There are many reasons whyIt is impossible to conduct a conventional cement floor screed. This is a limited time for preparation of the foundation for decorative floor covering, unfavorable climatic conditions of the premises for the full drying of the wet concrete layer or the need for permanent access to the paved communications. But we must not forget that the opportunity with minimal costs and in a short time to give the floor an ideal evenness with a dry screed has its own characteristics. 
Scheme of dry floor screed.
Features of dry floor screed
The floor tie is of two types: made of a damp cement-sand mortar or a collection, called still dry. The latter method is considered to be much more economical and therefore becomes more and more widespread during construction and repair work. Another reason for its popularity was the relative simplicity of the device of a dry floor screed, which does not require complicated preparatory operations and high professionalism of the masters. Alignment of the base occurs with the aid of bulk materials of a small fraction. Usually, for this purpose, expanded clay or perlitic expanded sand is used. Subsequent ramming allows to compact the backfill, making it perfectly smooth, and coating with gypsum-fiber sheets creates a stable and solid black base of the floor. Back to contents</a>
Disadvantages of floor screed, carried out by dry method
Scheme laying floor screed. The disadvantages of using a dry screed are less than the advantages it possesses. Despite this fact, the disadvantages of this means of leveling the base are quite serious. Before making a final decision on the application of this method, it is necessary to take into account all the factors that can subsequently affect the quality and durability of the substrate. The main drawback of a dry screed is the need to avoid any contact with moisture. In such premises as kitchen and bathroom, its device is contraindicated, since penetration of water into the backfill will inevitably lead to the formation of mold and fungus, which can be eliminated only with complete dismantling and replacement of the base. For the same reason, it becomes impossible to install a system of water-heated floor - the slightest leak will cause irreparable damage to the ground. Even the lining of reinforced waterproofing does not protect the backfill layer and GWL from the penetration of water. Perform work on the installation of dry screed better in dry and warm weather, so that the expanded clay or sand mixture does not absorb moisture. Do not level the floor with a dry screed in rooms with no heating and high humidity. Basements, basement floors and other similar places are unsuitable for its use. 
Tools for dry floor screed. Dry screed has a fairly soft base and poorly tolerates the impact of mechanical stress. The covering from gipsokartonnyh sheets does not maintain constant physical pressure on a surface in public places, therefore the dry coupler is more suitable for premises. The main criterion for the strength of this method is the good quality of the tamping of the dry mix. The violation of the technology of this process can lead to low stability of the substrate. A fine-grained filler is a loose and rather unstable material. Its uneven shrinkage can lead to differences in the level of the surface and the appearance of bends of the decorative floor covering. All this will contribute to the violation of its integrity and rapid wear of the floor. The surface of the floor, the basis for which is a dry loose screed, is not recommended to subject any increased physical pressure. This applies to the installation of massive partitions made of plates, blocks or bricks. They can force their weight basis, which will cause unplanned repairs. The same applies to heavy objects of the situation. In rooms with low ceilings, it should be noted that a large layer of dry backfilling will significantly reduce the height of the room. Before making a decision about the choice of the floor leveling method, it is necessary to make the necessary calculations and measurements, so as not to collide later with a significant deterioration in the interior and a decrease in the free space of the room. Another negative point of the device of tightening the dry method is the rustling of the claydite during the movement on the floor at the first time after the completion of the work. This effect will cease after the full shrinkage level of the backfill, but for some time will have to accept the unpleasant sound. Reproduction of insects and rodents in the dry mix layer is also the weak side of the dry method. Therefore, when it is used in private homes, it will be necessary to conduct regular disinsection and deratization in order to get rid of dangerous rodents and pests.
