When talking about screeds, we must first clarify how they differ from plasters, as they are similar construction concepts. The main difference is that screeds are applied to the floor of a room, while plasters are applied to the walls.
Screeds contribute to creating a flat and strong base for floor coverings. They not only level but also protect floors.
Screed is a floor covering that has a huge application in construction. Its main purpose is to level different types of floors, make the necessary slopes and directions for drainage systems and facilitate the laying of the final floor covering. It is used both in residential buildings such as apartment blocks, cooperatives, houses and the like, and in areas with industrial and commercial purposes - warehouses, retail spaces, parking lots and garages, factory halls, administrative buildings, etc.
TYPES OF GROUTS
Modern screeds are self-leveling mixtures based on cement or gypsum. Screeds come in several types depending on the composition of the materials they are made from and the method of application. The main and most common types of floor screeds are cement-sand and self-leveling. Cement screeds are used to level the surface after the concrete base. The minimum application is 3 cm. Self-leveling screeds are used to achieve ideal smoothness of the surface before laying parquet, laminate, PVC flooring or carpet. The thickness of the screed varies from 1 mm to 20 mm.
Cement-sand screed is placed on the supporting base, separating or insulating layer for indoor and outdoor use. Due to the degree of heat transfer, it is widely used in the installation of electric or other types of floor heating. Cement-sand screed, as well as other types of floor screeds, serves as a basis for the installation of the final floor covering, be it terracotta, granite tiles, linoleum, natural and laminated parquet, carpet or other type of covering. Self-leveling floor screeds are used mainly in cases where there are high and specific requirements for the screed. They are sanitary and hygienic, have high antistatic protection and chemical resistance. That is why they are most often used in the construction of production premises, sports halls, administrative buildings, etc. They are divided into thick-layer and thin-layer. Thick-layer self-leveling screeds are used for larger irregularities on the base, while thin-layer ones remove smaller irregularities, but thanks to their high flowability they are easier to use and provide ideal leveling of the horizontal level of the floor. Currently, there is a wide variety of self-leveling screeds on the building materials market. Different types of screeds are available, such as calcium sulfate for manual and machine application, cement sulfate liquid floor screed, high-strength self-leveling screed, outdoor primer screeds for terraces and balconies, self-leveling mixtures, etc.
Undoubtedly, the goal of applying the leveling screed is to create a flat and homogeneous base before laying any type of floor covering. Regardless of the type, it is very important to observe the correct ratio of the materials that make up it. In the event of a poor and incorrect ratio, cracking of the screed may occur in the future, which will lead to adverse consequences for the final coating or reduce its heat and sound insulation properties. When applying, there must be continuity of the process in order to achieve a homogeneous base. For this purpose, specialists recommend the use of screed machines. Other advantages of machine laying are shorter implementation times, low noise levels, dustiness and contamination with building materials, etc.
HOW IS SELF-FLOWING MORTAR APPLIED?
For all types of finishing, a perfectly flat floor is needed. Self-leveling floor screed will provide us with covering of irregularities and a solid base. Regardless of what flooring you decide to lay, the floor must be perfectly flat. This guarantees the durability of the coating.
Before applying the self-leveling screed, all cracks and other weak areas on the floor must be treated. To do this, they are mechanically widened and cleaned of any particles. The filling must be done before applying the self-leveling screed.
Irregularities are filled with quick cement, as the popular name of the product is. This is a product that provides fast work when time is needed to be shortened. It is a dry mixture of special cements and additives that control the setting time and strength characteristics of the material.
The substrate and parts must be sound and free of any separating agents. Loose areas on the substrate must also be removed.
When working with cement mixtures, it is necessary to moisten the base to ensure good adhesion. The mixture is mixed with the amount of water indicated on the package until a smooth solution is obtained. Depending on the application, it can be thicker or thinner. The resulting mixture acquires very high early strength. It is used for quick fastening of parts and elements, installation of frames, for openings of inspection shafts, filling holes.
Mineral fillers in combination with cement accelerate the hardening process. The material should be used within 4 minutes after mixing.
The ambient temperature plays an important role in the quality of the mixture. Therefore, at low temperatures, warm water should be used to stir the mixture, and at high temperatures, cold water should be used.
To achieve the product qualities guaranteed by the manufacturer, it must not be mixed with other substances.
30 minutes after the treatment with quick cement, the installation of the artificial flooring adhesive system can be started. The primer is one of the components of the flooring adhesive system, which ensures reduced and uniform absorbency of the substrate. It forms a layer that improves adhesion to the floor screed. It is applied without dissolving, using a trowel or roller. If necessary, the primer is applied once more in a direction perpendicular to the initial one, after the first layer has dried.
Before applying the leveling material, the primer must be completely dry.
If the amount of water is more than necessary, shortly after mixing the binders settle to the bottom, and the water with the dissolved cement remains on top. When pouring, the water that is on top is poured first, and the thick part remains in the bucket. The cement and water absorb into the base and in no way do we achieve the result of a self-leveling screed. If the water is not enough to achieve the desired consistency, the mixture cannot spread and self-level, which is its main task.
To achieve the desired result, the mixture is mixed in the specified water/material ratio and stirred with a mixer at slow speed. Slow stirring will make the mixture smooth and free of bubbles. To activate all the ingredients, it is necessary to wait 1-2 minutes and leave the mixture to rest. Then stir again and work can begin. Pour it onto the base and spread it over the entire surface with suitable tools. The application time is about 25 minutes. After that, it becomes impossible to spread and self-level the mixture. The layer thickness is from 1 to 10 mm. The drying time of the screed also depends on the thickness.
