Distance between floor joists in a wooden house. Floor joists: arrangement of wooden support

One of the important issues in building a house is laying the floor. Modern tendencies in interior design bring us back to using natural materials. Wood is the most environmentally friendly and practical of them. This coating adds not only comfort and aesthetics. It is durable and has high strength, retains heat well.

This floor is ideal for both a summer house and country house, and for a city apartment. Renew paint or varnish coating maybe once every 4-5 years. The tree will serve you for many decades. However, it is necessary to seriously approach the issue of preparing the base for its installation. Among the many methods, laying on logs is considered the most proven.

What are lags for?

Floor joists are floors made of wood, metal, plastic or reinforced concrete. As a rule, they have the form of beams that are laid across the future finishing surface. This is a kind of lathing that serves as the base of the floor.

Most often they are made of wood in the form of bars of certain parameters. It is more accessible, cheaper and is not inferior in quality to other materials. This method of installation is used to securely secure the floor to avoid sagging under heavy furniture, so that it does not vibrate or creak. According to statistics, it is used in 90% of cases.

The main advantages of the log:

• noise absorption;
• floor ventilation;
• increase in thermal conductivity;
• the ability to use empty space for various utilities;
• floor leveling;
• increasing the strength of the coating to several tons per square meter;
• ease of installation and replacement;
• low cost.

The material for logs is most often pine, spruce or fir. Larch is more expensive, so it is not so popular. Since they serve as a base for the floorboard, grades 2 or 3 are quite suitable. They may not be as neat as grade 1. The presence of knots and smudges of resin will not affect the reliability of the structure.

As a rule, wood is stored under certain conditions. The humidity of the material ready for use should be about 15-20%, but no more. Before starting work, the wood must be treated with special impregnations.

They are harmless to human health and often require simple dilution with water in certain proportions. This prevents the appearance of fungus and mold on the tree, protects against bugs and rodents. The procedure is quite simple, but requires reapplication after 3 or 5 hours.

Floor joists perform many useful functions. It's worth keeping in mind that incorrect installation may lead to dire consequences in the future. The shape of the beam must be rectangular.

They best withstand heavy loads in a ratio where the height is one and a half or two times greater than the width. The beam is always placed only on the edge. The table shows the size of the lag section for certain spans. The step between them in this case is 70 cm:

The size of the section depends on the strength of the material used and the expected load on the floor. For residential premises it is established that it does not exceed 300 kg per m2. These values ​​are recognized by experts. However, they can be made thicker depending on the situation. For example, it is necessary to increase the space for thick insulation. Or an increased load on the coating is expected. The stronger the material, the smaller its size can be. This applies, for example, to iron.

The length of the logs must correspond to the length (width) of the room minus 2.5-3 cm. This margin is necessary to maintain the strength of the structure in case of fluctuations in temperature and humidity. It is recommended to use long logs. It’s good if their size matches the length of the room.

If it is necessary to join them, then the joints should be shifted relative to the neighboring ones by about half a meter, or better yet, by a meter. A support is made at the splice site. It is usually done in column form. Splicing occurs using galvanized plates, but more often - half-tree.

Be sure to take into account the distance between the floor joists. Professionals call it a “step.” It is determined depending on the parameters of the floorboards. The thicker the floor covering, the larger the pitch can be. Accordingly, the thinner it is, the smaller the step we take.

A pattern can be deduced from the table. If the thickness of the board increases by 0.5 cm, then the pitch increases by 10 cm. For more durable coating(for example, plywood and OSB) calculations may be different.

Since these materials are more resistant to deflection, the pitch increases. With a thickness of 18 mm, the pitch will be up to 40 cm. With 25 mm, it will be up to 60 cm. We attach each sheet to three different lags. Be sure to fasten the center and edges, going halfway up the joists.

The logs are laid on wood, soil and concrete. First you need to know what tools are required for this. So, in addition to the bars themselves, you must have a level, a jigsaw or hand saw. We stock up on screws, screws, anchors and nails. Be sure to have a hammer drill with you (when laying on concrete), usually an axe, a screwdriver or drill, a hammer and a nail puller.

If the joist is attached to wooden floors it is necessary to fasten them to the sides of the beams. This is done based on the fact that beams are usually not level. In addition, this method helps not to raise the floor too high, saving precious centimeters in rooms with low ceilings.

