Choosing the optimal thickness of the floor screed. Self-leveling screed

They call it a screed upper part floor structure, which serves as the basis for laying decorative flooring. Modern renovation, carried out both in a new building and in apartments of old high-rise buildings, necessarily includes work on filling the floor with a screed. In order to independently engage in the arrangement of floors, you need to know what materials will be required and what thickness of the floor screed for your apartment will be optimal. The nature of the work will largely depend on the characteristics of the room and the desired characteristics of the future floor.

Primary requirements

The screed layer in the entire floor structure performs a certain list of functions. With this layer, the dynamic and static strength of the flooring is ensured, as well as the smooth surface necessary for quality styling tiles, laminate or linoleum. The screed allows you to evenly distribute the load on those layers of the floor that are under it, thereby extending their life. With the help of a screed, they not only level the floor, but also create the slopes provided for by the repair project.

The screed in the living area must be strong enough to withstand physical exercise resulting from the arrangement of furniture and the movement of people living in it around the room. The screed layer must be equally dense throughout the floor, any voids inside it, as well as chips and cracks, are not allowed. If the room does not specifically provide for the organization of the floor with a slope of a certain degree, then in standard cases the surface after pouring should be horizontally flat with a maximum slope of 0.2%.

The thickness of the screed has a direct relationship with the duration of the service life and the strength of the floor structure. A specific number representing optimal thickness subfloor, no. The thickness of the fill depends on the room in which the repair is being carried out, for what loads the floor is intended, and also what type of soil is used as a base. Both the choice of the thickness of the screed and the choice of the brand of cement for pouring it, the use or absence of reinforcing elements in the process of work depend on these indicators.

What can be a screed?

As a standard, there are three types of screed with respect to its thickness. The first type includes a draft floor of small thickness. What screed thickness is used in this case? To fill the floor, self-leveling mixtures are used, which are poured to a height of up to 2 cm. Preliminary laying of reinforcing elements in this case is not performed.

The second type of coating includes a floor with a height of up to 7 cm. Such a coating provides for the presence of reinforcement or reinforcing mesh and is made of reinforced concrete. The third type of subfloor is a screed with a maximum thickness of up to 15 cm, which is a monolith with reinforcement inside. A thick screed is used in cases where it must simultaneously play the role of both the floor and the foundation of the house, connected into one system.

The final thickness of the screed depends on the materials used in the process of arranging the floor. So, concrete pouring with the addition of crushed stone can no longer have a minimum thickness. In this case, due to the crushed stone fraction, a thin layer of the subfloor cannot be made. For pouring a thin layer, the best option would be to use self-leveling and other mixtures designed for finishing floor before laying the floor covering. With the help of the mixture, a thin and even layer of screed is created, which, after drying, can be immediately used as a base for decorative material.

Particular attention is paid to the thickness of the screed when arranging warm floors. It is important here that the filling completely covers the heating elements. At standard sizes pipes of 2.5 cm, the total thickness of the screed for a warm water floor can be from 5 to 7 cm. It is not recommended to pour concrete to a height of more than 7 cm. According to experts, for normal functioning floor and warming up the room, a layer of concrete above the pipes of 4 cm is enough. A thicker layer will complicate the adjustment of the heat supply, since it will spend most of the energy on heating the concrete itself.

The maximum thickness of the screed can lead to another unpleasant consequence in the form of wall deformation. The concrete part of the floor expands when heated and has a mechanical effect on the walls of the room. The thicker the screed layer, the stronger this effect will be. For exclusion possible consequences before pouring concrete mix it is recommended to paste over the walls around the perimeter with a special tape.

Minimum screed

According to SNiP minimum height screeds in the floor structure can be equal to 2 cm. But there is one feature here, which is that, depending on the material, the minimum height of the screed can be different. If the screed is made on the basis of metal cement, then a layer of 2 cm will be enough. If no reinforcing element is provided in the fill, then the minimum layer height cannot be less than 4 cm.

