Dry floor screed technology: selection of materials, step-by-step instructions. Dry floor screed, pros and cons of the KNAUF system Does dry floor screed shrink?

Reading time ≈ 9 minutes

Just like classic or semi-dry, dry has its pros and cons, which become decisive when choosing materials for the subfloor. This option, as a rule, is preferred when time for repairs is limited and it needs to be done quickly or you don’t have to deal with the liquid solution, for example, in winter or out of a desire to avoid “wet” work. Be that as it may, now you have the opportunity to familiarize yourself with several types and installation methods.

What are the differences between dry floor screeds?

Although top part dry screeds are made from gypsum fiber boards (GVL); five types of building materials are used for backfilling. This pillow serves for leveling and general insulation of the floor.

For reference. The abbreviation GVL stands for gypsum fiber sheet, according to appearance very similar to gypsum board ( plasterboard sheet). Unlike plasterboard, it is reinforced with cellulose waste paper, has a higher density (1250 kg/m³) and increased mechanical strength. In addition to conventional gypsum plasterboards, they also produce moisture-resistant ones - gypsum plasterboards, used in rooms with high humidity. The edges of the sheets can be either straight (PC) or folded (FC).

Prefabricated dry screeds

Expanded clay pillow

Four fractions of expanded clay

The bulk material called is produced by firing from clay or shale with a density of 350 to 600 kg/m 3 and its fraction can be of different sizes. It is usually classified into four sizes:

Large fraction - 20-40 mm.
The average fraction is 10-20 mm.
Fine fraction - 5-10 mm.
Expanded clay sand - up to 5 mm.

This material is used more often than others, most likely due to its availability, since expanded clay of any size is usually sold in most warehouses and bases selling building materials. It should be immediately noted that expanded clay sand is used to fill the pillow, but sometimes a fine fraction is used for this purpose, but the medium and coarse fraction is not in demand here.

Vermiculite pillow

Expanded vermiculite for bedding

The density of vermiculite is slightly less and ranges from 240 to 270 kg/m 3; it is a layered hydromica. But for backfilling they use recycled, expanded material, whose bulk density is even lower - 60-130 kg/m3. Due to its porosity (90-98%), this is not easy lightweight material– it has very low thermal conductivity plus good noise-absorbing properties. In most cases, expanded vermiculite is purchased to order.

Perlite pillow

Construction perlite for backfilling

Perlite is a natural material that is obtained as a result of the action of water on obsidian (this is precipitation, groundwater, etc.). But after this, perlite is not yet ready for use - it is brought to condition in special ovens by thermal shock at a temperature of 900-1100⁰C, as a result of which the granules swell. Perlite in an expanded state is divided into three categories:

Filtration fraction – up to 0.16 mm.
Construction fraction - 0.16-1.25 mm.
Agroperlite - 1-5 mm.

Compavite pillow

Dry filling with compavite

As everyone knows, the construction market is constantly updated and today the VIPole company offers backfill made using modern production technologies. This material is based on expanded clay sand, thanks to which the pillow has a very low thermal conductivity (up to 0.12 W/m*K) and sufficient density to support gypsum fiber boards and all kinds of furniture of any weight. But when purchasing compevit (it is sold in bags of 0.04 m3), it is better to request a certificate, since there are quite frequent cases of mixing this product with crushed stone. Bulk density is 500-600 kg/m3.

Note. Dry screed from gypsum fiber sheets can also be laid without concrete base– screed or floors where plane differences do not exceed 3-5 mm per linear meter, although this is a lot if you lay laminate on top. In any case, waterproofing is needed - GVL is not a moisture-resistant material.

Pros and cons of dry screed

Dry has its pros and cons, and the most basic of these indicators are discussed below. And before agreeing or rejecting such a rough coating option, it is better to compare these opposites.

What good can be said about dry screed

The advantages of this finish include:

First of all, due to the absence of “wet” work, very little dirt remains during installation;
low weight allows you to mount such a base under the front finishing on wooden floors;
the ease of installation of dry screed allows you to complete the work within one day;
there will be no moisture evaporation in the room after installation;
you can hide various communications (pipelines, cables) in the pillow under the gypsum fiber board;
Thanks to the bulk cushion, the floor is insulated and, in addition, has the ability to absorb noise.

Negative characteristics

There are also a number of disadvantages to consider:

with soft coverings (linoleum, carpet, vinyl laminate), large mechanical point loads cannot be created;
given the very low moisture resistance. It is better not to use GVL in bathrooms and kitchens, or to ensure a good cut-off over a rough coating like ceramic tiles or waterproofing paint, and you can also use GVLV (moisture resistant);
Laying a dry screed will cost more than a semi-dry or classic one.

Stages of dry screed installation

For dry floor screed, you will need certain materials and tools, as well as calculations for the thickness of the cushion, depending on the need for thermal insulation and. For the right choice and compliance with installation technology, use the step-by-step instructions below.

Necessary materials

To install a dry floor screed you will need:

gypsum fiber sheets (preferably from KNAUF) 1500x1200x20 mm;
bedding for a pillow (most often it is expanded clay sand);
lighthouses (galvanized or wooden);
waterproofing (polyethylene 200 microns thick, glassine or kraft paper);
edging tape or isolon cut into strips;
regular and double-sided tape;
self-tapping screws and dowels for installing beacons;
wood screws 25 mm long.

Required Tools

For such work you won’t need a lot of tools and most often you can have them at home:

water (laser) and/or hard long level;
chokeline (painting cord);
nylon (shoe) threads;
long rule;
screwdriver;
hammer drill or electric drill;
wood hacksaw with fine teeth;
construction knife;
construction square, tape measure, pencil.

Waterproofing

Laying polyethylene waterproofing with a turn on the wall

In this case, you can use any waterproofing material, which was discussed in the “Required materials” section. It is laid overlapping with the film overlapping by 50-100 mm, and then these joints are glued with tape so that the film does not move while filling the pillow. You should also take care to protect the wall and wrap the waterproofing horizontally so that it is a few centimeters above the zero cycle, as shown in the photo above. If the film is laid over a wooden floor, it can be nailed down with a stapler.

