Online calculator for floor beams made of wood. How to calculate the lag for the floor

Not so long ago, it seemed that laminate flooring would completely replace the usual wooden ones. Their relative cheapness attracted many developers. This continued until most of them realized that the cheapness of the material is quite consistent with its "cheap" performance. Now many people want to have a real wooden coating from natural materials. How to properly lay the boards on the logs?

What are lags and what are their advantages

Logs - powerful transverse beams that serve as the basis for laying boards, most often made of wood. It can be sawn square or rectangular bars of various sizes. Using lag allows you to:

Improve sound insulation between the upper and lower rooms. At the same time, thermal conductivity performance is improved.
To make the load on the bearing interfloor overlap more uniform - the appearance of cracks on the ceiling is excluded.
Most of the utilities are hidden in the free space between the lags and the flooring.
Makes repairs much easier if necessary. Repairs are carried out quickly, all materials are completely recyclable - the cost of the work is significantly reduced.

The choice of wood for the log and the calculation of their cross section

For logs, you can use inexpensive varieties of coniferous wood, etc. room conditions. During this time, they will "adjust" their humidity, which will eliminate excessive fluctuations in linear dimensions during changes in humidity.

It is better to make the cross section of the beam rectangular, the ratio of the sides is 1 × 2. This significantly reduces the cubature of the material and the total estimate, and at the same time has almost no effect on the bearing characteristics. Specific dimensions must be selected taking into account the width of the span between them and the calculated maximum load on the floor. The table shows approximate lag sections for various room sizes. It is taken into account that the distance between the lags is 0.7 meters.

If the dimensions of the room do not match the data in the table, it is better to choose a lag section “with a margin”.

The distance between the lags should be consistent with the thickness of the boards being laid. The table shows the parameters of the thickness of the floorboards, taking into account the lag step.

Installation lag

Logs, depending on the structural features of the building, can be installed directly on the concrete floor, on wooden floor beams or on brick columns.

Most often, logs are installed on concrete floors. During installation, three conditions must be met:

Be sure to lay a layer of reliable waterproofing between concrete and wooden structures. This will prevent them from being quickly destroyed due to increased humidity.
All lags should be at the same level. This condition is achieved with the help of a water level and an ordinary thread. According to the level, “zero” markings are made on opposite walls of the room, extreme logs are set. A thread is stretched between them and all other logs are laid along its level, observing the necessary distances.
The logs must be securely fixed on the stops. During flooring, they should not change their spatial position.

If desired, a layer of thermal insulation can be laid between the lags and floorboards. It can be mineral wool, and foam sheets, and a layer of expanded clay. The choice of insulation depends on the financial situation and personal preferences of the owner of the apartment.

Installing a lag on the ground

This method is used during the construction of country or country houses. Before starting work, it is necessary to remove the fertile soil layer, it is advisable to pour a ball of sand or gravel. After that, marking is carried out, the installation sites of brick or concrete columns are determined. The columns are laid out according to the level, it is better to level the height with a cement-sand mixture. It is quite risky to use various wooden spacers for these purposes - they can lose their bearing capacity, which will cause a violation of the rigidity of the entire structure. The floor will begin to "creak", its straightness will be broken.

The first columns should be at a distance of no more than 20 cm from the wall, it is better to make more rows of columns than to risk the stability of the entire flooring. remember, that brickwork cannot be in the ground, it must always lie on a concrete base and only with the use of a waterproofing layer.

Laying boards

Quite a laborious process, requires certain practical skills. The first fits with the opposite to entrance doors walls, do not forget to make a gap of 1 ÷ 2 cm around the perimeter to compensate for expansion phenomena. Do not rush to fix the first board, several times check its parallelism both to the nearest and to the opposite wall, these slots will then be closed with skirting boards. After fixing the first row, start laying the subsequent rows.

Each row of boards is pressed against the previous one. For this, special devices are used: metal U-shaped brackets, wooden spacers and wedges. The brackets are nailed to the joists, with the help of spacers and wedges, the boards are tightly fitted to each other and fixed in this position. There are times when the floorboard has large curvature. Then you will have to use wedges more often, press the board until the gaps completely disappear.

Finishing work

Flooring made of natural boards will have to be sanded with electric grinders. This will not only finally level the floor plane, but also prepare it for varnishing or paints. After grinding, it is necessary to carefully remove all sawdust and can be nailed around the perimeter of the baseboard. It is worth noting that today the cost of a natural floor is not affordable for everyone. But its high price is fully justified by its excellent performance.

A wooden house and a bathhouse are the dream of many citizens. Each of those who had to build a wooden frame with their own hands knows perfectly well the purpose of the log and beams. These are the supporting structures of the building, so you need to select the material for them, as well as their quantity, very carefully. Logs for the floor are recommended to be made from dry, first-class material treated with antiseptic and fire retardant compounds. The most common way to install them is on beams cut into the walls during the construction process.

Calculations of the lag for the floor are done, taking into account the basic parameters, the lags should be 1.5-2 times higher than the height of the flooring, otherwise the nails will not be able to firmly hold the floor boards.

