the previous one. etc., but the clays are semi-solid (you can dig with a shovel without resorting to a crowbar and a pick); loose soils, except for fine silty sand, are moderately saturated with water, and coarse soils with fine silty filling are 10-30% by weight.
• Medium heaving – increase in volume 3.5-7%. The clays are hard-plastic, crumpling with cracks when kneading for a sufficiently long time, i.e. lean, dense loams and sandy loams. All loose soils according to prev. n., saturated with water. Coarse - with fine dusty filling of more than 30% by weight.
• Highly and excessively heaving, volume increase of more than 7% - soft, immediately crumpling medium and very fatty clays, loose loams and sandy loams, water-saturated fine and silty sands. Soils that heave by 9-12% are considered excessively heaving. There is no more than 12%, because... When water freezes, it expands exactly this amount.

About deepening

All foundations according to the degree of penetration into the ground are divided into 3 categories, see figure:

• Deep burial, or normal depth, or simply buried: the base of the foundation, and in the case of a columnar foundation, the heels of the pillars, is located below the standard (calculated) freezing depth of the given area, see fig. lower, by 0.3-0.7 m in. For columnar foundations, the first value can be taken.
• Shallow - the soles (heels) are in the swelling layer. For a columnar foundation, the depth is taken from 40% of the calculated freezing on low-heaving soils to 70% on medium-heaving soils.
• Non-buried - used either on soils that are practically not heaving, or under fairly light and elastic non-residential wooden or metal buildings: summer country houses, sheds, greenhouses, outdoor toilet/shower, outbuildings, garage, etc.

When to go how deep?

It is best to make a concrete foundation for any residential building at normal depth: drilling 1 well under a pillar with a hand drill takes 1-2 hours, and all of them can be drilled in a weekend. As will be clear from what follows, the foundation pillars, even if they have a grillage, each work on its own in the depths. Figuratively speaking, the grillage helps to withstand an open battle with the forces of heaving, but is powerless against sabotage with undermining.

Specifically, this means that the groundwater level should not rise to the lowest points of backfilling for pillars closer than 1.5 m during the period of highest standing. Otherwise, due to random fluctuations in their level and, especially, capillary rise, it is possible to undermine one of the pillars, and then a sudden emergency drop in the bearing capacity of the entire foundation according to the domino principle.

Wells and boreholes of neighbors will not provide correct information, because... Water for drinking is almost never taken from the first and dirtiest aquifer - the perched water. Here you need to either request a local (municipal) construction geology service, or consult with experienced builders, or in the midst of spring, during May thunderstorms (or at the end of the wettest period in a given area; for example, in the Amur region - at the end of the summer flood ) carry out test drilling to the estimated freezing depth of + 1.7 m. There is no water - you can build reliably, in depth.

What if there is? Then, for a heavy structure, you will have to choose a different type of foundation; for self-building, a strip foundation is preferable. And under a frame/timber house, it is possible to lay a shallow columnar one. When is this possible and when is it not? We proceed as follows:

1. Based on the nature of the soil, we determine the degree of heaving; in the absence of accurate data, we take its maximum value for a given type of soil.
2. By multiplying the degree of heaving in decimal fractions (not percentages!) by the value of the estimated freezing depth (RFD), we obtain the amount of heaving in units of length.
3. We take the distance of sufficiently uniform heaving equal to 100 of its values. The house must fit into a rectangle of the appropriate size. For example, RGP = 1.2 m or 120 cm. The soil is dense loam, we take 7% heaving. 120x0.07 = 8.4 cm. A house with dimensions in plan up to approximately 8.5x8.5 m during seasonal soil movements will rise or fall by this amount without dangerous distortion.
4. We take a larger depth for the pillars, just to maintain the minimum distance to the high water.
5. For light non-residential buildings on a shallow foundation, we take the degree of heaving to 12% (humus is excessively heaving); further – according to paragraphs. 1-5.
6. If the proposed building does not fit into certain dimensions, nothing can be done; you cannot build on poles here.

This method of determining the uniformity of heaving can cause bewilderment: how is it that the soil heaves, the stronger, the more uniformly? Exactly. This is due to the fact that any soil containing moisture has, to one degree or another, the so-called. rheological properties. Soil heaving is caused by water freezing in it. The more the soil is saturated with it, the further the heaving forces propagate in it and it swells like a continuous medium. Frost cracks do not always indicate that the frozen ground has swelled up into mounds. By analogy: what is more uniform – fried potatoes or mashed potatoes? And if the puree has frozen, formed a crust, and it has cracked, the puree will not turn into potato pancakes?

Important circumstance

Because the site for a columnar foundation is not planned or is planned roughly; the depth is calculated along the column at its lowest point. The heels of the supports, just like the tops, must fall on some imaginary horizontal plane. If, for example, a depth of 1.5 m is taken, and the height difference on the site is 30 cm, then the well for the pillar on the hill itself needs to be drilled at 1.8 m. In practice, the shallowest well is drilled first, and the rest are drilled exactly according to her, using a homemade level, see the figure on the right.

So what's the difference?

Features that other foundations, as they say, have never even dreamed of, have already accumulated so many that it’s time to explain themselves. Why is a pillar a pillar and a pile a pile? When is a pillar a pillar and a pile a pile? How do columnar foundations differ from each other?

A rod of finite thickness buried vertically in the ground with an imperfectly smooth surface interacts with it both by a supporting platform (fifth) and by lateral friction. That is, it rests on the ground and clings to it. By the way, the bearing capacity of soils is determined taking this circumstance into account. During frost heaving, interaction becomes more complicated, because heaving forces tend to both pull the pile/pillar out of the ground (the earth swells up, there is nowhere to go down), and to hold it, squeezing it from the sides.

To simplify the mathematical description and calculations (if accurate and detailed, then, nevertheless, tooth-crushing), it is believed that under the pillar/pile a certain imaginary load-bearing cone is formed, with the apex facing upward and with the base gradually spreading out below. In soft soil, where they build on piles, it is wider and deeper, but less dense (force field vectors are smaller) than under a pillar on dense, strong soil. Again, figuratively speaking, the pillar rests more on the ground than clings to it, and the pile is the opposite.

But this is not the fundamental difference. In weak soils, the interaction forces between their particles extend far. The supporting cones of all the piles deep below merge into a kind of virtual surface, the area of ​​which is many times larger than the building in plan. That is why heavy and fragile stone buildings can be built on stilts for centuries even in a swamp. The Swedes did not build in the Neva delta, although this place is extremely important in terms of strategic importance, because it was a continuous swamp. There was a small, light fortification there, and that was all. Peter came with his energy, scope, heavy fists and baton - and behold, the whole of old Petersburg was built on stilts. And nothing, it’s worth it for now.

The pillars have a different task - to simplify and reduce the cost of the construction of prefabricated light buildings. The strength of, say, a reinforced concrete strip is determined by its cross section. As the size decreases, it falls in a square. Under a light house, the tape turns out to be so thin that it can crack from accidental load; the material is fragile. We increase the cross-section so that it can at least support itself - the volume grows (by the cube of its dimensions!), and with it the costs and labor intensity. Then we take the same, minimum required volume of concrete and reduce it into durable compact blocks. Since the main load is weight, we place them vertically, and this is how we get the pillars. But in the swamp they will not hold anything, they are short. But in dense soil it will be every man for himself: the support cones are narrow, short and quickly get lost before they come together. In order for a house to stand, special constructive measures and the selection of a suitable site are needed. What was stated earlier concerned more than the second, and now we can move on to the first.

We are mortgaging

Foundation pillars, in addition to those already mentioned from reinforced concrete, brick and wood, can be made from ready-made concrete blocks and rubble concrete. The bearing capacity of all these materials is much higher than that of the soil, therefore the calculation of the foundation is the same, the only difference is in the size of the supporting area. But the laying technologies differ radically, so let’s start with the calculation.

Calculation

The approximate method for calculating a columnar foundation given below is based on the fact that the lateral adhesion of the pillars to the ground is taken into account very roughly and with a large margin. For an individual residential building of small or medium size, this will result in 2-5 pillars more than the minimum required number. Because The columnar foundation itself is inexpensive and relatively labor-intensive; this is a completely legitimate assumption. But it allows you to fairly reliably calculate the foundation yourself, without having any special knowledge, which will save you about 30-35 thousand rubles on design. Such a foundation will also work “on paper”: let them, if they doubt it, check it as they wish; load-bearing capacity is always excessive. Actually, the proposed calculation of the foundation is carried out as follows:

1. According to the design documentation, the weight loads from the building structures, roofing, communications, insulation, and design of openings (doors, windows) are determined.
2. Based on zoning maps of climatic loads in the Russian Federation (see figure below), the estimated values ​​of snow and wind loads are determined.

   

3. Operating loads are determined independently - from people, including possible guests, furniture, equipment, plumbing fixtures (filled), and all others, for example. from an aquarium or a pig in the bath.
4. According to SNiP 2.02.01-83 “Foundations of buildings and structures” , SNiP 2.08.01-85 “Structures of residential buildings”, SNiP II-B.1–62 and other SNiPs to which these refer, the consolidated weight of the building is calculated, this procedure is called balancing the scales. Its essence is that all the loads on the building, incl. lateral from wind and snow, come down to the weight imposed on the foundation.
5. The estimated freezing depth (RFD) at the site is determined. The bottom map in Fig. – only a guide to the maximum value. It is advisable to check the data with local geologists or builders. On a dry hillock and in a wet lowland, the RGP can differ by up to 20%, which, in turn, can result in corresponding savings in material and work.
6. The nature and depth of the pillars’ depth is determined as described above.
7. For a depth of up to 1 m, the bearing capacity of the soil is taken to be 1.7 kg*sq. cm or 17 tf*sq. m, and for larger ones – 2 kg*sq. cm and 20 tf*sq. m respectively.
8. On dense soils (dry clayey and loamy, rocky, gravelly) freezing to a depth of less than 1.5 m, the resulting value is multiplied by 1.15.
9. The supporting area of ​​the pillar is calculated based on the dimensions of its heel; for brick and prefabricated it will be equal to the area of ​​the thrust bearing, see below. For concrete ramming in wells drilled with a hand drill, the limit value is 0.28 sq. m, this is a well with a diameter of the barrel or camouflage chamber (see below) of 60 cm.
10. The value of the bearing capacity of the soil is multiplied by the size of the supporting area, this will give the load per 1 column. For example, for a 60 cm rammed column buried 1.2 m in the Moscow region (RGP = 1 m), the result is 20 tf x 0.28 tf*sq. m = 5.6 tf on sandy loam and 6.44 tf on loam.
11. The total weight of the building is divided by the load-bearing capacity of one pillar, thus obtaining the minimum number n.
12. The sum of the number of corners formed by load-bearing walls and the number of crosshairs of load-bearing walls is subtracted from n.
13. The total length of the building perimeter and internal load-bearing walls is divided by the remainder; As a result, we obtain the spacing of the pillars along them.
14. We check its size, it should, as stated above, be within 1.5-2.5 m. It is better to take a 1.65-2.35 m fork, this will make it possible to adjust the pillars when arranging them, see below.
15. If the step is more than 2.5 m, add 1-2 pillars and recalculate according to paragraphs. 13 and 14. If less, you need to build not on pillars, but on a tape.
16. We calculate the weight of the foundation along with the rand beam or grillage, if provided, based on the reinforced concrete density of 27 tf/cubic meter. m, wood 8.7 tf/cubic. m, and for brick elements - 4 kg per brick with a layer of mortar.

    

17. We add the weight of the foundation to the total weight of the building according to paragraph 4 and recalculate everything according to paragraphs. 1-17. You may have to add 1-2 posts. However, because The bearing capacity of a pillar is much greater than its own weight; the calculation almost always converges in 2-3 iterations.
18. We distribute the pillars: at each corner or crosshair along the pillar, the rest - evenly. The latter rarely happens, because the lengths of the walls are not a multiple of the span between the pillars. Then in the most loaded spans (oven, bath, etc.) we move a couple of pillars to the middle! You can’t undo it evenly, but in a corner - as you have to, this will greatly weaken both the foundation and the building on it, see fig. on right. This is where the calculation ends.

Necessary additions. Firstly, to paragraphs. 7 and 8, they have a catch. But the catch is that you don’t have to skimp on deepening. Savings on the height of the column will be significantly offset by the overconsumption of labor and materials in their quantity, and according to point 15, the calculation may not at all converge in favor of the more expensive and labor-intensive one. It’s better to puff with a drill or a shovel.

Secondly, the placement of pillars according to clause 18 should be carried out from the least loaded and longest sections to the problematic ones. The last span, between the shifted pillars, may be less than 1.5 m, in this case it is not scary. The result will be a double pillar that works like a single one; the redundancy of the described calculation method allows for it. Again by analogy: no one will ever notice 1 tightened stitch of the seam, others will catch up to it. But if you tighten the entire seam (put the posts too often), the clothes or shoes will come apart.

