The thickness of the concrete screed underfloor heating. What should be the thickness of the screed underfloor heating

The period of operation of the heating system in many respects depends on what thickness of a coupler above a water heat-insulated floor will be provided. This indicator also affects the efficiency, uniformity of heating and other characteristics.

An overtly thin layer will cause uneven heating. As a result, after a few months, or even weeks, the pouring will lose its properties and will be unsuitable for operation. Too much screed thickness of the warm floor will force you to spend additional money on heating, because a significant part of the heat will go to its heating, and not the room.

general information

The optimum screed thickness is determined by several aspects. In particular, the following indicators are taken into account:

room configuration features;
type of mixture;
purpose of the room.

In rooms of complex shape or large area, it is difficult to lay pipes of a warm water floor so that they ensure uniform heating. Sometimes you have to leave a large distance between them, so the thickness of the screed should be increased by 30-60% of the standard.

Mixtures intended for underfloor heating have good deformation resistance and thermal conductivity than a mortar screed or self-leveling. The layer of special screed can be 20-40% less.

Non-residential premises can be heated unevenly (if there is no risk of damaging the screed due to thermal expansion). In such cases, you can save on the amount of solution or mixture and lay the screed of a smaller thickness.

Minimum and maximum indicators

The maximum diameter of the pipes used for such purposes does not exceed 25 mm. Accordingly, pouring a thickness of 5 centimeters will be quite enough. But, we must remember that during the operation of the floor heat is generated and as a result, the concrete part along with the finish will begin to expand. That is, the thickness should be such as to prevent the possibility of deformation of the finish.

If we are talking about an ordinary residential building, then the load is calculated at 2 kN per square meter. Accordingly, the minimum permissible thickness of the screed over the underfloor heating is 4.5 cm. The use of a reinforcing structure with a diameter of 0.3 cm and cells 10 * 10 cm is an opportunity to reduce this figure to 2.5-3 centimeters.

The use of such a reinforcing mesh reduces the distance from the pipes to the surface of the screed

Be sure to follow the rules

The thickness of the screed for a water heated or electric floor in the apartment is calculated separately for each case, since this value depends on specific conditions. Masters recommend responsible selection of materials and focus the attention of beginners: a large layer does not mean that the surface will be of high quality. Experts advise to perform roughing, but the presence of a modern reinforced slab will be an alternative.

The thickness of the screed over the warm floors is an important moment when arranging utilities. In order to get the most out of heating and to ensure optimum strength under external mechanical loads, the parameters of the base must be calculated correctly.

Sanitary standards indicate the thickness of the solution layer for the formation of a regular floor - this is 40 mm. With low traffic, a reduction in pour height is acceptable. But when arranging structures with heating, modern materials are in demand, complex schemes are collected, so the values \u200b\u200bare calculated individually.

A floor screed, the thickness of which is small, is easy to damage: heating too quickly and abrupt cooling contribute to the formation of a spider line. And the load from constant movements, furniture pressure will accelerate the process of destruction of the coating.

Heating a thick layer is problematic, so the meaning of operating the system is lost, the risk of failure of segments increases. And non-compliance with the technology leads to an early cracking of the surface.

For the equipment of screed underfloor heating, several preliminary layers are mounted:

Draft screed on a cleaned surface (it can be replaced by a strong floor slab).
Insulation (its approximate thickness is 1 cm).
For hardening, reinforcing mesh up to 10 mm thick can be used.
Next, a plastic pipe is laid. Or an electrical system is installed.

The final layer is possible from any relevant material with a thickness of 30 to 70 mm. A decorative finishing coating is laid on top. Determining the required values \u200b\u200bis difficult for every beginner craftsman.

Minimum thickness

There is no officially approved value that clearly indicates what the minimum thickness of the intended floor screed should be. Gosnormy are repelled from the initial 20 mm, not taking into account the use of metal cement. If reinforcement is not provided, professionals indicate a height of at least 40 mm with a standard pipe diameter. The meshing of the reinforcing mesh is 100x100 mm, 150x150 mm. In such dimensions for floor screed, the material will be suitable for strengthening the structure.

The minimum is not acceptable in places with heavy loads (for example, in technical rooms, common corridors, garages). SNiP 3.04.01-87 (the residential sector is considered) when organizing heating pipe layouts as the lower threshold calls the common layer within 500-650 mm.

