- What are the advantages of dry screed
- Application area
- The choice of material for bedding
- Dry screed filling and leveling
- Laying floor elements
- What flooring can be used
Perhaps you can’t think of a dirtier and more tedious type of repair work than pouring a floor with concrete or cement screed. We suggest paying attention to the method of dry leveling with the subsequent installation of the finished floor covering without dirt, dampness and with a guaranteed excellent result..
What are the advantages of dry screed
A dry screed retains all the advantages of dry construction: no dampness and drying time, cleanliness, the possibility of partial repair of the floor even after applying finishing coatings to the walls.
This is one of the easiest ways to level the floor and bring it exactly to the same level with the adjacent rooms. A dry screed, in contrast to a cement one, in itself is a good sound and heat insulator, in combination with wall insulation, it gives an excellent indicator of energy saving.
In the bulk of the bulk material, it is very easy to hide all kinds of communications: electrical wiring, water supply and heating pipes. As for the underfloor heating systems, their installation is also possible on a finished surface with a technical screed filling with a layer of 15–20 mm.
The dry screed is also advantageous for the price. When using original materials for the device 10 m2 floor with a thickness of 100 mm, their cost will be about 9500 rubles. against 12,700 rubles. for packaged cement-sand mixture of the same volume.
Due to its complete environmental safety, dry screed can be used in residential and office premises. The strength of the coating is sufficient even for rooms with a high flow rate, the floor perfectly perceives both the static load from furniture and dynamic vibrations when walking or jumping. Floor installation on a dry screed is possible with a backfill thickness from 30 to 120 mm.
For the installation of a dry screed, a solid and solid foundation is required: floors made of concrete slabs or on wooden beams, or a cement screed over the ground with a thickness of more than 35 mm. The base should be solid, cracks and dips should be pre-sealed with cement mortar M100.
Dry screed is very demanding on strict adherence to installation technology. Even the slightest violations can lead to strong and uneven shrinkage of the filler, which will lead to deformation of the floor..
The choice of material for bedding
One of the types of solid granular material with a fraction of 1-4 mm with low hygroscopicity is used as a filler: expanded clay, perlite or vermiculite.
Expanded clay is the most popular because of its cheapness and prevalence. Ordinary construction expanded clay is not suitable; for dry screed, sifted expanded clay of fine homogeneous fraction (less than 5 mm) is used.
Vermiculite is much lighter than other bulk materials and is used primarily for flooring on the upper floors of buildings. Perlite and perlite sand have the lowest shrinkage due to their high homogeneity. In terms of the performance of the finished floor, the choice of material does not play a decisive role, but only if the installation technology is followed closely.
Dry screed filling and leveling
To avoid moisture migration from the floor, it is covered with plastic wrap, the joints of which are soldered or glued. The film is adhered to the walls by 20-30 cm, a compensating tape made of expanded polyethylene is laid around the perimeter of the room.
The original technology involves leveling the filler using a special tool – guide rails and beacons. The lighthouses are laid on top of the fill at a predetermined level, between them the filler is distributed and leveled with a bar. Thus, after removing the beacons, an absolutely flat surface is formed..
In the absence of a special tool, the CD frame profile can be used. First, two paths are poured from the filler, one near the wall, the second at a distance of 150-200 cm, according to the length of the existing rule or rail. On the poured paths, the profile is laid with the ribs down and set in level using a laser level or cross lacing. Beacons must be aligned and across so that no gaps appear when laying the rule on them.
The filler is poured and leveled in strips between the lighthouses; floor elements are laid on a flat surface as islands for walking. After leveling, the beacons must be removed, their presence provokes an uneven settlement, which greatly deforms the coating. The resulting grooves are filled with a small amount of granulate.
Laying floor elements
As a preparatory floor covering, two layers of GVL sheets are used. An intermediate reinforcing layer of 10 mm sheets is first laid on the filler, tightly fitting the joints. The second layer of gypsum fiber board is laid in the other direction in order to overlap the joints with an overlap of at least 15 cm. You can also lay the finishing sheets directly on the backfill, if no serious loads are expected on the floor. With increased requirements for sound and thermal insulation, it is possible to install an additional layer of extruded PPS.
As the top layer, you can use GVL boards with a thickness of 20 mm, glued from two 10 mm sheets with an offset and the formation of connecting folds. Before laying the second layer, the surface of the lower one is lubricated with PVA glue, as well as the places of folded joints.
After laying, the plates are fastened with self-tapping screws for the gypsum board, screwing them strictly perpendicular to the floor and hiding the caps by 1–2 mm. Next, the excess damper tape and polyethylene are trimmed, then the joints and traces of self-tapping screws are covered with a finishing putty. After it dries, the surface is treated twice with a deep penetration primer.
Of course, no one forbids inheriting the fundamental principles of the technology and replacing, if necessary, GVL with OSB or moisture-resistant plywood. But in this case, it is impossible to give a complete guarantee that the floor will function for a long time and will not deform, since such a combination of materials has not been tested by time.
What flooring can be used
The hard layer of the floor on a dry screed absorbs the load and shrinks evenly under it. Therefore, almost any type of flooring can be used for cement screed – from linoleum to ceramic tiles..
It is also possible to use any type of self-leveling floors, but in this case the damper tape and the film must be cut off after pouring and final drying of the final floor covering..