Given the ability of a pillow made of porous bedding and gypsum fiber board to expand under the influence of moisture, an edging tape should be glued along the perimeter of the floor (it is usually adhesive-based). If there is none, cut thin isolon (foamed polyethylene) and fix it with double-sided tape.

Installation of beacons and laying of pillows

The bulk cushion is leveled along the beacons

Some craftsmen do not install cushions for leveling, but this is not entirely correct, so I do not recommend following their example - without guides it is impossible to achieve a perfectly flat plane. In this situation, it is best to use beacons made of wooden blocks, the thickness of which will correspond to the height of the pillow. To level three or more guides with each other, use nylon threads stretched across from above, but so that there is no contact (gap 0.5-1 mm) and wooden coasters for adjustment. The beacons are fixed to the black base (wooden or concrete floor) with self-tapping screws and dowels. The step depends on the size of the rule, but in any case it should be 15-20 cm less than the length of the tool.

After installing the beacons, they fill up with a cushion of bulk building materials, which were discussed in the section “What is the difference between dry floor screeds,” but most likely it will be fine expanded clay or expanded clay sand. The pillow needs to be compacted, but they do not do this with a tamper, but simply walk on it, after which they tie it together using the beacon rule, just like a regular classic screed. In those places where gaps have formed, it is necessary to add expanded clay or other material.

Laying gypsum fiber board on a pillow

Laying GVL on expanded clay sand over reinforced concrete floors

Now you can move on to the final stage - laying gypsum fiber board on the pillow, and in order to somehow reduce material consumption it is better not to use sheets with a large area (there will be less waste). GVL 20x1200x1500 mm from KNAUF is best suited. The thing is that branded slabs are made with an edge chamfer and they overlap each other - the result is a joint like a lock.

Installation begins from the far corner of the room and for this you will have to stomp on the pillow, which will lead to its loosening and failure of the plane. To avoid such damage, you can move on a board, or even better (more conveniently) on two squares with an area of approximately 50x50 cm, and in addition, standing on them, you can perform installation work. Laying can be done both lengthwise and crosswise; this has absolutely no meaning and in this case one should not believe those who insist on any of the directions, since this is not a front finish.

But, nevertheless, assembling a dry screed is best done in a checkerboard pattern and if the first sheet is whole, that is, 1500x1200 mm, then cut the one next to it in half to make 750x1200 mm - in this regard, no nothing complicated. The joining or overlay (call it what you want) must be done using glue from KNAUF, although experience suggests that there is no point in buying such an expensive composition - it will be perfectly replaced by our native and familiar PVA. But the fixation does not end there - the joints are additionally reinforced with self-tapping screws every 30-35 cm (screws with anti-corrosion coating optional).

Note. Facial Finishing work on dry screed (laying tiles, laminate, soft coverings) you can start the next day - this time is enough for the glue to dry.

Installation of dry screed with hidden electrical wiring

Conclusion

If, when comparing all the pros and cons, dry positive traits have gained the upper hand in your eyes, then you can get to work without any hesitation. Even if you have never had to make other types of ties, this is not so important - when you apply maximum diligence and care, and also follow the recommendations from the instructions above, then you will undoubtedly succeed

Not everyone knows what a floor screed is. Meanwhile, this is a very important component of repair, and like any element of this industry, it is constantly being improved, new materials and more modern technologies its creation. If until recently the most popular was concrete or cement screed, today the so-called dry screed is in demand. Of course, it has both its pros and cons, but for quickly leveling the floor without installation skills it is the best option.

What it is?

The word “screed” is quite common and is used in several meanings. However, they are all from the field of renovation and mean something that makes any structure, be it a prefabricated cabinet or the floor of an apartment, more resistant to damage and stress. If we are talking about the floor surface, then the screed is also designed to eliminate height differences.

Simply put, a screed is an intermediate layer between the subfloor and the finishing coating, which provides better and more durable floor service, and in some cases, additional functions.

Dry screed is a thoughtful alternation of materials that are laid in layers under the final floor covering:

Thin polymer film that provides protection from moisture. Regular polyethylene up to 2 mm thick will do. Dry screed is afraid of excess water, so it is better to protect it in similar ways. The film is laid over the entire surface of the floor and extends onto the wall to the level of the intended finishing coating. The sheets of film are overlapped, and the resulting seams are fixed with mounting tape. Its area must exceed the area of the floor, taking into account overlaps.

Damper tape (edge or edge). It is placed around the perimeter of the room, along the bottom of the walls, up to the mark of the finishing coating. The tape is necessary to neutralize the expansion of dry matter from the backfill (from 0.5 to 1 mm). When pressure occurs on the walls in a room, small cracks form in them, and the tape prevents their appearance. It is also required for use when installing heated floors. The required length of the tape is the sum of the lengths of all the walls around the perimeter of the room;
Beacons for installation and adjustment of the plane during the process of backfilling the screed;

Leveling layer. This is some kind of bulk substance (expanded clay, pumice, slag, sand), most often fine-grained, which forms the surface and thickness of the dry screed. A flat surface is formed from lighthouse to lighthouse, taking them out and leveling the mark from them so that the slab covering will lie flat in the future. The volume of the leveling layer depends on the area of the room and the desired thickness of the screed. The minimum allowable is 3 cm;

Sheet material forming new surface subfloor. It is necessary to evenly distribute the load on the dry screed. Plywood, chipboard, OSB boards, and absocement sheets are often used. Their total area should correspond to the area of the room plus margin.
PVC film for the top layer. It is designed to protect the screed from moisture and negative influences;
Glue and screws may be required.

Kinds

There are four types of screed: wet, dry, semi-dry and screed based on self-leveling mixtures.

Wet screed is a classic option that includes several varieties based on application different materials in the composition of the substance.

Depending on the characteristics and origin of the bulk component, dry screed can be:

Sand, cement-sand or cement-sand

This is a screed that is made on the basis of sand with the addition of other components. For example, cement. It can be purchased ready-made, or you can make it yourself, solving the issue of drying river sand and ridding it of microorganisms. Ready-made building mixtures are often made from quarry sand. It is easier to dry it because it forms far from water and there are fewer living organisms in it that can begin active life under the flooring if you do not get rid of them.