This requirement for a minimum screed is due to the fact that flooring should be characterized by a certain strength and wear resistance. A thin screed simply cannot provide the required performance.

Filling a thin coating can only be carried out under several conditions, which include an existing subfloor, a surface leveled with a rough screed and the absence of reinforcement. Thin screed is not recommended for indoor use technical purpose, as well as where the mechanical load on the floors is very high. In an apartment, such rooms include a kitchen, a bathroom and an entrance hall - here experts advise pouring a rather thick screed.

A thin screed is used to create a leveling layer necessary for further work. The sequence of work on a flat ground surface is as follows:

A layer of crushed stone and sand is poured, leveled and compacted with high quality;
Waterproofing is laid, which is suitable for a simple plastic film;
A reinforcing mesh is installed and beacons are set up;
The concrete solution is poured.

The minimum thickness of the floor screed using a reinforcing mesh cannot be less than 4 cm. Due to the presence of the mesh and the low height of the screed, the concrete used for pouring must be made from fine crushed stone. Compliance with this requirement will allow you to fill the solution with a thin layer, and the final screed will be quite strong. To increase the strength of the coating, it is recommended to add special plasticizers to the solution.

Maximum screed

There is no specific maximum possible thickness of the screed. The height of the fill will depend on many factors: the value is determined separately for each case. In terms of technology, a height of more than 15-17 cm does not make sense; structures with such a height are created only if necessary, since they require a lot of time and materials.

It makes sense to thicken the layer if you are arranging the floor in a room where there are heavy loads on the floor. by the most simple example a garage can serve as such a room: the weight of the car and its impact on the floor when moving are large, so the height of the screed of 15 cm is fully justified.

A high screed is also used in situations where it will be part of load-bearing structure. In this case monolithic fill of great thickness becomes not only the floor, but the foundation. Experts recommend increasing the thickness of the screed if problematic soil acts as the base of the floor structure.

Sometimes the height of the concrete pour is increased in order to hide significant surface differences. In practice, significant irregularities of the original surface are quite common, but a large thickness of the screed is not the only way eliminate them.

Before deciding to pour a 15 cm high screed, many builders advise evaluating the possibility of using crushed stone or expanded clay to level the differences. To correct sharp drops with a powerful jackhammer. If surface defects can be corrected in these ways, then the need for pouring concrete to a great height disappears by itself.

The minimum fill layer in this situation is also not suitable, however, you will need a much smaller amount of material to screed the floor. If you will even out huge surface differences of 15 cm in size only with concrete mortar, then your costs for the concrete itself and for the payment of the work of the builders will add up to a round sum. Most often, large expenses will not be justified, so you should at least do partial alignment using a bulk layer of crushed stone.

Filling the screed maximum thickness when installing warm water floors, it is also not financially justified. The large thickness of the cement layer above the heating elements will cause the floor to warm up slowly. The efficiency of such a design will ultimately be low, and heating costs will be simply huge.

How to fill?

Filling the floor screed can be done in two ways: either with cement mortar or with a special dry mix. With the first method, you will get a concrete screed as a result, in the second - a semi-dry screed. Which option to choose?

Concrete pouring is the most popular, but in order to use it, you need to know a few important points. The solution itself is prepared from cement, sand and water. Experts recommend buying cement not lower than the M-300 grade - with a particle fraction of 3-5 mm, such material will provide high quality final coverage. The use of not sand, but its screening for the preparation of a solution, will also have a positive effect on the final result: the adhesion of screening particles is much better.

To increase the strength of the future flooring and prevent cracking and destruction of the screed into crumbs in cement mortar plasticizers must be added. At this point, you should pay attention Special attention those who are going to make a screed for warm water floors. Plasticizers are special additives that increase the strength and plasticity of the concrete layer.

