In order for the building structure to be strong and reliable, it is necessary to carefully approach its calculations. For the rafter system, an ordinary wooden beam is most often used, the choice of which must be approached with full responsibility, since the safety and integrity of the entire house depends on it. It is best to calculate the cross section of a beam using special programs, but such work is quite feasible when using a number of formulas. Be sure to take into account wind and snow loads in the region, characteristics finishing materials and heaters.

What affects the cross section of the rafters?

To install a strong and reliable roofing system, make right choice, it is necessary to pay attention to which beam is used for work. It is important to correctly calculate the rafter system, for which the section is of primary importance. It depends on whether the rafters can withstand the weight of the roof.

The following parameters are taken into account in the calculation:

1. The total weight of all roofing materials used.
2. The weight of all designed interior decoration, including attics and attics.
3. All calculated values ​​​​of rafter legs, beams.
4. Weather effects on the roof.

Additionally, the following are taken into account:

• spans between individual rafters;
• calculation of the section of the rafters;
• step of mounted rafter legs;
• the shape of the truss truss, the features of fastening the rafters;
• wind and snow loads;
• other data that may affect the calculation.

To carry out calculations, it is best to use special programs or contact a specialist. Of course, there are a number of formulas that will allow you to perform calculations on your own, but for the construction of a large and complex roof, it is better to turn to professionals.

Requirements for the bar

In order for the rafter system to turn out to be strong and reliable, it is necessary to pay attention to the quality of the material itself when choosing a beam. For example, the humidity level should not be more than 20%. The bars must be treated with a special solution that will protect the material from decay, insect damage, and open flame.

It must be remembered that loads will be applied to the timber. They can be permanent or temporary:

1. The constants usually turn out to be the own weight of the entire truss structure, the lathing used, the roofing material chosen for cladding, and the insulation. This value is calculated for each material separately, after which the loads are summed up.
2. Temporary loads are divided into special rare, short-term, long-term. Earthquakes are one of the special ones. Short-term include wind, snow, the weight of people who are engaged in repair and other work on the roof. Long-term loads include all other types of loads that operate for a certain time.

Snow load and wind

When calculating the cross-section of a beam for rafters, it is important to take into account the snow load. For each region, this value is individual. To clarify the data, you need to use special tables.

To calculate all planned accurate snow loads, use the following formula:

1. Sg is the calculated exact value of the total mass of snow that falls on every 1 m² of ground horizontal surface (not to be confused with roof covering).
2. µ is the coefficient of load transfer to a horizontal (or sloped) roof surface. This coefficient is calculated taking into account the slope of the roof, it can take the following values:

• µ = 1 if the ramp has a slope of 25 degrees;
• µ \u003d 0.7 if the slope of the slope is 25-60 degrees.

If the slope angle exceeds 60 degrees, then the coefficient is not taken into account, since it does not significantly affect the cross section of the rafters.

In order for the rafter system to be calculated correctly, it is necessary to take into account wind loads, which have a significant impact on the structure.

Do not underestimate them, as this can lead to disastrous consequences. To find out the value of the average wind load on the roof system, you need to use a formula that depends on the height readings (there are exact values) above ground level:

• Wo is the normative value of the wind load, which can be found in special reference books for the region;
• k is the change for wind pressure, which depends on altitude. Determined from tabular data.

The table itself is not very difficult to use, you just need to remember that the first column always indicates known constant values ​​​​for desert regions, forest-steppes, steppes, tundra, sea coasts, shores of reservoirs, lakes, rivers. The 2nd column lists all known values for calculations relating to urban areas, areas where obstacles have a height of 10 m. It is important to use wind direction data during calculations, as this can have a strong influence on the result obtained.

Rules for calculating the section of a beam

The cross section of the truss system of any planned house depends on a number of parameters:

• length of one rafter leg;
• the step with which the truss system will be mounted;
• the calculated value of the load indicators, which is typical for a particular construction area.