If the house is on a slope

When building on a slope, firstly, under no circumstances should the house be placed obliquely towards it. Secondly, the foundation should only be deep. Thirdly, when designing, the pillars under the walls along the slope are first “scattered” evenly, as described above. And when the entire grid of pillars comes together, the same pillars under the walls are distributed along the slope, as shown in the figure, evenly increasing the span from maximum to minimum. If this is not done, the house may break away from the upper transverse row of pillars, or fall off the lower one and crawl down. The heaving forces acting on the lower and upper pillars will differ several times. Therefore, a continuous anti-heavy cushion is needed under the entire building, see the same fig.

Site preparation

The outline of the building is marked as usual, checking the rectangularity by checking the equality of the diagonals and measuring the sides. You cannot rely on diagonals alone, because... in an isosceles trapezoid they are also equal! If the house has extensions, then mark out the largest rectangle first, and then the adjacent rectangles are separated from it.

Next, you should make a cast-off, see figure, for the perimeter and all load-bearing walls. The cast-off trestles must sit firmly in the ground and be stronger themselves; a lot depends on them. The tragus slats are leveled horizontally using a hose level and, additionally, each horizontally using a bubble level. For a foundation with a grillage, a two-story cast-off is made. Places along the wells/pits of the pillars are marked with plumbs suspended from mooring cords, so they must be strong and tightly stretched. The best moorings are made from propylene twine: it is strong, cheap and has little sag.

The next stage is soil excavation. For a foundation with a lying/recessed grillage or rund beam, humus is removed to the mainland soil (mater) or to the amount of their depth plus a cushion, see fig. left. Again, it is measured from the lowest point of the foundation. The bottom of the trench must be horizontal; It’s convenient to check it to the horizon with the same homemade level.

If the grillage/beam is hanging, then the humus is removed within a radius of 0.5-1 m from the mouths of future wells, depending on their diameter. A larger value corresponds to a diameter of 60 cm. Under pits for brick pillars, humus is removed over an area of ​​1x1 m. The depth of wells/pits is counted from the level of the foundation; the heels of the pillars should be on the same horizon, see above.

Drilling and digging

The wider the base of the pillar, the greater the load it will carry and the less of them will be needed. The actual pillar core in a soft shell with a diameter of 350 mm or in an asbestos-cement pipe with a diameter of 250 mm, properly reinforced (see below) will withstand 10 tons, but the area of ​​​​its heel is small. During the pouring process, a larger diameter sole is formed, see below. But, firstly, it will turn out to be round and its effective supporting area will fall when the soil is moistened. Secondly, you still need a well with a diameter of 60 cm. For a strong, tenacious man in undisturbed soil, this will take at least 4 hours.

It is better to drill wells under the pillars so-called. TISE drill. Ready-made ones are quite expensive; the cheapest Belarusian ones cost about $100, but a TISE drill can be made with your own hands. This drill makes it possible to form an underground chamber - a camouflage - with a flat bottom with a diameter of up to 600 mm in a well with a diameter of only 250 mm. And the shape of the base of the pillar is hemispherical, ideal in terms of construction mechanics. The sequence of drilling with a TISE drill is as follows, see Fig.:

• Using drill 1 with a pressed camouflage scraper, the trunk is drilled to the calculated depth 2.
• The camouflage scraper 3 is activated and, by rotating the drill, a camouflage is formed, periodically removing the soil.
• A special reinforcement cage 4 is inserted into the well, see below.
• The shell 5 is used to form the support sole 6 as described below.
• The pillar rods are poured, also see below.

Note: An additional advantage of drilling with a TISE drill is that pillars with such soles can be moved closer to each other even by 1.2 m. This immediately expands the scope of application of a columnar foundation up to brick houses with an attic.

As for the brick pillars, they are laid in one and a half or 2 bricks. We will return to masonry methods later, for now we need to know the transverse dimensions of the brick pillars: 38x38 and 51x51 cm, respectively. Pits of suitable size for the work are also needed; Don’t stick your feet out of it into the heavens. For a mason of average build, a pit of 1x1 m is almost always enough. If the depth of the pillars, taking into account the height of the thrust bearing and the cushion (together about 40 cm), exceeds 1.5 m, then to prevent soil shedding, you need to dig with slopes of 4 cm/m.

Pillars, rand beams, grillages

Foundation pillars consist of a heel (sole), a rod (trunk), an insulating shell and a head. For concrete, brick and wooden pillars they are performed differently. We will start with concrete as the most common and reliable.

Concrete

The mortar for the foundation pillars is the usual M200-M300. There is no particular point in ordering a concrete truck: you need little concrete, and delivery is not cheap and does not depend on the volume supplied. It’s better to rent a concrete mixer and mix it yourself. The composition, per 1 cubic meter, is as follows:

1. Portland cement M400-M600 – 300 kg.
2. Construction sand – 750 kg.
3. Crushed stone of medium fraction – 1200 kg.
4. Technically pure water – 150 l.

Mixing is also done in the usual order: cement-sand-crushed stone-water. A concrete column is poured into the well as follows:

• Cover the pillow if necessary. For pillars of normal (deep) depth, they often make do with a 5-10 cm concrete footing directly on the ground; she needs to be allowed to set.
• The shell is inserted to the bottom, see below for details, making sure that the same distance is maintained from it to the walls of the well.
• Insert the reinforcement cage and center it, also see below.
• The shell is filled one third with concrete and raised by 200-300 mm; if the well was drilled with a TISE drill, to the value specified in its specification. The raised shell is securely fixed.
• If the well was drilled with a conventional drill, wait another 1-2 days for the concrete to set.
• In the same case, the gap between the shell and the wall of the well is backfilled, compacting the soil tightly.
• The column core with hydraulic seal is poured in layers of 15-20 cm, waiting for 10-20 minutes before pouring the next layer.
• A technological break for concrete to gain strength is sufficient for 7 days, after which work can continue.

Note: It is not advisable to use vibration compaction. Not every vibrator will penetrate 1.5-2 m deep, and the tip will easily hit the reinforcement. Then the formation of cavities with cement laitance is inevitable, sharply reducing the strength of the column.

Reinforcement

In reinforcement, the difference between a round pillar and a pile, as they say, is all in sight: the pillar necessarily needs a central (axial) rod. A pile can be reinforced like a pillar, it won’t be worse, only the excess iron will go away, but a round pillar like a pile, only around the circumference, is not possible.

The fact is that where it is advisable to use one or another foundation, the lateral loads on the pile are more bending, and on the pillar - shear. Simply, horizontal movements of the soil try to break off or cut off the pillar from what lies on it. This is what the central rod resists with all the strength of steel.

Note: there is also a feature inherent only to a columnar foundation; It could be written down as a minus. Fiberglass and other composite reinforcement, which work well in strips and piles, are unsuitable for poles. It holds shear loads in any direction no better than concrete - it delaminates or gets wet.

Another feature of the pillar is that for greater strength, the number of vertical branches of the frame must be even: 4, 6, 8, etc. 2 branches, of course, will not strengthen anything. The distance between vertical connections is 150-200 mm; The pitch of horizontal ties, as usual, is twice as large.

On the vertical there is AI reinforcement, usually 10-12 mm; on the horizontal – 6 mm wire rod. It is drawn around the diagonals, and the distance between the verticals and the centering of the central rod are adjusted by bending the horizontals, as on the left in Fig. This work, I must say, is hard: try bending the wire rod into a loop with pliers or pliers! Therefore, it is permissible to make rings from wire rod, connecting the ends by twisting 3-4 turns, and centering the rod with segments. Knit everything with 2 mm knitting wire, but only and only with a dead knot; highlighted in green on the trail. rice.

Under the grillage or rand beam, the ends of the side rods are released from the head of the pillar to the required length (usually 15-25 cm), in the center in Fig. higher, so the side verticals need to be cut longer in advance. On the contrary, a central rod is released under the wooden crown, on the right in the same figure.

For light outbuildings and wooden houses, a post in an asbestos-cement pipe with a diameter of 150 mm is most often sufficient. Such a required amount of reinforcement will no longer fit, there will not be enough space for concrete or it will not settle properly. Then they reinforce only in the center, but not with a rod, but with a round steel pipe with a wall thickness of 2 mm or more. The pipe diameter is needed within 70-80 mm, no more and no less. Then it, together with the hard shell, will work like the frame described above. A 76mm water pipe works very well.

Note: you can learn more about the soles of foundation pillars (this is a very important unit) from the video:

Video: columnar foundation - basic principles of construction

Shells

The simplest column shell is a pipe made of 2-3 layers of roofing felt, tied with wire, as in Fig. about reinforcement. It is cheap, lightweight and does not require additional waterproofing. However, when backfilling soil with a tamper, it often wrinkles and does not help the reinforcement work, which is generally unacceptable for small-diameter pillars. Therefore, the shells of foundation pillars are often made of pipes: asbestos-cement, plastic or steel.

The latter can serve as pillars on their own, without concreting. Under a grillage made of channel bars (see figure) seems to be the best option: pipes can be driven into the ground without any excavation work at all. But generally speaking, if the pipes are made of ordinary steel, then on soils suitable for a columnar foundation this is not an option - the pipes in them will rust through in 15-20 years maximum. Weak waterlogged soils, on which piles are usually built, are usually acidic. Then a dense crust of hydroxide quickly forms on the pipe, preventing further corrosion. On ordinary soils, under the pillars you need to take short ones; they are made of special steel. Then the calculation is simplified: the specification for the pile contains tables and/or nomograms, from which its load-bearing capacity at a given depth is immediately determined. This is for a foundation with a metal grillage and a load on it of up to 8 tf/linear. m is really a good option for up to 30 years. If you still want to build something on steel pipes, then keep in mind that their diameter should be in the range of 130-200 mm, and the wall thickness should be from 4 mm for the former and from 6 mm for the latter. If you do not comply with both, you risk that the pipe will bend or break under load.

Shells are rarely made from plastic pipes: they are also lightweight and are waterproofing in themselves, do not wrinkle when compacted, but are more expensive than roofing felt. And most importantly, they are very smooth and do not cling to the ground at all. Therefore, it is hardly possible to obtain a load-bearing capacity of more than 5 t from 1 post in plastic with a conventional heel. For thin poles, the use of plastic is also excluded: it will not create a working shell.

Most often, asbestos-cement pipes with a diameter of 150-300 mm are used on the shells of pillars. It is more difficult to move them and, especially, lift them out of the well. But they are very rigid and work together with the reinforcement; for thin pillars this is the only acceptable option. They also sit firmly in the ground, and waterproofing is ensured by treatment with bitumen mastic; It’s better to do it twice with an interval of 20-30 minutes, because asbestos cement is a porous material.

Why are square pillars needed?

At first glance, it may seem that foundation pillars with a square cross-section are bad. We need to dig pits, we need more concrete, we need wood for formwork. However, firstly, this greatly simplifies the pairing of the pillars with the grillage: from the point of view of construction technology, such a foundation is no different from a pile-strip foundation. And the pairing of the pillars with the grillage, it must be said, is a critical and technically complex unit, see, for example. video clip:

Video: grillage and columnar foundation assembly

Secondly, there is a whole range of economical advantages:

• Since the pit is wide, you can place a ready-made support sole under the post, see below. This increases the load-bearing capacity of the column several times and, accordingly, reduces their number. This alone can already cover the “extra” costs of the pillars themselves.
• An axial reinforcing rod is no longer required; It was not for nothing that it was said above about round pillars. The reason is that in a square bar, any lateral loads spread to the corners. Very often people who are strong-minded curse this feature of “squares,” but everything is poison and everything is medicine: in this case, reinforcement is placed in the corners.
• Because the middle of the column is already free, you can safely use vibration compaction of concrete.

In general, if a foundation with a grillage is planned, then the option of square pillars should be considered first. For example in Fig. – drawings of a monolithic foundation with a recumbent grillage, designed for a freezing depth of up to 1.2 m. If 1-2 sections of the pillar are less, you can remove them, but in any case at least 2 sections should remain. It should also be borne in mind that the grillage beam itself in this case is capable of bearing a load of no more than 8 tf*l. m, this must be taken into account when calculating the number of pillars and their placement.

Prefabricated ready-made

Concrete is a wonderful material, but it requires the correct alternation of continuous production cycles with technological breaks, which is often inconvenient, if not completely impossible, during self-construction. However, you can get out of this situation by constructing a concrete foundation from blocks supplied ready-made for sale. We don’t need large FSB blocks (not the Federal Security Service, Foundation Prefabricated Blocks!) of complex configuration and with metal embedded parts; they are designed for heavy prefabricated foundations and there is nothing to do with them without a crane.

Small FSB 200x400x200 mm will be enough for us. Columns from them can be laid like brick ones, depending on the availability of free time. Only simpler: a pillar of 2 blocks with a supporting area of ​​0.16 square meters. m will withstand a load of up to 3 tons. For light buildings this is enough, so dressing the seams comes down to turning the rows 90 degrees relative to each other, on the left in Fig.

The peculiarity of block masonry is that the masonry mortar needs to be very dry, viscous, with a minimum amount of water, so that the strength of the seam is comparable to the strength of the blocks. In practice, you need to work with the solution as dry as you can. Suddenly it turned out too dry - under no circumstances should it be diluted with water! Throwing away the batch is not cool, sorry, it goes against professional ethics. You need to use the edge of a trowel to chop the cake of the solution finely and finely along and across, like a cook making meat for Pozharsky cutlets, and at the same time distribute it in an even layer over the area.

