Monolithic belt- This is a reinforced concrete beam, which is made mainly under the ceiling in masonry walls.

At first glance, the purpose of such a belt is unclear: you can, after all, support the ceiling directly on the masonry and not install any belts. As they say, “cheap and cheerful.” Let’s look at the reasons for constructing a monolithic belt.
1. If the masonry material of the walls does not bear the load from the floor. In a brick wall solid brick, for example, a monolithic belt is not needed, but in a cinder block wall when supporting the ceiling of a large span, such a belt is necessary.

At the point where the slab is supported, a significant load is concentrated (from the ceiling, floors, people and furniture), and all of it does not fall evenly on the wall, but increases in the direction where the slabs are supported. Some masonry materials (cinder block, foam and aerated concrete, shell rock, etc.) do not work well when exposed to such a concentrated load, and may simply begin to collapse. This type of failure is called crushing. You can perform a special masonry calculation to determine whether a monolithic distribution belt is needed. But in some cases (when using cinder block, foam concrete), a monolithic belt must be made for design reasons based on experience in construction from these materials.

2. If the building is being built on weak soils(for example, on subsidence). Such soils tend to deform significantly after some time, due to soaking or other unfavorable factors - to shrink under the weight of the building. In this case, part of the house may sag, resulting in cracks in the walls and foundation. One of the measures that protects against the adverse effects of subsidence is the installation of a continuous monolithic belt under the floors. It serves as a screed for the house and, with minor precipitation, can prevent the formation of cracks. If you are going to build a house, first of all inspect the houses in the neighboring areas (preferably those that were built a long time ago). If there are inclined cracks in the walls, running from the ground up, from the roof down, or from the corners of the windows up, then this is the first sign that a monolithic belt in your house will not be superfluous.

3. If the house is being built in a seismic area, the installation of monolithic belts is mandatory.

4. B multi-storey buildings The standards also require the installation of monolithic belts.
Prefabricated floor or monolith?

It's time to decide on the type of flooring for your home. Here, as elsewhere, there are options that, first of all, depend on the number of floors.

If the house is one-story, and the top is only planned attic space, a lighter version is possible - wood flooring on metal or wooden beams.

For a house with an attic or a full second floor, a more reliable ceiling is needed. There are two traditional options: a prefabricated floor made of hollow-core slabs or a monolithic floor. And to help you finally decide on the type of flooring, we will consider in detail the features of each of them.

So, prefabricated flooring. If there is a factory for reinforced concrete structures in your city or surrounding area, then you can choose this option. The advantages of prefabricated floors are speed of installation, reliability, guaranteed good quality. In most cases, this ceiling is also cheaper than a monolithic one.

What should you pay attention to? Standard slabs are produced in predetermined sizes (here are some slab lengths: 2.4; 3.0; 3.6; 4.5; 6.0; 7.2; 9.0 m), and require load-bearing walls for support. The layout of your home must clearly correspond to the dimensions of the selected slabs. In this case, it is worth checking in advance with the supplier or manufacturer what size slabs they can deliver. If you have slabs 3 m long at your disposal, the clear distance between the walls on which they rest should be no more than 2.8 m (the minimum amount of support of the slab on the wall is 10 cm). From round walls and other delights will also have to be partially abstained.

The slabs should rest with their opposite short sides on the load-bearing walls. Leaning on walls on three sides is undesirable. But the construction of a balcony using the floor slab extending beyond outer wall simply unacceptable. Firstly, the floor slabs are designed so that the support zone is at their edge, but not somewhere in the span. And most importantly, when such a balcony is loaded, a collapse may simply occur. And another big drawback of such improvisation is that winter time part of the slab will freeze. As a result, winter will make its way straight into the house along the so-called “cold bridge.” The result is that if it doesn’t collapse, it will simply freeze, or even “cry” - due to temperature changes, the ceiling may well become moistened, overgrown with fungus, mold and other delights.