The use of plasticizers for the preparation of a solution is also necessary for thin flooring. The minimum thickness of the screed without them can be only 4-5 cm; for a concrete floor of a smaller thickness, the addition of plasticizers to the solution is a necessary condition.

Concrete screed takes a long time to dry. The solution must dry itself; it is strictly forbidden to turn on a warm floor for this. Drying of the floor is carried out within a month, and the surface is periodically wetted with water to avoid cracking.

Arrangement of the floor with the help of special semi-dry mixtures in recent times gain popularity. Such a screed does not require the addition a large number water, dries faster and is more durable. The range of special mixtures for the repair of floors today is quite large.

Unlike a concrete solution, a semi-dry screed will take a much shorter amount of time, the main thing is to wait for the period specified by the manufacturer. After its expiration, you can start laying decorative coating and turn on the heating system if you installed a warm floor. The use of dry mixes for pouring floors looks preferable when the time allotted for repair work, are limited.

Semi-dry screed requires less financial costs, but performance characteristics final coverage significantly exceed the indicators concrete screed. The coating of such mixtures has better noise and heat insulation, is more resistant to cracks and delamination. After the material hardens, a perfectly flat surface is obtained, ready for laying laminate or parquet boards.

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Oddly enough, underfloor heating in the toilet and bathroom is installed much more often than any other room. And this has its own practical meaning. Most often, the flooring in the bathroom becomes a comfortable and easy-to-use ceramic tile. The tile could be perfect coverage if she wasn't so cold. With the help of "warm floor" systems, you can ennoble comfort zones with pleasant warmth and eliminate problems with cold floors in the toilet.

Advantages of underfloor heating in the toilet:

Hygiene. The warm floor near the toilet dries quickly from water splashes and always remains warm and dry.

Security. It is impossible to slip on a dry floor, unlike wet ceramics. Even if you leave a rag or towel on the floor, it will dry instantly.

Saving. High level thermal conductivity ceramic tiles does not require heating elements high power and consumes a minimum of energy, heating the entire room.

Health. Your children will stop getting sick in the off-season, as the legs will always be warm. And visiting comfort zones will become their favorite pastime.

Beauty and comfort. Forget about all kinds of rugs, warm socks and wet rags in the toilet and bathroom. From now on, the floor there will be warmer than the sand on the south beach.

A warm floor in front of the bathroom will save you from winter drafts, it will always be warm and dry here.

It is possible to achieve constant heat in these zones without significant rearrangements and long-term repair. Modern warm floors or heating mats are laid directly under the tiles without a screed and have thermostats where you can always set optimal temperature gender. Sufficient power for drying and floor heating in a standard bathroom will be 140-200 watts per m2. For underfloor heating in the toilet, the power may be slightly lower.

It is not recommended to make underfloor heating in the toilet in a screed, since the level of the floors here should be lower than other rooms in the apartment or house. Such a difference in floor height will help to avoid spilling water throughout the house in case of flooding. The best option- heating mats, which are mounted without screed under tile adhesive.

So, the electric floor heating in the form of a mat is laid on concrete pavement. Next, a layer of tile adhesive is applied to the mat, on which a new tile is “planted”. With this technology, the height of the floor in the toilet remains at the same level, and the new floor will begin to delight you with its dryness and warmth in a few days. If the floor level allows - you can lay a warm floor on old tiles. Experienced owners say that it turns out even warmer. The only negative is the "loss" of a couple of centimeters of height.

The device of a water heated floor allows you to heat the house, saving on heating. By warm floor it's nice to walk barefoot, and if there are children in the house, your warm floor becomes a necessity. A warm water floor allows you to regulate heat transfer in winter and stop it in summer. Temperature regime heating the dwelling from the floor provides the most favorable microclimate - heat up to 20 ° C in the lower part of the room. Such heating at a low coolant temperature allows a third to reduce energy consumption. The disadvantages of this type of heating include the complexity of installation. For several layers of floor construction, careful preparation of the base is required. In the article, we will describe the laying sequence and consider in detail the technology of a do-it-yourself underfloor heating screed device.