Under more impressive buildings, the pillars are placed on thrust bearings, in the center and on the right in Fig. Most often, ready-made column bases are used on the thrust bearings, on the right in Fig. Their height reaches 1 m, so it is often possible to immediately pour a grillage or lay a rand beam. The supporting area reaches 4 square meters. m, and the narrowing upward provides anti-heaving properties, see below, so it is often possible to do without a large depth under a heavy structure.

In addition to the masonry mortar (it is the same as in the previous case), the blocks from the soles of the columns have other features. The first is that you still can’t do without lifting equipment, they are heavy. The second is also too heavy for a sand and gravel cushion, so the cushion is made of concrete; in fact, a thickened concrete base. Its bevels transfer the pressure of the column to the sides, without which a very heavy sole can begin to sink in the wet soil, like in a swamp. It is a swamp because it is completely rheological. And the trapezoidal cross section of the rigid cushion acts like wet shoes.

Finally, ready-made pillars for foundations are also sold, see fig. left. Left – normal; in the center - anti-heaving, on the right - for soils subject to horizontal movements. These pillars are already lighter, they can be lifted with hand hoists and turned over by two people. Available in different heights for different depths. The supporting area is about 0.5-0.65 square meters. m, which is very good. But what’s not very good is that finished poles, especially anti-height ones, cannot be cut to height with a grinder. Therefore, before drilling, you have to carefully plan the site, which is labor-intensive and expensive. In general, this is a good option for places with shallow freezing, but not a budget option.

Related question: why is a pyramidal pillar anti-heavy? Because the heaving soil not only pushes the pillar up, but also presses on it from the sides. If you tilt the side faces inward, then, according to the parallelogram rule from school physics, forces will arise that reduce the buoyancy. However, then it is necessary to make an anti-heaving backfill around the pillar; it will be a kind of damper that distributes lateral pressure and prevents the heaving forces (and their magnitude is enormous) from tearing the pillar, see fig. on right. The bearing capacity of the pillar will decrease by 7-10%

Prefabricated grillage for concrete

In general, the sequence of laying a columnar foundation with a grillage is shown in Fig. The bottom row of images on it can be quite tricky even for an experienced builder. If the grillage is lying or recessed, then it’s okay: the laying technology is completely the same as for a strip-pile foundation: the pillars can be made round and poured all at once, see the trace on the left. rice. You just need to remember about the anti-heavy cushion with backfill.

If the grillage is hanging, then, firstly, you need durable formwork made of high-quality wood, on the right in the same fig. Secondly, it is impossible to wait for the pillars to fully gain strength and only then fill the grillage; the result will not be a grillage, but a rand beam. In general, the “wetter” the pillars are by the time the grillage is poured, the stronger the whole thing will be in the end. But then the concrete poured into the formwork with its weight can simply collapse the pillars that have not yet gained strength. It is necessary either to reinforce the formwork with supports, but then the ground underneath them may give way and the upper surface of the tape will skew beyond repair, or to guess the period of time (very short) when it is already possible to fill and it is not too late, which requires considerable experience.

For buildings up to brick with a residential wooden attic, a way out of this situation is possible in the form of a prefabricated grillage; drawing - in fig. below. In lintels, ready-made or home-made, steel mortgages are provided for mounting brackets and openings for the vertical columns of the pillar frame, see the inset at the top left in Fig. Further:

• Lay the jumpers and connect them by welding with mounting loops; in the simplest case, these are straight sections of reinforcement.
• They make formwork on the sides.
• M200 concrete is poured to a height of 80-100 mm above the hinges.
• When the concrete has set, a reinforcing mesh of AI reinforcement with a diameter of 8-10 mm, with mesh dimensions of (100-150) x (100 x 150) mm, is placed in the formwork. The distance between the ends of the reinforcement and the edges of the tape is the usual 50 mm.
• The protruding ends of the reinforcement frame of the pillars are welded to the mesh.
• Fill with the same concrete for another 100-120 mm.
• After full strength has been gained (from 20 days, the surface should be covered with a film during this time and periodically slightly moistened), the walls are erected.

About TISE foundations

TISE means Technology of Individual Construction Ecological. Developed in Russia, designed for small low-rise self-building. Construction specialists, especially orthodox and literalists, who believe that only those with a diploma or professional certificate in their specialty should build, are wary of TISE, and there is no need to look for TISE in the codes of construction rules and regulations. But they build a lot according to TISE, the houses are well worth it. It must be assumed that, having passed the test of time (the orthodox are right in their own way, people live in a house), TISE will take its rightful place among construction technologies.

As for foundations, the highlight of TISE is the same hand drill with a camouflage scraper, which has already been mentioned. It allows you to obtain a fairly large supporting area of ​​the pillar with minimal labor costs, the amount of excavation work and disruption of the soil structure. Suffice it to say that according to existing technologies, camouflage chambers in wells are formed by explosion. Moreover, they turn out to be spherical, far from ideal from the point of view of load-bearing capacity.

The second feature of TISE foundations is versatility. They can be laid on any soil, except for those suitable only for piles (silt, peaty, waterlogged sand, etc.) at a freezing depth of up to 1.2 m without recalculation and design changes. TISE foundations are made of pile-tape and columnar-grillage foundations. They are often confused, but the difference is clearly visible in the figure; In the same inset at the top right - the working tip of the TISE drill:

Pile-tape (left)

Columnar grillage (right)

For soils of normal vertical structure: humus-loam-loam-sand. Suitable for other soils that are not uniform in depth. Pile wells - without camouflage. Piles - of a conventional design: circumferential reinforcement with transverse bracing. Piles are installed on a sand cushion. For reinforcement of piles and tape, it is permissible to use fiberglass reinforcement. When pouring piles, vibration compaction is used.

For soils that are uniform in depth: gravelly, gravelly, cartilaginous. The humus layer in them is often poorly expressed, because in well-ventilated and washed passages between solid inclusions, roots and insect worms are at ease. The holes for the pillars are with a camouflage chamber. The pillars are with hemispherical soles. The pillars are reinforced with a powerful central pipe and 2 narrow high U-shaped brackets with bent ends made of fittings with a diameter of 8-10 mm. The staples form 4 vertical branches, which are connected by transverse links of 4-6 mm wire with a pitch of 300-400 mm. The pillars are poured without a cushion, directly onto the ground. The shell of the pillars is soft or plastic, because heavy asbestos-cement or steel will push through the not yet hardened sole. Pouring the pillars - without interruption: The shell is inserted to the bottom. - Install the reinforcement frame so that the “whiskers” of the staples seem to snap into the recess in the bottom of the camouflage. - Concrete is poured to 1/3 of the height of the shell. - The shell is raised to the height specified in the drill specification and securely fixed. - Fill the rest of the column with hydraulic seal (layer by layer), as described above. After the pillars have set, wait 7-14 days, depending on the weather, and form a grillage. It can be hanging, as in the figure, or lying, or recessed.

For light houses

TISE foundations are suitable for a house with a plan area of ​​up to approximately 150 square meters. m, up to 2 storeys, incl. and for a brick house. The author of the technology guarantees the load-bearing capacity of 1 support on soils common in the middle zone up to 11 tf; however, if the building area allows the required number of poles to be placed, then until TISE is fully tested, it is better to limit the calculation to 7-8 tf per pole.

Prefabricated frame houses and houses made of aerated concrete can be built on foundations that are lighter and cheaper than TISE. For example in Fig. – diagrams for constructing concrete foundations for a frame house with heated floors and aerated concrete foundations with a ventilated facade. These foundations are shallow; bearing capacity of 1 column is about 4 tf.

Brick

Brick foundation pillars have only one advantage over others: they can be laid gradually, as free time is available. But after the appearance of concrete, it was also “eaten up” by blocks for prefabricated foundations. However, if you want to build a real Russian bathhouse according to all the rules, then you will have to master the technology of laying columnar brick foundations. It is not that complicated, but it differs in some ways from the methods of laying walls.

First, you need to place a concrete bearing under the pillar, this will also increase the supporting area of ​​the pillar, see fig. If the soil is dry and dense enough, you can not take a finished slab, but pour the concrete footing directly onto the ground, without a cushion. But laying the pole directly on the ground or in the sand is unacceptable.

Then, brick is a porous, hygroscopic material. Therefore, under the pillar it is necessary to place in advance a sheet of waterproofing of such a size that it can subsequently be used to cover the entire pillar; this is also shown in Fig. The pillar itself, when the masonry mortar has hardened, is treated with bitumen mastic.

For the same reason, not any brick is suitable for pillars. You need to take burnt iron ore, as it is denser and less porous; of course, not swollen or warped. It is distinguished from the usual one by its dark color and clear, sharp and short sound when tapped. Red ringing brick of the highest grade will work great on walls, but not on foundation pillars. Clinker bricks are even better, but for budget construction this is an expensive overkill.

Next, lay the foundation pillars in a fence manner, as in Fig. on the left is a gross error. And walling up a steel pipe into a concrete core “for strength” will also be of no use. The fence post does not experience prolonged pressure from all sides and nothing pulls it up. Without going into the subtleties that require special knowledge, the wind tormenting the fence is a kind of hussar: it swooped in, chopped it up, and bounced back. And then the ground is line infantry: advancing slowly but inevitably. Therefore, it is necessary to lay foundation pillars with a 3-row bandage of seams; how to do it for pillars of one and a half and two bricks is shown in Fig.

Nevertheless, brick as part of the foundation has a useful quality: it can be used to build rand beams under a light wooden house, without starting concrete work and without spending money on ready-made monoliths. The construction of brick rand beams is shown in Fig. on right. The pillars for them, if the construction is really on a budget and on weekends, it is better to make it from rubble concrete: the filler stone is inexpensive, and you only need a little mortar; in extreme cases, it can be mixed with a shovel in a trough. Although a concrete mixer is, of course, better in every way except for rent.

Bath foundation

If we are talking about a Finnish bathhouse, then no special foundation is required for it. The sauna was probably sold so widely because it was unpretentious in the design of the bathhouse, as long as the heat was retained. There are also apartment mini-saunas with electric heating on sale, but that’s okay, the Scandinavians themselves willingly take them for themselves.

Otherwise, it’s a Russian bathhouse. Real, original, old. With vigorous steam and topping with kvass. The Finns are avid bathhouse attendants, after taking a steam bath in one, they admit: yes, ours is far from yours. But it’s difficult to build yours and it’s not possible everywhere. They are right about this.

Without touching on the choice of location and features of the bathhouse itself (there are more than enough of them), we simply provide a diagram of the foundation for a bathhouse in a wooden log house; the pillow under the pillars and the fence is not shown. The brick needed for it is only smooth iron ore, the pillars are 2 bricks long, and the fence is made of brick. And 2 more conditions: without proper filling of the subfloor and preparation of the floor from a measuring slab coated with clay (shown in the figure), there will not be an optimal microclimate, that is, strong steam.

Wood

In the old days, those who were richer stood on bricks. And ordinary people placed on the foundations measured blocks of pine and oak logs (chairs) with a diameter of a span or more, this is from 18 cm. And surprisingly, the huts stood for 150-300 years. The fact is that they tried to build housing and household needs on acidic soils unsuitable for cultivation; they are most often excessively watered. In such conditions, the tree becomes stained and lasts for centuries. The structure of a wooden columnar foundation is shown in Fig.

Chairs and scaffolds for them were cut down only with an ax, so as not to wet the ends with a saw. Now it seems incredible: how is it possible to cut out an even and smooth perpendicular end with just an ax? But Kizhi is a witness: our ancestors did something else with this simple instrument.

Before use, chairs and scaffolds were fired over a fire (not in a fire!) to prevent immediate rot. The workpieces were periodically turned until a burnt crust about 1 cm thick was formed.

Nowadays, if you suddenly need the cheapest wooden foundation, there is no need for such difficulties. You can saw blanks and knock down blocks (now shields) from boards. However, all finished parts must be separately treated with biocides, and then, on a spread out plastic film, thoroughly (preferably until they seep through) the ends thoroughly impregnated with a water-polymer emulsion. The parts are placed vertically, the ends are impregnated, then they are turned over and the opposite ones are impregnated. They are dried in the shade for a week, and then treated in the same way and additionally on the sides (along the generatrix) with bitumen mastic.

Another version of a wooden foundation, now not buried, is suitable for the lightest country houses: a summer house, a toilet, a shower, a utility block. How it works can be seen in Fig. it must be assumed that no explanation is required for it. And if necessary, the structure can be moved, or loaded onto a conveyor and transported.

Self-repair

Repairing the foundation is always a difficult task for a builder. However, only columnar (we emphasize - only and only columnar!) in some cases (more emphasis - in some!) allows the owner-craftsman to eliminate some of its shortcomings. Firstly, small cracks that do not violate the integrity of the pillars. Let's say a dashing bulldozer driver ran over with a shovel, a piece flew off and the rebar showed. Then repair formwork will help out, see fig. If the defect is low, the pillar is dug up so that the upper edge of the formwork is under it. Then the formwork is assembled around the pillar and, supporting it from below, is gradually moved upward, while simultaneously filling the gap with repair mortar.