Where slabs cannot be placed (due to cramped dimensions or in places ventilation shafts from the kitchen and bathroom), monolithic sections must be completed. Let's say we have a distance between the walls of 3.15 m, and the available slabs are 1.0 m wide. In this case, there remains a gap of 15 cm between the two slabs, which needs to be filled with something. Here you have to place formwork from below, lay reinforcement and perform concreting (see figure - monolithic section 150 mm wide). Such a monolithic section is reinforced with rods with a diameter of 6 mm in increments of 200 mm. Concrete is used class B15 (M200). Be sure to rest it on the ceiling (size 200×30 mm) with the bends of the reinforcement placed on the slab. Sometimes there is a need for monolithic sections of large width (up to 1 m), if you need to create a hole in the ceiling (for example, for ventilation shaft ducts). Please note - the wider the monolithic section, the larger the diameter of the reinforcement resting on the ceiling (see figure - monolithic section 980 mm wide). More information about all types of monolithic sections in prefabricated floors can be found here.
When choosing a prefabricated floor, you should carefully consider the material of the load-bearing walls. So, if it is a brick, then the thickness of the brick wall should be at least 24 cm. If you use cinder block when building a house, you need to take into account its not very good load-bearing properties - in this case, under the ceiling you need to make a so-called monolithic belt - a reinforced concrete layer with a height 20-30 cm (see picture).
Now consider the option with a monolithic ceiling. Of course, it is multivariate and allows you to realize almost any fantasy regarding the layout of your home. Walls or columns can be positioned without the rigid restrictions imposed by the precast floor. Although it’s still not worth playing around with. The optimal distance between supports in monolithic reinforced concrete is 6 m. A larger distance, of course, is acceptable, but such an overlap must be calculated by a specialist. And this is where you need to take into account the importance of the issue and include the calculation of overlap in the expense item. Experienced specialist will help you not only ensure the reliability of the structure, but also save on material consumption - after all, the thickness of the ceiling can be from 140 to 200 mm, and reinforcement must be used according to calculation different diameters- from 8 to 16 mm (and more for large spans), and these are completely different costs. You can, of course, take everything by eye and with a reserve, but such savings will cost more.

Materials for the slab: concrete of strength class no less than B15, hot-rolled reinforcement of periodic profile. The slab is reinforced with meshes in two planes (in the lower and upper zones of the slab). The meshes can be welded (welded by contact spot welding; welding of reinforcement crosses with electrodes is not allowed due to the high probability of burning out the reinforcing bar) or assembled from separate bars. In the latter case, at each intersection of the reinforcement, the rods must be tied with special wire. The optimal spacing for laying reinforcing bars is 200 mm. At the same time, it is necessary to ensure protective layer concrete for working reinforcement (distance from the reinforcing bar to the concrete surface) - at least 20 mm. The protective layer not only ensures the safety of the reinforcement (if it is small, the metal corrodes and rusty streaks appear on the concrete), but also increases the fire resistance of the ceiling. Minimum support value monolithic ceiling on the wall is taken on the basis that the working reinforcement must be inserted onto the support by at least 10 diameters (i.e., when reinforced with rods with a diameter of 12 mm, the installation on the support will be 120 mm; add a protective layer of 20 mm and get a minimum support wall slabs 140 mm).

We've covered the theory, let's move on to practice. To install the floor, you will need scaffolding (a system of racks that support the floor until it has gained sufficient strength), formwork (metal or wooden boards, on which concrete is laid), reinforcement and concrete, and most importantly - experienced builders. Another point is that concrete must be vibrated after laying. If the builders you hire carry concrete with wheelbarrows and lay it without compaction, relying on gravity, drive them in the neck. Required condition for quality reinforced concrete structure is compaction by vibration - it is then that the concrete reaches the desired density and works with the reinforcement as a single whole. Concreting at air temperatures below 5°C is not allowed (there may be exceptions, but a number of measures must be taken - heating the concrete, using special additives). Concrete reaches its strength within 27 days. All this time, positive air temperatures must be maintained and loads on the still fragile ceiling must be eliminated.