For calculations, you must use special data tables that contain ready-made values. For example, for the truss system of a house in the Moscow region, the following values ​​apply:

• for Mauerlat, wooden bars are used, the cross section of which will be 150 * 150 mm, 150 * 100 mm, 100 * 100 mm;
• for rafter legs, diagonal valleys, wooden beams with a cross section of 200 * 100 mm are used;
• for runs, products with a cross section of 200 * 100 mm, 150 * 100 mm, 100 * 100 mm are suitable;
• for tightening, a beam is required, the cross section of which is 150 * 50 m;
• for crossbars it is necessary to use bars, the cross section of which is 200 * 100 mm, 150 * 100 mm;
• for racks, wooden beams with a cross section of 150 * 150 mm, 100 * 100 mm are used;
• for a cornice, filly, struts, bars with parameters of 150 * 50 mm are suitable;
• used as a future frontal board and for filing wooden plank, its cross section is 22 * ​​100 mm.

An example of calculating the cross section of a wooden beam

An example of calculating the rafters for the roof of a house shows what kind of material and in what quantity is needed, what section should be used. Initial data for calculation:

1. The estimated usable load for the entire roof is 317 kg/m².
2. The normative used load in this used case is 242 kg/m²;
3. The slope angle is 30 degrees. In the horizontal planned projection, the length for one span is 450 cm, while L 1 \u003d 300 cm, and L 2 \u003d 150 cm.
4. The step of all mounted rafters is 80 cm.

Bolts will be used to fasten the crossbars so that the nails do not weaken the material. At the same time, for wood of the second grade, the resistance value will be 0.8 with a weakened section of the timber used: R izg \u003d 0.8x130 \u003d 104 kg / m².

Future system load per linear meter of rafters:

• Qp \u003d 317 * 0.8 \u003d 254 kg / m;
• Qn \u003d 242 * 0.8 \u003d 194 kg / m.

If the slope for the roof is up to 30 degrees, then the truss system will be considered bendable. Maximum moment such bending is:

M \u003d -qrx (L 13 + L 23) / 8x (L 1 + L 2), that is, M \u003d - 254 * (33 + 1.53) / 8 x (3 + 1.5) \u003d - 215 kg / m.

Final value M = -21500 kg/cm. Here the “-” sign used means that the bend will act in the opposite direction from the entire load applied for work.

W = 21500/104 = 207cm³.

To make rafters, rectangular wooden beams with a width value of 50 mm are usually used. Based on this, you can get the height for the rafters, taking into account the received resistance data:

H \u003d √ (6x207/5) \u003d 16 cm.

The cross section of the rafters is b = 5 cm, and the planned height is h = 16 cm. Referring to the standards that are regulated by GOST, you can choose a wooden beam that best matches the parameters obtained: 175 * 50 mm. This value is used for the span L 1 = 3 m. After that, it is necessary to calculate the rafter leg for the moment of inertia:

J \u003d 5 * 17.53 / 12 \u003d 2233 cm³.

After that, you can get the value for the deflection, which is also regulated by the standards: F norm \u003d 300/200 \u003d 1.5 cm.

F \u003d 5 * 1.94 * 3004 / 384 * 100 000 * 2233, that is, the value F \u003d 1 cm is obtained.

When reconciling with the values ​​of the standard deflection data, it can be seen that the obtained value of 1 cm is less than the standard value of 1.5 cm. This indicates that the section of 175 * 50 mm was chosen correctly, such material can be used for the construction of the roof truss system.

In order for the roof truss system used to be strong and reliable, capable of withstanding all the planned loads, one should carefully approach the calculations for the cross section of the beam, which will be the main building material of the roof. For this, a number of formulas are used; during calculations, it is necessary to use special reference books with standard indicators. It is required to determine wind, snow loads and other important indicators.

When building any private house, you always have to make different kinds floors. These can be interfloor or attic structures, but in any case, their installation must be approached responsibly, and the most suitable materials must be chosen for this.

We can say that these structures are the same integral element of any home as walls, foundations or roofs.

Types of floors used in private construction

Depending on the type of buildings and the planned costs for their manufacture, the following can be used:

• reinforced concrete;
• foam concrete blocks and monolithic reinforced concrete beams;
• I-beam rails and wooden draft flooring;
• wooden joists.