Water heated floor is standalone system heating of residential premises, alternative to radiator and converter. Represents a system polymer pipes filled with coolant and laid on a specially prepared base with thermal insulation. It can be connected to a hot water boiler or external system heat supply. The laid pipe system is poured from above cement screed on which the selected coating is laid.

Water floor installation

The sequence of installation of a warm floor in cement-concrete screed includes steps:

1. Preparation of the base (rough floor).

The base is cleaned of dirt and dust.
Height differences are checked with a laser or water level (a long ruler with levels). If the height difference is not more than 1 - 2 cm, you can proceed to the next operation for installing a warm floor. With a height difference of more than 2 cm, the surface should be leveled with a floor leveler (self-leveling floor). How to fill the starting self-leveling floor is described in

2. Device for waterproofing and edge insulation on the subfloor

Waterproofing is arranged to protect against moisture from below. The need for it depends on the initial conditions: if the subfloor is laid on the ground (during the construction of a new house), then waterproofing is required. If there is the slightest risk of dampness from below, then it is better to make waterproofing, and if the work is carried out in an apartment (i.e. there is no humidity from below), then there is no point in waterproofing.
For waterproofing, a polyethylene film is well suited, laid with an overlap of at least 10 cm with gluing the joints with adhesive tape. The edges of the film are wrapped on the wall to a height of 10 cm.

3. Laying slab insulation

To insulate the floor, it is better to use expanded polystyrene sheet t. 2 - 10 cm. A vapor barrier is made on top of it, on which a mounting grid d. 4 - 5 mm with a cell of 50 mm is laid.

More modern insulation for warm water floors - a special foamed polystyrene mat, t. 2 cm. The spikes (“bosses”) on the insulation sheets serve as guides for laying plastic pipes warm floor. If such a heater is used, then reinforcing mesh do not need to be laid. The foam polystyrene mat already has a vapor barrier shell, which eliminates the need for a separate vapor barrier.

4. Installation of a warm floor

Experts offer several ways of laying pipes for heating underfloor heating. Of the proposed schemes, the "snail" is considered more convenient than the rest. Laying in this way starts from the perimeter of the room, in a circle is brought to the center, and then returns back to the perimeter. The advantage of such a scheme:

ease of laying due to the large bending radius of the pipe;
uniform distribution of heat over all areas of the room;
can be laid on the floor of a room of any shape and area.

Material and laying conditions:

Pipe diameter - 2 cm
Material - multilayer polyethylene
Step between pipes - 20 cm
At outer wall or window pitch 10-15 cm
Heat carrier characteristics: temperature up to +100°С, pressure up to 10 bar (± 1 bar)

If the screed area is more than 40 sq. m or the length of the room is more than 8 m, then a deformation seam is arranged in the center. Its purpose is to prevent cracking when the screed is heated and expanded. When arranging a seam for a warm floor, a damper tape is used. The loops of the underfloor heating pipe must not cross the expansion joint (only supply and return can pass at an angle of 45 degrees in corrugated insulation).

5. Filling the water floor screed

Filling the screed of a warm water floor has several size restrictions:

Screed thickness 30–70 mm
The minimum distance from the top edge of the pipe to the level of the screed is 30 mm
The maximum distance from the top edge of the pipe to the level of the screed is 70 mm

The inertia depends on the thickness of the screed heating system: thick screed heats up slowly and cools down slowly.

Before pouring a warm water floor around the entire perimeter of the fit to the wall, a damper tape of t. 10 mm and a width of the entire thickness of the floor is glued.

The damper tape prevents heat loss through the walls. In addition, the layer of poured concrete heats up and "breathes", and the tape allows it to move freely, preventing the formation of cracks.