Note: Repair formwork B is used to repair pillars damaged before the construction of the building. To repair round pillars under a building, round formwork B is used, detachable and tightened with clamps.

Secondly, replacing a pillar that has lost its integrity. On your own, this is only possible for pillars located along the perimeter, using the same TISE drill, and only for light, prefabricated wooden buildings. How this is done is shown in Fig.

Features, the essence of which is that instead of the damaged one there will now be a double or triple pillar:

• During the renovation period, all residents must be evicted and valuable property must be evacuated.
• The length of the shell of the pillar to be replaced must be calculated and adjusted to the correct size before lifting it under the crown: the pillar must snap into place end-to-end.
• If a corner post or a post with equal spans on both sides is replaced, 2 posts are placed symmetrically on both sides of the damaged one for repair.
• Otherwise, the replacement pole is placed on the side of the larger span; if the size of the smaller one allows, then a second substitute post is placed there.
• A damaged pole, if its reinforcement is not damaged or can be repaired, is repaired using repair formwork and remains in place.
• Replacement posts are not removed after repairing the main one.
• All soil backfilled is thoroughly compacted.

About errors

To do something correctly, without much experience, it is not enough to know how to do it. You also need to know what not to do. Therefore, finally, we offer another video about mistakes when laying foundations:

Video: mistakes when laying columnar foundations

Finally

The columnar foundation is really cheap and requires little labor compared to the others. But he is also cunning. Not through his own fault, but because he is very sensitive to the mechanics of the ground beneath him. Who will guarantee that it will not change during the operation of the building? They will cut down or plant a forest nearby, build a barnyard - in 2-5 years something will begin to change in the soil.

Therefore, a columnar foundation can be definitely recommended only for light buildings, mainly of the dacha-garage type, not intended for permanent residence.

As for residential buildings on a columnar foundation, firstly, children and grandchildren will only get them if they are built on suitable soil and in favorable natural conditions. If we build on generations, then it is appropriate, by analogy, to recall the immutable rule of lending: you need to borrow in the currency in which you earn. Otherwise, you can, as they say, get hit hard, which is now happening en masse.

For developers who are short on funds, there is a no less immutable rule: they save on the foundation last, and it is highly advisable not to save on it at all. It would be better to plan a smaller house and build it on a strip or on a slab. In the future, if the finances somehow work out, they will allow you to build extensions, but a columnar foundation - in no case.

In general, when choosing the type of foundation, you need to think very hard. And we will consider our task completed if the material in this article helps you make the right decision.

The choice of foundation for a house or other building is influenced by many factors. For each specific case, a different foundation design can be used. In first place in terms of frequency of use is the strip structure; for unstable soils, a pile foundation is common. It is quite simple to build a columnar foundation with your own hands, which in some respects is not inferior to the listed foundation options. This design has its own variations and nuances in the bookmark. Each of these points will be discussed in the article.

Benefits of the solution

During the use of this type of foundation design, users and builders managed to compile a certain list of positive qualities that were identified. Among them are:

• possibility of independent design;
• relative simplicity of calculations;
• possibility of use on various types of soils;
• Possibility of use in areas with level differences;
• the ability to avoid site planning;
• high construction speed;
• long service life;
• relatively low project cost.

Perhaps these nuances do not apply to all types of columnar foundation designs, but for a classic structure with a concrete grillage this is exactly the case. There are also disadvantages, of which there are significantly fewer. One of them is the impossibility of constructing heavy buildings whose walls are made of brick. The latter is capable of exerting significant pressure on the base, which often leads to destruction. This occurs due to shrinkage, although on an industrial scale this foundation design is used for brick buildings on soils with permafrost. Another unpleasant point is the inability to build a basement or garage directly under the house, since a foundation of this type does not provide for laying a monolithic structure to a great depth.

Note! Columnar foundations are most often used for the construction of structures that use gas-filled blocks or are made using frame technology. Construction of buildings made of rounded logs is also allowed.

Types of designs

The design of a columnar foundation will largely depend on the specific building it will be used for. If we are talking about an ordinary gazebo, then its dimensions will be significantly smaller than those needed for a bathhouse or cottage. Based on the material used, the types of columnar foundations can be divided into:

• monolithic with a concrete grillage;
• monolithic with a wooden grillage;
• brick;
• bud-filled;
• rubble concrete;
• wood;
• monolithic from asbestos pipes;
• columnar-pile.

The first design option is the most durable. This is due to the fact that the pillars and grillage are a single structure that is capable of evenly distributing the load exerted on all pillars. This design is more expensive than others, but will last much longer. Such a columnar foundation allows the construction of houses of several floors using frame technology or from logs. The next version of a columnar foundation with a grillage is made using a similar technology. Its pillars are also filled with monolithic concrete with reinforcement, only wooden beams are laid on them, which are the basis for the walls of the structure.

Most often, when they talk about a columnar foundation, they mean the third design option, which is laid using bricks. Unlike previous options, a columnar brick foundation is quite simple to construct and requires relatively lower costs. With good soil quality, as well as the right approach to construction, a service life of several decades can be achieved. Many ancient buildings that have survived to this day were built precisely on this type of foundation. In some areas, it is possible to build a house with several floors on a foundation of this type.

Note! Other types of blocks can be used as the basis for a brick foundation. In this case, the strength and stability of the base will depend entirely on the quality and strength of the material used.

A rubble-filled columnar foundation is laid using brick or stone from old structures. This solution is suitable for stable soils and for areas where there are no level differences, since the stability of such a foundation is significantly lower than that of previous options. The base of the structure made of rubble concrete is also built using the materials mentioned above, but the connecting link in this case is cement mortar. The result is a monolithic, but not reinforced structure.

The wooden base of the structure is now practically not used, but it still remains relevant for areas where it is necessary to raise the structure to a considerable height in order to avoid flooding. This applies to warm parts of the world. A similar method was used in other areas, but proper implementation requires special treatment of the wood to prevent rotting and drying out. A wooden columnar foundation is an excellent solution for additional buildings near the house. This applies, for example, to terraces. In addition to antiseptic impregnations, wood is also coated with waterproofing material. As the latter, bitumen mastics are often used.

Another interesting design option is a foundation made of asbestos pipes. Most often, it is manufactured using a solution similar to a monolithic columnar solution. In this case, the pipes act as formwork, into which reinforcement rods are inserted and concrete solution is poured. Usually a pipe with a diameter of 20 cm or more is used. A column-pile foundation is made using screw or other types of piles. In the first case, no special equipment will be needed to build the foundation, except for a concrete mixer. Screw piles can be installed in place by a small crew of three people.

The advantage of this solution is the greater stability of the structure base. This is due to the fact that the pile is immersed to a considerable depth, which passes the freezing level and reaches dense layers of soil, where fixation is carried out. The design with screw piles can be used for a log house or a frame house. If we are talking about bored piles, which are intertwined with a metal frame with a concrete grillage, then such a foundation is used when constructing houses from blocks.

Varieties by depth

The difference between foundations is made not only by the materials that are used to lay them, but also by the depth to which the foundation is mounted. To put it simply, then, as with strip foundations, there are two types:

• shallow;
• buried.

In the first case, the immersion is usually 50 or 80 cm, which somewhat reduces the cost of equipment for the base itself. This support structure is used for buildings that are light in weight. A recessed structure involves the use of supports that go 150 or 200 cm into the ground. This depends on the level of freezing. This design is more preferable for areas where there is heaving soil or high instability of the upper layers. In addition to the depth of the foundation, the height at which the grillage is located also varies. In this regard, the following are distinguished:

• aboveground;
• ground;
• buried.

Above-ground foundation design options are excellent for cases where the upper layers of the soil have a high degree of heaving. If the grillage is laid directly on the ground, there is a possibility of distortion or damage. In the case of constructing an above-ground version of the structure, the pillars are made of greater height in order to raise the grillage to a certain height. The disadvantage of this solution is the need for additional floor insulation. This is due to the free ventilation of the space under the house. Usually the sides are closed and only small openings are left for ventilation.

The ground version of the structure is built on a prepared bed of sand and gravel. It is placed so that it is flush with the surface. On the one hand, this eliminates strong blowing, as is the case with the above-ground version of the structure, but on the other hand, for such a structure there is a need for a correct approach to waterproofing. The shallow version of a columnar foundation is very similar to a similar strip foundation, but additionally, supporting elements in the form of pillars or piles are prepared in the trench, which are sunk to a considerable depth. The second and third options are most often implemented using a concrete grillage.

Basic Concepts

Almost all types of columnar foundations have one principle according to which they are constructed. Certain nuances are important to consider in order to achieve success. Among them:

• pillar pillow;
• heel support;
• column design;
• arrangement of columns;
• grillage device.

If we are not talking about pile supports, then preliminary backfilling must be done under the posts. For these purposes, medium-grained sand is usually used. The thickness of the pillow itself depends on the amount of moisture in the soil, as well as the expected weight. It can reach 30 cm, and the minimum permissible value is within 10 cm. If additional drainage is required, then an additional layer of crushed stone is laid under the columns, which allows water to pass through faster than sand. The functional purpose of such a pillow is to uniformly distribute pressure, as well as reduce the level of humidity under the posts.

For monolithic columns, which are made by pouring, soles are made, which are a small concrete slab with a thickness of up to 50 cm. It is wider and longer than the supporting column in order to increase the interaction area. The next nuance of such a foundation is the need for reinforcement. If we talk about a monolithic foundation, then there are no questions regarding reinforcement, but this also applies to other options. Only in this case is external reinforcement carried out, which eliminates the deformation of the columns. To prevent moisture from rising to the grillage and the building, it is necessary to approach the issue of waterproofing correctly.

It is important to correctly determine the number of columns in the foundation and distribute them throughout the territory. This will determine how the load will be distributed. The projection of the posts above ground level will depend on the placement of the grillage, as well as the topography of the area. In some cases, owners of houses on columnar foundations prefer to make a fence. This is an additional concrete structure that is placed between the columns to cover the underground space. Reinforcement is also required for it. The fence for the columnar foundation further strengthens the entire structure.

Note! In areas where flooding is possible, the height of the pillars can reach up to 2.5 meters above ground level. The calculation is based on the maximum level to which the water rose in the area.

Self-calculation

The key to successful completion of the construction of the structure is the calculation of the columnar foundation and preparation of the project. They begin even before the process of preparing and planning the site for the foundation. It is better if a professional in his field provides assistance in drawing up the project. Thanks to this, it will be possible to take into account all the nuances that relate to the soil and the expected load. The wishes of the customer himself are also taken into account. The main initial parameter for drawing up a design project is the area allocated for the building. The next important indicator is the mass of the structure. To correctly draw up all the documents, you will need a geodetic survey of the area and linking the future structure to a specific site.

During the design, the following points will also be taken into account:

• soil specifics;
• proximity of aquifers;
• soil freezing level;
• number of floors;
• materials for construction;
• possible additional loads.

The first and second factors will determine the required depth of columns or piles for the foundation structure, as well as their level above the ground. The third factor is necessary to determine below what depth the supporting elements of the foundation should be located. The number of floors affects the number of supporting elements, as well as the choice of material for construction. Additional loads that may be caused by wind, changes in soil or precipitation are taken into account. All these factors give a clear understanding of the number and parameters for the pillars of the future foundation.

With sufficient experience, you can try to perform the design work for the structure yourself. To do this, you will need to collect all the data relating to a specific area. They can be found on the official websites of various services or obtained directly from the services. When taking readings, knowledge of many formulas will be required. But even the use of online assistants may not help, since important factors that can only be assessed while staying at a specific site will be missed. If you turn to specialists who have already performed dozens of calculations for a specific region, you can be sure that they have a good knowledge of all the nuances of the soil in the area. In addition, professional services involve the issuance of specific documents that will be required when obtaining the necessary permits for construction.

Construction process

Each foundation design option has its own construction nuances, so it’s worth considering step-by-step instructions for several options. The first of these will be a monolithic columnar foundation.

Monolithic option

After drawing up the design design, it’s time for practical work. The first step is to prepare and mark out the area for a monolithic columnar foundation.

As you can see in the photo above, it is necessary to pre-mark the area where the structure will be located. To do this, the corners of the building are marked with pegs. A clearly visible rope or twine is stretched between the latter. Particular precision of angles is not required, since the marking of the structure is carried out for preliminary preparation of the area for construction.

The next step is to remove the top layer of soil along with the vegetation that is located on it. To make work easier, you can compact the area to make it easier to move around.

When the preliminary stage is completed, you can move on to more precise marking of the foundation structure. To do this, the corner pegs are placed exactly in their places, and the distance between them is checked. It is also necessary to determine whether the diagonals of the resulting figure of the future foundation structure are equal. If they do not match, then it is worth finding out which of the corners has the wrong angle and moving one or more columns.

In accordance with the developed project, markings are applied to the columns that will be installed later. For these purposes, additional stakes and ropes are used. The latter are stretched in places where the rows of columns will pass. The photo shows that the string, which is stretched in the middle, marks the edge of the pillars of the foundation structure. Simultaneously with this procedure, notes are made on where exactly the columns for the foundation will be located.