Since the screed under the underfloor heating slightly expands with linear heating, a compensator is required - along the perimeter of the rooms, a damper (or edge heat-shrink) tape is glued to take on excessive pressure. The width of such an auxiliary material is 10-15 cm. The tape is an additional insulation from adjacent chilled walls.

Above the heating distribution, the floor should rise by about 3-4 cm - this is the answer of the masters to those who first work independently and find out what is the minimum thickness of the floor screed to be installed. So the heat will be perfectly distributed on the surface, the structure will remain solid, and the room will not decrease.

The smallest thickness of the dry floor screed is 40-45 mm. At the rate of one bag of expanded clay mixture (50 l) per square meter. Ready formulations are accompanied by instructions and a description of the technology.

Maximum thickness

The largest screed for a warm floor is determined by the load, on average, the surface must withstand 200-300 kgf / m 2. The maximum thickness is not indicated in the regulatory documents and is determined by engineering calculations. The thicker the layer, the longer the heating will last; you can wait for a day or more for heat transfer from the inertial system.

For apartments, private cottages - 95-100 mm.
For public buildings - up to 200 mm.
For production - 300 mm.

The height of the floor must be at least 30 mm, so that the layer remains strong, and no more than 100 mm in residential buildings according to the principle of expediency. The organization of the floor on the ground requires additional insulation.

What is the thickness of the screed for water floor heating

The starting point for calculating the thickness of the screed over a warm water floor can be the diameter of the pipes that make up the structure. More often used material with an inner diameter of 16 mm and a total of 20 mm.

With the optimal thickness of the screed water underfloor heating, uniform heating is ensured. According to engineering calculations with a supply temperature of 45-55 ° C, the bottom warms up to 30 °.

You can take a traditional cement mortar, made independently, or purchase ready-made mixtures, which are presented in specialized departments. For screed over a water-heated floor, it is necessary to provide for the presence of expansion joints and a cushioning strip even in miniature spaces. Be sure to align the finish layer, carry out a rough screed. Heat engineers emphasize that it is the concrete flooded massif that will serve as a large effective radiator.

A warm water floor from a traditional concrete mortar will require a screened sand fraction and cement no lower than M-300 grade. The recipe must be proportioned: a part of cement, 3 - sand ingredient and water is added portionwise to a viscous state. The thickness of the concrete screed of the warm water floor is formed from an elastic "paste": the craftsmen successfully add a fraction of plasticizers to the mixture (liquid soap or degreaser for washing dishes at the rate of 0.5 l per square).

Ready mixes are used, guided by the manufacturer's instructions. The thickness of the screed for a water heated floor in a residential building more than 100 mm is a constant overpayment for energy, inertia and loss in the field of energy conservation.

Creative experimenters share their findings: expanded clay is laid on expanded concrete slab, EPSP (5-7 cm), mesh. Then make piping. And, wondering: what thickness of the screed for a warm water floor should be in this case, consider a value from 65 to 100 mm.

What layer of screed under the electric underfloor heating

This innovative heating option is universal: accidents with flooding are excluded, the ergonomic cable has a diameter of up to 7 mm. On a warm floor - laying of a vein is made by a snake - rational concrete pouring is required. Professionals for wiring recommend laying a reinforcing base, and also do not forget about expansion joints with a pitch of 4-6 mm, and a depth of up to a third of the thickness of the coating.

The thickness of the screed for an electric underfloor heating is determined simply: up to 450 mm above the mounted cables in rooms with medium and low load. The minimum height of the concrete mixture above the cable is 30 mm, which is safe and suitable for a normal bedroom or home bathroom.

If you are reading this article, then you probably thought about installing a water heated floor in your home. Now you are looking for information about what thickness of a water heated floor is necessary for a heated floor in your home.

In fact, you are probably interested in one of two questions:

the thickness of all layers of water floor heating;
thickness of a coupler of a water heat-insulated floor.

We will analyze each question individually. We introduce the concept of not the thickness of a warm water floor, but.

