In construction and repair, material such as plywood is often used. It has several positive characteristics. Plywood is a durable, high-quality and environmentally friendly material, which in addition to everything has a low cost and is universal in application. In addition, the material is used to prepare the floor for further finishing. By laying the plywood on the concrete floor, you can get the perfect platform for finishing. This is a fairly convenient and economical option.
How to put plywood on a concrete floor? Before starting work, you need to pay great attention to the selection of the right material. Now the market has a wide range of products. Plywood is distinguished by its technical and operational characteristics.
How to choose the right material?
When buying, you need to know several key properties of wooden sheets. There are a couple of evaluation criteria:
- Moisture resistance. According to this indicator, there are materials of the following types: FSF and FC. The first type is characterized by increased moisture resistance. But, despite this, this material can still not be used in the bathroom. Also, laying plywood on a concrete floor is not performed in bathhouses and in the kitchen. As for the second category, it has average moisture resistance. To glue the layers of wood, the manufacturer uses glue based on carbide resins. This material is not dangerous to humans. Therefore, it is possible to lay plywood on a concrete floor both in industrial premises and in an apartment. But, again, this should not be a bathroom or kitchen.
- The material of manufacture. There are conifers and deciduous. The first type is highly resistant to fungi and other microorganisms. But, such a material is not suitable for laying plywood on a concrete floor under a laminate in residential premises. But deciduous - this is the best option for arranging floors. Better to choose FC series birch plywood.
- Formaldehyde level. Although plywood is an environmentally friendly material, chemistry is used to glue it. Therefore, you should always pay attention to the level of formaldehyde content. There are two classes: E1 and E2. The first group includes materials where 10 milligrams of formaldehyde is produced per 100 grams. In the second case, about 30 grams may be contained. For residential premises, experts recommend the use of exactly E1 products.
Thus, if finishing is done in a house or in an apartment, you need to use plywood of the FC series. But you do not need to focus only on this class. This material can be further divided into subgroups:
- Material where there are no external flaws (the most expensive among all others).
- There are veneer inserts and knots.
- Material with a large number of cracks.
But at the same time, the sheets will be glued together quite qualitatively. Therefore, it will be financially impractical to use expensive and beautiful plywood for the rough floor. The best option, according to experts, will be that material that contains a small number of knots and veneer inserts. If we talk about brands, positive reviews receive products based on E1 wood and FC. The thickness of the sheet should be from 12 to 16 millimeters. There are also exceptions. These are sheets for installation on logs. But we will talk about this point at the end of this article.
We carry out cutting and fitting of plywood
So, we decided on the desired grade and grade of material. However, it is important not only to acquire the desired type, but also to calculate the quantity. So, the floor area needs to be increased by 10 percent (this part will be left for stock). Standard sheet sizes - 125 by 125 centimeters. But working with such large sheets is quite difficult. Therefore, we saw them into four squares with dimensions of just over 60 centimeters on each side. After that, we will be able to create the right amount of expansion joints that will compensate for the moisture and temperature deformations of the wood. At the same time, smaller sheets do not expand as much as large ones. For cutting pieces, use an electric jigsaw. This tool does not leave delaminations and chips. Further, the cut sheet is laid out on the base for preliminary adjustment (we do not use glue and screws yet). So we can approximately fit all the pieces, taking into account the existing protrusions.
Experts recommend observing certain seams between the squares (their size is from 8 to 10 millimeters) and the gap between the wall and the extreme elements of the flooring (about 15-20 millimeters). The sheets themselves are placed as in masonry, with offset rows. So we exclude the possibility of immediately crossing four seams in one section. What is done next? After adjusting the material, you need to number all the elements and draw a surface diagram, so that further laying of plywood on the concrete floor under the linoleum occurs quickly and effortlessly.
Methods of fastening the material to the base
It is recommended to fasten plywood in a complex way - using screws and glue. The choice of the first is determined simply - only the thickness of the wooden sheet is taken into account. But gluing plywood to a concrete floor is much more difficult. The main thing is to choose the right material. There are several options:
- Water based composition. Among the advantages is environmental friendliness. Such glue is completely safe for humans and does not have a pungent odor. Among the disadvantages is a long drying time. This nuance affects the speed of construction work.
- Solvent based adhesive. Its main advantage is the drying speed. But, at the same time, the glue releases toxic substances, which are dangerous to exhale. The room should be well ventilated.
- Two-component adhesive. This is a kind of alternative between the first and second type. This composition is chosen by many because it dries quickly and does not emit an unpleasant odor. Also, two-component adhesive can be used to install plywood even on an incompletely dried screed.
How does the concrete floor leveling with plywood? This operation consists of several important steps. Below we will consider in detail the procedure for attaching plywood to a concrete floor.
Checking the humidity of the concrete base
Before starting the operation, you need to check the humidity of the room. If this parameter exceeds the norm, subsequently the material can simply be stratified. It is not necessary to use special appliances. You can use plastic wrap and a couple of suitable weights.