Optimal in terms of its performance characteristics is alluvial or washed river sand. It undergoes a standard processing procedure (washed) necessary to filter out unnecessary components in the substance.

Alluvial sand has many advantages:

It does not settle over time, which is very important for screeds without the use of water and binding components;
It is environmentally friendly, has no impurities and living organisms;

There is no clay in it;
An ideal raw material for dry construction work due to the sand grains being not too small and not too large;
Cleaned sand does not enter into chemical reactions when adding other components;
The work is clean and not dusty.

Slag

A screed based on this material is popular due to its two advantages: high thermal insulation and low cost, since slag is an industrial waste.

For dry screed, you can use one of four types of slag:

Domain. This bulk material, which is shaped into a finely dispersed mixture for use in construction. Its composition is harmless, despite the myths, and is in many ways similar to the composition cement mixtures. Blast furnace slag is frost-resistant, which allows it to be used both in an apartment and in a private house, where the first floor is much colder.

Metallurgical. This type of slag is not used by itself. Rarely, a product of its production, mineral wool, is used as insulation or substrate when forming a dry screed. By her own mineral wool is one of the best insulation materials.

Coal. The coarse fraction of coal slag is used to form building blocks, and the artificially crushed one can be used both for pouring wet and dry screed. Mechanized processing of large fragments makes them suitable for various types of repair applications. Coal slag has excellent thermal insulation properties due to organic impurities composition (clay, ash, sand and others) and very low cost.

Fuel Dry filling with fuel slag, despite its slight popularity, is one of the best options, which is suitable for both houses and apartments. Due to the various impurities in its composition, it not only has high thermal insulation performance, but also copes well with sound insulation. Important nuance: The fuel slag should not be fresh. It can be used after no less than 3 months of storage in grooves.

Expanded clay

Expanded clay is a material widely used in repair and construction work. These are granules of low-melting clay. They undergo a firing procedure and have a hard shell and a porous structure. Expanded clay particles for floor screed are different different sizes and light weight. Often combined with sand concrete screed to level the floor surface with strong differences in height.

Expanded clay screed has a number of advantages:

Low cost of materials and work;
Significantly lower screed weight than when using other materials;
Good insulating qualities;
Organic origin of raw materials;
Quick installation.

Volcanic (perlite)

A related material to expanded clay is perlite. This is sand or crushed stone of volcanic origin. Does not apply on its own. The screed requires so-called “expanded” perlite, which undergoes a thermal shock procedure at very high temperatures. This makes its structure porous, like expanded clay, and eliminates excess moisture in the composition. After which it can be used for high-quality dry screed with sound and heat insulation properties.

Vermiculite is considered to be similar in properties to perlite and expanded clay. This layered material of organic origin is also subjected to a thermal shock procedure, which results in the formation of small elongated sticks, which are used as a bulk component when installing a dry screed. Its insulating qualities are also at a very high level.

Cement-bonded

Installation of a DSP screed is very different from the installation of a bulk dry screed, since this material is already pressed into slabs up to 50 mm thick.

This method of leveling the floor surface has several advantages:

The characteristics of the components of the composition and the multilayer nature of the plates make them very durable, withstand large weight loads and are resistant to mechanical damage;
The surface of the DSP board is already smooth and even and does not require additional leveling efforts;
The materials used in production include only organic substances, so DSP boards can be used in any type of premises, including a children's room;

With characteristics similar to other sheet materials, they are distinguished by a lower price;
The slabs are resistant to temperature changes and unfavorable environments and better withstand high humidity;
Possess good performance sound insulation and thermal insulation;

They are not subject to rotting and the formation of harmful microorganisms, since, in addition to wood fragments, they contain a mixture of cement and other substances;
Frost-resistant and difficult to burn.

Concrete

All types of dry screed using concrete (gypsum-concrete, sand-concrete, expanded clay-concrete) are among the repair tools that can be called timeless classics. No development of technical and scientific progress has yet offered a better and more reliable option than these materials. In addition, compositions based on concrete, cement, gypsum or sand can be used for both wet and dry screeds.

In the first case, the solution for pouring is diluted, and in the second, ready-made slabs are used. Dry concrete screed It is extremely rare that it turns out perfectly smooth. As a rule, it requires additional leveling of the surface, and it is important to supplement it with bulk mixtures.

Peculiarities

Dry screed is a fairly new method on the Russian market. Not everyone has had time to appreciate it, so there are many differing opinions about its quality.

In reality, dry screed has objective advantages and disadvantages.

Advantages of the technology:

Can be used for different types of premises: private house, cottage, cottage, apartment in apartment building and on the first floor, outbuildings;
Loose mixtures and sheets for leveling the surface together account for less weight (especially if it is not sand, but porous materials) than liquid concrete screed. It does not put a strong load on the floors in the structure of the room, extending its service life;
The work is clean, without dust or liquid;

Screed elements are made from substances of organic origin;
You can use dry screed in combination with floor heating systems, whether water or electric. The absence of glue and formaldehyde in the composition in this case is a big plus, since as the temperature rises, it inevitably begins to be released into the air;
You can make a dry screed alone, without professional skills;

Costs for materials and installation work are several times cheaper financially;
Installation of a dry screed does not require operational work. A large area can be covered in stages, which is impossible when working with liquid compositions that quickly harden in air;
Scroll necessary tools much shorter. You won’t need, for example, such a thing as a concrete mixer;

No cracks appear, there is no risk of liquid composition leaking to neighbors;
Dry screed helps to significantly increase sound insulation and thermal insulation in the apartment. You can also use tile materials for dry screed under a suspended ceiling to muffle sounds from above;

Using a dry screed, there is no need to postpone subsequent repairs for 30-40 days. It does not use water, so it does not require prolonged drying. You can make the floor covering in just a few days, when the screed has settled a little naturally;
Sheets covering the dry backfill make the surface of the subfloor as smooth as possible and suitable for any type of finishing;
Long service life, on average 20 years.