Calculation of the section of wooden beams

During the construction of most private houses, developers make the floor of the second floor from a bar. This is a relatively inexpensive, but at the same time quite reliable material that has been used for such purposes for several centuries. The only necessary condition is the correct calculation of the cross section of such cross members installed in the span as a lag.

In order to more accurately determine the cross-section of a beam for overlapping, special formulas are used, which, among other things, take into account the resistance of the wood used and its moisture content. These parameters are defined in SNiP II-25-80, with which any developer or private master must be familiarized without fail.

You can also find the necessary formulas and tables there, with the help of which the parameters of the beams for specific interfloor structures are determined.

When calculating wooden floors, it is also necessary to take into account the span width, the distance between the beams, and the shape of their section. When calculating each cross member to be laid, it must be remembered that the value of its deflection under load should not exceed 1/250 of the span length.

Since it is quite difficult for a technically untrained person to correctly calculate the lag parameters using formulas and tables, special calculators can be used to independently select beams. In such a program, it is enough to enter several basic quantities, and as a result, you can choose correct dimensions bearing lag.

Calculation of the beam section

As an example, using one of these calculators, we will try to calculate which beam to use to cover 5 meters.

For data entry we need to know:

• the material from which the crossbar is made (only coniferous trees are recommended);
• span length;
• beam width;
• beam height;
• type of material (log or timber).

In order to make the correct calculations, we substitute the span width equal to 5m to the input values, and set the beam type to the beam type. We will select the height and width empirically in the parameters “bar dimensions for floor beams”. Be sure to take into account such values ​​as the load per kg / m, and the step between the crossbars.

For interfloor structures, the load value should not be less than 300 kg / m, since it is necessary to take into account not only the weight of furniture and people, but also the weight of the materials themselves from which the floor is made. This includes floor beams, rough and finishing floors and, of course, insulation and sound insulation.

Advice. For non-residential attic structures, a load value of 200 kg / m will be quite sufficient.

Possible options

In almost all bases that sell lumber, floor beams are sold mainly in several sizes. As a rule, these are beams from 100x100 mm to 100x250 mm, and from 150x150 mm to 150x250 mm. In order not to waste time and money on searching for logs with non-standard sizes, the price of which can be much higher than the standard ones, we substitute into the program those parameters that are commercially available.

To do this, you must first find out on the basis of lumber what sizes they sell. Thus, we obtain that for interfloor structures the minimum size of the beam should be approximately 100x250 mm, and for attic structures 100x200 mm will be quite enough, with a step between them equal to 60 cm.

If you do not trust software calculators and want to independently calculate the size of the floor beam, then you will have to use the formulas and tables given in the relevant technical documentation. Or you can use general rule, which states that the height of each lag should be equal to 1/24 of the length of the opening, and its width is equal to 5/7 of the height of the crossbar.

Installation of interfloor and ceiling ceilings on wooden logs

Interfloor ceilings in a house made of timber begin to be mounted by laying a log. To do this, a prepared beam is placed on the walls, which is pre-wrapped with roofing material. This will protect the wood from moisture penetration, and as a result, from decay.

The extreme beams should be laid no closer than 5 cm from the wall, and the distance between adjacent crossbars should not exceed the previously calculated values, which in our case are 60 cm.

An important condition is that the logs must be laid over the entire thickness of the walls, having maximum support and stability. The gaps between the lags on the wall are laid with bricks or building blocks, after which a draft floor is stuffed from above. edged boards 150x25 mm.

Ceiling ceilings made of timber are almost completely identical to interfloor ones, with the only difference being that the thickness of the beams can be less, and the step between them is several centimeters larger.

prefabricated timber

Let's say you need logs of 150x250 mm in size, but there are no such sizes on sale, but there are always plenty of boards with dimensions of 50x250 mm at any lumber base. In order to get a beam of the desired size, it is enough to buy 3 of these boards and fasten them together.

As fasteners, it is better to use not nails, but wood screws, because over time the wood dries out, and the nails do not hold the boards together so firmly.

