Possibility of unsupported ceiling large areas significantly expands architectural possibilities when designing a house. A positive solution to the beam issue allows you to “play” with the volume of rooms, install panoramic windows, build large halls. But if it is not difficult to cover a distance of 3-4 meters with “wood”, then which beams to use on a span of 5 m or more is already a difficult question.

Wooden floor beams - dimensions and loads

Made a wooden floor in timber house, and the floor shakes, bends, a “trampoline” effect appears; we want to do wooden beams ceilings 7 meters; you need to cover a room 6.8 meters long so as not to rest the logs on intermediate supports; what should be the floor beam for a span of 6 meters, a house made of timber; what to do if you want to make an open plan - such questions are often asked by forum users.

Maxinova User FORUMHOUSE

My house is about 10x10 meters. I “threw” wooden logs onto the ceiling, their length is 5 meters, cross-section is 200x50. The distance between the joists is 60 cm. During the operation of the floor, it turned out that when children run around in one room and you stand in another, there is quite a strong vibration along the floor.

And such a case is far from the only one.

Elena555 User FORUMHOUSE

I can't figure out which beams are for interfloor ceilings needed. I have a house 12x12 meters, 2 floors. The first floor is made of aerated concrete, the second floor is an attic, wooden, covered with timber 6000x150x200mm, laid every 80 cm. The logs are laid on an I-beam, which rests on a pillar installed in the middle of the first floor. When I walk on the second floor, I feel shaking.

Beams for long spans must withstand heavy loads, therefore, in order to build a strong and reliable wooden floor with a large span, they must be carefully calculated. First of all, you need to understand what load it can withstand. wooden joist one section or another. And then think about, having determined the load for the floor beam, what roughing and finishing coat gender; what the ceiling will be hemmed with; whether the floor will be a full-fledged residential space or a non-residential attic above the garage.

Leo060147 User FORUMHOUSE

1. The load from the own weight of all structural elements of the floor. This includes the weight of beams, insulation, fasteners, flooring, ceiling, etc.
2. Operating load. The operating load can be permanent or temporary.

When calculating the operating load, the mass of people, furniture, household appliances, etc. is taken into account. The load temporarily increases when guests arrive, noisy celebrations, or furniture is rearranged if it is moved away from the walls to the center of the room.

Therefore, when calculating the operating load, it is necessary to think through everything - right down to what kind of furniture you plan to install, and whether there is a possibility in the future of installing a sports exercise machine, which also weighs more than one kilogram.

The following values ​​are taken for the load acting on long wooden floor beams (for attic and interfloor floors):

• Attic floor – 150 kg/sq.m. Where (according to SNiP 2.01.07-85), taking into account the safety factor, 50 kg/sq.m is the load from the floor’s own weight, and 100 kg/sq.m is the standard load.

If you plan to store things, materials and other household items in the attic, then the load is assumed to be 250 kg/sq.m.

• For interfloor slabs and slabs attic floor the total load is taken at the rate of 350-400 kg/sq.m.

Flooring with boards 200 by 50 and other common sizes

These are the types of beams on a span of 4 meters that are allowed by the standards.

Most often during construction wooden floors boards and timber of the so-called running sizes are used: 50x150, 50x200, 100x150, etc. Such beams meet the standards ( after calculation), if you plan to cover the opening no more than four meters.

For floors 6 or more meters long, the dimensions 50x150, 50x200, 100x150 are no longer suitable.

Wooden beam over 6 meters: subtleties

A beam for a span of 6 meters or more should not be made of timber and boards of standard sizes.

You should remember the rule: the strength and rigidity of the floor depend to a greater extent on the height of the beam and to a lesser extent on its width.

A distributed and concentrated load acts on the floor beam. Therefore, wooden beams for large spans are not designed “end-to-end”, but with a margin of strength and permissible deflection. This ensures normal and safe operation ceilings

50x200 - overlap for openings of 4 and 5 meters.

To calculate the load that the ceiling will withstand, you must have the appropriate knowledge. In order not to delve into the strength of strength formulas (and when building a garage this is definitely redundant), an ordinary developer just needs to use online calculators for calculating wooden single-span beams.

Leo060147 User FORUMHOUSE

A self-builder is most often not a professional designer. All he wants to know is what beams need to be mounted in the ceiling so that it meets the basic requirements for strength and reliability. This is what online calculators allow you to calculate.