If the height allows, then, as an option, the timber is laid on top across the beams. We secure them with 6 mm screws, having previously drilled a hole 2.5 mm smaller in diameter. This will prevent the wood from splitting. The length of the screw should be 2.5 times longer than the width of the joist.

When laying logs on the ground, it is necessary to clean and compact it in advance. Next, measurements are taken to install the pillars. They will serve as a support. The distance from the wall to the first log should be from three to twenty centimeters. Holes 10 cm deep are dug along the intended distance, filled with sand and filled with water for greater strength. This will be the foundation for the pillars.

It is recommended to make its size at least 40 by 40 cm. Then polyethylene is laid, and a column of two or three bricks secured with cement is erected on top of it. Then they are covered with roofing felt, and timber is laid on top. The logs are attached with galvanized corners to the walls or to the crown of the log house.

Joists are often laid on concrete base. Waterproofing in this case is extremely necessary, otherwise the floor will constantly become damp. A regular one will do just fine here. polyethylene film. However, experts are increasingly beginning to use foil insulation - this is foamed polyethylene with a layer of foil, which is placed towards the living space, reducing heat loss.

The beam is attached to the concrete using anchors. Insulation is laid between the joists, but not under them. Concrete screed, as a rule, eliminates the hassle of leveling joists before laying floorboards.

Make sure the wood is dried and treated with antiseptic or bitumen. This will significantly extend the service life of the structure. When the humidity is more than 20%, the tree can become warped, compromising the integrity of the structure. Boards brought from the warehouse must lie in room temperature a few days. This is especially true during the winter season. It is not recommended to lay the floor when the air humidity is less than 60%.

You should not saw or plane boards in the room where the floor is being installed. Sawdust can cause rot.

Don't forget to use waterproofing. For sound insulation, as a rule, fiberboard, rubber, polyethylene foam, slag or sand are used. The warmth in the house will remain longer if you fill the voids under the floor with mineral wool, expanded clay, expanded polystyrene or isospan.

Use the rule after installation. Lay it across the beams, remove gaps, leveling the height. This is easy to do with the help of special modern adjustable mounts appeared on the construction market. The floor is laid only after all leveling procedures.

The smaller the pitch, the longer the floor will last. However, the main indicator of durability is the material of the coating and base. The most durable wood is larch.

The installation of beams is usually carried out along the window, i.e. across the room. The floor boards are then placed along the length of the room, i.e. from the window. However, this is just a recommendation and a matter of taste.

The floor is laid from the corner, placing the boards perpendicular to the joists. The distance from the walls should be about 1 cm. This is left in case the wood deforms depending on temperature and humidity environment. This distance is covered by the baseboard. If the boards lie close to the wall, the floor may swell.

A board is attached to each beam. Holes for screws should be drilled in advance to avoid delamination.

The most common option for the space between the joists is from 50 to 56 cm. As a rule, it does not exceed a distance of 69 cm.

Remove the joists and wooden floor simple enough. It is necessary to remove all the furniture from the room, remove the baseboards, and open the boards or sheets of chipboard. After inspection, the old boards are replaced with new ones. The logs themselves can be partially replaced. Simply cut out a piece of rotten wood and install a new one.

Don't forget to use protective impregnation for new boards. Check the ends of the beams for rot, and inspect the base insulation, if any. Repairing the floor can be a reason to insulate your home.

Lags are deservedly the simplest and most popular way to create solid foundation of our gender. If desired, anyone can take up this interesting business and step achieve your goal step by step. The most pleasant reward for your efforts will be warmth and cozy atmosphere for many years.

Thanks to its environmental cleanliness, aesthetics, naturalness, warmth and comfort in the home, wood floors have not lost popularity to this day. When choosing them, many questions arise - what should be the distance between the floor joists in wooden house, what material to choose, how to install correctly, etc. This article will answer all your questions.

Choosing timber for logs

1. Select material from coniferous wood, the price of which is low - spruce, pine or fir. If the room is damp, purchase larch slats. It is more expensive, but it almost does not rot from exposure to moisture.
2. To save money, you can purchase grade 2/3 lumber with a moisture content of 18/20%.
3. The bars must have rectangular cross-section. At the same time, their height should be 1.5/2 times greater than their width. Having such a cross-section, the logs will operate optimally, withstanding high loads.
4. The dimensions of the beam must be selected based on the span, that is, the distance between the beams of the lower trim. The thickness of the insulation used is also important.