As the instructions for self-manufacturing prefabricated logs, if you use them for basement or basement floors, then before tightening with self-tapping screws, it is worth treating each board with an antiseptic.

This will prevent the appearance of wood pests and significantly increase the life of the entire floor. If you use prefabricated timber for interfloor ceilings, then no pre-treatment of the boards is required.

The admissibility of using this type of lag is obvious and not questioned. This material is also environmentally friendly, like conventional timber, since no adhesives are used during assembly.

Attention!
The load-bearing capacity of prefabricated timber is even higher than that of solid lumber, while the cost is somewhat lower.
From the foregoing, it becomes clear that in some cases the use of prefabricated elements is even more preferable than solid ones.

Glued laminated timber

This type of lumber is an acceptable alternative if the desired solid logs cannot be found, or their price is high enough for you, and it is not possible to make a prefabricated structure yourself.

Floor beams in wooden house from glued beams are distinguished by good strength and resistance to stress, but they also have some disadvantages.

1. In view of the fact that adhesives are used in their manufacture, such material can no longer be called environmentally friendly.
2. In their manufacture, a fairly large percentage of low-quality lumber is used. Significant shrinkage is possible after several years of operation, which means that a laminated veneer lumber floor may "lead" over time.
3. And the main disadvantage of glued beams is their limited service life, which is determined by the manufacturer at 20 years.

The main condition for any construction is the simplicity and reliability of the design, but in order to achieve this, it is necessary to make the correct calculations of the strength of the material. Since a wooden frame is used for the construction of wooden houses, an attic or an attic, its choice must be approached with all responsibility, because durability, reliability and stability will directly depend on what load the beam can withstand (100x100, 50x50, 150x150, etc.) built house.

For the correct calculation of the load withstood by the beam, special programs or formulas can be used, but in this case, additional loads will have to be introduced into the calculations, which directly affect the strength of the structure. In order to calculate the load on the beam correctly, you will have to indicate the snow and wind effects that are present directly in the building region, as well as the characteristics of the materials used (thermal isover, beam, etc.).

In this article, we will consider what kind of load a beam with a size of 50x50, 100x100, 150x150 can withstand in various structures, such as a timber house, a wooden floor and a truss system, and as an example, we will analyze the latter, because this is the most responsible and difficult work.

In the photo you can see the varieties of timber, which differ not only in shape, but also in the load capacity.

What will be discussed:

How does the cross-section of a log house affect its reliability?

When creating a roof, a prerequisite for its reliability is the cross section of the timber used and the type of wood, which affects durability.

Performing the calculation with your own hands, you will need to take into account such indicators as:

• what is the mass of all roofing building materials;
• the weight of the attic or attic finish;
• for rafter supports and beams, the calculated value is taken into account;
• the thermal and sedimentary effects of nature are taken into account.

In addition, you will need to specify:

• distance between beams;
• the length of the gap between the rafter supports;
• the principle of fastening the rafters and the configuration of its truss;
• the severity of precipitation and the effect of winds on the structure;
• other factors that may affect the reliability of the design.

All these calculations can be done manually using special formulas. But it will be simpler both in terms of time and quality to calculate the load of the beam using special programs, and even better when these calculations are performed by a professional.

What requirements must the beam meet?

So that the entire truss system is strong and reliable in quality building materials will have to take full responsibility. For example, there should be no defects on the beam (cracks, knots, etc.), and its moisture content should not exceed 20%. In addition, a log house of any size (50x50, 100x100, 150x150, etc.) must be processed protective equipment from shashel and other insects, rotting and fire.

Also, when choosing a material, you will have to take into account that additional loads may be applied to the timber, such as:

• Continuous load beam. These include directly the weight of the entire truss system, which includes: facing and roofing materials, heaters, etc. The data obtained for each material are summarized.
• Short-term loads can be of several types: especially rare, short-term and long-term effects. The first type includes incidents that happen very rarely (earthquakes, floods, etc.). Wind and snow impacts, the movement of people repairing the roof, etc. are short-lived. All other impacts that occur within a certain period of time are long-term loads.