We offer three options for pouring water floor screed:

concrete on fine aggregate;
semi-dry;
starting leveling mixture (floor leveler).

Concrete screed

The method involves the use of a concrete mixture based on coarse sand as a filler. Component ratio:

cement M 200 - 1 part by volume;
coarse sand - 3 parts;
plasticizer - 0.7 l per 100 kg of cement;
reinforcing fiber 1 kg per 1 cubic meter;
water until a homogeneous mobile mixture is formed.

Many people think that granite screenings of 3 - 5 mm in the mixture are preferable to sand.

If screenings are used for pouring, then its ratio with cement will be 6:1. Among the components shown is fiberglass, which is usually recommended for semi-dry screed. We believe that its use in a concrete screed is also justified.

Briefly fill technology. For the device of such a screed, you should:

Using a laser or water level, beat off the level of the screed surface on the walls of the room.
Approximately at a distance of 0.5 m from the wall, lay out a series of concrete "cakes" under the beacons.
After setting, use the mortar to set the level profile on the "cakes".
Glue a damper tape along the perimeter of the room on the wall to the thickness of the floor.
From the far corner to the exit, fill in the warm water floor, leveling the mixture with the rule according to the level of the beacons. Filling the floor with concrete must be continuous, without the formation of cold joints.
Beacons buried in the screed are removed after a few days, the grooves are leveled with a screed mixture.
The first few days after pouring, several times a day, the screed should be moistened with plenty of water.
After 3-4 days, the entire screed must be covered plastic wrap for two weeks. Full setting occurs after 26 - 28 days.

See the details of the concrete screed device below. The proposed video tells in detail how to properly perform the concreting of the water floor. filling technology, practical advice on the choice of method, the advantages and disadvantages of each of them, the selection of materials, will be very useful to someone who is going to fill in a warm floor.

Semi-dry screed

The method consists in using a semi-dry sand-cement mortar with the addition of a plasticizer and fiber. Proportions of the working solution:

cement M 200 - 1 part by volume
washed coarse sand - 3 parts
fiberglass - 0.5 kg per cube of solution
plasticizer - 0.3 l per 50 kg of cement

A detailed video on the device of a semi-dry screed can be viewed here:

The method is widely advertised on the web, but many experts note that it is problematic to make a water floor screed in this way. There are very few masters who know how to work correctly with semi-dry mixtures. An improperly laid mixture with increased porosity has a reduced thermal conductivity and actually isolates the heating circuit from the floor surface.

In addition, usually the filling has uneven strength: the upper crust is hard, and in the depths the screed material is loose.

Self-leveling screed

The screed device with self-leveling compounds has advantages over previous methods. These mixtures:

more durable and ductile;
do not crack;
dry faster (in 10-15 days);
relatively inexpensive.

For pouring a water floor screed, only starting mixtures are used, because. the finishing floor is poured to a thickness of 2.5 cm, and when poured in a thick layer it will crack. Filling the floor with the starting mixture is similar to the concrete screed device, which was described above. A slight difference is that floor levelers are more flexible and easy to install.

Important points when installing a screed

Errors in the installation of the screed can lead to its destruction or inefficient operation of the water floor. When performing work, pay special attention to:

water-cement ratio. Often, for ease of laying the mixture, add more water than necessary, which causes cracks in the screed.
Mandatory use of a plasticizer and reinforcing fiber in the working mixture.
The optimal thickness of the screed (cracks form in the thin one, the thick one heats up for a long time).
Device expansion joint and the use of damper tape around the perimeter of the room.
The temperature regime in the room and the absence of drafts.

Don't turn on water heating until the screed is completely set!

How to pour underfloor heating updated: August 31, 2017 by: Artyom

To lay an electric underfloor heating, it is important to correctly perform the screed, since the uniformity of heat distribution in the room, the strength of the structure and the efficiency of heating depend on it. Arrangement of a coupler is the most labor-consuming stage of laying of a heat-insulated floor.