If you pay attention to the photo above, you can see that the master specifically marks the boundaries of the pit for the post. To do this, four pieces of reinforcement are driven in along its edges, which makes orientation easier during digging. You can start with it immediately after marking a specific element of the foundation structure. This can be done mechanically or manually. Everything will depend on the quality of the soil that exists in a particular area. A square heel with a side size of 40 cm is considered standard, but in certain cases it can be increased to 80 cm. It is this size plus the gap for the formwork that the foundation pit for the column should be.

The distance between individual pillars of the structure can vary from one to three meters. When the pit for the foundation column is ready, it is necessary to waterproof the lower part, where the heel of the supporting element will be poured. In the photo above you can see that for this purpose a polyethylene oilcloth is laid on the bottom. The density of the oilcloth should be 200 microns. It is located with a twist on the walls. Additional waterproofing and at the same time formwork for the structure is bikrost, roofing felt or similar material that does not have powder. Waterproofing can be fixed to the wall using nails or other fasteners. Subsequently, it will be pressed down by concrete. The height of such formwork should be equal to the height of the heel, which will be poured under the column.

The next step in constructing a columnar foundation structure is the preparation of reinforcing elements that will be poured with concrete. For these purposes, rods with ribs that have a diameter of 10 mm or more are used. It is necessary to calculate the elements in such a way that the heel is larger in size, and the vertical reinforcement corresponds to the post. The height of the reinforcement must be sufficient to combine the pillars with the monolithic foundation grillage, which will be poured later.

To make it easier to bend the reinforcement, you can make a similar device to the one shown in the photo above. For this, two metal corners are used, which are screwed to the wall. Moreover, their length is equal to the length of the element that will bend. The distance between the two strips is equal to the diameter of the reinforcement that is used for the foundation. To make it easier to bend the rods, you can use a metal pipe as a lever.

To make it easier to assemble the sheathing, stands are made, as shown in the photo above. A support is screwed to the vertical plane, in which notches are made at a distance from the reinforcement bars that will be embedded in the column. Additionally, a stand is made that can be rearranged depending on the length of the reinforcement. She can be seen on the right.

After this, the horizontal structural elements are distributed at an equal distance. To do this, use a tape measure or other device. The next step is to lay two more vertical posts, as seen in the photo above. To fix the structural modules together, it is necessary to use a binding wire that securely clamps them in place. For knitting, you can make a small hook yourself, which will simplify the task.

Reinforcement under the heel is performed separately and is represented by a small square in which rods are laid perpendicularly, as shown in the photo above. They are tied at all intersection points to ensure reliable fixation.

Next, preparation of the support stands of the structure is carried out, which will raise the reinforcement under the heel and under the column a short distance from the ground. This is necessary so that the element is filled with concrete mortar and from below.

The reinforcement for the heel structure is installed on plastic legs, and the reinforcement for the posts is fixed on top. All elements are tied together with knitting wire. So that it turns out as shown in the photo below.

Once the reinforcing elements for the columnar foundation structure are ready, formwork is manufactured for each column. An OBS board with a thickness of more than 12 mm is perfect for this. If you take a material with a smaller thickness, it will bend under the pressure of the concrete solution. To properly reinforce a columnar foundation, concrete must cover the mesh by at least 5 cm on each side. This means that the length and width must be 10 cm greater than the reinforcing elements. The height can be 5 cm greater.

To fasten the walls of the formwork under the posts together, hangers for a plasterboard profile are suitable. In this case, the middle part of the structure is cut out and only perforated strips remain, which are bent into the corners, as shown in the photo below. They are screwed to the walls and combine them into the required structure.

When all the elements are ready, they are assembled into a common structure, which will ensure high-quality pouring of the foundation.

In order for the OSB structure under the foundation columns to have a sufficient water-repellent effect and not to swell under the influence of moisture from the solution, it must be covered with cold-prepared bitumen mastic. This is done both externally and internally.

The next step is to install the armored belt under the foundation structure in the prepared pits.

The frame must be placed exactly in the middle of the prepared pit so that the concrete solution can freely and evenly fill the space around the structure. In addition, the structure must be exactly vertical and level. To achieve this, you can resort to the trick shown in the photo below.

A regular bubble level is used to ensure the structure is vertical. After this, the reinforcing base is tied to an additionally laid beam so that there is no displacement during pouring. The beam is fixed with weights in the form of bricks or other devices.

In this way, all elements that are responsible for the stability of the columnar foundation structure are installed.

Next, concrete is mixed for the foundation structure. The columns will be filled in stages. The first step is to fix the heel of the column under the foundation. It is enough to knead for each heel. The mortar for the foundation structure can be laid with a shovel. Its level will be equal to the height of the prepared waterproofing. To evenly distribute the concrete in the heel under the foundation, you will need an electric vibrator. It is lowered into the solution to fill any voids and remove air that could weaken the foundation post structure.

All that remains is to wait for the time during which the heel under the foundation column gains strength. As soon as this happens, you can begin installing the formwork for the column, which was prepared from OSB sheets. The formwork is placed in such a way that the reinforcement is located in the middle.

If you pour concrete into the formwork without fixing it, this will lead to displacement of the formwork and disruption of the foundation structure. Therefore, it is necessary to perform backfilling, which will fix the formwork under the foundation column. When performing backfill for the foundation structure, soil may get into the column form. To prevent this from happening, the upper part of the formwork structure under the foundation is covered with a thick film, as shown in the photo above.

Additionally, it is fixed to the formwork using a construction stapler so that the oilcloth does not move during operation.

For backfilling, you can use the soil that was removed when digging pits for the foundation columns. It is carefully poured between the pit wall and the formwork under the foundation column. After this, compaction can be done using a hand tamper, which can be easily made from a log and a small handle-shaped crossbar.

To protect everyone who will move around the construction site, it is necessary to cover the protruding rods with plastic bottles. The latter are easy to find and will do the job perfectly.

To make the backfill dense, you can additionally compact it with water, which will allow the soil to sink under its own weight.

The protective film is removed from the formwork under the foundation column. There are small pebbles and other debris left at the bottom of the structure that may interfere with good adhesion. To eliminate this, you can remove them using a regular or industrial vacuum cleaner, the tube of which will be tied to a pole, as shown in the photo above.

Before pouring the next portion of concrete under the foundation, it is necessary to wet the heel under the foundation, as well as the formwork. This is done for better interaction between the components of the foundation structure. After this, you can fill the column into the prepared formwork. The solution must be compacted with a vibrator to eliminate the presence of air in the structure. To ensure that the foundation column does not lose too much moisture during the process of gaining strength, it is necessary to put an oilcloth on the foundation reinforcement, which prevents soil from getting inside the column.

After pouring the foundation columns, you can begin digging a trench between the foundation columns. In this case, a trench will be needed to construct a grillage for the foundation. Its depth is calculated in such a way as to accommodate a cushion of gravel and sand. The second in this case will be 30 cm, and the first will be sufficient at 15 cm. In this case, it is also necessary to decide at what level the foundation grillage will be located. If it is a little deep, then you need to go deeper to this level.

The first to be laid is a sand cushion under the foundation structure, which is well compacted. Next, the second cushion is backfilled under the foundation in the form of fine crushed stone. It also needs to be compacted well in order to achieve uniform distribution of the load from the foundation to the ground. For this, a gasoline or electric vibrator is used. It is best to work by placing it perpendicular to the trench under the foundation, so as not to collect rubble along the edges.

When the backfill for the foundation structure is ready, you can proceed to the construction of formwork for the columnar foundation. Wooden beams will be needed. The length of such a beam for foundation formwork should be such that it can be 45 cm immersed in the ground and protrude to the full height of the foundation grillage. To make it easier to hammer the timber into the ground, it must be sharpened from below with an axe, as shown in the photo.

After this, the element is leveled and driven in with a sledgehammer to the required depth. It is necessary to periodically check the level of the structure, as it may go astray. In addition, this will be the key to the correct installation of formwork under the foundation.

A board is nailed to the installed supports under the formwork. It is necessary to arrange the individual elements for the foundation formwork in such a way that there are no gaps between them.

The foundation formwork board will deform from exposure to moisture, so it must be protected. The easiest way to do this is to use plastic film. It is fixed to the boards using a construction stapler.

To strengthen the formwork structure, jibs are installed that rest against another rack. The elements are mounted through one rack. The free racks are connected to each other using a knitting wire, as can be seen in the photo below.

Additionally, transverse elements are nailed on top of the structure, which tighten the walls of the foundation formwork together. It is first necessary to lay reinforcement inside, since this will be problematic later.

Note! To reinforce the foundation, reinforcement with a diameter of 14 mm is used. In this case, the clamps can be made from rods with a diameter of 8 or 10 mm.

The reinforcement that remains protruding from the foundation columns must be bent to intertwine it with the reinforcement for the grillage. It is tied to the rods, which are laid in the formwork using a knitting wire.

When everything is ready, you can pour the foundation with concrete. This is easier to do with a concrete pump, which can be directed along the entire perimeter of the foundation. After pouring, the foundation grillage is processed with a vibrator and leveled with a trowel.

When the foundation has gained a sufficient measure of strength, the formwork can be dismantled and the foundation can be cleared of soil residues. You can clearly see the process of installing the structure of this foundation in the video below.

With brick pillars

This design option is constructed somewhat simpler than the previous one, but it is worth understanding that a columnar foundation made of blocks cannot be used for serious buildings. It is perfect for sheds or gazebos where the weight will be minimal. Marking for this type of foundation structure is carried out in a similar way as for the previous option.

The pits for the foundation columns are constructed with a small margin so that the support pad is slightly larger than the area required to support the blocks. Crushed stone is placed on the bottom of the prepared pit. Its layer can reach 20 cm. It is important to compact the material well. It not only ensures proper distribution of the load, but is also responsible for drainage, which will eliminate the impact of liquid on the laid blocks.

After laying the crushed stone, sand is poured. Its layer will be ten or more centimeters. It is important to compact it well and level it in a horizontal plane.

After this, you can proceed to laying the blocks. They are leveled and secured with cement mortar. The second row is laid out perpendicular to the first to ensure ligation of the seams for greater structural strength. Foundation waterproofing in the form of roofing felt is laid on top of the blocks. It is necessary to prevent moisture from entering the grillage, which can rot from it. A wooden beam with a cross-section of 15 cm is most often used as a grillage for such foundation structures. It is laid along the entire perimeter of the foundation.

At the intersections of the structure, weaving is done using a tenon joint. The photo shows that two beams can also be connected using the half method. In this case, in each of the elements for the foundation grillage, a cut is made to half the thickness and width of the log. After this, the two foundation elements are fixed to each other using a pin or a self-tapping screw with a hex head.

Pile option

The next option for foundation design, which can also be classified as columnar, is a pile foundation with a grillage. For independent construction of the structure, screw piles are suitable, which are easiest to install without additional equipment. Such a foundation is sufficiently reliable and allows it to be anchored in strong layers of soil. This is done quite simply, since piles for such a foundation can be selected in a wide variety of lengths. The only question will be the convenience of screwing them in. In some cases, additional platforms will be required when work begins. But most often such a foundation is installed without them.

The issue of marking for a foundation design based on screw piles at the initial stage is relative. This is due to the fact that during work you should push off from the first pile. Its installation for the foundation is determined by the plan, which indicates exactly how the house should be located on the site. It is necessary to choose any corner of the foundation from which it will be convenient to start work. This pile will be the starting point from which it will be easy to make the rest of the measurements for the foundation.

It will be easier to install the pile if you prepare a small pit for it. Typically, a depth of 30 cm is sufficient for these purposes. The diameter of the pit is made slightly larger than the diameter of the foundation pile. You can dig it out with a garden drill, if its diameter allows this, or with a regular shovel.

It will be easier to install such a foundation if you do not just screw in the pile using a lever that is inserted into the hole, but with a special device. You can rent a pile sleeve, as shown in the photo above. Thanks to the arcs that are located on the sides of the coupling, it is easier to transmit force from the lever, which is in any position. In this case, the immersion of the pile under the foundation proceeds smoothly. Rotating a pile under the foundation through a hole that is located on top is not always convenient, since there may be restrictions on the area of ​​movement around the pile.

As a lever that will be used to immerse the pile into the ground, one pipe will not be enough, since the direction of the force that will be applied with its help can change the position of the foundation pile, which is very inconvenient. To build the structure you will need at least two levers. The length of each is from three meters. In some cases, longer levers will be required to properly install the structure if the pile must lie quite deep.

To make installation of the structure easier, at least three people are required. Two of them act on levers. The third person’s task at the initial stage is to keep the pile in a vertical position. As long as the main part of the pile is on the surface, there is no point in using a bubble level for the structure. This is due to the fact that the pile still has a significant amplitude of movement.

Note! The wall thickness of the lever must be at least 3 mm in order to provide the required force for screwing in the pile.

Screwing occurs clockwise. This can be determined by the direction of the screw at the end of the pile structure. As you can see in the photo, the main load during screwing of the structure for the one who holds it in a vertical position falls not on the hands, but on the shoulder. Hands act as assistants, since it is almost impossible to grasp a pile of such diameter well. The emphasis is supported by half-bent legs and widely spaced legs.