We determine the wind and snow load on the beam

To determine what load the beam can withstand (100x100, 150x150.50x50, etc.) under wind and snow exposure, you can use certain tables.

To determine the snow effect on rafters of different sections, the formula S \u003d Sg * µ is used.

• Sg - is the calculated weight of snow lying on the ground, which affects 1 m².

Important! This value cannot be compared with the roof load.

• µ is the value of the load on the roof surface, which varies from horizontal to sloping. This coefficient can be various meanings, it all depends on the slope of the roof.

With a surface slope of up to 25 degrees, µ takes on the value 1.

When the slope of the roof is in the range of 25-60 degrees, µ is 0.7.

With a slope of 60 degrees or more, the coefficient µ is not taken into account because it practically does not affect the truss system.

In addition to the snow load, before the construction of the truss system, the wind load on the wooden beam is calculated 50 by 50, 100x100, etc. If these indicators are not taken into account, as a result, everything can end in failure. Table values ​​and the formula W=Wo*k are used for the calculation.

Wo - is a tabular value of the wind load for each individual region.

k is the wind pressure, which has different meanings as altitude changes. These indicators are also tabular.

The table of beam loads shown in the photo when exposed to the elements is easy to use, you just need to remember that the 1st column shows the values ​​\u200b\u200bfor the steppe, desert regions, rivers, lakes, forest-steppe, tundra, seashores and reservoirs. The next column contains data related to urban areas and areas with 10 meter obstacles.

Important! In calculations, it is desirable to use information on the direction of wind movement, because this can make an important correction to the results.

By what rules is the desired cross section of the beam calculated?

Several parameters influence the selection of the log section for the truss system:

• what is the length of the rafter construction;
• the distance between each subsequent beam;
• the results of load calculations for the corresponding area.

To date, for each specific area, there are special tables with data already entered on the load values ​​for truss systems. An example is the Moscow region:

• in order to install a Mauerlat, you can use a bar with a section of at least 100x100, 150x100 and 150x150;
• timber 200x100 can be used for diagonal valleys and rafter supports (legs);
• runs can be created from wood 100x100, 150x100 or 200x100;
• a log house 150x50 will be the best solution for tightening;
• it is best to use a log house 150x150 or 100x100 as racks;
• a 150x50 rafter is suitable for a cornice, struts or filly;
• crossbars are best installed from rafters 150x100 or 200x100;
• As a sheathing or frontal, you can use a board of at least 22x100.

The above data are optimal, that is, less than this value, the material cannot be used. Also, all dimensions are in millimeters.

Summarize

To create a reliable and durable wooden structure, you need to carefully calculate all possible loads, after which you only need to purchase timber. If you have doubts about the correctness of the calculations, it is best to use the services of a professional or use a special program that will calculate permissible load on a beam (150x150, 100x100, etc.).

In private housing construction, there are 3 types of structures that must be selected according to the calculation. This is the foundation, floor and roof. Of course, you can do this without calculation, relying on your own experience or the experience of your friends and acquaintances. But then you risk your security or your "wallet". In other words, structures may not withstand the loads that they bear, or they are built with more reliability than required, and extra money is spent on this.

The calculation of beams should occur in the following sequence:

1. Collection of loads on the beam.

For those who need to calculate the beam of an interfloor or attic floor and who do not want to collect loads, there is a universal method. It lies in the fact that for the interfloor overlap, you can take the design load equal to 400 kg / m2, and for the attic - 200 kg / m2.

But sometimes these loads can be greatly overestimated. For example, when building a small country house, on the second floor of which there will be two beds and a wardrobe, the load can be taken and 150 kg / m2. This is solely at your discretion.

2. Choice of design scheme.

The calculation scheme is selected depending on the method of support (rigid mounting, hinged support), type of loads (concentrated or distributed) and the number of spans.

3. Determination of the required moment of resistance.

This is the so-called calculation for the first group of limit states - by bearing capacity(strength and stability). Here, the minimum allowable cross-section of a wooden beam is determined, at which the operation of structures will occur without the risk of their complete unsuitability for operation.

