The logs are longitudinal beams on whichthe floor covering is laid. The joists are made of bars. They can be made of wood, polymer, metal or reinforced concrete. In most cases, wooden joists are installed, since this material has a low cost and is constructive in the case of laying a wooden floor. You should know that the process of installing a floor on joists made of other materials is no different.
Using floor joists will increase its sound insulation, will help distribute the load, and will ensure the strength of the structure. The advantages of using joists:
- increase the level of noise insulation;
- correct distribution of the load on the lower layers;
- The presence of a ventilated underground, in which it is possible to establish various communications;
- good level of thermal insulation of the floor;
- the creation of a flat base for the flooring of floorboards;
- ensuring the strength of the structure and resistance to various loads;
- if necessary, then any of the floor elements can easily be replaced.
Disadvantages of using lags:
- In the case of a log on the floor, the room will lose altitude;
- to install the logs, you will need to carefully mark and align these devices in one level, which is difficult to do.
How to choose the material for making lag?
Figure 1. Joist pitch for boards of different thicknesses.The logs can be made from solid wood of budget tree species: spruce, pine, fir. In some cases, larch is used, but it is more expensive. Wood of grades 2 and 3 is suitable. The humidity level should be approximately 19-20%. The timber should have a rectangular cross-section. The height of the slats should be 2 times greater than the width. Logs with such a cross-section can cope with heavy loads perfectly. The size of the logs should be selected based on the span, that is, the distance between the bars of the lower trim. It is also necessary to take into account the thickness of the insulating material used. When purchasing boards, it is necessary to inspect the material for defects. If there is a defect on the boards, they should be put aside. It is recommended to purchase the material with a 15% reserve. To protect the wood from beetles, fungus and mold, the entire structure will need to be treated with an antiseptic. The logs from the bottom will need to be treated several times, making an interval of 4-5 hours. The following can be used as protective agents against mold: sodium fluoride, VVK-3, and others. These agents are water-soluble and can be applied with a brush. Return to contents</a>
What is the distance between the beams of the floor?
Scheme of arrangement of logs for laying on the ground.The distance between the beams will depend on the thickness of the floor covering. If you plan to use thick boards for the covering, then the logs can be installed not too close together. If you have a thin covering, then the logs should be placed close together. In Fig. 1 you can see the step of the logs depending on the thickness of the boards used. It is not necessary to make exact calculations, it will be enough to take the distance between the beams by the value that depends on the thickness of the floor covering and the width of the structure. If at the end of the installation of the logs the distance between the bars turned out to be inaccurate, then you can make the step between the last structures smaller. In this case, the structure will have good strength. Return to the table of contents</a>
How to install floor lags?
Elements that will be needed for installation and fastening of logs:
Dimensions of log cross-sections for different span sizes.
The joists can be installed both on the earthen foundation and on the floors of houses. Return to the table of contents</a>How to fix joists on wooden floors?It is recommended to fasten the logs to the beams. However, in most cases, the beams are not level, so you can fasten the logs to the side surfaces of the beams. The horizontality of the logs can be checked with a control strip; there is no need to use spacers. The logs are fastened with screws with a diameter of 6 mm. The length of these fasteners should be 2.5 times greater than the width of the logs. In order not to damage the timber, it is recommended to first drill a hole in the beam and log. To do this, use a drill with a diameter 2.5 mm smaller than the fastener. If the beams are located far from each other, you will need to make double logs. First, install the first layer of logs on the beams, after which another one is mounted on top, but with a smaller distance. Return to contents</a>How to install joists on a concrete base?There are 2 methods of installing joists on a concrete surface. The first method involves pads of varying thickness between the beams and the concrete base. They are used to be able to level the floor. This method is used quite often, but you should know that it is not recommended. After some time, the pads may begin to dry out, change shape or fly out. As a result, the floor may begin to creak or bend.
Option for fixing the logs.The second method involves pouring a cement screed to level the floor base. The joists are installed on the screed. In this case, the floor base will not deform, and the screed will be able to provide reliable support along the entire length. Before installing the joists on the concrete base, you will need to do some things:
After these works it will be possible to installlogs. It is recommended to use bars longer than 2 m during work. If the length is not enough, the slats can be joined together with their end parts. If you plan to connect the logs, the joints of nearby rows will need to be placed not at the same level, but with an offset of 0.5-1 m. It is not allowed to install the logs on soft insulating material, since such a structure will be unstable. The insulating material must be installed in sheets between the logs. If there are gaps or cells left, they will need to be filled with scraps of insulating material. Return to contents</a>How to lay logs on the ground?First of all, you will need to level and compact the base of the soil. This work can be done manually, for which you should use a large log. A board is nailed to the bottom of the log. To compact the base, you need to move the manufactured device along it. The board should be 5 cm or more thick. Next, you will need to take measurements and mark the support posts for the beams. If you plan to use the bars of the lower trim as supporting elements for the logs, then the marks will need to be put directly on the bars with a simple pencil. If a grillage is used, which is covered with roofing felt, then the marks should be put on the roofing felt. The distance from the initial log to the wall should be approximately 15-20 cm. In some cases, the distance may be smaller. It is imperative to make a foundation for the support posts. You can make a separate foundation for each post or a joint foundation for a row of posts. The minimum dimensions of the foundation for one post are 40x40 cm, the height of the structure is at least 20 cm. The foundation for the columns is poured as follows:
Scheme of installation of logs on a wooden floor.
After the concrete mixture has dried, you will needperform waterproofing. To do this, you need to cut the material to the size of the post. The material is laid on concrete. There is no need to coat the structure with bitumen. The next stage is to lay bricks in 2 layers. The last layer should be perpendicular to the length of the log. During the laying process, a solution of cement and sand should be used. The brick must be of a grade not lower than M100. Next, waterproofing material is laid on the brick. To do this, you need to cut the roofing felt to the size of the brick post, and then lay it on top of the structure. Next, a soundproofing gasket is installed. It is recommended to additionally secure it so that it does not slip. The floor base on the logs must be level, so it is important to check the horizontality of the logs. To do this, you first need to lay the "beacon" logs. If the logs were installed with unevenness, then the excess can be removed with a plane, and linings can be installed under the deflections. The maximum deviation is 1 mm per 1 m. Then all intermediate beams are installed. The logs are fixed to the posts with corners. In this case, it is best to use self-tapping screws that should enter the beam by 4-5 cm. The other part of the corner is fixed to the support post with dowels. If you plan to place various communications between the beams, you should know some rules:
Installing logs with your own hands is quite simple if you have all the necessary tools and materials for the job.
