Screed

Smooth floors are one of the guarantees of a perfect apartment renovation. And the final flat surface can be obtained only with the help of a leveling layer of the floor.

The leveling layer of the floor (screed) acts as an intermediate layer between the upper coating and the base. the better and more professional the leveling is done, the more durable the flooring will be. We recommend that you contact an experienced specialist from the very beginning who will be able to perform floor leveling work of any complexity. You can find such specialists in the wizard application.

Regardless of whether you perform floor leveling work yourself or with the help of a professional, we suggest that you familiarize yourself with the types of floor leveling layer and the order of work.:

The meaning and importance of the leveling floor layer (screed)

Before you start leveling, you need to understand what the leveling layer of the floor is and what its characteristics are. A mortar containing sand and cement, as well as other materials, is used for the mortar.:

Currently, there are ready-made mixtures with various additives that accelerate setting and complete drying, as well as allow you to level the floor with minimal deviations.:

The quality of the flooring depends on the consistency of the mixture. The smoothing layer plays several important roles․

• raises the floor to the desired level
• It has sound insulation and thermal insulation properties
• increases the strength of the entire structure
• prepares a flat base for the final floor covering

Types of leveling layer for the floor

“The types of leveling layer for the floor are divided into the mandatory components included in the mixture, the method of laying on the floor surface and the type of mortar. In addition, depending on the water content in the mixture, the leveling layer can be "wet", "semi-dry" and "dry".”

Wet solution

A wet cement-sand mixture is one of the classic floor leveling options. The main disadvantage of this solution is the drying time (at least 21-28 days), and it is necessary to wait 2 months for the parquet to be laid.:

Wet solution with a modifier

To reduce the amount of water in the solution, various substances are added to the "wet" mixture, which make it possible to reduce the amount of water in the solution without loss of quality.

Advantages of a wet solution

• durability (if everything is done correctly, the structure will last a very long time after final fastening)
• relatively low price
• allows installation of any type of wiring
• allows you to apply a thick layer if necessary.

Disadvantages of a wet solution

• pollutes the territory during work
• it has a high weight (with a thick layer it can reach 70 kg/ m2);
• the layer thickness decreases after drying
• quite time-consuming and complex installation work
• labor-intensive production process

Semi-dry solution

The semi-dry mortar consists of a cement-sand mixture to which a minimum amount of water is added. it is laid on the base, fixed with legs and brought to the desired level. immediately after leveling, the semi-dry solution is leveled manually or with a device. advantages of semi-dry solution

• There is very little water in this solution, so the thickness of the layer does not change after drying.
• The wet solution may crack after a while, which is excluded in the case of a semi-dry solution.
• Thanks to its fast drying, it allows you to proceed to the next stage of repair in 15 hours. For this reason, heavy objects should not be placed on its surface for a month or so.:
• This type is considered the best option for repairing floors in apartment buildings, as it prevents the risk of flooding neighbors.
• Provides excellent sound and thermal insulation:

Disadvantages of semi-dry solution

• A high-quality mixture can only be prepared using a special tool.:
• It is very important to maintain the correct amount of water, as the wrong size can ruin the solution.:
• It is almost impossible to get the right mixture on your own. In most cases, improper mixing leads to cracking, brittleness of the coating, or too long drying time.:

Dry solution

This type of mix does not involve any wet work. A light sound and thermal insulation layer is laid, which is covered with a layer of drywall, plywood or cardboard.

It is important to protect the dry mixture from water, otherwise mold may form. Therefore, this type is not suitable for unheated or humid rooms. :

Advantages of a dry solution

• It has a high fire resistance, as non-flammable materials are used for the filling.
• It has excellent sound and thermal insulation properties.:
• It does not emit toxic fumes.:
• It is installed very quickly, you do not need to wait for the floor to harden, as is the case with a wet or semi-dry mixture.
• It's very light.
• Allows you to perform electrical work.