Note : Design loads are used in the calculation.

4. Determination of the maximum allowable beam deflection.

This is a calculation for the second group of limit states - according to deformations(deflection and displacement). According to this calculation, the cross section of a wooden beam is determined depending on the maximum deflection, if it is exceeded, their normal operation will be disrupted.

Note : normative loads are used in the calculation.

Now more specifically. In order to calculate a wooden floor beam, you can use a special calculator or an example below.

An example of the calculation of a wooden floor beam.

The calculation is carried out in accordance with SNiP II-25-80 (SP 64.13330.2011) "Wooden structures" and the use of tables.

Initial data.

Material - oak 2nd grade.

The service life of structures is from 50 to 100 years.

The composition of the beam is solid rock (not glued).

Beam spacing - 800 mm;

Span length - 5 m (5,000 mm);

Impregnation with flame retardants under pressure - not provided.

Estimated load on the floor - 400 kg / m2; per beam - q p \u003d 400 0.8 \u003d 320 kg / m.

Normative load on the floor - 400 / 1.1 = 364 kg / m2; per beam - q n \u003d 364 0.8 \u003d 292 kg / m.

Calculation.

1) Selection of the design scheme.

Since the beam rests on two walls, i.e. Since it is pivotally supported and loaded with a uniformly distributed load, the design scheme will look like this:

2) Strength calculation.

We determine the maximum bending moment for this design scheme:

M max \u003d q p L 2 / 8 \u003d 320 5 2 / 8 \u003d 1000 kg m \u003d 100000 kg cm,

L - span length.

We determine the required moment of resistance of a wooden beam:

W required \u003d γ n / o M max / R \u003d 1.05 100000 / 121.68 \u003d 862.92 cm 3,

where: R \u003d R and m p m d m in m t γ c \u003d 130 1.3 0.8 1 1 0.9 \u003d 121.68 kg / cm 2 - calculated wood resistance, selected depending on the design values ​​for pine, spruce and larch at a moisture content of 12% according to SNiP - table 1 and correction factors:

m p \u003d 1.3 - transition coefficient for other types of wood, in this case adopted for oak (table 7).

m d \u003d 0.8 - correction factor taken in accordance with clause 5.2. , is introduced in the case when permanent and temporary continuous loads exceed 80% of the total voltage from all loads.

m in \u003d 1 - coefficient of working conditions (table 2).

m t \u003d 1 - temperature coefficient, 1 is adopted, provided that the room temperature does not exceed +35 ° С.

γ ss \u003d 0.9 - wood service life coefficient, selected depending on how long you are going to operate the structures (table 8).

γ n/a = 1.05 - coefficient of responsibility class. Accepted according to Table 6, taking into account that the responsibility class of the building is I.

In the case of deep impregnation of wood with flame retardants, one more coefficient would be added to these coefficients: ma = 0.9.

You can find other less important coefficients in clause 5.2 of SP 64.13330.2011.

Note: the listed tables can be found here.

Determination of the minimum allowable beam section:

Since most often wooden floor beams have a width of 5 cm, we will find the minimum allowable beam height using the following formula:

h \u003d √ (6W required / b) \u003d √ (6 862.92 / 5) \u003d 32.2 cm.

The formula is selected from the condition W of the beam = b h 2 /6. The resulting result does not satisfy us, since the overlap with a thickness of more than 32 cm is no good. Therefore, we increase the width of the beam to 10 cm.

h \u003d √ (6W required / b) \u003d √ (6 862.92 / 10) \u003d 22.8 cm.

Accepted beam section: bxh = 10x25 cm.

3) Calculation by deflection.

Here we find the deflection of the beam and compare it with the maximum allowable.