These calculators are easy to use. To make calculations of the required values, it is enough to enter the dimensions of the logs and the length of the span that they must cover.

Also, to simplify the task, you can use ready-made tables presented by the guru of our forum with the nickname Roracotta.

Roracotta User FORUMHOUSE

I spent several evenings to make tables that would be understandable even to a novice builder:

Table 1. It presents data that answers minimum requirements by load for the floors of the second floor - 147 kg/sq.m.

Note: since the tables are based on American standards, and the sizes of lumber overseas are somewhat different from the sections accepted in our country, you need to use the column highlighted in yellow in the calculations.

Table 2. Here is data on the average load for the floors of the first and second floors - 293 kg/sq.m.

Table 3. Here is the data for the calculated increased load of 365 kg/sq.m.

How to calculate the distance between I-beams

If you carefully read the tables presented above, it becomes clear that with an increase in the span length, first of all, it is necessary to increase the height of the log, and not its width.

Leo060147 User FORUMHOUSE

You can change the rigidity and strength of the lag upward by increasing its height and making “shelves”. That is, a wooden I-beam is made.

Self-production of laminated wood beams

One solution for spanning long spans is to use wooden beams in the floors. Let's consider a span of 6 meters - which beams can withstand a larger load.

According to the type of cross section, a long beam can be:

• rectangular;
• I-beam;
• box-shaped

There is no consensus among self-builders as to which section is better. If we do not take into account purchased products (factory-made I-beams), then the ease of production in “field conditions”, without the use of expensive equipment and accessories, comes first.

Just Grandfather User FORUMHOUSE

If you look at a cross section of any metal I-beam, you can see that from 85% to 90% of the metal mass is concentrated in the “shelves”. The connecting wall contains no more than 10-15% of the metal. This is done based on calculation.

Which board to use for beams

According to the strength of strength: the larger the cross-section of the “shelves” and the farther they are spaced apart in height, the greater the loads the I-beam will withstand. For the self-builder optimal technology The manufacture of an I-beam is a simple box-shaped structure, where the upper and lower “shelves” are made of boards laid flat. (50x150mm, and the side walls are made of plywood with a thickness of 8-12 mm and a height of 350 to 400 mm (determined by calculation), etc.).

Plywood is nailed to the shelves or screwed with self-tapping screws (not black ones, they do not work for cutting) and must be placed on glue.

If you install such an I-beam on a six-meter span with a step of 60 cm, then it will withstand a large load. Additionally, an I-beam for a 6-meter ceiling can be lined with insulation.

Also, using a similar principle, you can connect two long boards, collecting them in a “package”, and then put them on top of each other on an edge (take boards 150x50 or 200x50), as a result, the cross-section of the beam will be 300x100 or 400x100 mm. The boards are placed on glue and tied together with pins or placed on wood grouse/dowels. You can also screw or nail plywood to the side surfaces of such a beam, having previously lubricated it with glue.

Also interesting is the experience of a forum member under the nickname Taras174, who decided to independently make a glued I-beam to span a span of 8 meters.

To do this, a forum member purchased 12 mm thick OSB sheets, cut them lengthwise into five equal parts. Then I bought a board 150x50 mm, 8 meters long. Freza " dovetail“I chose a groove 12 mm deep and 14 mm wide in the middle of the board - so that it turns out to be a trapezoid with an expansion downwards. OSB in grooves Taras174 glued it in using polyester resin (epoxy), having previously “shot” a strip of fiberglass 5 mm wide to the end of the slab with a stapler. This, according to the forum member, would strengthen the structure. To speed up drying, the glued area was heated with a heater.

Taras174 User FORUMHOUSE

On the first beam I practiced “pushing my hand.” The second one was done in 1 working day. In terms of cost, taking into account all materials, I include a solid board of 8 meters, the cost of the beam is 2000 rubles. for 1 piece

Despite the positive experience, such “squatter construction” did not escape several critical remarks expressed by our experts. Namely.

Beams in a house usually belong to rafter system or overlap, and to get reliable design, the operation of which can be carried out without any fear, must be used beam calculator.

What is the beam calculator based on?

When the walls have already been brought under the second floor or under the roof, it is necessary to make, in the second case smoothly turning into rafter legs. In this case, the materials must be selected so that the load on the brick or log walls did not exceed the permissible limit, and the strength of the structure was at the proper level. Therefore, if you are going to use wood, you need to choose the right beams from it, make calculations to find out required thickness and of sufficient length.

