What is log

What is log

Laga - the main element of the construction of the floor and horizontal floors in houses and outbuildings. Logs are not used in large-panel construction (they are replaced by panels and reinforced concrete floor beams), but such solutions are much more expensive, and lose by weight.

How to pick up lags

The lag in the classical building concept is a rectangular shaped bar made of building grades of wood. The logs are dried and kept for at least one year under a canopy to achieve the required moisture content of the wood.

Important! Before use, the logs are inspected for possible defects, cracks, and if necessary, the geometry of the bar is adjusted.


Since the logs will be at the base of the house in damp conditions, often with a lack of ventilation, the wood be sure impregnated with protective agents. This ensures the durability of floors, reduces the likelihood of deformation of the floor surface, the appearance of crevices and creaks of floorboards. An example of working with wooden logs can be seen in the following video:

Very rarely, but still there are structures in which exotic types of lag are used: the beams are made of high-strength polymers, metal, prefabricated structures. These advanced construction methods are cautiously perceived by designers, mainly because of cost and novelty.

Laying the log

Mounting Features

The installation of the log is made after the construction of the foundation, grillage or timber of the lower floor tie. Note! If there are points of contact with concrete or a brick base, the lag is waterproofed with polyethylene, roofing material before laying. In low-rise construction, logs are laid on the ground, performing additional support posts of red brick along the course of the lag's movement, also with waterproofing in the place of the lag's support.

installation features of the lag

Calculation of dimensions and distances between lags

The dimensions of the lag vary widely, even in one erected structure and depend on the design load on the floor covering. For standard living conditions, examples can be given of the estimated width and height of the lag, depending on the span of the span.

  • With a span of not more than two meters, it is recommended to use wooden logs with a cross section of 110 to 60 mm.
  • Increasing the span to three meters will require the use of logs 150 to 80 mm.
  • At a span of 4 meters, it will be necessary to use a beam with a cross-section of 180 per 100 mm.
  • For the distance between the points of the foot of the lag at six meters, the section of the lag is increased to 220 by 180 mm.

In all cases, the installation is done by laying the log with the larger side of the section vertically, thereby increasing the rigidity of the structure.

The distance between the lags is selected based on the planned thickness of the floor boards.

  • Using a 30 mm thick floorboard requires a step between the lags not more than half a meter.
  • Board thickness of 40 mm allows you to increase the distance between the lags up to 70 centimeters.
  • A floor board of 50 mm makes it possible to mount the log in steps of one meter.
  • For plywood and wood boards it is recommended not to exceed a step of 40 to 60 centimeters between the lags.
Attention! The above calculations are averaged, and can be adjusted in case of special construction conditions (bathroom, kitchen, heavy interior items).

Final steps

After miscalculation and preparation, lag laying is carried out using fasteners, corners, screws, depending on the type of foundation. When laying it is necessary to observe the horizontal position of the lag relative to the neighboring ones: this will save forces and resources in the next stages of construction.

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