In order to build a reliable wooden floor, it is necessary to select the correct dimensions of the beams, and for this it is necessary to calculate them. Wooden floor beams have the following main dimensions: length and cross-section. Their length is determined by the width of the span that needs to be covered, and the cross-section depends on the load that will act on them, on the length of the span and the installation pitch, that is, the distance between them. In this article we will look at how to independently make such a calculation and select the correct beam sizes.
Calculation of wooden floor beams
In order to determine how many wooden beams and what sizes will be required for the floor installation, you must:
- measure the span that they will cover;
- decide on ways to secure them on the walls (to what depth they will go into the walls);
- make a calculation of the load that will act on them during operation;
- using tables or a calculator program, select the appropriate pitch and section.
Now let's look at how this can be done.
Length of wooden floor beams
The required length of floor beams is determined by the size of the span that they will cover and the margin required to embed them in the walls. The length of the span is easy to measure using a tape measure, and the depth of embedding in the walls largely depends on their material.
In houses with brick or block walls, beams are usually embedded in “sockets” to a depth of at least 100 mm (board) or 150 mm (timber). IN wooden houses They are usually placed in special notches to a depth of no less than 70 mm. When using a special metal fastening(clamps, angles, brackets) the length of the beams will be equal to the span - the distance between opposite walls on which they are attached. Sometimes, during installation rafter legs roofs directly onto wooden beams, they are released outside, beyond the walls by 30-50 cm, thus forming a roof overhang.
The optimal span, which can overlap wooden beams, is 2.5-4 m. Maximum length beams from edged boards or timber, that is, the span that it can cover is 6 m. For a longer span (6-12 m), it is necessary to use modern wooden beams made of laminated veneer lumber or I-beams, and you can also rest them on intermediate supports (walls, columns). In addition, to cover spans longer than 6 m, wooden trusses can be used instead of beams.
Determination of the load acting on the floor
The load acting on the floor along wooden beams consists of the load from the own weight of the floor elements (beams, inter-beam filling, lining) and permanent or temporary operational load (furniture, various household devices, materials, weight of people). It usually depends on the type of floor and its operating conditions. The exact calculation of such loads is quite cumbersome and is carried out by specialists when designing the floor, but if you want to do it yourself, you can use its simplified version given below.
For an attic wooden floor that is not used for storing things or materials, with light insulation (mineral wool or etc.) and hemming, the constant load (from its own weight - Rown) is usually taken within 50 kg/m2.
The operational load (Rexpl.) for such an overlap (according to SNiP 2.01.07-85) will be:
70x1.3 = 90 kg/m2, where 70 is the standard load value for this type of attic, kg/m2, 1.3 is the safety factor.
The total design load that will act on this attic floor will be:
Rtot.=Rown.+Rexpl. = 50+90=130 kg\m2. Rounding up we take 150 kg/m2.
In case the design attic space heavier insulation, material for inter-beam filling or lining will be used, and if it is intended to be used for storing things or materials, that is, it will be used intensively, then the standard load value should be increased to 150 kg/m2. In this case, total load for the overlap will be:
50+150x1.3 = 245 kg/m2, round up to 250 kg/m2.
Using attic space to construct an attic, it is necessary to take into account the weight of floors, partitions, and furniture. In this case, the total design load must be increased to 300-350 kg/m2.
Due to the fact that an interfloor wooden floor, as a rule, includes floors in its design, and the temporary operating load includes weight large quantity household items and the maximum presence of people, then it should be designed for a total load of 350 - 400 kg/m2.
Section and pitch of wooden floor beams
Knowing the required length of wooden floor beams (L) and determining the total design load, you can determine their required cross-section (or diameter) and laying step, which are interconnected. It is considered that the best is rectangular section wooden floor beams, with a height (h) and width (s) ratio of 1.4:1. The width of the beams, in this case, can be in the range of 40-200 mm, and the height 100-300 mm. The height of the beams is often chosen so that it matches required thickness insulation. When using logs as beams, their diameter can be in the range of 11-30 cm.