As soon as most of the pile structure is in the ground, it is necessary to increase the force, since screwing will be more difficult. To do this, the levers are extended to their maximum distance so that only a small part engages the coupling arcs.

As soon as it becomes clear that the pile has taken a good position and is firmly held by the soil, you can proceed to the precise vertical positioning of the structure. To do this, you will need a level that can be fixed to the body of the pile with a magnet. The photo shows that the level is located on the pile for a reason. It is placed perpendicular to the two support arms. This is the only way to correctly track the position of the pile. To make monitoring easier, you can use another level, which is installed directly under the lever.

When the level is in place, you need to position the structure in a slightly different way. If in the previous version the pile was held by the shoulders, now it must be leveled with the weight of the body, directing it in the opposite direction from the one in which the pile is tilting. Support is also provided on legs widely spaced and bent at the knees.

The deeper the pile goes, the more effort will have to be made to guide and rotate it. You may have to enlist the help of a few more people, as can be seen in the photo.

When the installation of the first element of the foundation structure is completed, it is necessary to determine the point at which the second corner pile will be located, which is in line with the first. It is best to take measurements at the centers of the circles. This means that the end of the tape measure is installed on the central part of the pipe. The distance to the center of the second pile for the foundation is measured. It will be equal to the total length or width of the house, from which the width of one wall is subtracted. Once the distance is determined, it is necessary to position the foundation piles on the same line. The easiest way for these purposes is to find a common landmark, for example, a fence, and place the foundation structure at the same distance from it.

The second pile is screwed in in the same way as the first. But now it is necessary to monitor not only the vertical level of the foundation pile, but also the distance at which it is located from the first pile. If in the process there is a need to adjust the position of the structure, then you should not act by simply tilting it in the intended direction. The photo shows that the pile must be tilted in the opposite direction to the one in which it is necessary to align the pile. After this, two turns of the pile are made under the foundation, and it is leveled to a vertical position. If this fails to achieve the desired effect, then the operation must be repeated.

When two piles are already in place, you can proceed to the installation of the third. The point of its installation is calculated somewhat more complicated than in the first and second cases. To install the third pile of a columnar foundation structure, you must be guided by the Pythagorean theorem. The width of the building is known, the length is also known, now you need to calculate the diagonal or hypotenuse of the right triangle. To do this, the thickness of the wall is subtracted from the width and length, since the measurement is taken at the centers, and each figure is squared. The sum of the resulting numbers will be the size of the diagonal. The photo shows that one of the ways to mark the third point of the foundation structure is to use two tape measures. At the intersection of the required values, the location of the third pile is located.

Note! If you don’t have two long tape measures, then you can use twine on which the required size is marked.

After determining the location of the third pile under the columnar foundation, preliminary installation of the pile is carried out in the pit prepared for it. Once it is securely in place, it is necessary to re-measure to ensure that the foundation pile is in place. If there are certain errors, then it is necessary to level the foundation pile in the manner described above.

When the installation of the pile in place is completed, it is necessary to further secure it. To do this, the pit that was dug earlier is filled with soil. It is important to compact the latter well so that the upper part of the foundation pile does not become loose.

The fourth pile under the foundation is also mounted using the diagonal and wall dimensions. In this case, all the indicators are known, so you can use tape measures or twine and screw the pile into place under the foundation. Periodically, when screwing the pile into place, it is necessary to check whether the distances at which it should be in relation to other piles are maintained.

The support of the entire structure is ready, now it will be easier to install the remaining piles under the foundation. For these purposes, a string is stretched between all risers. It must be located as close to the ground as possible. It will be easier to operate if two strings are pulled between the foundation piles, which will mark the corridor in which the piles should be located. Each wall is divided into two halves. The resulting size is marked on a stretched string and a pit is dug under it for the pile of the future foundation. This must be done on all four sides of the house.

During screwing, you must ensure that the marked point is in the center of the pile pipe. All foundation piles are immersed to the required level.

Foundation piles will also be required for interior walls. To mark them, you can use the intersection points between the lines of existing piles. To do this, ropes are stretched between the piles, which are clearly visible. At the intersection points, where necessary, a pit is prepared and the pile is screwed in. At the same time, it should be positioned in such a way as not to strain the rope or deflect it. It is important to monitor the level of the foundation pile throughout the screwing process.

The pile should be located at the intersection of the stretched ropes as shown in the photo above. The ropes are tangential, so the center of the foundation pile does not coincide with the center of the pile that will be screwed in.

Once all the piles are in place, it is necessary to trim them horizontally. This will allow you to correctly position the foundation even on an inclined area. For this purpose, you can use two tools. One of them is a laser level. It's easier to use. It is enough to position the beam at the required height and project it onto the body of the piles. After that, markings are applied to the foundation piles and trimming is done with a grinder.

Another option is to use a water level. Before use, it must be well aligned to avoid any bends. Next, the container containing water for the hydraulic level is installed on one of the piles. One of the craftsmen lowers part of the tube into a container, and the second creates a vacuum so that water under its own pressure begins to fill the tube.

Next, the functionality of the hydraulic level is checked. Its two ends are connected together and a certain time is waited. After this, the liquid in the two pipes should reach the same common level. If this happens, then you can proceed to the process of measuring the height for the foundation piles. If not, then you should carefully examine it and identify kinks or places where airing has occurred.

Note! The longer the hydraulic level, the more time it takes for the liquid inside it to calm down.

On one of the corner piles of the foundation, a point is drawn where all foundation piles should be located. One part of the hydraulic level is applied to it, and the second is brought to the next corner pile. Once the water level has calmed down, you can make a mark on the pile to guide the cutting. This way the mark is transferred to all corner piles of the foundation.

To mark a line over the entire area of ​​the foundation pile, it is necessary to make a pattern from a plastic pipe, which will be cut on one side for ease of installation on the pipe. Using a marker, draw a circle.

To transfer the marking line to the remaining piles, which are located in the middle of the foundation structure, it is necessary to pull a strong fishing line along the marks on the outer piles. It will be the indicator of the required line. After this, marking is carried out with a marker at the selected point. Using the prepared pattern, a line is drawn over the entire area of ​​the piles.

Once the marking of the piles for the foundation is completed, you can proceed to cutting all the elements along the drawn lines.

The next step is to fill the installed screw piles for the foundation. This is not done with concrete, but with an ordinary cement-sand mortar in a ratio of three to one. The solution must be liquid enough to fill the pile cavity. The purpose of this procedure is not to impart additional rigidity to the foundation, but to prevent the exposure of the internal walls of the pile to oxygen, which could lead to corrosion and destruction of the foundation. Filling is not done to the very top. It is necessary to leave a gap of 10 cm. It is filled with a dry mixture, which can be purchased ready-made.

The next step is to install the head on the pile. It must be located on a horizontal surface. The purpose of the head is to hold the grillage on which the walls will be fixed. The head is welded to the pile so that the fixation is as reliable as possible.

Welding seams are cleaned and coated with paint, which will protect them from corrosion. A video of the complete process of constructing this type of foundation is below.

Summary

As you can see, a columnar foundation is a fairly common design. It is an indispensable option when it is planned to build a small lightweight building. The last one can be a rounded log or frame. When laying the foundation, it is important to take into account all the features of the soil, as well as other parameters that were discussed in the article.

Only a professional builder can design and implement a columnar foundation according to the recommendations of SP 50.100, 22.13330, 32.13330, 45.13330, 27.13330. These grounds are too unreliable; the results of geological surveys should be studied in as much detail as possible.

The technology for installing a grillage along pillars depends on the construction technology of the building for which the foundation is being constructed. Columnar bases are made from structural materials:

• reinforced concrete - pouring into formwork on site, installing the finished product in a 1F or 2F glass;
• wood - logs with a widening base;
• brick - clinker, solid ceramics;
• blocks - wall, only with dense fillers, hollow;
• rubble concrete - stone is introduced into the formwork after partial filling with ready-mixed concrete.

In addition to the strip grillage, a slab structure can be used. This is the only option for a columnar foundation suitable for a brick cottage on sandy soils with a groundwater level (GWL) below 1 m. In all other cases, columnar foundations are created for log houses, half-timbered buildings, buildings made of SIP panels, panel and frame buildings.

Types of columnar foundation by depth

Depending on the geological characteristics of the building site and wall materials, columnar foundations are:

• buried - below the freezing mark, groundwater level, but may not reach the bearing layer;
• shallow - 40 - 70 cm below ground level;
• non-buried - instead of the removed fertile layer, non-metallic material is filled in, the underground part is absent.

The height of the pillars above the zero mark depends on the grillage design and the technological solutions used in the project. The head is embedded into a monolithic grillage at 20 cm, the beams of the prefabricated grillage are installed on top of the piles. Therefore, the height above the surface is always individual. The construction of buried pillars is justified if there is a bearing layer at this level. This type of shallow foundation is stabilized by soil against lateral shift. Non-buried has a minimal construction budget.

Columnar foundation design

The fundamental difference between columnar foundations and piles is the occurrence of the base, as a rule, above the freezing mark, the level of groundwater level, and layers with bearing capacity. Therefore, in any case, the support-column foundation is protected from heaving forces and movements in several ways:

• a sand cushion under the base slab; if the base of the foundation is located below the freezing depth, a sand cushion is not required;
• drainage of soil by drainage system;
• insulation of the blind area and basement.

For the last two activities, open excavation of the soil in the building area is required.

Even with a small depth of the pillar itself, you will have to take into account the thickness of the widening (20 - 40 cm slab) and the underlying layer (cushion of 20 cm sand + 20 cm crushed stone). In addition, you will need a ring ditch for laying drains and access for workers to the lower level. Therefore, the size of the well and trench increases several times; it is inconvenient to carry out work from the ground at depth.

Manufacturing columnar foundations by analogy with bored piles is a gross violation of technology. It is difficult to widen the sole; there are heaving forces underneath it. The side walls without backfilling with sand are subject to tangential forces of the same processes.

Thus, the correct design of a columnar foundation looks like:

• preparation - sand (layer thickness 20-40 cm) with layer-by-layer compaction with a vibrating plate, pouring;
• footing - serves exclusively for laying waterproofing, is a 5 cm screed;
• stepped plate (sole) – distributes loads due to the increased surface of the sole;
• pillar - a vertical post made of monolithic or precast concrete;
• grillage - reinforced concrete products, monolithic structure, timber or rolled metal (channel, I-beam).

Unlike piles, pillars do not have spatial rigidity, so the grillage beams must not just rest on their heads, but must be attached to each pillar to be connected into a single structure.

Step-by-step instruction

Due to the variety of operations for constructing a grillage on pillars, step-by-step instructions are necessary for the individual developer as a guide. If you skip any stage, you will have to redo the work later or return to it, spending more effort and money.

For example, the instructions recommend laying drains at the excavation stage. If you forget about them at the beginning and remember them when landscaping the area, the trenches will have to be dug again, construction will be delayed, and the site will again be clogged with soil. The height of the pillars is selected 20 cm above the bottom of the grillage for walling in concrete.

Below we will tell you how to make a columnar foundation correctly.

Geological surveys and calculations

The technology for constructing a columnar foundation depends on the results of geotechnical surveys, wall material, and construction technology. For example, it is prohibited to leave unloaded poles in the winter even if they are tied with a grillage.

Prefabricated loads (the weight of the building, residents, furniture, belongings, wind, snow loads) may not be enough to compensate for the extrusion forces, or the building will gradually sink into unstable soil with excess weight.

Unlike the test screwing of screw piles in the technology of the same name to find the depth of the bearing layer, full-scale surveys are required here, costing at least 30 thousand rubles. The designer needs the following data:

• layered arrangement of layers;
• composition and characteristics of the three upper layers;
• GWL level;
• frost mark.

The cross-section of the pillars should be greater than 40 x 40 cm for concrete or brickwork, 20 x 20 cm or 20 cm in diameter for a monolithic reinforced structure.

Marking and excavation work

Unlike bored piles that reach the bearing strata, it is much more difficult to pour columns into wells. The main problem will be the lack of sand filling in the sinuses:

• after a few years, the soil near the body of the pile will self-compact;
• will gain moisture and freeze in winter;
• heaving forces will pull the pillar out like a carrot from a garden bed;
• if there is a lower widening, the column will rise upward due to heaving forces, and soil will crumble under the base;
• the slab will not allow you to pull out the entire column, but it will no longer be able to get back into place.

We dig holes to widen the columnar foundation.

Therefore, the only correct way would be to mark the trenches, taking into account the width of the base, the drainage contour, and the construction of formwork. Instead of a square shaft of 40 x 40 cm, you will have to remove much more soil, 1 x 1 m minimum. In this case, the thickness of all layers of the foundation pie and the height of the groundwater level are taken into account. If the last characteristic is slightly below a meter, you need to go deeper by 0.6 m, no more.

Preparation

By default, the construction of a monolithic foundation of a dwelling should provide protection from corrosion and destruction. In the absence of oxygen, the only aggressive environment underground remains moisture, which should be removed from the base with drains and stopped at the surface of concrete structures along the entire height with a waterproofing carpet.

