In residential and industrial construction, the concrete base is currently one of the most popular. It is suitable for almost any decorative coatings, and it can be used in its original form if appropriate processing is carried out. Subject to the pouring technology, the main advantages of such a coating are preserved, among which it is worth highlighting:
- shatter resistance;
- high strength;
- durability.
Which solution to use for pouring
Pouring a concrete screed may involve the use of one of several mortars known today. The mixture must be selected taking into account further lining and minimum strength. The M-150 coating will be able to withstand a force of 150 kg/cm2. If you plan to use a self-levelling compound, then the requirements here are even higher - from M-200.
Classic mortar, which is used for the installation of ordinary concretescreeds, it is considered a cement-sand mixture that will close in a ratio of 1 to 3. This recipe is time-tested, but for the preparation of concrete you should not use washed river sand that has not been pre-treated. The frozen surface in this case will not be strong, but over time it will crack and begin to crumble. This is due to the fact that the grains of sand under the influence of water smoothen the edges, which prevents proper adhesion.
Quarry sand is much better in this matter. When choosing, you must ensure that there are no clay inclusions in it, which reduce the strength of the screed. An important condition for durability and strength is the right amount of water. Some craftsmen try to make the job easier by using an excess amount of liquid, getting a semi-liquid solution. At the output, the screed does not have the required quality.
Excessively liquid mixture will shrink, and a flat surface in this case is not to be expected. If the cement-water balance is disturbed, the surface turns out to be unbound, and the floors during operation form an increased amount of dust.
Concrete screed technology may involve the use of ready-made dry composition. It has outstanding performance and durability. There is no need to use heavy manual labor or powerful machinery for mixing. A mixer or a powerful electric drill will suffice. There should be no problems with the dosage of dry ingredients, because everything is already provided by the manufacturer. Many mortars are lighter, which reduces the load on the floor and makes it easier to lift the material tofloor.
Surface preparation
Before you make a concrete screed, you must prepare the surface. If the floor is laid on the ground, then the work is carried out in a certain sequence. The soil is selected to a depth of 500 mm. A pillow of sand 100 mm thick is poured into the bottom.
The preparation is compacted, and a gravel layer is poured on top. Next, you can pour concrete with the addition of expanded clay. The thickness of this layer is 200 mm. It is necessary for surface insulation.
After the base has hardened, it is waterproofed with polyethylene or roofing material to prevent the penetration of ground moisture. The waterproofing material is laid on the lower part of the wall, and the height should slightly exceed the thickness of the planned screed. If necessary, another layer of insulation is poured on top, after which you can start pouring the reinforced finishing screed.
If the work is carried out in the apartment, then the old screed is removed. It does not guarantee integrity, over time it may begin to crack and peel off, and deformations will be transferred to the poured layer. This stage is also important for the reason that there are permissible loads on the floor slabs. In serial high-rise buildings, the permissible load is 400 kg per square meter.
Another factor that favors the need to remove the material of the old screed is the height of the ceilings in apartments, which is not always significant. You can remove concrete with a perforator, but there is no way to prevent destruction or damage to the floor slabit is forbidden. The remains of construction waste are removed, and then the surface is cleaned and dust-free.
Repairing the rough surface
The installation of a concrete screed at the stage after the removal of the concrete layer provides for repair work. If the screed is tied, then the existing recesses are cleaned out, and the cracks and cracks are divided by a width of 5 mm so that the concrete mortar can penetrate there.
When a floating screed is planned, all flaws are repaired. There should be no voids under the waterproofing layer, because condensate will accumulate there. These areas will become areas of high humidity. Defects can be repaired with a repair compound, concrete mortar or epoxy putty. Mounting foam is suitable for large defects.
The corners between the floor and the walls should be repaired. When pouring the screed, water from the solution may end up in the ceiling or leak to the neighbors from below. Before the concrete floor screed is poured, the floor surface is primed with a penetrating compound. This measure allows you to remove dust from the surface and improve adhesion to poured concrete. The overlay will not so actively absorb moisture from the mortar.
The soil is poured over the surface and evenly distributed with a roller. In hard-to-reach places, it is better to use a brush. Along the perimeter of the walls, it is necessary to stick an elastic damper tape, which will act as a compensator for expansions in the screed and prevent the material from deforming or cracking. If the screed will be located on the separating layer, thenthe ceiling should be covered with plastic wrap. The strip is laid with an overlap of 100 mm. Joints should be glued with waterproof tape.
The film is especially neatly placed in the corners so that wrinkles and jams do not form. There may be air pockets. The edges of the film should be 10 mm higher than the tie.
Installation of beacons, reinforcement and determination of the zero level
In order for the screed to be horizontal, it is necessary to create a system of beacons. If the farm has a laser level, then you can determine the zero level of the floor. There are horizontal stripes on the walls. For this, it is most convenient to use a rail. The step between the guide and the wall should be 300 mm. If you make this distance longer, then a poorly aligned area or a failure will form along the wall.
The distance between adjacent guides is not regulated. Not so long ago, improvised materials such as pipes or wooden blocks were used as guides. Today metal profiles act as lighthouses. Self-tapping screws can be used as fasteners.
Pouring grout
At the next stage, you can begin to form a concrete screed. To do this, a solution is laid out between the guides above the zero level. When it starts to set, you can begin to form a plane. The process uses a rule by which the base is smoothed to hats.
The use of a reinforcement system can becomeuseful measure, especially for thick screeds. For this, a metal mesh made of galvanized steel wire is purchased. The mesh size can vary from 50 to 100 mm. However, many people make mistakes when laying reinforcement, placing the bars on the waterproofing layer.
In order for the reinforcing cage to perform its function, it must be placed in the thickness of the solution. For this, polymer coasters are purchased. You can make wire supports or raise the mesh by laying it on a lining of broken tiles or fragments in a concrete screed. The use of wooden linings should be avoided.
Screed insulation
Insulation of a concrete floor screed can be carried out with slab materials. Communications are laid before the installation of thermal insulation. In the insulation, it is necessary to cut grooves for pipes and wires. The insulation must be adjacent to the damper tape glued around the perimeter. The plates are mounted in a checkerboard pattern, this will eliminate temperature corridors.
Waterproofing
The next layer will be waterproofing, which is laid with an overlap. Sheets are fastened together with construction tape. If you plan to use mineral wool as a heater, then another layer of waterproofing is laid from below to prevent moisture from penetrating from below. An additional layer of film is not required if the insulation is carried out with foam plastic or polystyrene.
Reinforcement and pouring
Concretefloor screed will consist of several layers. A reinforcing mesh is located on top of the waterproofing, it is laid with an overlap and the elements are connected with wire. Next, beacons from aluminum corners are exposed, and the slats will serve as formwork. The next step will be the preparation of a screed solution, the components of which are:
- sand;
- cement;
- water.
Screed thickness selection
The thickness of the concrete screed may vary depending on the composition. When the base is reinforced concrete, the thickness can be equal to 2 cm. If there is no reinforcing element, then the minimum thickness is 4 cm. The maximum parameters are not regulated. But it makes no sense to fill to a height of more than 17 cm. Structures of this type are created only when necessary, because the cost of materials and time will be quite large.
In conclusion
Concrete screed may be thicker if heavy loads are applied to it during operation. The simplest example of such a room is a garage, where the weight of the car and the impact on the floor during movement are large. At the same time, the 15-cm floor is quite justified. A concrete screed can be part of the supporting structure, while it should also be high enough.