We determine the deflection of the accepted beam according to the formula corresponding to the accepted design scheme:

f \u003d (5 q n L 4) / (384 E J) \u003d (5 2.92 500 4) / (384 100000 13020.83) \u003d 1.83 cm

where: q n \u003d 2.92 kg / cm - standard load on the beam;

L = 5 m - span length;

E \u003d 100,000 kg / cm2 - modulus of elasticity. It is taken equal in accordance with paragraph 5.3 of SP 64.13330.2011 along the fibers 100000 kg/cm2 and 4000 kg/cm2 across the fibers regardless of the rocks when calculating for the second group of limit states. But in fairness, it should be noted that the modulus of elasticity, depending on humidity, the presence of impregnations and the duration of loads, only in pine can vary from 60,000 to 110,000 kg / cm2. Therefore, if you want to play it safe, you can take the minimum modulus of elasticity.

J \u003d b h 3 / 12 \u003d 10 25 3 / 12 \u003d 13020.83 cm 4 - moment of inertia for a rectangular board.

Determine the maximum deflection of the beam:

f max \u003d L 1/250 \u003d 500/250 \u003d 2.0 cm.

The maximum deflection is determined according to table 9, as for interfloor floors.

Compare deflections:

f beams = 1.83 cm< f max = 2,0 см - условие выполняется, поэтому увеличения сечения не требуется.

Conclusion: a beam with a section bxh = 10x25 cm fully satisfies the conditions for strength and deflection.

Wooden floor beams provide not only the strength of the horizontal structure. Overlapping is designed to give rigidity to the entire building. It is for this reason that the choice of load-bearing elements and their installation should be given special attention.

Pros and cons of wood flooring

To install the ceiling with your own hands, you need to prepare. The floor in the house should be based on a solid and rigid structure. Before starting work, you will have to study the requirements for the elements, the features of their calculation and the types of sections.

The following advantages of wood flooring can be distinguished:

• attractive appearance, the ability to make a wooden floor without additional measures;
• light weight, reducing the load on walls and foundations, saving on construction;
• the possibility of carrying out repairs during operation;
• speed of installation, performance of work without additional machines and mechanisms.

Wooden beams do not weigh down the structure and are quickly mounted

But it is also worth highlighting the disadvantages:

• combustibility of wood, the need for special impregnation with flame retardants;
• lower strength compared to reinforced concrete or metal elements;
• shrinkage and deformation during temperature and humidity changes;
• susceptibility to rotting, fungus and mold at high humidity, it is necessary to carry out antiseptic treatment at the construction stage and periodically during the service life.

wood flooring requirements

Wooden floor beams must meet the following requirements:

• correspondence of the cross-sectional dimensions to the load, span and step, this requires the calculation of beams;
• good strength and rigidity;
• Fire safety;
• absence of serious defects of wood and damages.

For work it is necessary to prepare high-quality material

There are also certain requirements for the material from which the beams are made. It is recommended to choose softwood. It contains a lot of resin, so it better resists various microorganisms. The best material is those trees that have grown in harsh conditions. Their stem density is higher. For this reason, it is worth buying pine or spruce, which grew in the northern regions of the country.

You also need to pay attention to the preparation time. The best period is at the end of winter. At this time, the tree is in a dormant state, there is less juice in it, therefore, the moisture content of the material will be less.

What are wooden floors

Wooden floor beams are used for almost all levels of the house. The beam frame must be provided for the following types of construction:

• basement or basement floor (floor of the first floor);
• interfloor overlap;
• attic cover.

The thickness of the supporting beam for the attic is from 10 to 20 cm

The type depends on the normalized payload, which is taken into account wooden beams floors. Also, the difference will be in the thickness of the insulation and its need.

Between the beams above the basement, usually 5 to 15 cm of mineral wool, polystyrene foam or extruded polystyrene foam are laid. In interfloor structures, it will be enough to provide a couple of centimeters for sound insulation. A cold attic requires the most material. Here the thickness can be from 10 to 20 cm. The exact values ​​\u200b\u200bdepend on the climatic area of ​​\u200b\u200bconstruction.

Between the beams of the basement are laid mineral wool

Sometimes the basement ceiling is preferred not to be made of wood, but of metal and reinforced concrete. In this case, an I-beam or channel is used as load-bearing beams, and concrete is poured into the formwork from a profiled sheet. This option will be more reliable with the likelihood of flooding. It will also better resist dampness from the basement.