Its functions are as follows:

heating element protection mechanical influences and negative impact air;
uniform distribution of heat over the surface of the floor radiator for heating the entire space of the room;
creating a level ground top coat.

Please note the following during installation:

the thickness of the entire screed, as well as the upper and lower layers around the heating element;
which manufacturing method to choose;
taking into account the features of the preparation of the solution and the technology of pouring the cable.

Wet screed is the most common, although dry screed is beginning to be widely used, allowing you not to waste time drying the solution, during which heating cannot be turned on.

With the apparent simplicity of the composition, the screed is made in several versions:

Sand-cement mortar with a ratio of components 3:1 is suitable for electric underfloor heating.
Concrete based on fine-grained filler is used in water floor systems. The plate is durable and does not crack.
The self-levelling compound is well suited for pouring electric underfloor heating when a thin layer is required.
Mixtures for underfloor heating, produced in a wide range.
used as a thin screed for electric underfloor heating.

The strength of the screed increases significantly if you use reinforcing mesh or microfiber.

The compositions are obtained with high resistance and plasticity, if plasticizers are added to them.

thermal insulation

Thermal insulation is used to prevent heat loss through ceilings. When choosing it, heat-shielding properties are taken into account, on which the total thickness of the screed depends. On the ground floor, 5 cm thick slabs are used as thermal insulation; if there is an apartment with heating from below, insulating layers of no more than 2-3 cm can be used.

The heat insulator is taken with a metallized coating. Aluminium foil does not withstand prolonged contact with the screed and collapses. It is necessary to use metallized coatings in the form of spraying with lavsan, etc.

Laying of plates is done without gaps. The resulting gaps are filled mounting foam, all joints are glued with adhesive tape.

Underfloor heating installation

How best to lay an electric underfloor heating depends on the type of heating elements. For any underfloor heating, it is important to ensure that the heating elements do not touch the thermal insulation. To do this, they are separated from it by a reinforcing mesh.

Cabling

The location of the thermostat is selected. It is mounted at a height of more than 30 cm from the floor. If the device is of a hidden type, strobes are punched in the wall under it, as well as under the power wires and the temperature sensor. In places with high humidity thermostats are not installed. They are taken to neighboring rooms.

A mounting tape is attached to the base at intervals of 50-100 cm and indented from the walls by 30 cm. Markings are made on the floor, taking into account the indents from the furniture. From the walls, the distance is 10 cm, and from pipes and radiators - 15 cm. Then heating cable it is connected to the power one using a coupling, and then it is attached to the mounting tape.

The power cable is led out through the groove prepared in the wall to the thermostat, and the heating cable is laid according to the diagram. In this case, the radius at the bends should not be less than 5 cm. The bends are made smooth, without undue tension. Fixation is made with staples or mounting tape. Contact or crossing of coils is not allowed. The convergence should not be less than 8 cm. All indents are strictly observed according to the scheme, which is developed in advance.

The temperature sensor is freely placed inside the corrugated pipe along with the supply wires. The corrugation at one end is hermetically sealed with a plug so that cement mortar does not get inside. The pipe with the temperature sensor is located between the turns of the cable at a distance of at least 50 cm from the wall and fits into the prepared strobe, after which the wires are connected to the thermostat.

After installation and connections, check electrical resistance heating cable and sensor. The values should differ from the passport ones by less than 10%.

The strobes are sealed with mortar or putty, and after hardening, the performance of the underfloor heating system is checked.

Heating mat laying

Heating mats are easier to install because the cable is already fixed to the mesh base, which only needs to be laid out on the base. In places of rotation, the mesh is neatly cut without violating the integrity of the cable. In places where obstacles are located, the mesh is removed, and the cable is laid in compliance with the distance from neighboring turns within 6-8 cm.

An important advantage of the heating mat is its small thickness, which makes it possible to pour a thin screed or lay heating elements in a layer of tile adhesive. Then the thickness of the fill will be only 8-10 cm, which will allow not to occupy an extra volume of the room.

