Subfloor

In the case of a concrete subfloor, it must be ensured that the unevenness of the floor remains within the standard limits of ±2 mm in a 2m section. Covering the unevenness of the concrete with a leveling layer is not recommended because the leveling layer (definitely not less than a 5 mm layer) is not strong enough and the glue can pull the leveling layer away from the concrete. After pouring the concrete, it must dry for 1 month or more (depending on the thickness of the concrete layer). At the start of the installation, the relative humidity must remain within ~60% RH. Concrete moisture must be measured before installation.

If the old concrete floor is smooth, unevenness must not exceed ±2 mm in a 2m section, clean and dry (max 65% RH), the floorboard can be glued directly to the subfloor. If the subfloor is not flat enough, see the section "Uneven concrete floor." If there are doubts about the moisture content of the concrete floor, take the same measures as for a damp concrete floor. See section "wet concrete floor."

If, despite the ventilation, the moisture content of the subfloor does not fit within the permitted limits, it is necessary to start looking for and repairing possible irregularities. To determine the cause of the dampness, the following must be done:

• check whether the moisture insulation outside the building is in order;
• check that the thermal insulation of the floor is not wet;
• check whether the moisture insulation of the floor is intact and correctly installed;
• check whether, for example, moisture does not get in from above the balcony doors;
• if there is a swimming pool in the lower room, check whether there is lower moisture insulation in the floor and whether it is in order;
• check if there are hot and cold bridges in the floor.

Defects found as a result of checks based on the previous list must be corrected before installing the floor covering. If the moisture content is caused by capillary moisture, the situation can be improved a little by making the floor covering moisture-proof, but even then the humidity of the concrete floor must not exceed 68%.

NB! When considering this option, it must be remembered that excess moisture in the substrate will try to escape in any case. If the moisture does not escape upwards from the floor, it is absorbed into the wall structure, causing moisture and mold damage there.

• Epoxy primer - used for moisture insulation of the concrete floor
• Roofing felt (polymer bitumen roll material) or specially adhesive materials that are glued to the whole subfloor.
• It is possible to use a film on which to place a layer of waterproof plywood.

Before gluing the parquet flags, the adhesive for fixing the moisture patch must be completely dry.

If the concrete surface is rough, it must be leveled or, if possible, sanded over. Leveling is carried out with mixtures intended for this purpose in accordance with the manufacturer's instructions. General recommendation—use leveling compound as little as possible and only use the highest quality products.

If the floor is on wooden layers or an intermediate layer in the form of plywood or OSB board is placed on top of the concrete, the boards must be attached to the layers with wood screws and, in the case of concrete, glued, in addition, they can be attached with dowels. It is not recommended to use chipboard (PLP) because its moisture resistance is lower and linear expansion differs from that of wood. When installing the tiles, gaps are left on the tiles e. expansion joints 3 5mm.

First, it must be checked whether the subfloor made of boards is suitable for use as a base layer, the unevenness must not exceed ±2 mm in a 2m section. If this condition is not met, the floor must be leveled by filling in the depressions or sanding, and in case of large unevenness, cover with an additional layer of tiles. Check that the subfloor is stable. Before gluing, the floor must be cleaned using a slightly damp cloth and cleaning agent.

The beams and layers of the subfloor must be rigid and their distance in accordance with the thickness of the material. Floor layers must be min. 45 x 45 mm, maximum moisture content 12%. The optimal distance between the shelves is 40-60cm (recommended 45cm) for 20mm thick floorboards.