They are installed taking into account the fact that insulation material is usually placed between them. It can be expanded clay, polystyrene, but most often mineral wool is used, pressed into slabs 50-60 cm wide. Logs are mounted at the same distance from each other. A wooden floor spreads over them, which, when correct installation last for several decades. Logs are made of bars, beams, boards. They serve to redistribute loads from the floor, and are also a latch that combines all components and parts into an integral system.

Benefits of using lag

The floor on the logs has a certain degree of functionality. In the space between them, pipes, wires, heat-insulating materials can be laid.

The bars are relatively inexpensive. Their installation is available to everyone.

These floor supports are able to withstand a load of 5 tons per square meter.

Figure 1. Scheme of fastening wooden beams.

When repairing the floor, it is often enough to repair the lag. It is not necessary to re-lay the floor.

The design does not have a large mass. The load on the floor is much less than with a cement screed.

The space filled with mineral wool will keep the heat in the house and protect it from excessive noise.

Bars allow you to bring the floor plane to any height.

The structures laid in place do not require additional work. You can immediately lay the floor covering.

Disadvantages of the floor on the logs:

The room loses a few centimeters of height.
High labor intensity. It is required to carefully mark and align all structural elements.

Calculation of some lag parameters

The calculation of the lag for the floor is carried out, taking into account the main parameters. Floor joists should be 1.5-2 times higher than the height of the flooring, otherwise the nail will not be able to firmly hold the floor boards. If the thickness of the floorboard is 50 mm, then the height of the bars should be about 100 mm. If the subfloor is made of plywood or other sheet material having a thickness of 20 mm, the bars can be much lower, 30-40 mm.

The material for the manufacture of wooden logs should be selected from conifers. The humidity of the blanks should not exceed 20%. The cross section of the bars is chosen rectangular. They can be cut from a board with a thickness of 50-60 mm. Lay finished products across the light coming from the windows. The laying step is from 40 to 70 cm. Knowing the laying step and the dimensions of the room, it is easy to calculate required amount elements. Before installation, all wooden elements are treated twice with an antiseptic composition. The antiseptic can be replaced with ordinary hot bitumen.

Picture 2. Adjusting sleeves. They are used for leveling floors on logs.

In practice, very often the height of the lag is chosen taking into account the thickness of the insulation layer. Commonly used as floor insulation mineral wool, produced by plates, the thickness of which is 50 mm. The floor joists should also be of the same height. If it is decided to lay the thermal insulation in a double layer, then the bars are needed with a height of 100 mm. The distance between them depends on the thickness of the subfloor material. The thinner the rough flooring, the more often logs are installed. With a thickness of plywood that can be used as a substrate for finishing flooring, 12 mm, the size of the gap between the bars is 30 cm.

Most often, the subfloor is made of grooved boards. Boards should be spruce, pine or fir. They are not suitable for a finished floor, since the wood is very soft, even traces of thin heels remain on it. From above it is necessary to lay a laminate or other topcoat. The thickness of the boards with a normal lag step of 50 cm is recommended to be at least 35 mm. In most cases, the calculation of the step of the bars is made taking into account the thickness of the floor material:

Figure 3. Fasteners. It is applied to fastening of wooden designs.

Board thickness (mm) - step lag (mm):

20 – 300;
24 – 400;
30 – 500;
35 – 600;
40 – 700;
45 – 800;
50 – 1000.

For the manufacture of these parts, not only wood is used, but also reinforced concrete, various polymers and metals. Reinforced concrete products are highly durable. They can be used when building a house outside the city. Other materials can be used for floor repairs.

If the floor is based on wooden beams, the logs can be installed by attaching them to the side using self-tapping screws (Fig. 1). The size of the fasteners should exceed the thickness of the bar by 2.5 times with a diameter of 6 mm. positive moment This method consists in the fact that when adjusting the height of individual logs, the use of additional adjusting pads is not required.

In construction, special wooden or plastic products are sometimes used that have holes into which small plastic adjusting sleeves are inserted. They contribute to the rapid leveling of the surface formed by the lags. Such products are mounted very quickly and do not require the use of linings (Fig. 2).

Figure 4. Scheme of mounting the floor on the logs.

Before installation, wooden elements must be protected from various microorganisms and wood-boring pests by treating the material with a disinfectant, then with a water-repellent composition.

In rooms with low ceilings, it is better to use other floor installation methods. When performing the calculation, we must not forget that the bars reduce the size of the room in height by 10 cm or more.

Floorboards or sheets of rough flooring should be attached to each log.

The ends of structural elements should not touch the walls of the building. There must be a gap of at least 5 cm between them.

Instead of a certain section of a wooden beam, you can use boards connected in pairs to each other and reaching the dimensions of the desired beam in diameter. Several big sizes are not allowed. Boards are installed on the edge.

Logs can be attached to the concrete base with special galvanized metal corners, which are fixed on the base with dowels and self-tapping screws. Instead of corners, U-shaped fixtures are often used (Fig. 3).

If necessary, the bars from which the logs are made are joined to each other to achieve the desired length. There must be a strong support under the junction. This support is often a brick pillar. Under its construction, you need to dig a hole about 10 cm deep. It is covered with sand and watered abundantly. From above, the sand cushion is covered with a layer of polyethylene. A cement-sand mortar is placed on it and a red brick column is laid out.