The subsidence or partial destruction of the ceiling can be due to various reasons, for example, too large a step between the lags, deflection of the cross members, too small their cross-sectional area or defects in the structure. To eliminate possible excesses, you should find out the expected load on the floor, be it basement or interfloor, and then use a beam calculator, taking into account their own weight. The latter can change in concrete lintels, the weight of which depends on the density of the reinforcement; for wood and metal, with a certain geometry, the weight is constant. The exception is damp wood, which is not used in construction work without pre-drying.

On beam systems in floors and rafter structures load is exerted by forces acting on section bending, torsion, and deflection along the length. For rafters, it is also necessary to provide for snow and wind loads, which also create certain forces applied to the beams. It is also necessary to accurately determine the required pitch between the jumpers, since it is too a large number of crossbars will lead to excess weight ceiling (or roof), and too little, as mentioned above, will weaken the structure.

You may also be interested in the article about calculating the amount of unedged and edged boards cubed:

How to calculate the load on a floor beam

The distance between the walls is called a span, and there are two of them in the room, and one span will necessarily be smaller than the other if the shape of the room is not square. Interfloor lintels or attic floor should be laid over a shorter span, optimal length which is from 3 to 4 meters. Longer distances may require beams non-standard sizes, which will lead to some instability of the flooring. The best solution in this case would be to use metal crossbars.

Regarding the section wooden beam, there is a certain standard that requires that the sides of the beam be in a ratio of 7:5, that is, the height is divided into 7 parts, and 5 of them must make up the width of the profile. In this case, deformation of the section is excluded, but if you deviate from the above indicators, then if the width exceeds the height, you will get a deflection, or, if the opposite discrepancy occurs, a bend to the side. To prevent this from happening due to the excessive length of the beam, you need to know how to calculate the load on the beam. In particular, permissible deflection calculated from the ratio to the length of the jumper as 1:200, that is, it should be 2 centimeters by 4 meters.

To prevent the beam from sagging under the weight of logs and flooring, as well as interior items, you can grind it from below a few centimeters, giving it the shape of an arch; in this case, its height should have an appropriate margin.

Now let's turn to the formulas. The same deflection mentioned earlier is calculated as follows: f nor = L/200, where L– span length, and 200 – permissible distance in centimeters for each unit of timber subsidence. For reinforced concrete beam, distributed load q which is usually equated to 400 kg/m 2, the calculation of the limiting bending moment is performed using the formula M max = (q · L 2)/8. In this case, the amount of reinforcement and its weight is determined according to the following table:

Cross-sectional areas and mass of reinforcing bars

Diameter, mm	Cross-sectional area, cm 2, with the number of rods									Weight 1 linear meter, kg	Diameter, mm
Wire and rod reinforcement
Seven-wire ropes class K-7

The load on any beam made of a sufficiently homogeneous material is calculated using a number of formulas. To begin with, the moment of resistance W ≥ M/R is calculated. Here M is the maximum bending moment of the applied load, and R – design resistance, which is taken from reference books depending on the material used. Since most often beams have rectangular shape, the moment of resistance can be calculated differently: W z = b h 2 /6, where b is the width of the beam, and h– height.

What else should you know about beam loads?

The ceiling, as a rule, is at the same time the floor of the next floor and the ceiling of the previous one. This means that it needs to be made in such a way that there is no risk of combining the upper and lower rooms by simply overloading the furniture. This probability especially arises when the step between the beams is too large and logs are abandoned (plank floors are laid directly on the timber laid in the spans). In this case, the distance between the crossbars directly depends on the thickness of the boards, for example, if it is 28 millimeters, then the length of the board should not be more than 50 centimeters. If there are lags, the minimum gap between the beams can reach 1 meter.

It is also necessary to take into account the mass used for the floor. For example, if mats are laid from mineral wool, That square meter the basement floor will weigh from 90 to 120 kilograms, depending on the thickness of the thermal insulation. Sawdust concrete will double the mass of the same area. The use of expanded clay will make the flooring even heavier, since the load per square meter will be 3 times greater than when laying mineral wool. Further, we should not forget about the payload, which for interfloor floors is at least 150 kilograms per square meter. In the attic, it is enough to accept a permissible load of 75 kilograms per square.