Below are the sections of the logs (with a step between them of 0.7 m) for different spans.

1. When the span width is of an intermediate value, you need to choose the closest option, taking into account the safety margin.
2. When purchasing timber, inspect it for defects. Before calculating floor joists, take into account their margin of 10/15%.

Note! To protect wood from harmful insects, mold and fungi, it must be soaked with an antiseptic. The underside of the beams must be treated twice, allowing the first layer to dry for 4/5 hours.

How to determine the pitch between joists

This value depends directly on the thickness of the floor covering.

Table you can use

When thick boards with good strength are used for flooring, logs can be installed relatively rarely. If the finishing coating is thin, the timber must be positioned frequently. Below is a table of distances between floor joists based on the thickness of the boards.

To more accurately determine the step between the lags, you will need to carry out calculations.

Calculation example

1. Let the length of the room be 11 m.
2. The width of the beam will be 0.15 m.
3. We will choose floorboards with a thickness of 25 mm (0.025 m) for flooring. Therefore, the gaps between the logs should be from 40 to 50 cm. Let’s average these figures to 45 centimeters, that is, 0.45 meters.
4. Let's denote the number of lags as x.
5. The width of all our logs will be equal to 0.15∙x.
6. The first beams will be installed at a distance of 30 mm (0.03 m) from the walls. Based on this, the step between the lags will be: x-1. The distance between all lags will be equal to 0.45∙(x-1).

To find out the distance between the floor joists, we create the equation:

length of the room = width of the beam + gap between all the joists + distance from the walls.

1. We substitute the values: 11=0.15∙x+0.45∙(x-1)+0.06.
2. We solve the equation:

11=0.15∙x+0.45∙x-0.45+0.06;

11=0.6∙x-0.39;

1. The number of lags must be an integer; based on this, we round the value to 19.
2. The sum of all the gaps between the logs will be equal to 11-0.06-19∙0.15=8.09 meters.
3. We divide this figure by the number of distances - 8.0919-1=0.4494.
4. The result obtained: the exact distance between the floor joists should be 44.94 centimeters.

Frame installation

Floors with joists can be installed both on the floors of the house and on the ground base.

Installing joists on wooden floors

1. The logs must be fixed to the strapping beams. It should be taken into account that they are unlikely to have an absolutely even level. Therefore, it is best to attach the timber to the sidewalls of the beams.
2. In this case, determine the horizontalness of the joists using a control strip; no backing can be used.
3. Fix the logs with screws with a diameter of 6 mm. They should be 2/2.5 times longer than the width of the beam.
4. To prevent the lumber from cracking, drill holes in the joists and beams. In this case, use a drill that will have a diameter 2.5 mm smaller than the size of the screw.
5. When the beams are located far from each other, you need to install double logs. First, lay the first row of joists on the beams, and on top of them, with smaller steps, another one.

Laying timber on the ground

1. First, level and compact the soil with your own hands. This work can be done using a large log. Nail a board to it from below and, moving the tamper along the ground with a partner, compact it. The board should be at least 5 cm thick and slightly larger than the cross-section of the log.
2. Next, mark up for support pillars for lag. When the supports for the frame are the beams of the lower frame, marks can be left directly on the beams. If the support is a grillage covered with roofing felt, place marks on the waterproofing material.
3. The distance from the initial logs to the walls should be 3/20 cm.

Before installing the support posts, you need to make a foundation for them. It can be poured separately under each support or placed under a row of posts.

The dimensions of the foundation for the column are minimum 0.4×0.4 m, height 0.2 m, 5 cm of which should protrude from the soil.

The instructions for arranging the foundation are as follows.

1. Set aside 0.2 m from the log axis marked on the strapping beams in both directions.
2. Pull the string between the marks.
3. Perform a similar operation in a plane perpendicular to the joists to mark the corners of the posts located at the intersection points of the cords.
4. Drive stakes into the corners. Next, remove the cords.
5. When the foundation is laid under a row of supports, only the edges of the row are marked with cords.
6. In the marked areas, remove upper layer soil. Compact them, pour in crushed stone and compact it.
7. Assemble the foundation formwork, which has a height of 0.1 m.
8. To waterproof concrete, place polyethylene film in the holes. If the soil is clay, then you don’t have to do this.
9. Reinforce the foundation with a frame welded from rebar, 0.8 cm in diameter. It should be laid slightly below the center of the future concrete layer.
10. Next, fill in the solution. Its composition should be the same as for the foundation of the house.
11. Allow the concrete to set for 2/3 days.
12. After this, lay the waterproofing. For this purpose, cut pieces of roofing felt according to the size of the supports, in other words, 40x40 cm. You can also make overlaps of 1 centimeter. Lay the insulation directly on the mortar; there is no need to coat it with bitumen.
13. Now you can start laying bricks. Two rows of them in height are enough, the top one should be oriented perpendicular to the length of the beam. To fasten the material, use sand-cement mortar, brick use grades not lower than m-100.
14. Lay waterproofing along the bricks.
15. Place soundproofing pads on top of it. To prevent them from moving, secure them.