Hello! The foundation is not buried. Partially - self-construction, but the path of construction was determined by a man who has been involved in foundations for more than 50 years, a professor at our University, an honored builder of the Republic of Karelia (and other regalia).
With normal soil, crushed stone of a large fraction was brought, in very large quantities, filled to a height of about 50-70 cm above the ground level, and in area protruding beyond the perimeter of the future foundation by a couple of meters on each side. Leveled. Then a large construction vibratory roller was found (it was working half a kilometer away at the site), which hammered this crushed stone for a couple of hours. To be honest, only the first “passes” of the vibratory roller apparently drilled through the crushed stone. After this, to level the horizon level, thin layer on top of the crushed stone there is sand. Next is waterproofing along the top, formwork and reinforcement. I knitted the reinforcement for the first time, myself. 14th reinforcement, along the perimeter and in the area of ​​load-bearing walls (under the wall and a meter to the right and left) every 10 centimeters, the rest - 15 cm. Two planes at a distance of 30 centimeters from each other. They recommended knitting the reinforcement less frequently, and a thickness of 30 centimeters is sufficient. A foundation of 12 by 12 meters took 5 tons of reinforcement, and with a thickness of 42 cm - 66 cubic meters of concrete grade 250. I understand that I may have over-laid the foundation a little, but that year I was looking for people to foundation work. For the work they asked for 200 thousand rubles. and higher. I decided that it was better to invest this money in the foundation than in improving the well-being of strangers. During the two weeks of vacation, we slowly tied the reinforcement with the help of my father. I was confident in every detail. They filled it with imported concrete in 5 hours using a concrete pump at the Isuzu vehicle base. I plan to start laying the walls as soon as the snow melts; the bricks are already on the site. I will reinforce the walls conscientiously. Now I'm looking for decent masons. They have too many demands at the moment. They ask for 2800 rubles for rough masonry. per cube, and additional payments for every movement of the hand and turn of the head.
They push it under the slabs to make an armored belt 5 cm thick, with two thin reinforcement bars inside. It is clear that this, like an armored belt, is of little use. Just a leveling screed. It’s clear that you’ll have to do the screed this way, but is it worth bothering with a full-fledged armored belt 30-40 centimeters thick and appropriate reinforcement - THAT’S THE QUESTION! I will be grateful for any constructive advice. The fact is that with aerated concrete there would be no questions, I would definitely do it. And with bricks - it’s not clear yet. It seems that brick, as a material for load-bearing walls in private housing construction, has generally gone out of fashion. All are built exclusively from aerated concrete.

To a person who is far from construction, the phrase “monolithic belt” will seem incomprehensible. However, to control the construction own home or a cottage or when purchasing an apartment in a newly built building, it is necessary to have an understanding of what an armored belt for floor slabs is and how it is produced.

The installation of a reinforced concrete monolithic belt will significantly strengthen the structure of your house and help avoid the formation of cracks in the walls.

Structurally, a reinforced concrete or monolithic belt is a kind of continuous closed beam made of concrete reinforced with graded metal on the walls or foundation of a building under construction.

The reinforced concrete monolithic belt must be closed and in no case interrupted along the entire perimeter.

For the construction of a reinforced frame it is used construction fittings diameter 12 mm.

It is worth mentioning one more point. In the description, for ease of understanding, we will assume a rectangular building with external load-bearing walls. But if a wall or walls are designed inside the building on which there will be, then a foundation must be provided for such walls to reduce the load from the external load-bearing walls. Under slabs resting on such walls, a monolithic reinforced belt. This will have a positive effect on strengthening the entire structure.

Before starting work, it is recommended that you familiarize yourself with the rules set out in the document SP 31-114-2004 “Rules for the design of residential and public buildings for construction in seismic areas." The requirements set out in the set of rules will help you make more accurate calculations and understand the principle of construction.

Application of the belt

If aerated concrete and foam concrete blocks are used to lay the load-bearing walls of a house, then the installation of a monolithic reinforced belt is mandatory.

1. In the case of using lightweight blocks and materials for laying load-bearing walls that do not easily resist the load from the floors. For example, cinder blocks, foam concrete and aerated concrete blocks, natural shell rock and limestone. It is worth explaining that in walls made of these materials, under the influence of the load on the foundation from the floor slab unevenly distributed over the area of ​​the wall, deformation processes called crushing can begin. They can cause subsequent destruction of the masonry wall. There are special methods for determining the feasibility of installing a reinforced belt. They take into account the resistance characteristics of the material various types loads using special coefficients. However, the experience of building from lightweight blocks, especially from foam and slag concrete, shows that monolithic masonry from these materials is necessary for structural reasons.
2. When building on weak, subsiding soils, the installation of a belt is due to the danger of the building subsiding under the influence of factors unfavorable to the soil. For example, when wet under the influence of the load from the weight of the house, the soil will begin to deform. In this case, a continuous monolithic belt will be able to “keep” the wall and foundation from cracks and destruction. It is worth mentioning that the presence of a belt can help avoid wall destruction only up to certain deformation loads. Therefore, it is worthwhile to thoroughly study the properties of soils and evaluate the possibility of constructing a building, for example, near streams and rivers. If damage in the form of vertical cracks is visible in the walls of neighboring buildings, then a monolithic reinforced belt is required.
3. When constructing a building in a seismically dangerous region.