Dry screed also has disadvantages:

The screed is not a monolithic solid formation, therefore, over time, smaller particles settle down, so the height of the screed itself changes;
It is not advisable to use it under soft floor coverings such as carpet and laminate due to their lack of a strong base. High point loads on the screed will make it uneven over time;

Not suitable for use on unpaved surfaces;
Subject to abrasive wear;
Organic substances are a good breeding ground for bacteria, microorganisms, and in a private home even rodents;

Dry screed made from most materials, especially slabs, is afraid of moisture. It cannot be used in rooms with high humidity, as the floor will blister and become uneven;
The fixation is not as rigid as with a concrete screed; there is a risk of air bubbles forming in the backfill layer and damage to the heated floor pipe system, since they can move slightly under water pressure and with temperature changes.

Comparison with other materials

The advantages and disadvantages of dry screed are important not only in themselves, but also in comparison with other technologies for strengthening the floor and increasing insulation in the house.

There is an opinion that dry screed is better than wet mortar screed. Repair professionals do not give a clear answer on this matter, since optimal view screeds are selected taking into account many aspects. These include the operational condition of the room, especially load-bearing structures, and its functional purpose, and the requirements for the screed, and the type of finishing coating, and the budget for repairs.

The advantages of dry screed compared to wet screed include:

The ability to use this type of screed in old houses and buildings where it is prohibited to place too much load on the supporting floors. As a rule, such premises have big problems with poor sound and thermal insulation, and a lightweight screed made of organic porous materials helps correct the situation. At the same time, the liquid screed is powerless, since its installation will not even be issued with permission from the appropriate authority;

It is beneficial to use dry screed if you have limited financial resources. Many mixtures do not even need to be purchased ready-made; you can make them yourself. At the same time, the cost of the necessary tools, materials and raw materials will be much cheaper than for installing a wet screed. And you won’t need to hire skilled workers;
Wet screed requires great professionalism. The mixture hardens quickly, so pouring large areas in one go can be very problematic;

Under unfavorable environmental conditions, a wet screed may crack after drying;
Wet method takes a long time to dry;
Cleanest possible installation work

In some respects, a dry screed is still inferior to a wet one:

It does not combine well with warm floors and soft floor coverings;
A wet screed (cement, concrete, mixed) after drying becomes an even monolithic layer and does not settle, which cannot be said about dry screed;

All types of materials and mixtures are afraid of moisture; they cannot be poured under the floor in a bathroom or toilet. Only cement bonded particle board suitable for this purpose;
The service life of high-quality liquid screed is from 20 to 40 years.
Under it, it is necessary to first level the surface of the subfloor with large differences in height.

Between these two technologies lies semi-dry screed, which also has competitive advantages.

Comparing it with a dry screed, we can conclude that they are similar in many ways:

Low cost of materials with high quality;
Does not require additional effort to level the surface;

Saves financial and time resources on installation and cost of tools;
Due to the smaller amount of water in the composition, it freezes and hardens more slowly, so the installation process can be long, like a dry screed;

You can begin installing the finishing coating already on the 4th day after laying the mixture;
Semi-dry or dry-pressed screed is not done by hand. A machine is needed to compact it, and this increases financial expenses and limits the technology's use in small spaces.

In some aspects, dry screed is inferior to semi-dry:

Semi-dry settles less and is more resistant to stress, and accordingly, its service life is longer;
Fiber fiber increases wear resistance;
The porous structure increases insulating qualities with less abrasive wear.

It is worth considering separately new technology, which is often called self-leveling floor or self-leveling mixture. Self-leveling flooring is sometimes used instead of or together with a screed, and this method also has its pros and cons.

In some aspects, dry screed is similar to potting mix. So, the mixture also gives a flat and smooth surface without additional effort, dries quickly, allowing you to start finishing the floor earlier, and works well as a soundproofing layer. It is more wear-resistant than dry screed. Additional benefit The point is that the self-leveling floor can simultaneously serve as a decorative coating, that is, there is no need to finish it with other materials.

Despite positive properties self-leveling mixtures, there are still more arguments in favor of dry screed:

It is better to level floors with large differences in level using a screed, since it is easier to pour a layer of the required height;
The mixture for filling the floor is very expensive, and the thicker the layer, the more expensive it is square meter;

A dry screed is less demanding on the condition of the subfloor, while a liquid mixture requires the most flat and dry area possible;
Self-leveling flooring – not for use on large areas;
The dry mixture weighs much less.

Technology and device

The dry screed design is a prefabricated system consisting of backfill intended for leveling the floor, gypsum fiber sheets and components. The ideal base for the floor are reinforced concrete floors from 14 to 22 centimeters thick.

Before proceeding with installation, you must ensure that all recommendations and requirements are met:

If renovation work are produced on the ground floor of an apartment or private building, the design must additionally include a polymer film up to 0.3 mm thick, bitumen-polymer materials and mastic. They are necessary to protect the screed from condensation, freezing, and moisture ingress;
At the junction of the floor and walls, it is necessary to leave a gap of 9-10 millimeters to fill it with a soundproofing pad (you can use damping tape, soft wood fiber, mineral wool and other insulating materials). Also, the walls along the height of the entire screed should be covered with edge tape made of foamed polyurethane foam to avoid cracks on their surface;

Ready-made kits for self-execution work must be accompanied by documentation and instructions. The strength of the dry screed is 20-24 MPa (from 200 kilograms per 1 square meter to 240);
Optimal conditions to carry out work occurs when everything is wet, plumbing and electric installation work have already been completed. The room must have a minimum level of humidity and a temperature of at least 5 degrees;
Before starting work, all components of the system must spend 1-3 days in the installation room in order to adapt to the microclimate of this room.

Work progress:

Preparation of the working surface. Dry screed is not the most demanding mortar to level the floor surface, however, the smoother and drier the surface of the floors is, the better the installation of the screed will be. To do this, the subfloor must be dedusted, in some cases covered with film, and the joints between the ceiling elements and the junction of the walls and the floor must be sealed.
Determining the level of height (thickness) of the screed. To carry out geodetic work, you will need a laser or water level, as when installing a wet screed. With its help, you need to mark on each wall at several points the total height (top) of the screed and the height of each leveling layer separately.

Installation of the leveling layer. This stage is not always necessary. Some of the floors are in good condition, but in some cases the height differences are too large, and the surface of the floors has many flaws. They need to be removed with cement-sand mortar or factory leveling mixtures (for self-leveling floors).

