Wooden floors. Calculation of wooden beams

Despite the variety of materials used for the manufacture of floors in houses, wood remains the most popular for small residential buildings with two or three floors. This is due to their special properties:

  • hardwood floors have a small weight compared with counterparts from reinforced concrete and especially monolithic, and at the same time maintain good performance;
  • it is easy to process, therefore installation work on installation is carried out without the use of special equipment, which is impossible for other materials;
  • the design feature of wooden floors allows the use of any insulating materials;
  • prefabricated hardwood floors are the best basis for finishing the ceiling or ceiling;
  • wood is still the most environmentally friendly and safe material.

The only drawback of its use is the limitation in permissible load, which reduces the scope of their application.

Hardwood floors

Types of floors in the house

Depending on the layout, the presence of the basement, the heating and the number of floors, the following wooden floors can be used:

  • basement or basement;
  • interfloor or mansard;
  • attic

Each overlap, depending on the type of room, the planned temperature and humidity levels, performs its function. To do this, during installation, the required insulation is laid, which prevents sound, moisture and heat from passing and allows you to reliably separate the rooms in the house.

Overlap structure

The construction of wooden floors depends on their functional purpose, but they all have a very similar structure. Their main component, which serves as the basis for other elements, are wooden beams, fixed to the supporting structures of the house, that is, to the walls. All future load during the operation of the house will fall on them. Therefore, the calculation of wooden floor beams occupies an important place in the preparatory stage.

For the manufacture of beams used wooden beams from coniferous trees, almost not bending over time, as opposed to hardwood.

On the installed beams fixed draft or auxiliary floor. For this purpose, plywood, sheets of OSB or particleboard are used, on top of which, after completion of the work, the topcoat, floor or ceiling, is attached. The space formed between the subfloor and the ceiling is filled with different insulators depending on the parameters of the room.

Wooden flooring

Overlap options for different rooms

Depending on the type of room, wooden floors may have a different structure. There are three possible options:

  • for socle ceilings, where the temperature difference and high humidity are characteristic, the use of vapor barrier, increased thermal insulation layer and special reflective film or foil is required;
  • for interfloor overlappings, which are characterized by a simpler structure, in connection with a uniform temperature regime and a stable humidity level, noise isolation is required;
  • for attic floors, if they are not heated, the same filling is used as for the socles, with the difference that the location of the insulators occurs in the reverse order due to the direction of the cold effect.

More details about the structure of different floors will be written below.

Types of designs

Wooden floors in the house, depending on the size of the opening, can have a different design that must withstand the specified loads and provide for the placement of technological elements, including those that impart rigidity, as well as various fixing accessories.

Hardwood floors in the house

Today, wooden floors are constructed using three main types of structures:

  • with the help of beams, the oldest of all forms, in which the reliability of the structure is ensured by beams from a square or rectangular array, arranged in increments from 60 cm to 1.0 m;
  • using ribs in which stiffness is created by a board up to 7 cm thick and not less than 20 cm wide, laid on an edge with a step of not more than 60 cm;
  • beam-ribbed, used for spans up to 15 m and consisting of beams and perpendicularly installed ribs attached to them.

Below are the indicators of each type of structures.

No. pp

Type of overlap

Span overlap

standard, m

maximum m












Thus, the type of floor construction is determined for each aperture individually.

Methods of mounting the beam to the wall

To create a robust design all beams must be firmly fixed in the bearing walls. This can be done in several ways. Some are used, like the hardwood floors themselves, for several centuries, others have become possible relatively recently.

The first way istraditional.It is used for brick houses or built of timber. The beams are placed inside the wall in a specially made niche to a depth of 10 to 15 cm, subject to several rules:

  • recommended depth is 2/3 of the thickness of the load-bearing wall;
  • the part of the beam in contact with the walls of the niche is covered with two layers of roofing felt;
  • end parts are cut at an angle of about 60 ° to allow air to reach the tree;
  • the distance between the beam and the walls of the niche is not less than 5.5 cm;
  • the beam rests on a wooden substrate treated with an antiseptic;
  • empty space is sealed with insulation;
  • the sides are coated with cement mortar;
  • every fifth (often) beam is additionally fixed to the wall with an anchor.

Wooden beams

If this method of fastening is used for wooden houses, the depth of the niche is no more than 7 cm with the obligatory laying of insulation between the wall and the beam. This reduces the likelihood of squeaking.