Core floor laying

Rod infrared heaters outwardly they look like a rope ladder. They contain transverse heaters and 2 longitudinal connecting wires through which power is supplied.

The core roll is rolled out on the floor, starting from the thermostat. At the turning points, the connecting wire is cut, after which it is necessary to reconnect the ends with a piece of wire. This reduces the reliability of the warm floor. It is advisable to choose rolls of suitable length. Then you don't have to cut anything.

After laying in the insulation, windows are cut in a checkerboard pattern for better adhesion of the screed to the base. All connections must be carefully insulated.

Compositions and types of screed

A concrete screed for an electric underfloor heating will turn out to be of high quality if you choose the right proportions of materials and mix them thoroughly.

Only cement and sand is not enough to prepare a screed. It requires plasticizers and additives that increase the plasticity and uniformity of the mass.

Dry screed

Advantages of a dry screed over a wet screed:

no special equipment is required: mixers, solution containers, etc.;
less effort is spent on the delivery of material;
speed of work (in 1-2 days);
there is no need to wait for the maturation of the screed;
possibility phased installation underfloor heating, broken down into zones;
lack of dirt and excess moisture;
small specific gravity screeds;
the floor acquires the properties of sound absorption and thermal insulation without the use of special materials, the price of which is sometimes high;
the possibility of laying communications in the thickness of the material;
the surface is smooth and ready for the arrangement of finishing floor coverings on it.

With all the advantages, the coating is quite light and durable. It will not bear the load of interior partition from gypsum boards or brick, but frame structures from drywall can be installed on it.

Dry screed is not used in the following cases:

if there is a slope in the room;
in the presence of large dynamic loads (vibration effects or high intensity of the human flow);
in rooms with high humidity or with the possibility of water spills on the floor;
in cramped spaces where it is not possible to compact and level the composition with high quality.

When preparing a dry screed, the following materials are used:

Waterproof film.
Damper tape around the perimeter to compensate for thermal deformation.
Dry backfill of fine gravel, expanded clay, slag pumice, perlite. Instead, insulation boards with high density, for example, etc.
The top layer is sheets of moisture-resistant plywood, asbestos cement, chipboard, OSB. They are also used for large thicknesses. Best Option is the use of waterproof gypsum fiber sheets suitable for any floor finish.

Manufacturers building materials produce special complete and balanced dry floor systems. For premises different types a whole line of dry screeds "Knayf" is produced. Among them, two-layer GVL with the ability to assemble on locks is popular. For housing, “Vega” compositions are produced based on small expanded clay screenings in bags and other components.

When using production waste for dry screed, for example, solid expanded clay or slag, the size of the fraction should not exceed 5 mm. Otherwise, the floor will begin to sag and creak.

The backfill thickness must be more than 30 mm, otherwise the required quality cannot be achieved. If a upper limit above 60 mm, an intermediate sheet spacer will be required. From above, the screed is additionally covered with a sheet covering, the thickness of which is about 20 mm.

The base for the backfill must be even.

Semi-dry screed

The screed is a cement-sand mixture with the addition of fiber and plasticizers, but with a low water content. Distinctive feature is a large layer thickness of 70-100 mm. At a smaller thickness, the layer may crack.

The advantages of a semi-dry screed are its warmth, and soundproofing properties due to its porous structure.

The disadvantage is the need to use construction equipment, but in small spaces the screed can be laid by hand.

The ratio of components, which include cement, sand and water, respectively, is 1:3:0.4. Fiber is added to them in the amount of 600-800 g/m 3 .

The screed is laid along the beacons, similarly wet method. For grouting, a special machine is used, which can be rented. It is difficult to seal the screed by hand.

Wet screed

A screed is a layer of mortar or concrete applied to the base surface.

