Wooden logs are one of the most popular building materials, most often used in individual construction, so it is important to maintain the correct distance between the logs of a private house.
Logs are wooden beams that serve as the basis for fastening elements of the subfloor (boards, plywood sheets, chipboard, etc.). As a rule, for a lag, a timber obtained from coniferous trees (pine, spruce, fir, larch) is chosen.
As a rule, before installing the log, they are additionally treated with antiseptic and fire-fighting impregnation.
The moisture content of wood at the time of application of the log should not exceed 18-20%. For the log, a rectangular beam is chosen with a sectional aspect ratio of 1.5-2. The shorter side of the beam section is installed in the direction of applying the static load.
If you do not have a beam of the required section, then it is allowed to use stacked logs from boards or a beam of a smaller section than the calculated one. In this case, an increasing factor of 1.2 is applied. In order to ensure the evenness of the finished floor, it is necessary to mount the base logs according to the level.
Lags for the floor solve several problems:
LAG INSTALLATION OPTIONS
Most often there are three options for installing a log as a base for flooring.
Subfloor base
Logs can be used as a base for mounting a subfloor and are mounted on an existing ceiling.
In this case, as a rule, the logs are fixed on concrete floors, or on an earthen floor, and their main function is to keep the draft and finishing floor from deformation and destruction.
Legs on poles
Logs can be installed on support poles mounted in the subfloor of the house. In this case, the lags transfer the load to these foundation elements. The task of the lags is to withstand the load acting on the flooring and redistribute it to the supporting pillars.
Logs - interfloor overlap
Logs can play the role of not only the basis for the floor, but also be an element of interfloor overlap and carry static and dynamic loads, redistributing it to other floor elements.
It is clear that the most insignificant requirements for the strength properties of the log are made in the first case. The thickness of the beam for lags is taken as the minimum section. In this case, they are more often guided by the thickness of the heat-insulating layer located between the lags than by calculating the strength.
The distance between the lags is selected based on the minimum sagging of the elements of the subfloor, whether it be a board or plywood. The recommended distance is 0.5-0.7m. It is possible to create a box-shaped structure from logs by connecting them in perpendicular directions in the floor plane.
In the third variant of using the lag, an accurate calculation of the cross section and the distance between the lags is required. And in the second option, it is necessary to calculate the cross section of the beam, since the distance is determined by the gap between the supporting pillars.
There are several ways to correctly calculate these parameters: using construction tables, using special construction programs, or contacting a specialist designer. Let's try to do this calculation ourselves.
CALCULATION OF LAG PARAMETERS FOR THE FLOOR
For a correct calculation, it is necessary to understand what other characteristics the strength of this structure depends on, and these are:
So here's an example calculation.
You have chosen a rough floor board with a standard thickness of 2.4 cm, the width of your room is 3 m. The length is 11 m. According to two basic tables, the beam section and the distance between the lags are selected. For a board thickness of 2.4 cm, the distance between the lags should be 40 cm. For a span width of 3 meters and a design load of 300 kg / sq.m. timber with a section of 15 * 8 cm is recommended.
Another feature of the calculation is that it is necessary to take into account the minimum distance between the supporting wall and the extreme beam, from practice it is 3 cm. The number of lags is calculated by the formula:
DP \u003d RL * (CHL-1) + TL * CHL + KB * 2, where
- DP- the length of the room, for our example - 11m = 1100cm.
- RL- the distance between the lags (from the table) - 40 cm.
- TL- the thickness of the log (from the table) - 15 cm.
- KB- the distance from the extreme log to the wall - 3 cm.
- CHL- the number of lag - the number to be determined.
We substitute the values in the formula, we get:
1100=40*(CHL-1)+15*CHL+3*2
1100=55*CHL-CHL-34
CL=1134/55=20.62 rounding up to 21 pieces
Now let's calculate the distance between the lags:
1100=RL*(21-1)+15*21+3*2
1100-6-315=20*RL, RL=38.95 cm.
Using the above method, you can quickly calculate the distance between the lags and their number for the subfloor in a private house.