Structural objectives of the armored belt:

• the foundation and frame of the building are connected;
• uniform distribution of load around the entire perimeter on the walls and foundation;
• alignment of horizontal planes of load-bearing walls under the floor slab.

Materials and tools

Using a special ratchet wrench for tying reinforcement will help save a lot of time.

1. Special ratchet wrench for .
2. Corners to strengthen the frame.
3. Welding machine.
4. Concrete mixer (or mixer, or drill with a mixing attachment).
5. Scoop and regular shovels.
6. Bucket.
7. Cement, water, sand, crushed stone.
8. Board for formwork installation.
9. Nails, screws.
10. 12 mm steel reinforcement.
11. Wire for knitting.
12. Good quality polyurethane foam.

Step-by-step device technology

Board formwork

To wooden formwork has withstood the pressure of the concrete poured into it, it must be securely fastened.

The foundation or wall is covered with formwork made of boards. The reinforced monolithic belt is usually arranged with a height of 30 cm, and its width is equal to the width of the masonry (taking into account the distance for the insulation, see below). The bottom part of the board (approximately 5 cm high) is attached to the outer and inside walls with self-tapping screws. Both parts of the formwork are fastened with transverse pins. The horizontality of the upper part of the formwork is controlled by the water level. It must be strictly horizontal. The assembled formwork is a kind of gutter over the building frame.

Reinforced frame

Because of his heavy weight device reinforcement cage done directly on the wall. Typically, heavy floor slabs are not used for buildings made of light blocks, so it is enough to use two 12 mm reinforcement bars. From these, by means of fastening with a special wire for knitting reinforcement, steps of a ladder with crossbars are made approximately every half meter. In the corners of the building it is necessary to strengthen the “ladder” by welding special corners. The frame is also assembled for the foundation.

It should be taken into account that the distance from the edge of the formwork to the frame rods should be 50 mm on each side. That is, the width of the frame should be 100 mm less than the width of the wall.

For heavier floor slabs, four reinforcement bars are used, welded in the shape of a quadrangle. This design is used for armored belts under the foundation. When constructing such a frame, it is also necessary to take into account the dimensions that should be set back from the wall.

From below, the frame also needs to be raised from the wall by 50 mm. This can be done by placing pieces of timber, brick or any available material under the reinforcement structure.

There are recommendations from experienced builders for driving nails or pieces of reinforcement into the top row of masonry at certain distances in order to further “connect” the foundation and the reinforced belt. The need for this work remains at the discretion of the owner of the house.

Pouring a monolithic belt

A monolithic reinforced belt is poured cement-sand mortar 1:3 with the addition of crushed stone. That is, for 1 part cement 3 parts sifted sand. With constant stirring, add water, checking the mixture for fluidity. It should not be too liquid so that it does not flow out of the formwork. We perform continuous pouring, constantly “bayoneting” the concrete to compact it and prevent the formation of voids.

When preparing a solution for concreting an armored belt, use cement grade M-400.

To ensure continuity of the belt in the event of a need to stop work, it will be necessary to make a crossbar that only stops the process vertically. You can use a brick or block. When resuming work, remove the jumper and continue work, pouring plenty of water on the joint.

In good sunny weather it is approximately four days. Then the wall formwork or foundation is dismantled.

Insulation of armored belt

In conclusion, I would like to dwell on the issue of insulating the armored belt. This need disappears if, according to the design, the walls of the building are subject to insulation. Otherwise, the belt will act as a kind of conductor of cold, freezing in winter. This will lead to not very comfortable temperature in interior spaces, and subsequently to dampness and mold on the walls. Therefore, it is recommended to insulate it.

To do this, when installing a monolithic reinforced concrete belt, it is worth taking into account the width of the proposed insulation and the support depth of the floor slab, which must be determined according to SNiP 2.08.01-85.

Thermal insulation must be made with outside home to avoid mold on the walls.

For insulation, holes must be made every 2-3 cm and foamed. polyurethane foam. Foaming occurs in two stages: first, every second hole, and after a day or two, when the foam hardens, the remaining holes are foamed. The costs of insulation are quite serious, but this procedure cannot be avoided.