So, we spread the film on the floor and crush the edges with any load. The center of the film should be free. In this form, the design should stand for a couple of days. After this time, you can do a check. If condensation has accumulated under the film, it is not possible to lay plywood on the concrete floor under the laminate. Before this operation, an additional layer of waterproofing is performed. Only then can you proceed with further installation.
Mopping base
It is necessary to polish all the bumps. How to do it? To do this, use a grinder with a special nozzle. Next, traces of old paint and putty are removed and recesses are made, if any. What if cracks in the floor are detected? They must be removed by cement-sand mortar. You also need to clean the surface of dust. To do this, use a powerful vacuum cleaner or a broom. The latter can not be wetted, as the humidity of the floor will increase, and plywood will swell in the future.
Padding
The following is a primer. As a consumable, experts advise using a primer. This product must be applied with a short-haired paint roller to the floor surface. What is the plus of the primer before the usual primer:
- The primer has a good penetration depth, which ensures the strength of the upper layer of the structure.
- The composition eliminates the presence of dust on the surface.
- It is capable of increasing the adhesion of various materials.
Plywood laying
After cutting sheets and applying a primer, you can start laying. It is necessary to focus on previously completed numbering. The operation is performed in several steps:
- Concrete floor is treated with glue for plywood. The layer thickness should be up to two millimeters. Experts recommend applying glue to small areas so that plywood can be laid out before the composition grasps.
- Pieces of plywood must be laid on the treated base in accordance with the established scheme.
- Next, the sheets are fixed using self-tapping screws. They are screwed around the entire perimeter and diagonally. The step should be from 15 to 20 centimeters. The maximum indent from the edges of the flooring is 2 centimeters. It is necessary to use self-tapping screws with a length that is 3 times the thickness of the sheets used. For example, for 12-mm plywood sheets, it is recommended to use self-tapping screws with a length of 40 millimeters.
- The stacked sheets are processed by a grinding machine with the appropriate nozzle. It can also be processed manually with sandpaper (but if the area is large, it is better to use the tool). Thanks to this operation, we will smooth out differences in the height of adjacent sheets and eliminate burrs.
We check the quality of work
After laying the plywood on the concrete floor, you need to carefully inspect the surface. It is important that the plywood sheets do not touch the walls. Expansion joints should be provided on all sides. You also need to make sure that there are no differences in height. A transition of 2 millimeters is allowed, but no more. In addition, after laying, you need to tap the wooden surface with a mallet. If there is a heterogeneous thud, you have to redo the work. This knock indicates the detachment of plywood from concrete.
Laying logs on a concrete floor under plywood
Earlier we looked at the installation method without lag. It is quite simple, but you can use it only if you need to hide minor irregularities. If the floor is too crooked or if a warm floor is to be installed, this is the method chosen. It is important that the lags are installed correctly. To check their position, you need to use the building level and the ruler.
As in the first case, surface preparation is preliminarily performed. If this is not a new screed, it must be completely cleaned of the old coating. This is a carpet, laminate or linoleum. It is important to check for cracks on the surface. If any, use a cement mortar and close up the defects. Next, you need a substrate. As it can be used ordinary polyethylene. But the film must be solid and tight, otherwise it will not bring any effect. The edges of the film are fixed with tape.
Next, the work is performed in the following sequence:
- The lowest point in the room is determined. It is from here that you need to start installing the lag. How to fix plywood to a concrete floor? They should be installed perpendicular to the incident light. In this case, the distance between the lags should not exceed 50 centimeters. It is also taken into account that the joints of plywood sheets will be located on the lags. For the horizontality of the latter, you can put wooden blocks.
- Logs are attached to the concrete base of the floor using anchors.
- A lathing is performed between the lags.
- Insulation is installed. She points to the cells of the crate.
Please note that installing lag on a concrete floor under plywood has its own nuances. So, the thickness of waterproof plywood should not be less than 18 millimeters. A two-millimeter gap is left between the sheets. It subsequently needs to be filled with mastic. Clearances are necessary in order to exclude warpage of the base, as well as the occurrence of creaking during walking. As for the fasteners, self-tapping screws are used as such. As we said earlier, their length should be three times greater than the thickness of the wooden sheet itself.
However, it is worth remembering that when laying plywood on a concrete floor by means of a crate, the ceiling height is reduced. But this is a slight deviation. However, if the ceilings in the apartment are low, it is better to refuse this method and level the surface differently.
Why is plywood laying relevant?
Whatever the method of laying the plywood, in the end you get a practical, reliable and durable floor covering with good thermal insulation properties. The service life of plywood is more than 20 years, subject to the presence of expansion joints and waterproofing (if condensation has accumulated on the film after tests). Also, if necessary, it will be possible to easily dismantle the finish floor covering (for example, a laminate).
Conclusion
So, we found out how to lay plywood on a concrete floor with our own hands. As you can see, this operation is very laborious. However, as a result, you can get a fairly high-quality (and most importantly - even) flooring. Depending on the curvature of the floor, two methods can be used. As a rule, specialists resort to the first method. But in the case of installing a warm floor or the presence of large defects, one can not do without a lag.