What are the beams

There are several signs by which the classification of wooden floor beams is carried out: by size, material, type of section. The length of the floor beams depends on the distance between the walls. To this value you need to add a margin for support on both sides. Optimally, it is necessary to provide for 200-250 mm.

According to the material, the elements are divided into the following types:

• from a solid bar or board;
• from glued timber.

Bent beams are made from glued beams

The latter are significantly more expensive. But on the other hand, such material is suitable for covering large spans. A regular beam can work at 4-6 m, while a glued beam copes well with distances of 6-9 m. Glued laminated timber practically does not shrink, is fireproof and resistant to moisture. It is possible to produce not only linear elements, but also bent. A significant drawback of such a material will be the presence of non-natural components (glue).

The beam section can be of the following types:

• square;
• rectangular;
• I-beam.

The latter has broadened elements at the top and bottom. In the middle of the section, it is reduced to the maximum possible size. This option allows you to rationally use wood and reduce its consumption. But to make such an element is not easy. For this reason, the I-beam is not so often used in construction.

Most often, a rectangular bar is used.

The best option would be a rectangle. In this case, the long side is located vertically, and the short side is horizontal. This is due to the fact that an increase in height has a better effect on strength than width. Installing a beam from a board flat is almost useless.

The most unfavorable of the presented can be considered a square section. It is the least fitted to the diagram of forces in the element.

You can also use logs to cover. But this option has not gained popularity. The cross section of the board is much more profitable and easier to install, so it is used much more often.

Calculations

The calculation of the section will allow you to have no doubt about the strength and rigidity of the structure. This determines the maximum length that is allowed for any section. To perform the calculation, you need the following data:

• the length of the wooden floor beam (more precisely, the distance between the bearing walls);
• the distance between the beams (their step);

For the calculation, you need to know the distance between the beams, the span width and the load on the structure

The load consists of two values: permanent and temporary. The constant includes the mass of the beams themselves (so far preliminary), insulation, ceiling filing, rough and clean floor. A temporary load is a mass of people and furniture. According to regulatory documents for residential premises, it is taken equal to 150 kg / m2. For the attic, you can take less, but it is recommended - the same. This will not only provide a certain margin of safety, but will also make it possible in the future to convert your attic into an attic without reconstructing the load-bearing elements.

The beam frame should be calculated according to the following formulas:

• Mmax = (q*l2)/8;
• Wreq = Мmax/130.

In these formulas, q is the load per sq. m of overlap, which includes a lot of structures and 150 kg of useful value. In this case, these values ​​\u200b\u200bmust be multiplied by the distance between the beams. This is due to the fact that the calculations require a load per linear meter, and initially the value is calculated per square meter. l2 - the distance between the bearing walls on which the run rests, taken in a square.

Knowing Wreq, you can choose the overlap section. W = b*h2/6. Knowing W, one can easily write an equation with one unknown. Here it is enough to specify one geometric characteristic b (width of the section) or h (its height).

Most often, a wooden beam already has a known width. It is more convenient to make it from a board 50 or 100 mm wide. You can also consider the option with a composite section. It is made from several boards 50 mm thick.

Calculation in this case find the required height of the element. But there are cases when you need to fit into a certain floor pie so as not to reduce the height of the premises. In this case, as a known value, the height of the section is added to the equation, and the width is found. But the lower the height, the more uneconomical the floor frame will be.

To tighten two or three boards together, it is convenient to use metal studs. In this case, when tightening the nuts, wider washers must be used. They prevent metal from being pressed into more soft wood. It is imperative to provide insulation between wood and steel fasteners. To do this, you can use a material such as TECHNOELAST brand EPP.

Wooden blocks must be waterproofed before installation.

Before using wooden elements, they are treated with an antiseptic composition. This is necessary to prevent mold and decay. It is also recommended to perform fire retardant treatment, which will increase fire safety. When the runs are supported on a brick or concrete wall, their ends are wrapped with technoelast, linocrom, hydroisol or roofing material.