First, lay the lighthouse logs, the first from the walls. Secure them at intervals of 2 meters from each other.

Note! Check that the material is laid horizontally relative to the ground, as well as to each other. If the logs lie unevenly, the protruding areas can be removed with a plane, and pads can be installed under the sagging parts. It should be taken into account what maximum deviation is permissible - it should be one millimeter per 1 meter of timber.

Conclusion

The strength and reliability of the structure of all floors depends on the pitch of the joists, their cross-section and the wood used. Therefore, you need to take the choice of these parameters seriously. In the video presented in this article you will find Additional information on this topic.

When I determined the distance between the columns for the logs, I was guided by some article from the Internet. The same article recommended taking into account the option of laying insulation between the joists. After all, with a floorboard thickness of 35 mm and the expected width of the carpet mineral wool 60 cm (120/2). The distance between the lags was chosen to be 58 cm (2 cm for cotton wool compression). Considering that the log itself has a width of 7.5 cm, the distance between the axes or centers of the columns is 65.5 cm. In older paper publications, these distances are slightly different and I have not seen a clear calculation anywhere.

After preparation, brick columns are laid out of lean concrete with a pitch (along the axes) of 0.7...0.9 m and with a distance between rows of 100...120 cm. Two layers of roofing material or roofing felt and an antiseptic wooden lining 3 cm thick are laid on top of the columns (Fig. 7.24). The logs are supported on them, and a plank floor is laid on top of the logs.

Rice. 7.24. Cold floor with warm underground
1 - base; 2 - waterproofing made of two layers of roofing material; 3 - lower trim;
4 - top harness; 5 - external cladding tongue and groove boards;
6 - non-ferrous metal plate with holes; 7-outer wall made of boards;
8 - plaster; 9- plinth; 10 - plank floor; 11 -lag; 12 - brick column;
13 - antiseptic wooden lining; 14 - underground

HA. Stern. Carpentry work. Stroyizdat 1992

Under the logs resting on brick pillars, to ensure waterproofing, you need to place scraps of roofing material, which also protects the wood from mold.

Plank floors laid directly on the beams if their pitch is relatively small. In case of sparsely located beams, additional logs are laid on them with the right step, and a plank floor is already laid on them. The logs are placed at a distance between the axes of 800-850 mm for boards with a thickness of 35-40 mm. With thicker boards, the lag pitch can be increased to 1 m, with thinner ones - reduced to 500-600 mm. The humidity of the boards should not be higher than 12%.

A wooden floor must have a zero slope, so beams and joists must be constantly checked using a level or level along and across the room. The pitch of the columns depends on the thickness of the logs - with a thickness of 40 mm - up to 900, with 50 - up to 1100, with 60 - 1200-1300 mm. The pitch of the posts in the transverse direction depends on the thickness of the floorboard.

Construction of a house from foundation to roof

The maximum distance between rows is selected from the cross section of the log. I used the Calculator to calculate the load-bearing capacity of single-span wooden beams" → (download). For a 150x75 log, it turned out to be more than 2.5 meters, but the width of the entire room is 6.2 meters. Hence the distance along the rows is about 2 meters

In general, of course, longer distances can be taken, but then there is a greater likelihood of all kinds of deflections and creaks occurring. Much depends on what will subsequently stand on this floor, whether the future residents will put some kind of piano or a tub with a palm tree and whether the floor will become curved or creaky.

Increasingly, owners are trying to furnish their apartment, dacha or Vacation home. This choice is justified, because it allows you to save money and produce renovation work as far as possible. One of the important construction processes is the installation of lag. But here many questions arise: how to choose the right material, at what distance the floor joists are laid and what are the installation rules.

What are lags?