Construction is carried out in stages:

• layer-by-layer backfilling - 20 cm of sand with moistening, vibration compaction twice (total height 40 cm);
• footing – screed height 5 cm, no reinforcement;
• waterproofing – 2-3-layer carpet of rolled material on a fiberglass base;

Reinforcement

The technology for constructing an armored belt for a column with an expanded base is as follows:

• knitting reinforcing mesh to the size of the slab, taking into account the side protective layers (40 mm from the formwork to the metal) with a cell of 15 x 15 cm or 20 x 20 cm with a thickness of 12 - 16 mm;
• joining to the mesh rods bent at right angles of 12 - 16 mm, protruding 20 - 30 cm above the base of the grillage (usually 4 pieces in the corners, one in the middle of each side);
• vertical rods are reinforced with horizontal square clamps made of 6–8 mm reinforcement;
• the structure is installed on a waterproofing carpet, which extends 10-15 cm beyond the dimensions of the sole, for subsequent bending onto the side edges of the sole.

It is prohibited to lift the reinforcement structure with metal scraps, bricks, or crushed stone to provide a protective layer.

Widening the pillar

The construction of the sole involves pouring the slab into the formwork. The widening area is twice the cross-section of the column, the height of all elements is a multiple of 30 cm. The formwork is simple - four boards fastened with screws, corners or bars at the bottom of the pit or trench.

Reinforcement of the widening and pillar.

The sides of the formwork should be slightly higher than the design level in order to properly level the concrete surface. The permissible error in the horizontal plane is 1 cm. Filling is carried out after installing the reinforcement structure.

Formwork

We install and strengthen the formwork for the columnar foundation.

Drainage and waterproofing

From the perimeter of the building it can be made at any stage, from foundation pit to backfill. To install drains, a circular trench with a uniform slope towards the underground tank is required. Dornite or geotextile is spread at the bottom, and 10 cm of crushed stone is backfilled. Perforated pipes in the filter are laid in it, and inspection wells are installed. After which, the communication is filled with another 10 cm of crushed stone and covered with the remains of geotextiles.

Waterproofing device - several technologies using different materials:

• impregnations - contain penetrating additives that change the molecular structure of concrete, making it waterproof throughout its entire depth;
• rolled materials - Bikrost, TechnoNIKOL and other analogues on a fiberglass base, laid in two layers;
• coatings – epoxy and bitumen based mastics;
• paints – enamels based on bitumen resins.

Most often, combined methods are used to achieve a 50-70 year service life. Rolled coating materials will have to be renewed every 15 years.

Ready-made columnar foundation with reinforced concrete grillage.

backfilling

After installing drainage and a continuous waterproofing layer over the concrete surface, it is necessary to protect the side surfaces from heaving forces. The sinuses are filled with sand; compaction is necessary, since loose soils are extremely unstable. The chernozem of the fertile layer is saturated with organic matter and settles after it rots. Other soils contain clay, which swells in cold weather. Therefore, exclusively non-metallic materials are used, in which there is less heaving.

A pillar foundation is a universal option. Such a foundation is constructed without taking into account the type of soil, and it does not require serious waterproofing and insulation work. Therefore, they decide to build a columnar foundation without doubt, even without having the knowledge of a builder.

Unique foundation made of “rods”

To understand what a columnar foundation is, it is worth considering in detail its pros and cons, tasks and structure.

A column foundation is significantly different from a strip foundation, since it is not built along the entire perimeter of the building

Advantages and disadvantages of a columnar base

The indisputable advantages of a foundation made of support pillars are:

The disadvantages of a columnar foundation are attributed to:

All the disadvantages of a foundation made of pillars can not be considered as something important if you build this structure taking into account its purpose.

Challenges of Pillar Construction

It is advisable to build a columnar foundation for such objects as:

• a house without a basement with walls made of lightweight materials;
• a brick building, which for economic reasons cannot be built on a strip foundation and is therefore built on pillars buried 2 meters into the ground;
• a building erected in an area with soil prone to heaving due to low temperatures and, as a result, negatively affecting any foundation other than a columnar one.

It is wise to place only small houses made of lightweight materials on poles, because the supports will not withstand the weight of other buildings

It is better to completely abandon the construction of a structure from support pillars in the following cases:

• the soil at the construction site is weak or mobile, which can cause an insufficiently stable foundation to overturn;
• the land on the site contains a large amount of peat, sedimentary rocks or clay saturated with water;
• the house is planned to be built from heavy raw materials, for example, bricks more than 5 cm thick or standard reinforced concrete slabs;
• finances and time for arranging the base are significantly reduced (when creating a columnar foundation, the base does not form by itself, as happens during the construction of a strip base);
• The soil on the site for building a house is characterized by a sharp difference in height (from 2 meters).

A columnar foundation can only be built on solid and level soil, since it is not ideally stable

View of a foundation made from individual supports

A columnar support structure for a house is a system of pillars placed in corners, areas where walls intersect and where load-bearing partitions or beams are located, which bear the weight of the entire building. In order for the pillars to function as a single structure and be as stable as possible, they are combined by means of a grillage - strapping beams.

The most commonly constructed columnar foundation is a structure made of monolithic reinforced concrete blocks.

The foundation can be made of concrete blocks, and the grillage can be made of wood

Typically, the pillars are placed leaving 2 to 2.5 meters of empty space between them. But in some cases, builders go beyond the traditional option of arranging supports.

When the pillars are installed in the ground every 2–2.5 meters, the grillage is created as a standard reinforced lintel. At the same time, the veranda, porch and terrace attached to the house are not combined into a single ensemble.

For places like a porch, separate bases are organized, separated by an expansion joint. This is a necessary measure, because the weight of additional premises is always different from the weight of the house, which is why the shrinkage of these buildings cannot be the same.

Usually the pillars are placed at a distance of 2–2.5 m from each other

The distance between the pillars is large (from 2.5 to 3 meters), referring to the significant power of the strapping beams. The most reliable grillage is created in the form of a single or prefabricated beam. A simple structure connecting the supports can be made of metal parts, for example, channels or profiles.

Variations of the pillar base

What the columnar foundation will be like is decided based on the amount of finances and the ability to independently engage in construction.

Block supports

A columnar foundation can be made up of concrete or reinforced concrete blocks, manufactured separately and installed directly when arranging the supporting structure for the building.

Each pillar of the structure can be assembled from separate blocks - a very reliable material

GOST states that the blocks that will be used for the construction of the foundation must be made from concrete of a grade not lower than M-100. As for the size of the blocks, private developers are accustomed to taking raw materials with parameters of 20*20*40 cm and a weight of 32 kg. Foundation blocks made of expanded clay concrete, a material that is resistant to thermal effects, are considered relatively light.

Large block structures made of reinforced concrete can only be laid by a construction crane, because their weight can even be equal to two tons. Such blocks are reinforced with special reinforcement with a diameter of 9 to 15 mm and are used exclusively for the construction of strip and slab foundations for huge brick buildings.

Most often, for independent construction of a columnar foundation, light small blocks are taken, since it is possible to build supports from large raw materials only with the use of technology

The best depth for fixing a pillar of blocks in the ground is from 50 cm to 1 meter. If the type of soil and the weight of the building dictate other requirements, then it is more reasonable to build not a block foundation, but a foundation made of asbestos-cement pipes filled with concrete. Laying blocks to a depth of more than 1 meter is too difficult.

Brick pillars

Having decided to build a columnar foundation of brick, you need to purchase only red solid ceramic building raw materials. This material meets all the necessary requirements: it is waterproof, extremely durable and frost-resistant.

This characteristic of brick, such as frost resistance, is considered extremely important. The higher the indicator of immunity to low temperature, the longer the construction raw material lasts. For example, frost resistance 70 indicates that the brick will deteriorate no sooner than after 70 years.

To build the foundation, it is customary to use red solid ceramic brick, because it is the most durable

Bricks can be used to construct both a shallow and recessed columnar foundation. The depth of the first version of the foundation varies between 40 and 70 cm. And the buried foundation is always installed below the freezing level of the soil by 30–50 cm.

It is decided to locate the supporting structure at a considerable distance from the surface of the earth when the soil on the construction site is heaving and the groundwater level is unstable.

To make the foundation reliable, the brick supports of a columnar foundation need to be created in 2 bricks

The main foundation pillars (supports located in the corners of external walls and at the intersection of internal partitions) are usually made of 2 or 2.5 bricks. In other cases, the pillars are allowed to be made of one and a half bricks and placed at a distance of one and a half or two meters from each other.

"Legs" made of wood

A base made of wooden “legs” is the most economical option. Logs suitable for the foundation can be easily cut down and processed on your own.

It is customary to build a columnar foundation of wooden supports for a house for living during the summer or a tiny structure made of wood.

Wooden poles are intended only for the lightest temporary structures, as they can break under excessive pressure

The best raw material for creating wooden supports is pine, oak or larch wood.“Rods” are cut from the butt part of a log with a diameter of 2 to 40 cm. When placed in holes, the wood posts are secured on the sides with bricks, stones or a compacted embankment of crushed stone.

Sometimes wooden supports are fixed in place with concrete mortar. In this case, the pillars are immersed in liquid concrete by 10 cm. Another good fixation for wooden supports can be a cross made of two plates 0.8 meters long, arranged in a crosswise position.

To secure the post to the crosspiece, a spike is cut out in its lower part. It is inserted into a groove made in the central area of ​​the cross. Then the pole is fixed on a kind of platform with scarves.

To securely fasten the pole in the ground, use a cross and jibs.

Wooden supports must be protected in a special way from rotting. First, they are covered with clay so that a layer 1 cm thick is formed, then burned with hot coals. The last task is performed slowly, making sure that literally 1.5 cm of wood is charred. The burned pillars are treated with heated bitumen or tar and dried.

Under the outer walls, wooden supports are immersed in the ground to a depth of 70 to 120 cm. And the pillars to support the partitions inside the house are placed at a depth of 50 cm.

The main pillars of a wooden foundation should be immersed to a depth of 70–120 cm

Monolith

It is preferable to construct buildings with 2 or 3 floors on a columnar monolithic foundation. Such a foundation will not sag even under significant pressure.

A columnar monolithic foundation can serve for more than 100 years without problems. Each pillar of this support structure is capable of supporting an object weighing 100 tons.

Monolithic foundation is considered the most popular design compared to other columnar foundations

A monolithic base of pillars is created from concrete, reinforced with metal rods and poured into special forms - pipes or formwork. This foundation turns out to be unusually durable, as it is completely devoid of seams.

Do-it-yourself columnar foundation: step-by-step instructions

The construction of a columnar structure for a house begins only after calculations have been completed and the construction site has been prepared.

Necessary calculations

A calculation is needed to find out how many pillars are needed and what size they should be.

Before computational actions, it is necessary to test the soil at the construction site - drill a well with a depth of 60 cm below the level at which it is planned to install the foundation pillars. If soil is found under the load-bearing soil, saturated with water and therefore weak, it is better to cancel the decision to build a columnar foundation. Posts under load are unlikely to be able to stand still in unstable soil.

The first well on a construction site should be a test well - to check the condition of the soil

Determination of soil load

After making sure that a columnar foundation can be built on the site, you should find out what pressure the earth will experience. To do this, you need to determine the weight of the future house.

When calculating what the pressure on the ground will be after building a house, you should add the weight of the foundation to the weight of the structure. To do this, it is necessary to determine the approximate volume of the structure and multiply the resulting figure by the specific gravity of the material. For example, for reinforced concrete this figure is 2500 kg/m³.

Table: approximate specific gravity values ​​for building elements

Constructions	Specific gravity, kg/m²
Walls
Brick walls (half a brick thick)	200–250
Walls made of foam concrete or aerated concrete blocks 30 cm thick	180
Walls made of logs with a diameter of 24 cm	135
Walls made of timber 15 cm thick	120
Frame insulated walls 15 cm thick	50
Floors
Basement and between floors on wooden beams (insulated with material with a density of up to 200 kg/m³)	100
Attics on wooden beams (insulated with material with a density of up to 200 kg/m³)	150
Concrete hollow core slabs	350
Monolithic (made of reinforced concrete)	500
Operational load for basement and interfloor slabs	210
105
Roof including rafters, sheathing and roofing material
With a roof made of sheet steel, metal tiles or corrugated sheets	30
With roofing felt in 2 layers	40
With slate roof	50
With a roof made of natural ceramic tiles	80
100
50
190

*When the roof slope is inclined more than 60 degrees, the snow load is reduced to zero.

Total area of ​​pillar bases

As soon as it becomes known how much the future house will weigh, they find out the minimum required total area of ​​​​the bases of all pillars. To determine this parameter, use the formula S = 1.3 * P/R 0. The number 1, 3 denotes the safety factor, P is the total weight of the building in kg (including the foundation), and R 0 is the calculated resistance of the load-bearing soil in kg/cm².