Pie water-heated floor is called all layers of water-warm, connected together. It looks something like this:

The cake of the warm floor or the so-called thickness consists of the following elements:

, which is mounted on the edging of the walls and serves to compensate for the expansion of the concrete screed. Its height is 15-20 cm from the rough screed. It is not taken into account in the calculation of thickness.
used more often in the form of polystyrene. It serves to cut off the lower layers from heating by warm floors. Thus, you save on coolant flow and warm water floors work as they should. The thickness of the polystyrene on the ground floor in cold regions should be 10 cm. In regions with a temperate climate, a thickness of 5 cm will pass. But it’s better to overdo it than overdo it. Therefore, take as a basis a thickness of 10 cm.
Polyethylene. Mounted on thermal insulation to create an additional greenhouse effect. We will not take into account its thickness in general.
Grid MAK. It is mounted on thermal insulation and serves as a convenient way to lay pipes on it. Its thickness is 4mm ideally.
. Our main distributor of heat. The height of the 16th pipe is approximately 2cm.
Concrete screed. Today, manufacturers recommend M-300 brand concrete mix for pouring. From my practice, I recommend the brands M-200, 250, 300. The thickness of the screed of the warm water floor is 5 cm from the top of the pipe! That is exactly what is needed for the competent operation of a water floor heating.
Fine coating. Parquet or tile. The thickness of 2cm is taken as the basis.

Thickness of a coupler of a water heat-insulated floor

As mentioned above, the thickness of the underfloor screed recommended by the manufacturer is approximately 5 cm. Of course, there are options when pouring the screed for an underfloor heating under a thickness of 10 cm. Here the system already begins to work on the principle of heat storage.

Rigid binding in the height of the screed does not exist. As practice shows, it is very rarely possible to achieve the recommended values. Therefore, the main thing is that the minimum thickness of the screed over the underfloor pipes should be at least 5 cm. The maximum thickness of the screed should not exceed 10 cm. And then the size of the screed will be ideal for the operation of a warm floor.

The building structure will perform its functions without complaints, if preliminary calculations are performed without errors. A precisely selected screed thickness for a water floor heating will provide sufficient strength and even distribution of heat on the surface. To determine all the important parameters of the project, a detailed study of technologies, materials, tips of specialized specialists is necessary.

The figure above shows a typical scheme of screed water floor heating, which is used in the recommendations for the creation of floor heating systems.

In this example, several practical issues should be noted:

An ideal foundation in domestic construction is a rarity. Therefore, it is necessary to eliminate cracks and other defects of floor slabs. Creating a screed with a thickness of 4-6 cm will help to solve the problem.
The fastening of the screed pipes of the water heated floor can be performed in various ways. Depending on the chosen option, the project cost, speed of execution and complexity of work will change.
A single layer of thermal insulation is sufficient, but to obtain good results, modern materials must be used.
Experts recommend maintaining the surface temperature of the screed water heated floor at a level of + 28 ° C to + 30 ° C. But to fulfill this condition, it is necessary to take into account: the laying step, the type of the main screed, the type of finish coating.

From this information, we can conclude that the thickness of the screed over the water heated floor depends on many different factors. It cannot be considered separately. Coordination with other technical parameters of the heating system design is required.

If the finish coating of the screed water underfloor does not have sufficient strength (linoleum), it is necessary to install an additional layer of plywood under it.

How to determine the main characteristics

To figure out which screed is best for a warm water floor, you need to make a calculation. The table below shows surface temperature data for different finishes.

In all cases, the following initial data are accepted:

Type of pipe: cross-linked polyethylene, diameter 20 mm, wall thickness 2 mm.
Supply / return water temperature: + 50 ° C / + 40 ° C.
Bottom on the reinforced concrete floor between the floors of the building, thermal insulation made of expanded polystyrene foam 80 mm thick is installed.
The height of the main screed water underfloor heating is 7 cm.

Surface temperature for different types of screed

Heavy concrete with granite aggregate
The distance between the lines, mm	100	150	200
Linoleum without insulation, ° C	29	28	27
	26	25	25
Ceramic tile, ° C	33	31	30
A mixture of sand and cement
The distance between the lines, mm	100	150	200
Linoleum without insulation, ° C	28	27	26
Laminate on a wooden substrate, ° C	26	25	25
Ceramic tile, ° C	31	30	29
Semi-dry mortar
The distance between the lines, mm	100	150	200
Linoleum without insulation, ° C	25	24	23,8
Laminate on a wooden substrate, ° C	24	23,5	23,2
Ceramic tile, ° C	27,3	26	25,5

From the data obtained it can be seen that the rather popular “dry” mortar is the worst option. They are convenient to use. But the created coating of the screed of the warm water floor will have low thermal conductivity.

It should be noted not only the first position in the comparative table, but also the high strength of heavy concrete. Instead of gravel and other traditional fillers, fiber can be used.

The data in the table also shows how losses are varied when installing different finishes. Linoleum, laminate, natural parquet do not conduct heat well. Even at high temperatures in the supply line, it will not be possible to approach the ideal heat of the surface. The best option is ceramic tile.