You can lay out the columns in rows and fix the logs on them (Fig. 4). The size of the columns is 25x25 cm. Calculating the number of bricks is not difficult.

The design of the floor on the logs allows you to immediately mount the rough and finish flooring.

Legs can be made from various materials. Most often, a wooden block or board is used for their manufacture. And there are a lot of materials for finishing. Their choice depends only on the preferences of the owners and the contents of their wallet. To make a calculation of materials for the manufacture of a log for the floor, a plan of rooms made on paper with exactly the indicated dimensions will help. All calculations are best done before the start of the main installation work.

The topic of this article is the calculation of the floor lag and their do-it-yourself installation. We will find out what and what section the logs are made of, with what step it is better to lay them with different types of flooring, how to disinfect to prevent decay and how to mount them on different types of bases.

Why is it needed

Even a primary school student can probably give a simple answer to this question. To avoid laying boards on an uneven floor, right?

Yes, but this answer is, to put it mildly, incomplete.

The log under the deck has many other functions.

They provide full ventilation of the underside of the wooden flooring, prevent its decay.

Please note: this item is especially important when laying the floor on the ground. If you have high level groundwater, dampness can create serious problems even with a high subfield.

The joists improve sound insulation by providing a buffer space between the flooring and the base.
The place under the flooring is often used for laying insulation and for laying engineering communications.

Between the lag insulation is laid - glass wool.

Finally, when the base is uneven, it is generally much more durable, creating support points for the flooring with a constant small step.

Applicable materials

In theory, logs can be made of any material of sufficient strength and constant linear dimensions - from metal, plastic, a compound based on synthetic resins and cellulose. However, the price of these materials makes them uncompetitive against the background of wood. As a rule, a regular bar is used.

What breeds are allowed? The best option is rot-resistant and durable larch, but cheap spruce, pine and fir are used much more often. Resin pockets and longitudinal cracks in this case do not affect the functionality of the beam, so you can safely take grade 2-3 lumber.

The only thing you should not save on is the moisture content of the bar. The bar of the so-called atmospheric humidity is guaranteed to be deformed during drying.

The humidity of the material for the log should not exceed 20%. First of all, this applies to cases when the logs are laid on the posts on the ground, without reliable fixation.

Here are the step values for flooring from boards of various thicknesses.

If the planned thickness of the flooring is 20 millimeters, the maximum step does not exceed 30 centimeters.
For a 25 mm board, it is already 40 cm.
30 mm - 50 cm.
35 – 60.
40 – 70.
45 – 80.
50 - 100 centimeters.

For plywood or OSB, the instructions are somewhat different.

These materials have greater bending stiffness but are produced in a smaller range of thicknesses.

With a flooring thickness of 15 - 18 millimeters, you can focus on a step of 40 centimeters.
With a thickness of 22 - 24 mm, it is permissible to increase it to 60 cm.

To calculate the material, in general, it is easy to find a floor lag calculator on the net. With a given span length, it will allow you to calculate the required cross-section of a beam from an arbitrary type of wood and indicate the maximum allowable load.

Mounting

How to lay logs on different grounds?

Concrete

If the room is located on the first floor, the ceiling is waterproofed with polyethylene.

Tip: if you use folgoizol - foamed polyethylene with a foil layer - at the same time it will significantly reduce heat loss due to radiation. It is laid with foil up, towards the room with a higher temperature.

The bar is laid out with a given step; then it is leveled with the help of linings - pieces of bar and plywood. Not only a separate beam is exposed to the horizon, but also neighboring logs. Any three bars should be located on the same line (it's easy to check the rule).
Then the beam is fixed to the floor. Better - screwdriver anchors: in this case, holes can be drilled directly through the tree, and the nuts do not have to be drowned, drilling holes of considerable depth and weakening the material.

Pictured is an alternative. Stands are attached to the ceiling, the logs are attracted to them with self-tapping screws.

wooden beams

When fastening the bar across the beams, it is attracted to them with ordinary self-tapping screws of sufficient length - also, of course, with linings that allow you to bring the floor to the horizon. In this case, the pre-treatment of the floor log, in addition to impregnation with an antiseptic, includes the mandatory drilling of holes - otherwise the bar is easy to split.

If the beam is attached along the lag to compensate for their spread in height, it can not only be laid on top, but also hemmed to them from the side. In this case, the floor will be leveled with less loss of room height, and the logs themselves may be noticeably narrower.

Priming

Briefly, we have already touched on the laying on the pillars.

The main steps look like this:

Under each pillar, a hole is dug with a depth of 10 cm. It is covered with sand and spilled with water for better shrinkage.
The sand is covered with polyethylene. Then, a column 25x25 cm in size (a brick in length and width) is constructed on a mortar cake.
The bars brought to the level by the solution are covered with roofing material; dried to 16-18% moisture content, the timber is laid on them without fixation. The edges of the logs are laid on the grillage, one of the lower crowns of the log house, or they are hemmed to the walls with galvanized corners.