It is important to take into account that cement mortar with a thickness of less than 3 cm will crack after drying. It can only be used in cases where the ceiling allows additional weight to be loaded and the thickness of the screed is required to be sufficiently large. The second method will help to save its height - a ready-made mixture for pouring the floor. Its thickness can be any, and much less than 30 millimeters.

Installation of vapor barrier and waterproofing. Another one not mandatory stage. It is only needed in cases where there is a risk of condensation or increased level humidity. The choice of insulating materials and the method of applying them to the work surface depends on the type of floor.

If this concrete plates, then a film covering is required, which is overlapped by 15-20 cm and placed above the level of the screed along the wall. Edge tape is glued to the top.

If the subfloor is wooden, the optimal solution is paraffin or bitumen paper with an overlap of 5-10 cm. There is no need to put it on the wall.

Installation of thermal insulation and sound insulation. Depending on the type of screed, different manufacturers offer different solutions at this stage. In some cases, additional slab material, which is placed under dry backfill; in some there is enough porous bulk material, which already absorbs sounds well and prevents heat loss.

Dry backfill tends to “flow” beyond the boundaries of the room in places doorways and transitions from room to room. It is recommended to install barriers in such places that the screed remains level and dense on all areas of the floor.

To level it, you do not need special equipment; you only need guides (beacons) and a leveling rod. You need to start from the wall that is opposite the doorway. Installation of beacons and backfilling are done simultaneously. There are no recommendations regarding the uniform distribution of the backfill; this is done by eye, with alignment with a lath and orientation to the marks on the wall. The rail moves along the guides and smoothes out all surface irregularities.

Installation of roof sheets. Lay the sheets, focusing on the geometry of the room. The gap between them should not exceed 0.9-1 millimeters. The sheets are applied in two layers. After the first one, it is necessary to apply adhesive mastic and lay it on it. upper layer gypsum fiber boards. It is important that the joints of the first layer do not coincide with the joints of the second. They need to be shifted by 25-30 cm.

Before the mastic dries (to remove excess glue that will come out at the joints when fastening with self-tapping screws), it is necessary to fasten 2 layers of sheets together with self-tapping screws, then putty the joints of the sheets. The fixer is attached along the edges of the sheet in steps of 30 cm.

Not all types of screeds provide for such a complex finishing procedure. In some cases, the gypsum fiber already has double thickness, and then one layer is enough.

After completion of the work, you must wait 3-4 days before proceeding with installation. flooring.

Thickness

Some installation nuances require more detailed consideration. One of the pressing questions is what minimum thickness(height) of dry floor screed.

If everything is clear with a wet screed (from 30 mm to 50 mm according to the standard), then when using a dry screed everything is a little more complicated. It is important to consider the following factors: floor condition, ceiling height, heat and sound insulation requirements.

The situation with the ceiling height is also quite obvious. If repairs are made in typical apartment, where the standard height does not exceed 2.5 meters, a fifteen-centimeter screed (and this does not take into account the finishing of the floor) is not suitable. In this case, you need to choose either the optimal combination of materials for the prefabricated screed, or give preference to a dry-pressed or leveling mixture. With a ceiling height of 2.7 m, the thickness of the screed will not significantly affect the appearance of the room if it raises the floor by 10 centimeters or more.

Information about the condition of the working surface can be easily obtained through a simple inspection. If there are large differences between the floor slabs (boards), there are dents, irregularities, chips, gaps and cracks, the required height, taking into account the leveling layer, will be from 50 to 100 mm. The difference depends on what material was used as leveling. If it is a cement mortar, then its minimum thickness should be 30 mm. If there is a leveling mixture, you can get by with much lower values.

For high-quality thermal insulation and noise protection from below either increase the thickness of the screed to 150 mm, or use thin insulating materials between the protective layer on the ceiling and the dry backfill. On average, the thickness ranges from 60 to 100mm.

To improve sound insulation, additional layers of dry matter and gypsum fiber sheets are also used, but the thickness of the structure (vapor barrier + leveling layer + insulation height + dry backfill + first layer of gypsum fiber + mastic + second layer of fiber) should not exceed 15 centimeters. Also, a thickness of 150 mm is necessary for leveling a heavily damaged floor surface and when working with complex wooden flooring.

We can conclude that the minimum thickness of a dry screed is 5-6 cm, the recommended thickness is 9-10 cm, and the maximum allowable is 15 cm.

How to calculate the quantity?

One of the most difficult tasks is calculating the required amount of materials to perform a dry floor screed.

Manufacturers are making attempts to facilitate this work by indicating the approximate consumption of materials in the passport for ready-made kits. In reality, these materials may not be enough, given that dry screeding is often done by non-professionals.

Accurate calculations will help you avoid unforeseen situations.

Items required to complete the work:

Vapor barrier film;
Edge tape;
Soft wood fiber or mineral wool;
Dry backfill;

Gypsum fiber boards;
Mastic or glue for gypsum fiber;
Profile for beacons;
Self-tapping screws for fixing gypsum fiber board layers to each other.

This is not a complete list of necessary tools and materials, but the rest (screwdriver, cutter, level, wooden or plastic slats, and others) are needed in a single copy and do not require preliminary calculations.

The calculation is carried out in stages, in the order in which the materials will be needed during the work:

Vapor barrier and waterproofing. It is necessary for her sheet material based on polyethylene, bitumen or fiberglass. The required amount of film is the area of the room plus 15-25% for allowances (overlap and wall). The width of such material is usually from 1 to 2 meters. The length is limited by the length of the roll.
Lighthouses. They require a profile, and if it was not included in the factory kit, it must be made manually from wooden slats or polymers. The minimum number of profiles per room area is 1 per meter. That is, if the room is 12 square meters with sides 3 by 4, it is wiser to purchase 4 profiles of 3 meters each.

Any sheet material for dry backfilling(insulation, base, insulation). It is calculated in an intuitive way: the area of the room is divided by the area of one sheet. It is important to take into account that the sheets may be damaged during transportation and the entire sheet will not fit everywhere; fragments will have to be cut out. Taking into account errors, it is necessary to purchase sheet material with a reserve of 1-3 pieces. The same applies to the finishing coating of the screed with gypsum fiber panels.
Damper tape and material for sealing joints. The length of the tape is taken from the calculation of the perimeter of the room (minus the doorway). The material for sealing cracks and joints is calculated different ways depending on its density and type. Leaf - in centimeters, weight - in grams.