The freshly poured layer must be protected from drying out too quickly. This will prevent cracking of the surface layer. The base can be walked on after about 3 hours, but the flooring can be laid after 24 hours at the earliest.
HOW IS SELF-LEVELING SCRATCH APPLIED?
Self-leveling screed is used to create a strong and even base for subsequent floor coverings. It is spread with special tools, and floor coverings can be laid after 24 hours. Self-leveling screeds are a very quick and safe solution for leveling bases with a small amount of unevenness. Their important advantage is their resistance to mechanical impact.
Self-leveling screed is applied to a primed base after the primer has completely dried. An electric mixer is used to mix the floor screed. It is recommended to mix at a slower speed so as not to entrain too much air and form bubbles. The mixture takes about 2-3 minutes to set. Then it is mixed again and poured onto the floor. It is spread with a notched trowel or a special needle roller. The application time is about 25 minutes.
The thickness of the layer of the ready-mixed solution determines the drying time of the screed. Too rapid drying should be avoided. It can be walked on after about 3 hours, but the flooring can be laid after 24 hours at the earliest. The temperature of the base must be at least 15°C. The cement screed must be made no earlier than 1 month before proceeding with the application of a self-leveling screed on it.
To achieve a good final result, the condition of the substrate is essential. With good preparation and condition of the substrate, time, materials and nerves can be saved when applying subsequent coatings. The substrate must be dry – or more precisely, its humidity must be within the permissible limits.
What could happen after applying self-leveling screed on a substrate with high humidity, even if all the manufacturer's requirements and recommendations for working with this material are followed? The moisture remaining in the base under the flooring necessarily rises to the surface. This causes the flooring to become damp and deform. Deformation can occur even with ceramic coatings - cracking of the joints and peeling of the tiles themselves.
Once the base has an acceptable humidity and is cleaned and dust-free, it can be primed. Primer is mandatory before applying self-leveling screed. Regardless of the base surface, conditions must be created for the surface coating to adhere to it permanently. This is why primers are used that penetrate deep into the base and improve its adhesion to the next layer. Thanks to their bonding and strengthening properties, primers strengthen the base. Another task of the primer layer is to reduce and level out absorbency. The result of using a primer that meets all these requirements is a stabilized base with reduced and uniform absorbency and ensuring a strong bond between the boundary surfaces of different materials.
After the primer has completely dried, the self-leveling screed is applied. After the initial mixing of the mixture, it must be left to rest for some time to mature and then mixed again. The spreading of the mixed mixture must be carried out within 20 minutes. If there is a delay, the mixture begins to harden and self-leveling becomes impossible.
The thickness of the layer is from 1 to 10 mm. This layer thickness is different for different screeds.
The use of special tools and devices makes the work easier and ensures a perfectly smooth surface.
The hardening of the self-leveling screed depends mainly on atmospheric conditions. In order to avoid the negative consequences of rapid drying, the surface must be protected from direct sunlight and drafts. The flooring can be walked on after 3 hours, and heavier loads can be tolerated after a minimum of 24 hours, depending on the thickness of the flooring.
HOW IS CEMENT-SAND MORTAR APPLIED?
Before applying cement-sand screed, it is very important to accurately determine the level throughout the apartment and to apply the screed in accordance with the final flooring - parquet or granite tiles, which can be of different thicknesses.
Therefore, the screed must be laid with different thicknesses in different rooms, but the end result must be the same - an even level everywhere in the apartment.
The floor screed is suitable for laying on concrete and solid cement-sand substrates.
The solution prepared for work is applied in one layer with a machine onto the base. The floor screed is leveled with a metal trowel, observing the layer thickness. The strength and durability of the screed depend on the percentage ratio of water/cement in the solution. When the water/cement ratio is increased above the recommended one (often, to make the solution easier to apply, more water is added than necessary), the strength of the screed decreases, it has lower compressive and tensile strength, and its drying time is extended. A large shrinkage of the applied material occurs. As a result, stresses arise, which also lead to the appearance of cracks.
The thickness of traditional soluble screeds should be no less than 30 mm, usually varying around 50 mm, but it can reach much more. If the floor screed is thinner, it will begin to separate from the base and crack. If something like this happens, it is best to replace the screed with a new one. Why is this actually so important? If, for example, you are going to cover the floor with ceramic tiles and the screed under them has poor adhesion to the surface of the concrete slab, an irritating noise will be heard when walking on the floor. In addition, over time, as a result of operation, the floor will become uneven and the tiles will begin to separate from the base.
A significant disadvantage of classic soluble floor screeds is the long drying time and reaching maximum strength. Between laying the screed and applying the finishing coating, a relatively long break of about 28 days is technologically required, necessary for the concrete to gain strength. Without this, the cement-sand screed does not guarantee a perfectly flat surface.
WHAT DO WE OFFER?
With us you can find universal cement-sand, self-leveling and self-leveling screeds. In addition, we also offer cement screed with fibers. All products are in 25 kg packages. From our store you can also get a convenient 30-liter plastic container designed for mixing self-leveling screed.
Detailed information about the characteristics of the products is contained in their technical data sheets. The screeds are from the brands BAUMIT, WEBER, CERESIT, ARDEX, KNAUF.
The prices are affordable.