Disadvantages of the dry solution

• It does not withstand moisture. Drywall or plywood deforms from moisture, which leads to the formation of irregularities on the floor. If the leveling layer gets wet or gets wet, you will have to disassemble the floor to dry it.:
• During installation, it is necessary to work with special masks, as a lot of dust is generated.:
• It has a relatively high price.

The type of leveling layer depends on the method of laying

Depending on the installation method, the mixture can be՝

• filling in the base
• leveling layer on a separating base
• floating layer

Filling in the base

In this version, the mixture is poured onto the base, where there is no separation layer. This type of leveling layer is performed only with a wet mortar. The solution must contain a large amount of water, as the thickness of the layer decreases when pressed after drying.

Leveling layer on a separating base

To avoid contact with the base, the layer is poured onto a waterproofing separation base. for such a dividing base, pergamine, roofing material, bitumen paper and, of course, plastic film are used. for the required strength, the thickness of the leveling layer should be at least 30 mm.:

Floating layer

The floating mortar is a structure that is not connected to the base, in this case, a layer of waterproofing is applied to the base, layers of thermal insulation and sound insulation are applied to it, on top of which a wet mortar with a thickness of at least 50 mm has just been poured.:

This type of leveling layer has excellent thermal and sound insulation properties. However, the floating layer does not stand out for its strength, and the floor covering requires additional reinforcement to ensure durability. It is because of its filling that floating solutions are thicker.

Types of floor leveling layer by structure

“Leveling layers are divided not only by mortar, but also by type of structure. They can be complete or assembled.”

Full

Leveling layers prepared from a wet solution are considered completed. When the alignment is done in a single layer, this type is called a single layer. The layers are stacked sequentially, and each subsequent layer is applied completely dry on top of the previous one and should adhere well to it.:

Combined

The assembled layer is a layer made of large sheets: particle board (chipboard), fiberboard (fiberboard), gypsum fiber sheets, etc.:

The dry prefabricated layer of gypsum fiber sheets is characterized by fire resistance and moisture resistance. It is environmentally friendly and chemically neutral.:

Types of leveling floor layer depending on the mortar material

According to the required ingredients, dry mixes can be cement, cement-polymer, gypsum and gypsum polymer.:

Cement mix. it can be used to level the floor both in an apartment and in a private house. The most optimal ratio of cement and sand mixture is 1:3.

Sand-concrete mix. leveling is done with a ready-made mixture, which can be purchased at any hardware store. The biggest disadvantage of this method of leveling the floor is the lack of a layer of material after drying. when working with the mixture, it is necessary to monitor the thickness of the solution, as well as the uniformity of the solution distribution. To obtain a smooth and durable surface, the sandstone layer must be regularly sprayed with water for 2 weeks. It will take at least 20 days for the layer to completely dry.:

This type of layer is very easy to install, highly flexible, and the layer does not shrink over time. The only disadvantage of this material is that the gypsum mixture is not suitable for rooms with high humidity.

Concrete mix: the installation work is the same as in the case of cement mix.

Work on the preparation of the leveling layer of the floor

In order for the leveling layer of the floor to fully perform its functions, it must meet a number of requirements. If you do not have the relevant knowledge and experience, we recommend that you refrain from experimenting, save time and money by seeking help from experienced Master craftsmen.

• The leveling layer must have a certain strength and ability to withstand weight.
• The density of the leveling layer should be the same on the entire surface of the room.
• The thickness of the mixture layer applied to the heat and sound insulation layer should be at least 4 cm.
• If the pipes will be installed in the floor, the thickness of the layer should be 1.5-2 cm thicker than the diameter of the pipes.
• Before starting work, the surface should be prepared, the base should be free of cracks and defects.
• Before manufacturing a floor covering, it is important to determine its type, consider the main advantages, disadvantages and requirements.:
• The mixture is poured onto a waterproofing layer, the edges of which reach the walls around the perimeter to the height at which the leveling layer will be.
• A sound insulation material can be placed under the leveling layer, but you will need to fill the layer at a distance of 5 cm from the wall so that thermal insulation can be installed later.