Dry backfill. The indicators are different for different types of backfill; they are indicated on the packaging or in the online calculator. For example, one of the most common and high-quality materials, expanded clay, is required in an amount of 30-50 liters per square meter. The exact figures depend on the desired screed height. How larger area, the greater the run-up. It is better to purchase material at maximum consumption, since in practice it is usually higher than the average.
Glue. Its consumption is quite large. 500g of glue is needed per 1 m2.
Self-tapping screws for fastening sheets. The exact number of fixing elements for gypsum fiber board depends on the size of one sheet. The screws are screwed in at a distance of approximately 30 cm from each other. Knowing this, it is easy to carry out calculations based on individual sizes. Having determined how many screws are needed for 1 sheet, their number must be multiplied by the number of sheets. One sheet requires about 10 pieces, plus or minus 2.

How long does it take to dry?

One of the most problematic aspects when pouring a wet screed is the long period of complete drying. The advantage of dry screed is that practically no liquids are used during its installation, but it needs some time to shrink before installation of the floor covering begins. The question is how long should it take

Exact time depends on the complexity of the screed. So, if the design used a semi-dry or liquid base as a leveling layer, it will dry in approximately 28 days. The leveling liquid hardens faster - from 2 to 7 days. If there was no leveling layer, it will take 2-4 days for the excess moisture to evaporate from the dry backfill and shrinkage

The mastic or glue between the gypsum fiber sheets dries over different periods of time. Depending on the thickness of the layer and the microclimate of the room (humidity, air circulation), the mastic hardens completely in 12-28 hours.

The drying time of the glue depends on the surface area, layer thickness, temperature and humidity in the room, and preliminary degreasing of the working surfaces. Approximate time – days.

Scope of application

Dry screed is an almost universal means for strengthening the floor, leveling the height, and improving the insulating qualities.

The scope of its use is very wide:

For installation in a private house (country cottage, country house, frame or modular, block, brick or wooden), apartment in apartment buildings. Cottages and dachas can be residential or used only as a seasonal vacation spot. In the first case, a dry screed will ensure a comfortable stay in the house, since it will be quiet and warm, and in the second, it will protect the house and the heated floor, if any, from freezing at sub-zero temperatures. Since a rarely heated house freezes through, and overcooling of heating systems is undesirable, this is a very important function.

In an apartment building, in addition to the cold floor due to concrete floors between floors, there is another problem - good audibility. A dry screed 10 centimeters thick can isolate extraneous sounds from an apartment on the ground floor. This is especially true in new buildings. The problem of a cold floor can also arise in a “Khrushchev” building, but in this case it is better to choose a self-leveling floor that will not take more than a couple of centimeters from the height of the rooms.

For installation on different surfaces and floors: wooden floors, bricks, concrete slabs, blocks. Wet screed - no The best decision for leveling floors whose surface is highly absorbent. A lot of moisture will go into the wood, there will be a risk of fungus, and the screed may crack after drying. This is difficult to prevent, even using numerous layers of primer. The best way out from the position - dry screed using a thin insulating layer.

Carefully lay the screed on the ground. To avoid the greenhouse effect, it is recommended to use high-quality waterproofing with penoplex for insulation. Using a sand layer also helps. Dry screed fits much better on sand. But, if possible, combination with soil (soil) is best avoided.

For combination with heated floors. The problem can occur when a water heated floor falls asleep. Since the dry screed will not be monolithic, there is a risk of damage to the pipes. The way out is a dry-pressed screed. For a semi-dry screed, protecting the water floor pipe system is a feasible task.
For different rooms functional purposes. Warm floors are required in many rooms: in the children's room, bedroom, kitchen, bathroom and toilet, in the sauna. At the same time, it is not always necessary to combine the screed with the heating system; a good layer of backfill and gypsum fiber board with a total thickness of 15 centimeters is sufficient.

Problems can arise with high humidity in the bathroom. For such places, a prefabricated screed made from DSP boards, which are not afraid of moisture, is more suitable. They can also be used for screeding on balconies and loggias, and for insulating walls in rooms close to the street (in the attic, in the attic, in vestibule rooms).

For use under different kinds floor coverings. Dry screed can be safely laid under tiles, boards, laminate, parquet, and porcelain tiles. With an additional layer of rigidity - under carpet and linoleum.

Manufacturers and reviews

An important role when choosing materials for dry screed is played by the reputation of the manufacturer and reviews of owners of houses and apartments who use different products.

According to numerous estimates of those who have tested dry floor screed technology, the undisputed leader is the German company Knauf. There are several reasons for this:

Knauf are pioneers in this industry. It is they who are responsible for the development of an alternative to wet screed, and it is they who supply the construction market with a complete set of necessary tools and materials. All elements are produced on modern equipment using patented technologies.
Knauf is impeccable quality. It is customary to expect high standards from German companies, and this manufacturer fully lives up to these expectations. Reviews confirm that working with the elements is not difficult. Also praised performance product. The floor does not sag, there are no smells of dampness, which means good waterproofing and no condensation, the floor surface remains comfortable temperature even without an additional heating system, the insulating qualities of the coating are excellent.
Knauf is practically the only supplier of all components for dry screed on the domestic market. He is a kind of legislator, and if other components are present, they have received the approval of the pioneer company.

There are also negative reviews about this product: mold, dampness, floor sagging, high cost. The cost is mentioned in many reviews, but other shortcomings arise only when mistakes are made during installation. If you strictly follow the manufacturer's recommendations, the screed will be of high quality and will serve for many years.

The manufacturers that received the go-ahead from the Knauf flagship include two companies: Kerafloor and Kompevit. Both production facilities are located in Belarus and specialize in dry backfill for screed. With decent quality, this product is noted as cheaper.

Successful examples and options

Dry screed - good way save on installing heated floors. It is perfect for apartments and country houses, both in combination with an underfloor heating system and without it. A well-made dry screed is the key to successful installation of any type of floor covering, and a well-made floor is an integral part of a beautiful interior.

To learn how to lay dry screed, see the following video.