Depending on the type and cross-section of the material used, the pitch of the wooden beams 
the ceiling can be from 30 cm to 1.2 m, but most often it is chosen within the range of 0.6-1.0 m. Sometimes it is chosen so that it matches the size of the insulation boards laid in the interbeam space, or ceiling sheets. In addition, in frame buildings, it is desirable that the pitch of the beams corresponds to the pitch of the frame posts - in this case, the greatest rigidity and reliability of the structure will be ensured.
You can calculate or check the already selected dimensions of wooden floor beams using reference tables (some are given below) or using the online calculator “calculation of wooden floor beams”, which is easy to find on the Internet by typing in the corresponding query in a search engine. It is necessary to take into account that their relative deflection for attic floors should not be more than 1/250, and for interfloor - 1/350.
Table 1
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Step,m\ span,m |
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table 2
Table 3
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Step,m/ span,m |
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Table 4
Installation of wooden beams in the floors of houses is not uncommon. Their main purpose is to evenly distribute the load on the walls and foundation of the building. To beam structure performed its functions, it is necessary to select the right material for it, calculate the length and cross-section.
All wooden beams are divided among themselves according to their purpose and the type of material from which they are made. According to their purpose, they can be: interfloor, attic, basement and basement. Depending on the type of material, beams can be made of solid wood or laminated wood.
wooden floors in aerated concrete house
The interfloor span must be strong and reliable. Sound and vapor barrier fillers are placed in the internal volume between the ceiling and floor. The ceiling part is sewn up necessary material, the floor is laid on top.
The attic floor can be installed as an element of the roof, being part of it truss structure. Can be installed as a separate independent element. In order to preserve heat, it must be equipped with steam and thermal insulation.
Basement ceiling and ground floor must be of great strength and withstand high loads. These spans are equipped with heat and vapor barriers to prevent the penetration of cold from the basement.
Beams differ in types, which have their own advantages and disadvantages.Hardwood is used to make solid beams. A significant disadvantage of solid wooden beams is the length limitation, which cannot exceed 5 meters.
Beams made of laminated wood combine high strength and aesthetics. Their use significantly increases the maximum length, which can be up to 20 meters. Considering that glued floors look beautiful, they are often not covered with a ceiling and serve as a design element.
They have several more significant advantages, which include:
- ability to cover large spans;
- ease of installation;
- small weight;
- long period of operation;
- high level of fire safety;
- cannot be deformed.
The wooden parts of the floor beams can have a rectangular cross-section, which is typical for timber or boards, or round, made from logs.
Requirements for wooden floor beams
Installation of wooden beam floors entails a number of requirements that must be taken into account. They are as follows:
- Beam products must be made coniferous species wood, which have a high margin of safety. At the same time, the moisture content of the wood should be no more than 14 percent, otherwise the joists will have a large deflection under load.
- It is prohibited to use wood that is susceptible to fungal diseases or damaged by insects to make beams.
- Before installation, beam elements must be treated with an antiseptic.
- To ensure that the ceiling or floor does not sag even under load, it is necessary to perform a construction lift. The ceiling of the lower floor will receive a slight rise in the center, which will become even under load.
- If the beams are planned to be laid with great frequency, then instead of them you can use boards that need to be installed on the ribs.
The procedure for calculating wooden beams
Before installing a wooden floor, it is necessary to carry out calculations in which to determine the number and dimensions of beams. To do this you need:
- determine the length of the span on which they will be installed;
- calculate the possible load they will bear after installation;
- Having the specified data, calculate the cross-section of the beams and the step with which they will be installed. For this, special tables and programs are used.
Beam length consists of the length of the span that needs to be covered and the stock of the beam that will be mounted into the wall. The span can be determined using any measuring device. The supply of beams that will be mounted in the wall depends on the material from which the wall is made.
Important!
If the building is built of brick, then the margin for beams made from boards should be at least 10 cm and at least 15 cm for beams made from timber. IN wooden buildings special grooves are made, with a depth of 7 cm or more, for laying beams. If the beams serve as the basis for the roof rafters, then they are made 4-6 cm longer than the span.
The most used span, which is covered with beams, ranges from 2.5 to 4 meters. The maximum length of beams made of timber or boards cannot exceed 6 meters. If the span length exceeds this size, then it is recommended to install beams made of laminated veneer lumber. In addition, to cover spans longer than 6 meters, you can install a wooden truss.