This picture was taken with a thermal imager. Red tones highlight the areas of screed water floor heating with a higher temperature. It can be seen what happens if the distance between the lines is chosen too large. A similar result will be the case when the temperature of the water is insufficient or the pipes are installed too close to the surface. By moving them below, you can get an even distribution of heat. But this will increase the inertia of the system. You will have to increase the concrete layer, reduce the height of the ceilings.

For residential premises, the main screed of the underfloor heating is from 6 to 8 cm. If you plan to install the piano, other heavy products, double reinforcement is installed under the corresponding section.

Project preparation

High-quality water heat-insulated floor consists of the following layers:

A rough screed 5-6 cm thick. It is poured with pre-installation of a damper tape around the perimeter of the room.
Insulation screed water floor heating. It is better to use foamed polypropylene of factory production with a density of 40 kg or more. m3 and higher. The greater the thickness, the lower the heat loss. It is convenient to work if there are special cutouts on the ends of the products. They simplify precise joining and ensure tight joints.
A plastic film (125-150 microns) is installed over the insulation plates. It prevents the penetration of moisture from the screed. If high-quality polypropylene plates with lock joints glued with tape are used, additional waterproofing is not needed.
The fittings not only reinforce the screed. On such a frame it is convenient to fix the pipes. Instead of traditional, metal, they begin to use composite and polymer products in construction. They weigh less, are not destroyed by corrosion processes.
To speed up the work, you need to purchase the required number of plastic clamps. Apply 3-4 products for each linear meter of the line.
Where the screed pipe runs through expansion joints, a protective corrugation is put on it.
When the whole structure is assembled, a cement-sand mixture with fillers is poured from above.
Next - establish the finish coating.

The structure of the structure is selected taking into account the characteristics of the installation site, the structure itself. It is simpler to mount a water heat-insulated floor on a special substrate with ledges. Corresponding kits are offered with edge and connecting elements. In the lower parts of some mats embedded layers reflecting infrared radiation, increasing the efficiency of the heating system.

When choosing a water heated floor, it is necessary to check its technical parameters according to the manufacturer's accompanying documentation. The numbers in the names do not necessarily indicate density.

Using the data of the selected project, make a list of necessary things, supplies, tools. When determining the thickness of the screed, the load capacity of the power structures of the real estate object must be taken into account. Layer 1 sq. M. concrete with a thickness of 6-7 cm weighs from 300 to 340 kg.

Performance of work operations

The exact sequence of actions depends on which screed for a specific warm water floor is selected as a result. Nevertheless, the following expert advice will come in handy when reproducing specific technological processes with your own hands.

Before pouring the rough screed of a water heated floor, it is necessary to install power cables, other engineering lines. The walls and ceiling are leveled with plaster mortar. If you perform the work in the reverse order, you will have to wait until the screed hardens. Further it will be necessary to clean it of new pollution.

During the formation of these building structures, the perpendicularity of the corners is controlled to ensure the tightness of the joints with the insulation plates. On a well-created surface, differences of more than 5-6 mm in height for one contour are not permissible. This will prevent the formation of “plugs” from the air.

When choosing slabs of expanded polystyrene with sufficient density, special precautions are not needed. This product without deformation and damage can withstand the weight of an adult. However, the cleanliness of the shoes should be checked, and potentially dangerous contaminants removed from the sole and surface. It is better to install ladders from the boards for movement. It should not be forgotten that when pouring mortars, heavy loads will have to be moved.

With a large area of \u200b\u200bscreed water floor heating, it is necessary to install expansion joints for every 20-25 square meters. area. They will prevent cracking when the temperature rises / falls. A tape made of foamed polymer (polyethylene) with a width of 100-130 mm, a thickness of 7 to 12 mm is suitable. Such elements are installed only in the main screed.

At this stage, high-quality wall plaster is useful (at least up to 40 cm from the floor). Some types of specialized damping tapes are coated with an adhesive layer on one side. They join flat surfaces quickly and firmly.

At the stage of preparation of drawings for screed water floor heating, it is necessary to accurately establish the intersection of the pipes with expansion joints. They are located only at the intersection of the supply and return lines. In open sections of pipelines (from the screed to the collector and vice versa), insulation is installed.

Concrete grades from 150 to 300 are suitable for creating a building mixture. Such a range is indicated in reference books to provide for different purpose of surfaces. Stronger screeds (M300) are needed in commercial facilities, in warehouses, in production shops. In residential and office premises, concrete is created from 1 part of cement M150 / 200 and three parts of sand.