A dry floor screed is a two-layer structure made of insulation - usually expanded clay or other small fractions - and a top level of OSB boards, plywood or gypsum fiber sheets, securely and tightly fastened together. It is used in cases where it is necessary to quickly begin finishing, reduce the load on floors or when laying floors in winter.

Pros and cons of dry floor screed

In addition to the obvious advantages, dry floor screed also has significant disadvantages, which you need to know about before making a choice in its favor.

The advantages of dry screed include the following:

Lightweight design. The ease of screeding is one of the main advantages of this technology. Therefore, it is preferred when it is necessary to lighten the load on floors. For example, if they are wooden.
Easy and quick installation. Dry floor screed is characterized by ease of installation and speedy installation work. The floors are filled with dry mixture, then the layer is leveled and covered with slabs.
No dirt. There is no “wet” work during the installation of a dry subfloor. After completing the work, the site is relatively clean.
High speed drying. Drying is not required for this screed. You can begin laying the finishing coating almost immediately after installing the dry floor. This allows you to quickly complete the work.
Good characteristics. Dry screed does not creak or crack during use of the premises. Demonstrates good sound and heat insulation. Knauf dry floor screed has good characteristics in this segment.
All-season. Laying dry screed can be done at any time of the year, including winter period. For comparison, a semi-dry screed is laid at a temperature range from - 5 to + 40 ° C, and the traditional “wet” screed is not performed in winter.

Disadvantages of dry subfloors:

High cost of dry floor screed. It is about 1,200 rubles per m2 and significantly exceeds the prices for semi-dry screed, which at the Master Floor company range from 420 to 740 rubles per m2. A dry subfloor will cost about twice as much as a semi-dry one.
Low moisture resistance. Dry floor screed strongly absorbs moisture. This imposes restrictions on the scope of its application. The installation technology necessarily requires steam and waterproofing. So, in basements, in bathtubs and toilets, in basements and unheated rooms Dry screed cannot be used. If moisture gets on it, it will require, at a minimum, opening and drying the floor, and at maximum - complete replacement rough layer. Therefore, it is not suitable for arranging warm water coverings. For comparison, semi-dry screed is not afraid of moisture and is successfully used in all the rooms described above.
High consumption insulation. A bedding layer of 6-8 cm is considered optimal. For rooms with low shelves, such a thick layer of insulation will be prohibitive. In this case, you also need to take into account the thickness of the upper covering plates. The required thickness of the semi-dry screed layer is only 4.5-5.5 cm.
The need for additional manipulations. If the floor is leveled in an old house with wooden floors, in order to raise the level fire safety the bedding must be treated with a refractory compound. And this, including the need to level the dry screed with slabs, requires additional manipulations that take time and require additional financial investments.
Dust. When laying, the dry fraction produces a lot of fine dust, which can harm the respiratory system. Laying dry floors is only possible while wearing a respirator. A semi-dry screed does not require this.

If you need to quickly complete rough work on the floor, avoiding dust and dirt in the process, if reliable, high-quality, moisture-resistant, ideal smooth screed at a favorable price, which does not require additional leveling and which can be used under any finishing coating, it makes sense to give preference to the semi-dry screed from the Master Floor company.

One of the simplest and quick ways To level the base of the floor, use a dry screed. For industrial, retail premises and offices, this option will not be suitable, since its compression force is less than that of a traditional screed, but for arranging a floor or apartment - this is an excellent choice.

Depending on the method of installation, there are several types of dry screed:

Using expanded clay. This is the most common method; first, a layer of waterproofing is applied to the surface; it can be rolled or in the form of a solution, after which expanded clay is poured in and gypsum fiber sheets are laid.
Without the use of backfill. This method is recommended to be used if the differences in the height of the base are small, then the gypsum plasterboard is laid directly on the base, without the use of backfill.
Application between the base and gypsum fiber sheets of modern porous fibrous or foam materials.
Complex method. In this case, the above options are combined: first, a layer of waterproofing is laid, then a layer of expanded clay is poured in and covered with gypsum fiber sheets. At the next stage, a substrate is made, for this purpose porous or fibrous materials are used and covered with gypsum fiber sheets with locks.

Before choosing this method of floor leveling, you need to know what advantages and disadvantages it has.

pros

“wet” processes are not used during the work, so there is no dirt in the room, which will certainly be present when laying a concrete screed, and this is very important, especially when the work is carried out in an apartment;
it is convenient to hide various engineering communications in the resulting cavities;
This solution not only allows you to level the floor, but also improves its heat and sound insulation characteristics;
light weight;
long service life;
no time is required for the solution to harden, so the finishing coating can be laid immediately after creating a dry screed;

Despite such a large number of advantages, this type of screed also has disadvantages.

Minuses

relatively low mechanical strength
higher cost.

Materials and tools

Before you begin work, you need to purchase the required amount of materials and tools.

You will need the following supplies:

waterproofing material, it can be a film or a solution. The film is laid in such a way that there is an overlap of 10-15 cm on the walls. If it is not possible to cover the room with a whole piece, then when connecting two canvases, you need to overlap them by about 15-20 cm;
dry backfill(expanded clay), to fill a square meter of floor with a layer thickness of 10 mm, you will need 0.01 cubic meter of the specified material;
edge tape, its length should be equal to the perimeter of the room, minus the doorways;
glue, PVA is used to glue sheets together;
profile for beacons necessary in order to level the expanded clay, it must be laid in increments of 0.5 to 1 m;
GVL, you can use chipboard, OSB, moisture-resistant plywood, asbestos sheets for this, but they are used much less frequently;
self-tapping screws, you will need 8-12 of them per sheet.

From tools you will need a jigsaw, a screwdriver, a water or laser level and a tape measure.

More often Expanded clay is used as backfill, and there should be no sand or dust in it, buy only clean material, but besides this, they can be used and other materials:

vermiculite– this is a material of natural origin, it is light in weight, only expanded vermiculite should be used for screeding;
perlite– volcanic material, it is processed at high temperature, which allows you to completely remove moisture, perlite sand can be used as backfill;
compevit– this is expanded clay from the Vipol company, the granule size is about 4 mm, such backfill does not sag or deform during the use of the floor.

