Structure of the floor covering.
Standard flooring in apartments mainly consists of the following layers:
- reinforced concrete base (slab);
- waterproofing layer (bitumen, roofing felt);
- noise and heat insulating layer (expanded clay, granulated slag);
- screed (cement, cement-lime);
- flooring (linoleum, tiles).
All significant changes that occur in the layers affect the condition of the screed.
Let us consider, using examples, possible reasons leading to the occurrence of a certain type of defect.
Causes of screed damage.
Every injury has a specific cause. The following defects exist:
1. Surface abrasion.
Occurs in floors cast from low-quality materials. The top layer is always covered with cement dust.
2. Cracks and potholes.
They are formed when the main slab bends, the heat-insulating layer is destroyed, the thickness is insufficient (less than 30 mm), when cement-sand mortar is laid on an improperly prepared base, or there are no expansion joints.
3. Layering.
Appears if the general layer was poured in several stages, and the surface was poorly cleaned.
4. Porous structure.
Present in those floors that were filled with mortar with impaired density.
Methods of screed restoration depend on the type of defect. The most common damage includes cracks, chips, peeling and hidden voids. If the structure of the floor is damaged by more than 30%, it must be re-cast; for lower values, it must be restored.
Repair of cracks.
Using a chisel and hammer, deepen and widen the crack. Using a construction vacuum cleaner or a broom soaked in water, remove the resulting debris and dust. The clean surface is generously moistened with a solution made from epoxy primer and solvent in a ratio of 1: 10. This way ensures good adhesion between the damaged base and the applied element. After the primer has dried, the solution is poured into the treated gap with a spatula and leveled according to the floor topography.
Repair of moving parts of the screed.
Several deep cracks placed nearby can form a free segment that will wobble and fall through the solid flooring. Such areas are not filled with mortar from above, but are dismantled and restored.
Damage repair procedure:
- using a chisel and hammer, carefully chip away the edges along the entire perimeter of the movable element for free removal from the coating;
- when the piece is removed, large debris is removed from the vacated opening and cleaned of dust;
- for strong adhesion of the new solution to the old one, a reinforcing layer is attached to the bottom or in the middle of the defective area, which may consist of a metal grid, rods, etc.;
- re-clean the area from dust;
- coat with primer several times (the preparation recipe is described above);
- fill with cement-sand mortar in a ratio of 1 to 3;
- the surface is leveled and smoothed with a spatula to the floor level;
- to strengthen the top layer, the fresh, leveled mortar is covered with a thin layer of cement.
Elimination of delamination.
If the thickness of the outgoing layer is small, it is dismantled, the surface is cleaned, primed and covered flush with the floor with a self-leveling mixture. If the delamination has penetrated deeply, then determine the size of the defect, cut it out and perform the same operations as when repairing moving parts.
Elimination of voids.
When the main slab sag, the heat-insulating layer ages, or errors are made during floor installation, voids appear under the screed. They contribute to the appearance of a type of defect such as cracks. To eliminate emptiness:
- use a hammer or a metal rod with a blunt tip to tap the surface to determine the location of the void;
- outline the contours of the identified defect with a pencil;
- holes are drilled at the designated points with a diameter of 16 mm at a distance of 200 mm from each other;
- using a construction syringe, gradually fill the voids with a repair filler of low viscosity;
- after the injection, the repair hole is sealed.
When drilling holes in the tie, remember that this must be done carefully in the same way as the electrical cables are placed under it.
Surface hardening.
Due to daily loads and poor-quality materials, the screed becomes thinner and becomes covered with dust, even if it is under the floor covering. To prevent surface dusting, special hardening impregnations are used. They are applied using a roller to a perfectly clean base. They are selected depending on the loads that act on the floor.
Leveling the base.
To lay flooring such as laminate, the screed must have slight differences in height. But in fact, few owners can boast of the evenness of their floors. The photo shows an example of a typical deflection for apartments.
It can be easily eliminated if you use a self-leveling mixture.
Filling order:
- qualitatively clean the surface from dust;
- wash the floor with soda solution at least 2 times;
- moisturize;
- the mixture is applied in small portions and leveled evenly;
- using a needle roller, the concentration of air bubbles in the composition is reduced.
The floor can be leveled with OSB sheets with a thickness of 12 mm. For this:
- clean the base from debris, old floor layer, dust;
- the middle of the deflection is leveled with sand;
- OSB sheets are laid closely and secured to the floor, leaving a gap of 10 mm between the wall and the slab along the entire perimeter;
- differences between sheets are sanded or covered with fiberboard.
