What are the advantages of semi-dry floor screed

In modern construction works an alternative to the usual option of wet or dry screed on plasterboard is – semi-dry floor screed. This method, above all, accelerates the formation of the basis of the floor during construction. Semi-dry screed, in fact, is designed to form a layer using auxiliary special equipment. But, among other things, it can be done independently.

Выравнивание стяжки

The main advantages of this option – low water demand during the preparation of the mixture and, consequently, reducing the risk that excess moisture will penetrate into the floor or to the neighbors. The absolute drying period is reduced and further phases of the repair or construction work can be carried out immediately.

Another important advantage of this method is the possibility to form a perfectly flat surface directly to the screed without the help of self-leveling poured floors, which, although they give an opportunity to perform reliable and even coverage on top of the surface of the screed, but it greatly increases the period spent on the implementation of the work. And one more advantage – the risk of cracks and shrinkage processes during drying is reduced.

What are the main stages of screeding

Полусухая стяжка пола

Semi-dry floor screed is basically similar to the method of forming a wet screed and includes several of the following steps: surface preparation, the formation of a waterproofing layer, installation of beacons, distribution of the mixture, alignment, grouting the surface.

The use of a waterproofing layer is associated with the technological nuances of this method. As on completion of the layer is formed, which has an increased water vapor permeability compared to the method of wet screed.

This type of floor leveling is referred to as floating. What can be attributed to the disadvantages and disadvantages of semi-dry screed at the same time with the disadvantage that the final coating is able to withstand somewhat less load. Waterproofing layer protects against excessive absorption of moisture by the base of the floor (floor slab) and allows the mixture to fix properly.

Semi-dry screed floor is made with the formation of a layer of not less than 30 mm and even up to 80 mm. Under the screed you can perform thermal or acoustic insulation layer. Dense and reliable materials are used as thermal insulation. For example, polystyrene foam, Penoplex. If the thermal insulation layer is required to be of insignificant thickness or when forming a large thickness of the screed, expanded clay is used.

How to prepare the surface

If the repair work and replacement of the outdated coating, the old coating is removed in its entirety almost to the ground. There is no need to save the places where it still seems to be attached acceptably. After the removal work, you can begin to clean the surface of contaminants. It is preferable to coat the base over the entire surface with primer, but it is allowed to do without this step when applying a waterproofing layer. At this stage measurements are taken to calculate the required volume of mixture. Check the level of the horizon on the walls. To do this, one marking is noted on the surface of the wall, and from it across the entire area is marked with a line that defines the horizon.

Horizontal transfer of the markings on the remaining walls can be performed using a water and hand levels or laser level, it projects a line on each wall. Applying the latter device, it is easier to find the highest point on the surface of the floor. In the other case, measurements are taken manually by comparing the height of all parts of the floor to the marked line on the wall surface. Finding the highest point makes it possible to determine the height differences of the floor to change the volume of the required mixture. Approximately 0.16 cubic meters of mixture is needed per 100 square meters with a difference in height of one millimeter. The same is true for every uneven surface on the subfloor.

How to lay a waterproofing, thermal insulation layer

PE film up to 200 microns thick may be used for the execution of the waterproofing layer. Its strips are placed overlapping one another. The water proofing layer shall rise on the wall surface by about twenty centimetres. PE film is not fixed to the floor surface in any way. Allowed for ease of work to fix the edges of the film on the wall surface, but it should be done with caution so as not to bend it in the corners and the junction of the surface of the wall and floor. It is enough to fix the film on one edge only.

On top, if necessary, place sheets of thermal insulation. They should be placed tightly to each other, without a strong pressure between them and the walls. If expanded clay is used, then select a composition of sand, which has a particle size of up to 6 mm. Seramsite layer is carefully compacted and flattened. Auxiliary placement of reinforcing mesh is not necessary. This technological process is not designed for this reinforcement. It is preferable, if necessary, to add propylene fiber to the mixture. This will ensure the strength of the coating. In addition, the fiber will give more elasticity to the mixture, and it will be easier to level it.

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