Knauf dry screed technology and design

Knauf floors represent hollow-core, quick-installed dry screeds, which can be laid on both concrete and wooden surfaces. Superpol KNAUF can be laid in rooms with high humidity, but waterproofing must be done correctly.

Dry mixtures for floor screed KNAUFdivided into the following types:

Alpha - used on a flat surface;
Beta - laid on flat surfaces, but using a backing made of porous-fiber materials;
Vega - placed on a leveling layer of dry backfill;
Gamma - laid on dry backfill and porous-fibrous materials.

Important! Regardless of the type used, KNAUF dry floor screed can be used at a room temperature of at least 10°C and a humidity of about 60-70%.

Step-by-step instruction

Preparing the base

First you need remove the old screed, there is no need to perfectly level the surface, but if there are cracks, their need to be repaired using a solution. After that remove all debris and treat the floor with a primer. Conduct zero level marking, for which a water or laser level is used.

Steam-waterproofing

For organizing a vapor barrier layer, a film is laid on the floor, while the overlap of the canvases between each other and on the walls should be 10-15 cm, all seams are properly taped with construction tape.

Can be used for concrete pavement vapor barrier materials or polyethylene film with a thickness of 200 microns, and for a wooden base, glassine or bituminized paper is suitable. Along the perimeter of the entire room edge tape is glued, whose width should not be less than the height of the backfill, it will provide good sound insulation.

Attention! Moisture is destructive for a dry screed, and if you treat the stage of laying waterproofing irresponsibly, then the sheets will subsequently swell, which will lead to damage to the floor covering.

Installation of beacons

According to the level of the future screed in increments of 50-70 cm lay out beacons, which are U-shaped profiles, it is best to use plaster or alabaster to fix them, as they harden quickly. After installing the beacons, fall asleepdry mix for screed, it can be quartz or silica sand, expanded clay screening, expanded perlite sand, fine-grained slag, and using the rule they level it along the installed beacons; this should be done just above their level.

Usually a layer of backfill 3-5 cm thick is sufficient, but if it exceeds 6 cm, then it is necessary to strengthen the screed with an additional layer of slabs.

If the surface of the base is perfectly flat, then the backfill can be omitted, and instead, sheets of extruded polystyrene foam are laid, which should fit tightly to each other; they can significantly increase the thermal insulation characteristics of the dry screed.

Now you can move on tolaying dry screed(gypsum fiber sheets). The folds on the first sheets are cut off so that later a double layer of gypsum fiber board can be laid. The sheets are laid offset, according to the principle of brickwork, they are fastened together using self-tapping screws, usually their length is 19 mm, but longer ones can be taken. Self-tapping screws are screwed along the folds in increments of 10-15 cm.

Depending on the condition of the base, the number of layers of GVL sheets may be different. A feature of this type of screed is that You can begin installation of the finishing floor covering immediately after laying the gypsum fiber board, and you don’t have to wait for the concrete screed to harden.

Although this coating has many advantages, it also has certain disadvantages. Most often, when installing a dry screed with your own hands, home craftsmen make a grave mistake - they do not cut off the fold of the first sheets adjacent to the wall, and this leads to the fact that in such places the floor begins to sag over time.
If you leave the beacons after backfilling, then after some time the expanded clay gives, albeit a small, sediment, while the beacons remain in place, which leads to problems with the coating. It is recommended to either remove the beacons after leveling the backfill layer, or pour a layer of it slightly above the level of the beacons.
Necessarily pay attention to the quality of expanded clay, if there is dust or sand in it, then over time such a floor will begin to creak. Buy better bulk material, so you can visually check its cleanliness. The material must be well dried; if it has high humidity, over time this will lead to deformation of the sheets.

Dry or wet floor screed is a mandatory step before laying parquet or flooring roll covering. The choice of wet or dry technology is determined by the requirements for surface strength and operating conditions. Concrete screed is a solution for damp rooms; in other cases, dry screed is a more preferable option, since the installation process is cleaner, takes less time and is cheaper.

Technology

Lay " layered cake“Dry screed is not difficult if you have the skills to work with a level, rule and gypsum fiber panels. The whole process is divided into three stages:

Preparatory. Setting the floor level, measuring the minimum and maximum values, marking the horizon using a pendulum and a laser level.

Basic. Installation of guides, filling of expanded clay, leveling the layer along the horizon using the rule.

Finishing. Laying a subfloor from reinforced gypsum fiber panels, fastening them together with glue and self-tapping screws.

A few hours after laying the gypsum panels, you can lay linoleum on them, fill plywood on top of which the parquet will lie, or lay the tiles on a special hydrophobic adhesive.

Peculiarities

A dry screed is a multi-layer frame for a finished floor. Installing it is no more difficult than leveling a layer of concrete or a semi-dry mixture with hardening-accelerating polymers and other impurities. For household or office renovations, the timing of which depends on opening a business or moving, a concrete screed is not suitable - you will have to wait at least three weeks for hardening.

The dry screed subfloor is assembled from gypsum fiber boards. The material can withstand loads of up to 300 kg/sq.cm, which is enough to install furniture, including trade chests and heavy safes. And in the filler it is convenient to hide communications: water, wires, heating.

Advantages and disadvantages

The main disadvantage of dry screed is its hydrophilicity. If a water heating pipe breaks under the floor, you will have to dismantle the entire structure and re-screed it. In the bathroom and shower, it is advisable to make a concrete screed.

Dry technology has many advantages:

Easy installation. Specialists will assemble such a screed in a room of up to 50 sq.m in one day.
No wet processes. You can lay the finished floor immediately after laying the gypsum fiber screed boards.
Heat and sound insulation. Expanded clay filler prevents the floor from cooling down, and it also prevents excessive noise from entering the room.
Environmental Safety. The sandwich structure contains no toxic components.
Ease. The load on the floors is up to three times less than when pouring a concrete screed.

For a warehouse, shower or bathroom, choose a concrete or semi-dry screed; in other cases, dry technology is more profitable. There is no need to dry such a screed, because apartment repairs with it will be reduced by almost a month. The heat and sound insulation qualities will be appreciated by owners of premises in office buildings and apartments in panel houses, and lightness is the determining factor when choosing screeds for frame and wooden houses.