Second wayconsists of using special metal fasteners:

  • corners;
  • hose clamps;
  • brackets.

Selected fasteners are fixed to the wall and to the beam with screws or dowels. Sometimes a metal mount can be used to reinforce a structure.

This method allows you to install wooden beams faster and easier. At the same time, the traditional version still remains the most reliable.

Making calculations

Having decided on the type of construction, it is necessary to prepare a calculation of the wooden floor, first of all, the required number of beams, taking into account the required section and order of location. Accurately performed calculations will avoid unpleasant surprises during operation.

The length of the beam is calculated based on the size of the opening and the chosen method of attachment. For the traditional method, the total length includes the width of the aperture and the length of the parts placed in the niche. If fasteners are used, the length of the beam is equal to the width of the opening.

The distance between the beams, or step, is usually greater than 60 cm and less than 1 m, but can be placed more often. The quantity is calculated by dividing the length of the opening by the selected step with the mandatory displacement of the extreme beams from the wall by at least 5 cm.

Features of calculation

The beam section depends on three parameters:

  • opening width;
  • distance between beams;
  • planned load.

The average load is usually considered to be about 400 kg per square meter (its weight is about 200 kg and the permissible load is 200 kg). For non-residential premises, this value may be two times less.

The cross section is directly related to the width of the opening. The wider it is, the greater should be the value. It uses the rule of the ratio of the size of the aperture and the height of the beam, equal to 1/25. For example, for an aperture 5 m wide, a beam 200 cm high is needed. The most commonly used section is 5-16 cm wide and 14-24 cm long, rectangular in shape.

Calculation of wooden beams

Today, it is possible to calculate wooden floor beams using calculators that are freely available online or ready-made tables.

Calculation table sections in centimeters for a load of 400 kg per square meter

Opening, m / step, m









75 x 100

75 x 100

75 x 200

100 x 200

100 x 200

125 x 200

150 x 225


75 x 150

100 x 150

100 x 175

125 x 200

150 x 2001

150 x 225

175 x 250

After completing the calculations, you can begin to install hardwood floors.

Features of the installation of a basement floor

The installation of a basement slab can be made using any of the three types of structures described.

When installing on beams, an additional element is used - the cranial bar - 50 x 50 cm in size. It is attached to the beam at the same level from the bottom and the auxiliary coating is attached to it. Next, fit a layer of insulation (foam, polystyrene foam, wool) with a thickness of at least 10 cm, which is covered with vapor barrier, preferably in rolls.

Hardwood floors between floors

When the distance between the beams is more than 60 cm, lags are first installed to which the second draft coating is attached (plywood, OSB or chipboard). From above it is possible to lay the finishing floor covering.

For installation along the ribs, cranial bars are not used. The draft ceiling (plywood or OSB) is sewn directly to the ribs in increments of not more than 15 cm. The thermal insulation fits tightly between the ribs. Next fit the vapor barrier and the subfloor.

Beam-ribbed flooring is installed in the same way.

Features of the installation of interfloor overlap

When wooden floors are installed between floors, the main task is to ensure good sound insulation. The same temperature and lack of moisture can not use vapor barrier.In other words, if the budget is tightly restricted, you can backtrack on some of the mandatory rules.

When installing the overlap of the second floor on the beams, as a rule, logs are always additionally applied to which the draft floor of plywood or chipboard is attached. In addition, the use of cranial lumber is recommended.

Wooden attic floor

Hardwood floors between floors differ from all others by using rubber or cork substrate up to 5 mm thick, which is placed twice:

  • between beams and logs;
  • between the auxiliary floor and the finish.

For the installation of overlap on the edges of the crate is not applicable. Another feature is the implementation of crates for the ceiling of the first floor of wood, as the metal profile can produce noise during operation.

Features installation attic floor

As mentioned earlier, the wooden attic floor is very similar to the basement. The difference is in the movement of cold air, which in the attic moves from top to bottom, and in the basement - vice versa.

That is why most often one serious mistake is allowed. Instead of placing the vapor barrier under the insulation, it is placed on top, as on the basement floor.

For additional security, the insulation can be put waterproofing in rolls, protecting from direct moisture through the roof.

Operation and prevention

Properly selected, well-processed and well-laid beams can serve for a long time. But this does not exclude the need for periodic prophylaxis and testing. If there is a suspicion of damage to any structural member, it is recommended to replace or reinforce it in a timely manner.

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