Necessary preparatory work

Preparatory and installation work on leveling the layer depends on the mixture, design and type of material, as well as on the initial condition of the floor, but there are some steps that are performed regardless of the above circumstances. .

• Partially or completely dismantle the old coating
• Dispose of construction debris
• To remove dust, vacuum the surface with a vacuum cleaner or a wet brush.
• If there are oil stains, they also need to be removed.
• Determine the maximum possible floor height using a laser level
• Install beacons:

Installing a wet leveling layer for the floor

“Wet floor screeding is carried out in several stages.”

• Marking the screed level and taking measurements.
• Preparing the subfloor.
• Installing the thermal insulation layer. Polystyrene boards or expanded clay are typically used for this purpose.
• Waterproofing. This layer is mandatory in rooms with high humidity, such as kitchens, bathrooms, and toilets. Roofing felt or thick polyethylene film is commonly used as the waterproofing material.
• Installing screed guides (beacons). To achieve a perfectly level surface, the screed guides must be installed correctly beneath the screed. These guides are horizontal metal profiles that serve as leveling rails for the wet mixture. Their height determines the final screed thickness. The guides should be installed approximately 20 cm from the walls and spaced 1–1.5 m apart. Screws and cement mortar are used to secure them.
• Preparing the screed mixture. The sand and cement mixture is prepared at a ratio of 1:3. The materials are mixed until a uniform consistency is achieved. A construction mixer is recommended for faster and more efficient mixing. Water is then added to the prepared dry mixture.
• Installation. The wet screed should be poured starting from the far end of the room. The mixture is evenly distributed between the screed guides. The freshly poured mortar should be pierced in several places to release trapped air and prevent air bubbles.
• One to two days after pouring, the screed guides should be removed and the resulting grooves filled with mortar.

Installing a Dry Floor Screed

The installation of a dry floor screed is carried out in several steps.

• Waterproofing. A polyethylene membrane is laid over the prepared subfloor with the edges extending approximately 15 cm up the walls. Around the room's perimeter, an edge insulation strip made of foamed polyethylene should be installed. The strip is approximately 15 cm wide, 4–10 mm thick, and supplied in rolls up to 50 m long.
• Installing screed guides (beacons). This process is carried out in the same way as for a wet screed.
• Installation. Expanded clay is poured between the screed guides and leveled. It is recommended to fill the base section by section while simultaneously installing the screed boards.

Important.

The thickness of a dry screed depends on the presence or absence of pipes and other installed elements, the characteristics of the subfloor, and the required level of thermal insulation. Specialists recommend installing a screed with a thickness of 3–5 cm.

• Installing the boards. The boards should be laid in a staggered brick pattern and fastened together with screws. For greater reliability, the joints should also be glued.

Installing a Semi-Dry Floor Screed

The installation process for a semi-dry screed is almost identical to that of a wet screed. Only a few additional details should be taken into account.

• After the measurements and markings are completed, the subfloor is covered with a polyethylene membrane.
• The screed mixture should contain just enough water so that it holds together when squeezed in your hand.
• The mixture should be evenly distributed between the screed guides and compacted and leveled using tools.
• The final stage of installing a semi-dry screed is surface finishing with a power trowel or specialized screed-finishing machine.
• The surface can only be walked on after 12 hours.
• Unlike a wet screed, the screed guides are not removed.
• The decorative floor covering can be installed 4–5 days after completing the semi-dry screed.

When a Floor Screed Should Not Be Installed

During winter, maintaining the proper temperature is the most important condition for concrete curing, allowing it to achieve at least 70% of its design strength. Concrete is often poured in buildings where the roof and walls are already completed but the heating system has not yet been installed. Therefore, it is recommended to heat the space before starting the work. To ensure a high-quality screed, the indoor temperature should be maintained at no less than +10°C throughout the installation and curing process.