You need to foam in parts. Those. first, foam each odd-numbered hole, wait a couple of days (or, according to the instructions for the foam, after hardening), then foam each even-numbered hole - this will allow you to foam efficiently and at the same time slightly reduce foam consumption. Subsequently, the cladding can be placed along the armored belt.

This node is an alternative solution to node 2.0 for supporting brick cladding walls In it, the cladding is placed not on the foundation, but on a heat-insulated ledge of a monolithic belt. Let's look at this node using the example of a house with a basement:

Rice. 1. Normal of the basement wall and the outer wall with brick cladding.

This node is discussed in more detail in Fig. 2. The “step” of insulation is made to reduce the eccentricity of the load from the cladding, as well as the protrusion of the cladding relative to the base.

Rice. 2. Supporting unit for the cladding masonry.

In plan, the monolithic belt is made as follows:

Rice. 3. Monolithic belt, top view.

It can be seen that the belt consists of two parts: a main width of 350 mm, on which the wall and floor slabs are mounted, as well as a cantilever belt 100 mm wide, on which the cladding is mounted. The cladding belt is insulated from the main one with 100 mm thick EPS inlays and connected to it by isthmuses 100 mm wide, which act as short cantilever beams on which the cladding belt is supported.
And a 3D view of this solution:

Rice. 4. 3D view of the node.

As befits beams, the isthmuses are reinforced in the upper and lower zones with 10A500S rods. For reliable anchoring in the body of the cladding belt and in the main belt, the reinforcement is made in the form of a bracket with bent ends, which also serves as a clamp. To reduce the likelihood of inclined cracks, an 8A500S rod was added with an anchoring hook for the longitudinal reinforcement of the cladding belt (replacement for clamps). It can also be made from 8A240 reinforcement, if A500C of this diameter cannot be found. Another option is to replace it with two rods of a similar profile from BP 2 5mm, they are then placed on both sides of 10A500S.

Below is the calculation of reinforcement in Robot for a belt load of 1.4 t/m with isthmuses 100x200 mm with a pitch of 600 mm. Before making the calculation, let's understand the geometry of the node. Let's look at the node in detail:

Rice. 4a. Rear view of the isthmus is enlarged. The finishing and insulation are hidden.

The location of the insulation in the unit was not chosen by chance, but in such a way as to reduce the cantilever overhang of the belt. Let's look at the cut:

Rice. 4b. Section of the node along the isthmus.

The section shows that the distance from the wall on which the belt rests to the center of the cladding is 100 mm. Uniform distribution of the load from the cladding across the entire width allows it to be specified as a concentrated load in the center (case 1). But to be sure, we will also consider the worst case, when the entire mass of the cladding falls on the edge of the console, and even taking into account the protrusion of the brick (blue line and case 2).

The calculation model in Robote will look like a rigidly clamped beam 100x200 mm long 560 mm made of B15 concrete with a cantilever overhang of 160 mm. And two cases of applying force:

Rice. 4c. Calculation with central application of force.

Rice. 4g. Calculation when applying force to the extreme point of the console.

When calculating, a load of 8.5 kN was taken on each beam. The reinforcement was provided with two 10A500S bars at the top and bottom. The program checks the bending moments of several sections (bar/position) and determines the required reinforcement area in cm2 (red arrow in Fig. 4c), as well as the required % reinforcement of the section according to the calculation. The green arrow shows the actually accepted % of reinforcement. It can be seen that in the worst case (Fig. 4d) the reinforcement margin is large. The zeros in the red callouts indicate the deformation of the beam under load (there is none).

This reinforcement allows you to support the lining of the belt on the belt. ceramic bricks with a height of 5-6 meters.

The solution was seen in “large” housing construction, for example, in the Design Guide monolithic houses The following unit is proposed for supporting the external brick cladding:

Rice. 5. Solution from monolithic housing construction.


Rice. 6. Fragments of the solution.

Rice. 7. With lower loads from the cladding, the ratio of the width of the thermal liner to the isthmus increases.

Rice. 8. Reinforcement option in “large” housing construction.

Rice. 9. Purlin unit from the article by Orlovich and Derkach.

Despite the presence of cold bridges in the form of isthmuses, this solution is quite effective in terms of thermal insulation:

Rice. 10. Heat map of node operation.

To simulate the operation of cold bridges in the 2-dimensional Elcut program, the isthmuses were reduced to an equivalent solid bridge (shown in Fig. 10 by an arrow).

This node is executed similarly for MZLF. We also have for this type of node.