Table: approximate values ​​of load-bearing soil resistance at a depth of 1.5 meters

An example of determining the number of foundation pillars

Let's try to calculate how many round supports will be needed to construct a columnar foundation for a small frame-panel house with dimensions of 5x6 meters. At the same time, we take into account that the height of the first floor is 2.7 m, and the same parameter at the pediment is 2.5 m. We also do not forget to use data such as roofing material (slate), type of load-bearing soil (loam) and freezing depth ( 1.3 m).

The frame house can be installed on 10 pillars

The weight of the building is calculated as follows:

1. The area of ​​all walls is determined, taking into account the pediments (72 m²) and their mass (72 × 50 = 3600 kg).
2. The total area and mass of floors are found. Since the house has a basement and intermediate floors, their area is 60 m² and their weight is 6000 kg (60 × 100 = 6000 kg).
3. The operational load is also present on the 1st and attic floors. Its value will be equal to 12600 kg (60 × 210 = 12600 kg).
4. The roof area in our example is about 46 m². Its weight with a slate roof is 2300 kg (46 × 50 = 2300 kg).
5. We take the snow load equal to zero, since the angle of inclination of the roof slopes is greater than 60˚.
6. Let's determine the preliminary mass of the foundation. To do this, we conditionally select the diameter of future pillars and their number. Let's say we have a drill with a diameter of 400 mm, let's take this value. The number of pillars is preliminarily taken based on the condition - one pillar per 2 meters of the perimeter of the foundation. We get 22/2 = 11 pieces. Now we calculate the volume of one column 2 meters high (buried 0.2 m below the freezing depth + 0.5 meters above the ground): π × 0.2² × 2 = 0.24 m³. The mass of one pillar is 600 kg (0.24 × 2500 = 600 kg), and the mass of the entire foundation is 6600 kg (600 × 11 = 6600 kg).
7. We sum up all the obtained values ​​and determine the total weight of the house: P = 31100 kg.
8. The minimum required total area of ​​the bases of all pillars will be equal to 11550 cm² (S = 1.3 × 31100/3.5 = 11550 cm²).
9. The base area of ​​one column with a diameter of 400 mm will be equal to 1250 cm². Therefore, our foundation must have at least 10 pillars (11550/1250 = 10).

If you reduce the diameter of the base supports, their number will increase. For example, armed with a drill that creates holes measuring 30 cm, you will need to install at least 16 pillars.

Preparation for construction

Before pouring a columnar foundation on a site, you need to take care of the following:

1. Clear the site of debris and remove the fertile soil layer 30 cm thick.
2. Take coarse or medium sand found under the removed soil as the basis for the foundation, and clay soil, which is found no less frequently than sandy soil, is strengthened by covering it with a layer of two materials - sand and gravel.
3. Level the area for construction, eliminating bumps and holes, and check its horizontalness using a level placed on a two-meter flat board.

   The evenness of the prepared area is checked with a rack

4. Bring construction materials to the site and install cast-offs around the perimeter of the future structure (pillars at a distance of 2 m from the building and boards nailed to them with marks for the size of holes and supports). The correctness of the center lines must be monitored by measuring distances with a tape measure. In addition, you need to check whether the corners of the foundation in the shape of a rectangle or square are straight.
5. Lay out a plan for the future house on the site, that is, mark its parameters using pegs.
6. Create holes for installing pillars (if necessary, you can use a drill to make holes for wooden supports, and if installing reinforced concrete pillars, you should arm yourself with a shovel).
7. Fill the bottom of the holes with gravel and sand and moisten. The finished “pillows” need to be compacted and covered with polyethylene or roofing felt.

   The bottom of the drilled holes is reinforced with hard material, for example, Proce gravel

Creating formwork for pillars

An excellent option for formwork for supports under a house can be a temporary structure made from planed on one side (the planed part is installed facing the concrete) boards of any type of wood, with a thickness of 25 to 40 mm, a width of 12 to 15 cm and a humidity of no more than 25%.

Instead of boards, when constructing formwork, you can use particle boards, waterproof plywood or metal sheets. However, it is preferable to choose boards, since they adhere less to the concrete mortar.

Wooden columnar foundation formwork is a standard option

The temporary auxiliary structure must be installed close to the walls of the dug well and perpendicular to the base. It is recommended to check the correctness of the completed task with a plumb line.

If boards were chosen as the material for constructing the formwork, then it must be borne in mind that they must be thoroughly moistened with water. If you ignore this condition, you can get weak pillars, because dry wood absorbs moisture like a sponge, and because of this, it worsens the properties of concrete.

Roofing felt formwork is an innovation

An auxiliary structure during the construction of a columnar foundation can also be permanent formwork made of roofing felt. This material simultaneously performs several tasks: it serves as a form for pouring concrete and protects the supports from moisture.

Formwork made from roofing felt is a good solution if the soil in the created well is dense and non-crumbling.

To make an auxiliary structure from roofing felt, proceed as follows:

Features of pouring the foundation

If a home craftsman is a supporter of the traditional method of pouring a foundation, then to accomplish this mission he must do the following:

Anyone who is not averse to alternative methods of constructing a foundation for a house can make a foundation using a TISE drill. The tool will allow you to create a columnar structure with a widening at the base, which will provide a unique opportunity to support a heavier building on supports or reduce the number of pillars.

A column with widening (using TISE technology) is formed in stages:

Video: example of constructing a columnar foundation using TISE technology

Even one person can cope with the construction of a columnar foundation. For this work, you do not need to look for equipment, hired workers, or a large amount of materials.

The durability of each building directly depends on the strength of the foundation underneath it. But is it always justified to install a massive continuous foundation strip if you plan to build a light wooden or frame building? Increasingly, in this case, a columnar foundation that is less expensive and can fully withstand the expected load is installed. Support pillars are made from various materials, using different methods and technologies. Next we will talk about the foundation of the building, made of concrete pillars.

Features of a columnar base

Such a foundation resembles a pile foundation, with the difference that the finished piles are driven (screwed) into the ground, and the pillars are poured or laid out in place in prepared recesses. A base made in this way makes the work much cheaper and less labor-intensive.

However, a columnar foundation is not always suitable. If the mass of the above-ground part of the building is significant (the walls are made of brick, concrete, cinder block or other heavy building material), a large area of ​​​​support on the ground is assumed. In this case, it is better to prefer the construction of a buried or shallow (depending on the soil structure) strip base with a sufficient base area.

If the house is supposed to be built from lightweight building materials (wood, foam concrete, materials for frame construction), a columnar foundation, or rather the area of ​​its support on the ground, is sufficient.

Important! The area of ​​the base of the columnar foundation is also calculated. This indicator is regulated by the number of vertical supports and their own transverse area.

A symbiosis between the strip version of the house foundation and the columnar one is the columnar-grillage foundation, when the vertical supports are additionally reinforced and connected to each other by a shallow reinforced concrete strip. This is done not only to strengthen the pillars, but also in situations where the usual shallow strip foundation of a building may be unreliable due to loose or heaving-prone soils on the site. In this case, the pillars, resting their soles on deeper and more reliable soil layers, act as piles that strengthen the main belt.

Advantages and disadvantages of a pillar foundation

The installation of concrete piles has a number of obvious advantages, such as:

• relatively low consumption of materials;
• much less labor intensive (compared to a strip base);
• greater efficiency and strength in waterlogged, loose soils and those prone to heaving;
• the ability to combine with other foundation structures.

However, there are also disadvantages that limit the construction of a columnar foundation in some cases:

• cannot be constructed in case of a large expected load on the foundation (heavy buildings);
• impossibility of constructing a basement;
• instability to horizontal movements of soil layers;
• void under the base floor (to cover it, a fence is constructed around the perimeter of the base).

That is, the construction of a foundation structure from pillars, including concrete ones, is not always permissible, but only under certain conditions. However, taking into account the trend towards accelerated construction of buildings from lightweight materials, the construction of inexpensive foundations from pillars is becoming more relevant every year.

Principles for calculating a columnar foundation

The construction of such a foundation for construction also requires calculations. It is necessary to calculate the number of support pillars, their location and the total area of ​​support on the ground.

The supports are arranged according to this principle. The pillars must be at the corners of the building and in places where the piers adjoin the external walls. The location of the remaining pillars depends on the calculations of the load on the base. However, regardless of the calculated area of ​​the sole, the distance between adjacent supports should not exceed 2-2.5 m (depending on the chosen grillage design). The minimum appropriate distance between pillars is 1 m.

If the calculation of the required total area of ​​the foundation base shows the need to further reduce the distance between the supporting structures, it means that a columnar foundation may be ineffective for the mass of a given building. In this case, it is better to choose a strip foundation for the building or its combination with pillars or piles (if the type of soil does not allow pouring a simple shallow concrete strip).

Methods for pouring concrete pillars

Before proceeding with the installation of concrete foundation supports, the site for construction is marked according to the project. With the help of stretched threads, external contours and right angles are formed. If it is planned to install a column-grillage foundation, the inner perimeter corresponding to the edge of the trench is also hammered out with threads, after which the latter is dug to the calculated depth.

The most common way to construct pillars is to pour concrete into pre-prepared forms. The process looks like this.

1. Along the perimeter of the future foundation of the building, the installation locations of the supports are marked according to the calculations performed.
2. The holes are prepared using a hand drill. Their depth depends on the degree of soil freezing in the region and the level of occurrence of stable soil layers. Even if the stable soil is shallow, the base of the pillar is 15-25 cm below the freezing level. The diameter of the supports must correspond to the calculated area of ​​each pillar.
3. A cylinder (2 layers) is formed from rolled waterproofing material (roofing felt, waterproofing), 3-4 cm deep into the already prepared recess. The longitudinal joint is secured with tape, and several fixing stitches are made around the prepared cylinder.
4. The form for pouring concrete is placed in a recess, and a sand and gravel cushion is poured onto the bottom. A reinforcing structure formed from several metal rods is welded or twisted with knitting wire. One reinforcement, usually the central one, is made 30-40 cm longer than the others so that it protrudes beyond the head of the cylinder. It will be connected into one structure with the reinforcing frame of the concrete strip.
5. The pipe formed from waterproofing material is gradually filled with liquid concrete. It is advisable to shake the cement mortar layer by layer using a vibrating device. The upper edges of the poured pillars must be located in the same horizontal direction, for which purpose the pipes are aligned using a water (laser) level before pouring. The poured pillars are allowed to stand until the concrete has completely set, after which they move on to constructing a grillage.

The most common method of arranging supports is described above. As an option, they often use ready-made pipes (PVC sewer pipes) or lay out pillars from ready-made concrete blocks. The second method is more labor-intensive, since you have to dig a hole under each post. With a large depth of placement of the base of the pillar, this is very inconvenient.

Options for grillage installation

One option is to pour a shallow concrete foundation tied and supported by columnar supports. To fill it, a trench is dug (as described above) and vertical wooden formwork is installed around the perimeter of the future building and under the internal walls.

Before pouring the tape, a reinforcing structure must be formed, which is connected to the protruding reinforcement of the pillars. This results in a monolithic structure, where a surface-constructed concrete strip rests on formed pillars. This achieves the following goals:

• cheaper design (compared to the installation of a buried belt);
• sufficient strength of the base;
• a solid base for the construction of walls (there is no need to make a fence between the supports).

After reinforcement, the formwork cavity is filled with concrete, and when it hardens, the wooden enclosing structure is dismantled. Before starting the construction of wall structures, the concrete is allowed to gain strength (mature), after which the foundation surface is waterproofed.

The second option for a grillage is to install wooden logs (beams) on top of the pillars. This design is prepared for lightweight frame, frame-panel type buildings or wooden houses. In this case, an empty space is formed between the bottom of the house and the ground surface. In order to protect the lower structures from weather influences and to improve the overall appearance of the building, a fence is made between the supports - a fence that covers the space between the ground surface and the bottom of the walls.

Collection device options

Nowadays, fencing the space between foundation pillars is done in several ways using various materials. Wood is often used to cover the base between the pillars under a wooden house. Also used as building materials:

• brick (masonry);
• concrete (pouring with reinforcement);
• sheet materials (corrugated sheets, flat slate, dense insulation (extruded polystyrene foam).

The peculiarity of the construction of the fence is that the structure should not be rigidly connected to the foundation supports and have ventilation holes. The first condition is met so that the enclosing structure does not collapse due to possible settlement of the foundation and ground movement. Ventilation holes prevent excess moisture from accumulating in the space under the building, which has a detrimental effect on building structures. One of the most popular options is to make a wooden fence like this.

1. Between the pillars along the perimeter, a trench is dug about 30 cm deep at the lowest point of the ground. The bottom of the ditch is covered with crushed stone and sand and a beam (log) is placed on the formed cushion after it has been compacted and leveled. The second beam is attached to the bottom of the building’s perimeter wall.
2. Boards are vertically attached to the beams and protected with waterproofing material from below to ground level. Afterwards, the trench is filled with crushed stone or expanded clay and concreted on top.
3. The above-ground part of the boardwalk is processed and painted or sheathed with some external finishing material. If cladding is intended, the boards are not attached continuously, but with a certain step, forming a sheathing for fixing the finishing material.

A columnar foundation made of concrete supports costs owners about half as much as a strip foundation, even taking into account the need for a back-up device. In terms of strength, the foundation of the building, made of pillars, is not inferior to a solid reinforced concrete strip.