A dry floor screed is a fairly old, but reliable method of leveling the floor, where gypsum fiber sheets are laid on the layer of a loose heat-insulating coating.
This method of leveling the floor has many advantages, among which - a small weight, which allows you not to exceed the load on the floor. In addition, leveling the floor with a dry screed is much cheaper, faster, avoiding excessive pollution, unlike the wet cement-sand method. However, the dry floor screed also has its drawbacks: it is afraid of moisture, that is, it is not recommended for use in rooms where leaks are possible (kitchens, baths, attics), and requires waterproofing of the floors.
At the base of the dry screed there is a layer of vapor barrier - a polyethylene film protecting the upper layers from wetting by pairs of concrete floors. The film is laid tightly, overlapping the walls, up to the upper level of the mound of the dry screed. Dry screed on the wooden floor requires the laying of paraffin, or bitumen paper as a vapor barrier. If necessary, the film is additionally covered with a sound insulator - polystyrene foam, mineral wool, glass wool or other foamed materials. Usually the soundproofing is laid along the perimeter, with a clearance of 10 mm from the wall. The next layer is the backfill. It not only level the floor surface, but also strengthens the sound and vapor barrier. Contrary to many misconceptions, a dry floor screed with expanded clay is forbidden, as an alternative only clay sand (screening), quartz sand, or fine-grained slag is used. The last layer is laying of plasterboard, or particle board.
Dry floor screed - technology
A dry floor screed is produced after the completion of all "wet" repair works (water supply installations, fillers, etc.). Before making a dry floor screed, it is necessary to withstand all materials in the conditions of the repaired room, to adapt all the physical characteristics of materials to the conditions of temperature and humidity , but for now we are carrying out basic work on cleaning the floor from the old coating and sealing the cracks in the floor.
Now, using a special laser beacon, we mark the level of future decking on the walls and then proceed to laying the vapor barrier film. The laying of the film, as it was noted earlier, occurs with an overlap on the walls and adjacent sheets, at least 15-20 cm, and all joints are strengthened by a dummy (edge) tape. Backfill is made depending on the degree of unevenness of the overlap, usually a layer of expanded clay sand does not exceed 30-50 mm. Align the layer of the coating with the plaster rule located between the two profiles: smoothly move the rule, using profiles as a rail, and marking the laser beacon as a guide. Next, we lay the sheets GVL with a displacement and a gap between the plates of 1 mm. We start from the door, right - to the left, after removing the folds from the plates adjacent to the wall. Gypsum fiber sheets are reinforced with self-tapping screws, with a cone-shaped slot, and special glue, which is applied wave-like movements over the entire surface. The correct layout of the slabs and strong reinforcement are the two main components of a reliable dry screed. Lastly, we cut off the excesses of the damper belt and the vapor barrier.
Time to lay a dry screed is much less than for laying concrete, you can interrupt the process at any time, and inaccuracies can easily be corrected at almost any stage of the work. With all the rest, the floor, leveled with a dry screed, will serve not less than its concrete kindred.