Many owners of suburban areas in the construction of houses choose wooden floors. This is due to the fact that wood is an environmentally friendly material that has an aesthetic appeal and natural naturalness. In most cases, the installation of a wooden floor requires a lag - wooden beams laid on the main floor. When installing it is very important to choose the right distance between the floor lags.
Scheme of laying lags.
Purpose and methods of mounting the lag
Logs (beams) perform several very important functions:
- increase in noise and heat insulation of the base;
- creation of a ventilated space under the floor, in which engineering communications can be laid;
- correct redistribution of the load on the subfloor;
- creation of an even and solid base for the installation of the finishing flooring.
Scheme for calculating the distance between the lags.
In most cases, logs are made from wooden beams of coniferous and hardwood. Sometimes metal, reinforced concrete and polymer analogues are installed, but this is not economically viable. In the absence of a wooden beam, logs can be constructed from several boards knocked together. In this case, they fit on the ribs.
When choosing a beam for the manufacture of logs, the following recommendations should be followed:
- Choose inexpensive wood (fir, pine or spruce). If the room in which the floor is mounted will have high humidity (for example, a bathhouse), then hardwood should be used.
- To save the budget, you can choose building materials of 2 or 3 grades with a moisture content of 17-22%.
- Beams must have a rectangular section of a certain size.
- The dimensions of the beam should be chosen based on the span, that is, from the distance between the beams of the lower interchange.
How to choose the right lag section?
Scheme of installation of the subfloor on the logs.
The cross section of the beam for the manufacture of logs is determined by 2 factors: the span length between the support points (pillars, linings or transverse beams) and the maximum load that the floor will be under during its operation (for a dwelling it is no more than 300 kg / m 2).
The cross section of the beams should be rectangular with a width that is a multiple of 1.5 and a height of 2, that is, the aspect ratio in the section should be 1.5x2. When laying beams, the large side should be vertical. This will allow to achieve maximum rigidity of the structure with minimum volumes of wood and, accordingly, minimum costs. Table 1 shows the dependence of the cross section of the beam on the dimensions of the span.
Table 1
Also, the cross section of the beam will depend on the thickness and strength of the flooring. When installing the floor, you should pay attention to the layer of heat-insulating material.
Between the final floor and the insulation laid between the lags, there must be a small gap for natural air ventilation with a width of at least 2 mm.
This means that the beam must be purchased taking into account the size of the ventilation gap.
Log docking options.
The use of columnar supports allows you to save on the thickness of the wood. So, with a log length of 400 cm, just one support installed in the middle will allow you to reduce the cross section from 180x100 to 110x60, which in the end will significantly affect your budget.
Calculation of the distance between the lags when installing the floor
The distance between the lags (step) is a very important parameter, on the basis of which calculations are made of the required amount of building material. When thick boards with good strength are used as a finishing floor, beams can be mounted relatively rarely. If the flooring is carried out with thin elements, then the step must be reduced. Table 2 shows the dependence of the distance between the lags on the thickness of the finish coating.
table 2
The data shown in Table 2 are approximate. For a more accurate calculation of the step, an example can be given when it is necessary to find out what distance should be between the beams when constructing a floor in a room 9 m long. In this case, a bar with a section of 180x100 mm is used, and boards 30 mm thick are used as a finishing coating.
Scheme of laying plywood on logs.
Since the thickness of the board is 30 mm, then, according to table 2, the step should be 0.5 m. The total number of beams will be indicated as k. Therefore, the width of all lags will be equal to 100 * k (mm). The first bars will be laid at a distance of 30 mm from the wall. Based on this, the step between them is equal to k-1, and the distance between all elements is equal to 0.5*(k-1).
To find out the step between the beams, you need to create an equation: the length of the room \u003d the width of the beam + the distance between all the lags + the distance from the walls. The result is: 9 m = 100 mm * k + 0.5 * (k-1) m + 30 mm * 2. Bringing all the values into a single system of calculation, you get: 9 \u003d 0.1 * k + 0.5 * (k-1) + 0.03 * 2.
By solving this equation, you will see:
- 9 \u003d 0.1 * k + 0.5 * k - 0.5 + 0.06;
- 9 + 0.5 - 0.06 = 0.1*k + 0.5*k;
- 9.44 \u003d 0.6 * k;
- k = 15.7 pcs.
The number of beams must be an integer, so the resulting value should be rounded up. That is, to construct the floor, it is necessary to prepare 16 logs. The sum of all the gaps between the lags will be equal to: 9 - 0.06 - 16 * 0.1 = 7.34 m. Dividing this value by the number of gaps, you get: 7.34 / 15 = 0.489 m. For the above example, it is necessary to set the lags through every 0.489 m or 48.9 cm.
Scheme of floor insulation with lags.
Follow the tips to make the resulting design reliable:
- The base on which the floor is supposed to be mounted must be thoroughly cleaned of debris and treated with a deep penetration primer.
- All wooden elements should be treated with an antiseptic, which can increase the operational life of a wooden structure.
- It is necessary to lay the beams along the window with gaps between the walls of 3-4 cm.
- After mounting the lag, the surface is checked for horizontal evenness with a long level. If there are no gaps between the level and the beams, then all the work has been done correctly.
The reliability of the entire structure depends on the section of the lag and the step between them. Therefore, the choice of these parameters should be taken seriously.