Load carried by a wooden beam consists of a mass of span parts (beams, internal filling, ceiling and floor coverings) and a mass of temporary elements (furniture, Appliances, people present in the room).
Accurate calculations bearing capacity beams are usually carried out by specialized organizations. At independent execution The following system is used for calculation:
- an attic floor with a lining, in which the insulation is mineral wool, carries a constant self-load of 50 kg per square meter. With such a load, according to SNiP standards, the standard load will be 70 kg per square meter with a safety factor of 1.3. Finding out the total load is not difficult: 1.3x70+50=130 kilograms per square meter;
- if a heavier material than cotton wool is used as insulation, or thick boards were used as lining, then the standard load will be 150 kg per square meter. And the total load will have a different value: 150x1.3+50=245 kg per square meter;
- if the calculation is carried out for attic room, then the weight of the material from which the floor is laid and the objects located in the attic is taken into account. The load in this case will be 350 kg per square meter;
- in the case where the beams serve as interfloor spans, the calculated load is 400 kg per square meter.
Calculation of wooden floor beams
Determination of the section and pitch of wooden beams
By calculating the load and length of the beams, you can determine their pitch and cross-sectional dimensions or diameter.
These indicators are interrelated and are calculated according to established rules:
- The width and height of the beams should be in proportion 1:1.,4. In this case, the width of the beams should be in the range from 4 to 20 cm, and the height from 10 to 30 cm, taking into account the thickness insulation material. Logs for floors should have a diameter in the range from 11 to 30 cm.
- The installation step should be in the range from 30 to 120 cm, taking into account the insulation and lining materials that will be in the space between the beams. If the structure is frame, then the step should correspond to the distance between the frames.
- The cross-section of wooden beams is determined using developed tables or using certain programs. When calculating sections, it is necessary to take into account that the maximum bending attic beams should not exceed 1/200, and between floors 1/350.
Application of wooden trusses, advantages and disadvantages
Floor trusses made of wood look like two parallel logs or bars located above each other, which are connected to each other by supports located at an angle or vertically in relation to these logs or bars. The main task that trusses solve is covering long spans if the installation of additional support posts is impossible.
For the manufacture of trusses, developed tables and programs are used, which take into account the type of connections, installation pitch, cross-section of structural parts and its overall dimensions. Often, trusses are made industrially using high-precision equipment. Along with this, you can make a farm with your own hands.
By comparing wooden beams and floor trusses, you can determine the advantages and disadvantages that the trusses have. The advantages include:
- the ability to cover a span of significant size without additional support posts;
- insignificant mass, which entails a small load on the load-bearing elements of the building;
- high strength and resistance to deflection, which entails long-term operation of lining and flooring materials;
- ease of installation on any load-bearing elements of the building, regardless of the material from which they are made;
- the ability to change the width of the truss laying step;
- possibility of installing internal communication lines;
- excellent sound insulation;
- beautifully made trusses can be left unsewn and used as a decorative element.
In addition to advantages, farms have some disadvantages, which include the following:
- due to design features, the thickness increases significantly interfloor ceilings;
- significant labor costs when making a farm with your own hands, the need for special equipment;
- high price for a finished structure.
Design wooden trusses
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The possibility of unsupported covering of large areas significantly expands the 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 make wooden floor beams 7 meters long; 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 what kind of beams are needed for the interfloor floors. 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; will the floor be a full-fledged living space or uninhabited attic above the garage.
Leo060147 User FORUMHOUSE
- The load from the own weight of all structural elements of the floor. This includes the weight of beams, insulation, fasteners, flooring, ceiling, etc.
- Operating load. The operating load can be permanent or temporary.
When calculating the operating load, the mass of people, furniture, household appliances etc. 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 ceilings and floors 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 meets the minimum load requirements 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.
By appearance cross section a long beam can be:
- rectangular;
- I-beam;
- box-shaped
None among self-builders consensus, which section is better. If we do not take into account purchased products (factory-made I-beams), then the ease of manufacture in “ field conditions", without use expensive equipment and equipment.
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, the forum member purchased 12 mm thick OSB sheets and 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 with 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.