The structure, which consists of transverse beams and serves as the basis for the flooring, is logs. Bars or beams can be used for such a design, with self-installation Most often, wood is used, but materials such as metal, reinforced concrete, and polymer are widely used in construction. By installing logs, you can take advantage of the following advantages:

• Increase the level of sound insulation;
• Increase the level of thermal insulation;
• Correctly distribute the load;
• The presence of underground ventilation is especially important if the installation of utilities is planned;
• Ideally flat floor surface;
• Strength and resistance to external loads;
• If necessary, it is possible to replace a separate structural element.

Materials such as wood are valued for their naturalness, environmental friendliness, and beautiful appearance.

Choosing material for logs

The quality and strength of the structure will depend on the choice of material; if you follow some rules, the logs will ensure reliable and durable operation.

• Relatively cheap types of wood are suitable for the construction. It could be fir, pine, great option spruce. You can use larch, but such material will be more expensive.
• For design wood will do 2 grades, do not give up 3, the moisture content of the material is important, it should be up to 20%, but not less than 18.
• You need to pay attention to the cross-section perfect option, when the height dimensions are 1.5-2 times the width of the beam, in other words, the section should have a rectangular shape.
• Also, the size will depend on the insulation, namely its thickness.
• The span of the room is taken into account.

This table shows the section dimensions for different spans, provided that the step corresponds to 70 cm.

If the span size has an inaccurate value (intermediate), you should take an approximate option, but take into account the safety margin.

Choosing a decking material

The type of wood must be selected taking into account the characteristics of the room. Of course, it is also important financial side, the highest grade of material will cost much more, but if the floor will be covered, for example, with paint, then it is better to choose the second grade. If a varnish coating is provided, then the first grade is required. When the floor is laid in utility rooms, preference can be given to the 3rd floor. Which breed is better to choose:

• Fir, pine and spruce belong to soft breeds. Such a coating will not be practical or durable, since even heels leave marks on such a surface. Such flooring is possible if the room has low traffic and if it is treated very carefully.
• Oak is the most durable material, but such flooring is expensive. It can be used in any room.
• Another species is highly durable - this is Siberian larch, it has the peculiarity that the wood contains resins that protect it from rotting, so this flooring is often used in bathhouses.
• And for arranging children's premises, alder or aspen is ideal.

When choosing, you need to pay attention to the moisture content of the wood. If you use damp material, then after some time the flooring will dry out and cracks will begin to appear. But overdried material can create cracks. The ideal humidity is 12%. You need to carefully inspect the material and do not use defective boards. You need to purchase material with a 15% reserve.

Wood is a very high-quality and durable material, but in order for it to justify itself in operation, it needs to be processed. Now you can buy various antiseptics that will protect wood from rotting, fungi, mold and beetles.

How to calculate distance

The pitch of the lag will depend on which flooring is chosen. Here you should use the following rule, if the flooring is thin, then the logs should be placed with minimum distance. When the coating is thick and durable, logs are placed relatively rarely.

In order to find out the exact distance data, it will be necessary to carry out the following calculations.

For example, there is a room 11m long, the joists are 0.15m wide, and the flooring is 25mm thick. If you follow the table, then the distance between the logs should be from 40 to 50cm, you should take average, which corresponds to 45cm.

While the total number of lags is unknown, it is denoted by - x, respectively the width total number lag is 0.15x. Since the first joists are laid at a distance of 30mm from the wall, the value will be as follows: x-1, to indicate the total distance - 0.45 (x-1).

Having such data, you can create an equation that looks like this:

11(room data) = 0.15x (lag data) + 0.45(x-1) (lag step) + 0.06(distance from the wall).

It is necessary to find out x, in this case it is equal to 18.9, this value must be rounded to 19 - this is the number of lags. Next you need to find the sum of all distances. For this, 11-0.06-19x0.15 turns out to be 8.09 m. Then we divide the amount by the quantity, it turns out 44.94 cm - this is the exact distance that should be between the logs.

Such accurate calculations are used quite rarely and they are not at all necessary; you can use these tables. If, when installing the log at the final stage, the distance does not coincide slightly, there is nothing wrong with that, you can take a smaller step, thereby making the structure stronger.

Conclusion

As you can see, when laying a floor, each stage is important. Therefore, it is necessary to pay attention to each process, but if you take into account all the recommendations and follow the rules, then laying the floor will not bring difficulties, and the result will be reliable and durable.