What is needed to calculate the load on the timber? Wooden beams on floors for a large span How much vertical load can the timber withstand 150

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

To correctly calculate the load withstand by the bar, you can use special programs or formulas, but in this case, additional loads will have to be introduced into the calculations, which directly affect the strength of the structure. To calculate the load on the timber correctly, you will have to indicate the snow and wind effects present directly in the building region, as well as the characteristics of the materials used (heat exchanger, timber, etc.).

In this article, we will consider what kind of load a 50x50,100x100,150x150 timber can withstand in various structures, such as a timber house, a wooden floor and a rafter 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 withstand load.

What will be discussed:

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

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

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

• what mass do all roofing building materials have;
• weight of attic or attic finishing;
• 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 have to indicate:

• 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 can affect the reliability of the structure.

All these calculations can be performed with your own hands using special formulas. But it will be simpler both in time and in quality to calculate the load of the timber using special programs, and even better when these calculations are performed by a professional.

What requirements should the timber meet?

In order for the entire rafter system to be strong and reliable, the quality of building materials will have to be approached with all responsibility. For example, the timber should be free from defects (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 treated with protective agents against woodworm and other insects, decay and fire.

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

• Continuous beam loads. These include directly the weight of the entire rafter system, which includes: facing and roofing materials, insulation, etc. The data obtained for each material are summed up.
• Short-term loads can be of several types: especially rare, short-term and long-term effects. The first type includes accidents 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 in a certain period of time are long-term loads.

Determine the wind and snow load on the timber

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

To find out the snow effect on the rafters of different sections, the formula S = 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 inclined. This coefficient can take different values, it all depends on the slope of the roof.

When the slope of the surface is up to 25 degrees µ takes on the value 1.

When the roof slope is between 25-60 degrees, µ is 0.7.

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

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

Wо - is a tabular value of wind load for each separate region.

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

Shown in the photo, the table of the loads of the timber under the influence of the elements, is simple to use, you just need to remember that in the 1st column values ​​are given for steppe, desert regions, rivers, lakes, forest-steppe, tundra, sea shores and reservoirs. The next column contains data related to urban areas and areas with 10 meter obstacles.

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

What are the rules for calculating the required section of the bar?

Several parameters affect the selection of the cross-section of a log house for a rafter system:

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

Today, for each specific area, there are special tables with already entered data on load values ​​for rafter systems. The Moscow region can be cited as an example:

• so that the Mauerlat installation can be used a bar with a cross 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;
• log house 150x50 will be the best solution for tightening;
• it is best to use a log house 150x150 or 100x100 as racks;
• rafter 150x50 is suitable for cornice, struts or filly;
• the crossbars are best installed from the rafters 150x100 or 200x100;
• As a cladding or frontal, you can use a board of at least 22x100.

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

Summarize

To create a reliable and durable wooden structure, you need to carefully calculate all possible loads, and then only purchase a bar. 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 the permissible load on the timber (150x150, 100x100, etc.).

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

Wooden floor beams - dimensions and loads

We made a wooden floor in a log house, and the floor is shaking, sagging, a "trampoline" effect has appeared; we want to make wooden floor beams of 7 meters; you need to overlap a room with a length of 6, 8 meters so as not to rest the logs on intermediate supports; what should be the floor beam for a span of 6 meters, a house from a bar; what if you want to make a free layout - such questions are often asked by members of the forum.

Maxinova FORUMHOUSE user

My house is about 10x10 meters. On the ceiling, I "threw" wooden logs, their length - 5 meters, section - 200x50. The distance between the lags is 60 cm. During the operation of the floor, it turned out that when children are running in one room and you are standing in another, there is a fairly strong vibration on the floor.

And this case is far from the only one.

elena555 FORUMHOUSE user

I can't figure out what kind of beams are needed for the floors. My house is 12x12 meters, 2-storey. The first floor is made of aerated concrete, the second floor is attic, wooden, covered with a 6000x150x200mm beam, 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 a shaking sound.

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 kind of load a wooden log of a particular section can withstand. And then think over, having determined the load for the floor beams, which rough and final floor covering will need to be done; how the ceiling will be hemmed; whether the floor will be a full-fledged living space or a non-residential attic above the garage.

Leo060147 FORUMHOUSE user

1. Self-weight load of all structural elements of the floor. This includes the weight of beams, insulation, fasteners, flooring, ceiling, etc.
2. Operational load. The service 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 with the arrival of guests, noisy celebrations, rearrangement of furniture, 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 over everything - down to what kind of furniture you plan to install, and whether there is a possibility in the future of installing a sports simulator, which also weighs more than one kilogram.

For the load acting on wooden floor beams of great length, the following values ​​are taken (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 / m2 is the load from the floor's own weight, and 100 kg / m2 is the standard load.

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

• For intermediate floors and attic floors, the total load is taken at the rate of 350-400 kg / sq.m.

Overlapping boards 200 to 50 and other running sizes

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

Most often, in the construction of wooden floors, boards and beams of the so-called running sizes are used: 50x150, 50x200, 100x150, etc. Such beams meet the standards ( after checkout), if it is planned to block the opening of no more than four meters.

For an overlap with a length of 6 meters or more, the sizes 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 running dimensions.