It is laid in several layers, the functions of which differ:

Base leveling. The first layer is always used for uneven surfaces. It is necessary even when a dry screed is placed on top.
A layer on top of thermal insulation for laying heating elements. If the cable touches the insulation, it may overheat at that point.
The third layer covers the warm floor, evens out the temperature field and keeps flooring. It is often combined with the second layer, if the thermal insulation is covered with a waterproofing film from above.

In all cases, it is advisable to reinforce the layers to prevent their cracking and maintain the integrity of the warm floor. At the same time, the thickness of the floor increases significantly, which leads to a decrease in the height of the premises. It can be reduced through the use of leveling compounds.

The classic screed is cement-sand. But the composition is not limited to only two components. Plasticizers are added to it, as well as crushed stone or expanded clay. A mixture of 3 parts of sand, 1 part of cement and PVA glue, added in an amount of 1 kg per bag of cement, performs well.

When using ready mixes high quality of a coupler is reached. Each composition has its own instructions for preparation.

Any warm floor should be done on flat surface. To obtain an even base, use the usual cement-sand mortar, and leveling compounds are most often placed under the finish coat. Their cost is high, and the filling is perfect.

The thickness of the screed depends on the diameter of the cable and is 3-5 cm. If it is made smaller, then the required strength of the plate and the uniformity of heating will not be ensured.

When cracks appear in the screed, the reliability of the warm floor is sharply reduced. Due to the violation of the integrity of the layer, the heating of the floor becomes uneven. Areas appear with high temperature, as a result of which the cable overheats, and its resource is reduced.

The technology of laying the screed must be correctly performed. The strength of cement is gaining 4 weeks, no work can be carried out during this period. It is important to ensure uniform fixing of the layer. To do this, it is covered with a film and kept a wet surface.

The main screed is arranged after leveling the base and laying the cable. First, a damper tape 10 cm wide is rolled out along the perimeter of the walls from below and fixed with adhesive tape at the points of contact with subfloor. It is also laid in places of transition to other rooms.

Cracks do not form in rooms with an area of more than 40 m 2 if they are divided into rectangular zones and T-shaped strips of porous material are laid between them. The damper tape is not suitable here, as it is flexible. Typically, thin foam sheets are used. In places where the cable passes through expansion joints, a short corrugated hose is put on the cable so that it does not break from temperature deformations.

Reinforcing is laid under the cable polymer mesh. It should be rigid and located at a distance from the insulation.

The laid warm floor must be tested - apply voltage and check the uniformity of heating.

In order for the screed to be exactly horizontal, beacons should be installed at a given height. For this, it is applied laser level. If it is not there, the usual one is applied, but then the upper boundary of the fill should be drawn on the walls.

With an indent from the wall, the first beacons are installed, and the next rows are made at a distance slightly shorter than the rule. Lighthouses are made on the solution, after which you need to wait for it to seize.

The underfloor heating is poured with careful alignment and filling of all voids by hand. The solution is thrown 1 cm above the level of the beacons and compacted with a manual rammer. Then another layer of screed is applied on top and pulled out by the rule. After that, you should immediately wipe the surface with a trowel, making circular movements. It is regularly checked horizontal level with the addition of the solution in the pits and the removal of excess.

The work on pouring the screed is done within one day with minimal interruptions during manual mixing.

The drying surface is covered with a film and moistened for a month until the concrete matures. If you hurry and turn on the warm floor earlier, it will crack and all Previous work will be wasted. In addition, it will not be easy to remove the frozen screed.

Video: installation of a heating cable

The screed is an important element of the warm floor, on which its quality depends. At correct installation it will provide comfortable conditions and durability of the heating system. Great importance has a screed thickness. If the surface is uneven, it can be improved with a leveling layer. The base must be strong and durable, as it is subjected to constant alternating temperature effects. It should be erected according to certain rules, maintaining the thickness, the ratio of the components of the screed and the time of its maturation.