A rule should be remembered: the strength and rigidity of the floor depends 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 safety and allowable deflection. This ensures normal and safe operation of the floor.

50x200 - overlap for an opening of 4 and 5 meters.

To calculate the load that the floor will withstand, you must have the appropriate knowledge. In order not to delve into the formulas of resistance (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 FORUMHOUSE user

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

These calculators are easy to use. To make the calculations for the required values, it is enough to enter the dimensions of the lag and the length of the span, which they should overlap.

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

Roracotta FORUMHOUSE user

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

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

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

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

Table 3. Here are 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 FORUMHOUSE user

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

Self-made wooden glued beams

One of the solutions for bridging long spans is the use of wooden beams in the floors. Consider a span of 6 meters - which beams can withstand the heavy load.

By the type of cross-section, a long beam can be:

• rectangular;
• I-beam;
• box-shaped.

There is no consensus among self-builders which section is better. If you do not take into account purchased products (prefabricated I-beams), then the first place is the simplicity of production in the "field conditions", without the use of expensive equipment and tooling.

Just grandfather FORUMHOUSE user

If you look at the 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 accounts for no more than 10-15% of the metal. This is done by calculation.

Which board to use for beams

According to the strength of materials: the larger the cross-section of the "shelves" and the further they are spaced from each other in height, the more loads the I-beam will withstand. For a self-builder, the optimal technology for making an I-beam is a simple box-shaped structure, where the upper and lower "shelves" are made of a plank 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 (only not black, they do not work for cutting) and must be set 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 heavy load. Additionally, an I-beam for a 6 meter ceiling can be installed 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 the edge (take boards in 150x50 or 200x50), as a result, the cross-section of the beam will be 300x100 or 400x100 mm. Boards are planted on glue and pulled together with pins or planted on wood grouses / dowels. Plywood can also be screwed or nailed to the side surfaces of such a beam, having previously greased 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 cover the span of 8 meters.

For this, the member of the forum purchased sheets of OSB 12 mm thick, cut them lengthwise into five equal parts. Then I bought a board 150x50 mm, 8 meters long. With a dovetail cutter I chose a groove 12 mm deep and 14 mm wide in the middle of the board, so that a trapezoid with a downward extension was obtained. OSB in grooves Taras174 glued with a polyester resin (epoxy), having previously "shot" a strip of fiberglass 5 mm wide with a stapler to the end of the plate. This, according to the forum member, would strengthen the design. To speed up drying, the glued area was heated with a heater.

Taras174 FORUMHOUSE user

On the first beam, I practiced “getting my hand in”. I made the second one in 1 working day. At cost, taking into account all materials, I include a solid board of 8 meters, the cost of a beam is 2,000 rubles. for 1 pc.

Despite the positive experience, such a "squatter" has not escaped several critical remarks expressed by our experts. Namely.

One of the most popular solutions for the construction of interfloor floors in private houses is the use of a supporting structure made of wooden beams. It must withstand the design loads without bending and, moreover, not collapsing. Before proceeding with the construction of the floor, we recommend using our online calculator and calculating the main parameters of the beam structure.

Floor beams or ceiling beams are the supporting structure of the house, therefore, before you start to independently mount the floor beams in the log cabin of a house or bathhouse, we strongly recommend that you be especially careful approach the choice of material and calculate correctly floor structure.

For the manufacture of floor slabs, it is best to use a dry, first-grade material impregnated with a fire-retardant composition.

Beams are most often embedded in:

How to ensure the strength of the floors and convenient installation

Having previously marked the places where the beams are cut in, cuts are made in the log and tightly beams are inserted into them at a distance of about 600 mm from each other. This distance between the beams provides the necessary strength of the floors. Most types of insulation are produced with a width of exactly 600 mm, which ensures convenient installation of thermal and noise insulation. With this method of mounting the lags, there is no need to attach them additionally to the wall.

Floor joists can also be mounted after assembling the log house, fixing them to the wall using special brackets and self-tapping screws. The construction market now hasa huge variety of fasteners. But more correct and reliable installation method is the first!

Questions arising during the construction process

During construction log house , baths from a log Naturally, questions arise: What section should the floor beams (floor, ceiling) be embedded in? What kind of load can wooden logs (beams) withstand? What is the maximum length of the beam possible for which section of the board, timber, log?

Based on the table below, it is easy to calculate the cross-section of the log, depending on its length. The data are given for standard spans with a width of 2 to 6 meters, with a frequency of logging through 600 mm (distance between logs 600 mm) Design load 300 kg per 1 sq. meter. The table shows the breaking loads for these lags in kg per square meter.

Simply put, the numbers on a colored background are the load in kilograms per 1 m2, at which the overlap will simply break. But in order for the floor not to "spring" there is also an indicator of the bending of the beam. Blue background - the floor will not "spring", yellow - the maximum allowable, and the red background of the floor will bend under a load of 300 kg more than the allowable norm.

Table for calculating the breaking load (kg / m2) on the logs (beams) of the floors of a log house.

In blue highlighted in the table safety values

In yellow the values ​​in the table are highlighted maximum allowable for beams deflection for these conditions

In red highlighted values inadmissible in deflection(more than twice the permissible norm) of beams for these conditions.

Note: Additional rigidity to the beam can also be made by splicing two or more thick boards together.