Strengthen the composition of the screed water floor heating using fine granite chips. Since it is supposed to operate in a mode with a change in temperature, it is necessary to increase the ductility of the screed. Experimenting with PVA and other series adhesives is not worth it. Relevant “free recipes” can be found on the Internet, but it is difficult to confirm their true benefits.

In order for the screed for a water warm floor to turn out reliable, it is necessary to use specialized additives. They are subject to official warranties. Detailed descriptions of manufacturers provide instructions for proper use.

The following algorithm is used to fill the main screed of a water floor heating:

Work is performed at a room temperature of at least 0 ° C.
First, check the tightness of the system, eliminate identified leaks. To do this, raise the pressure (up to 4 atm.) For one day. Next - set the nominal pressure (from 1.5 to 2.5 atm.). Control values \u200b\u200bwith a pressure gauge.
Markings are applied to the walls, indicating the surface level of the future layer. To create an even screed, mounds (“beacons”) of the required height are created in the room.
To move the long rule, support rails are installed. The device is moved along them, removing surface irregularities.
The filling of the solution begins from the far section, shifting to the entrance. Bubbles of gases are removed from it by tamper. A simple method, multiple impacts with a metal rake, is associated with large labor costs. A specialized floor vibrator for building mixtures will help to complete the necessary processing faster.
During the execution of work operations, check the height of the screed according to the marks applied to the walls.
The amount of solution is created so that a portion of the mixture is laid in a few hours, no more. It is necessary to calculate the technology so that one room is completely flooded per day. To speed up the processes, mixers and other means of mechanization with electric drives should be used. This technique does not have to be bought. It can be rented.
Not later than 3 days later, the guides (beacons) are removed. The deepening of the screed water floor heating level with mortar.
To freeze the screed is not accompanied by the formation of defects, it is moistened 2-3 times a day.
Three days later, a film is rolled on the surface to prevent moisture from evaporating too quickly.
Under normal temperature conditions, the screed will be ready for laying the finish floor in 25-30 days. During this period, the coolant should not be heated above + 28 ° C.

Piece parquet and some other products made of valuable wood species are mounted at a relative screed humidity below 55-65%. If this level is not obtained, extend the drying period.

Video: cement screed for underfloor heating

Even the minimum thickness of the screed (5-6 cm) is an effective heat accumulator. In the event of an emergency in the winter, it will prevent freezing of pipes for 2-3 days. Proper installation of the system in the depth of the concrete layer will ensure uniform temperature distribution on the surface. This design is well protected from external influences. It has been working for decades. The listed advantages can be used in full if you take into account the above tips when implementing the project.

The system of warm water floors involves the installation of screed pipes on top of heat exchanger pipes, which serves as the basis for laying floor materials. Many are interested in what the minimum thickness of the floor screed should be so that the heat transfer occurs as efficiently and quickly as possible, while the strength of the concrete base is enough to withstand the expected surface loads. In order to fully understand this issue, it is worth considering various options, both in the sense of the features of the heating system itself, and the materials used to construct the final floor base. The recommendations set out in this regard in SNiP, as well as some video materials, will help in this.

Layered construction of water floor heating

To make the correct system of underfloor heating, you need to create several consecutive layers. From bottom to top, the cake of the warm water floor should be like this:

draft base;
waterproofing;
thermal insulation;
complex reinforcement plus heating pipes;
finishing screed;
finish floor material.

Due to the creation of a rough base, primary leveling occurs, which allows the finishing layer to be uniform. Moreover, the rough screed should be not only when installing the floor on the ground, but also on the floor slab in the apartments. If the basic leveling of the base is not done, the final layer of concrete can be very uneven, which will affect the quality of floor heating. What a warm floor cake looks like, is clearly demonstrated in this video

Functions of finishing floor screed

A finishing foundation is created with the following objectives:

reliable protection of pipes from mechanical influences;
heat transfer to the surface and its uniform distribution.

To perform the first task, the screed must be thick enough, therefore, strong. However, with an excessive height of the finishing base, the second function will not be fully implemented. Therefore, it is important to create a layer of optimal thickness.

How many centimeters should be the top layer of sand concrete depends on several factors, such as:

type of floor material (tile, laminate, parquet);
diameter of floor heating pipes;
problems of underfloor heating (main heating or addition to radiators);

At the same time, one should not forget about the requirements for a clean base, which are indicated in SNiP, and are recommended for mandatory implementation.

Minimum thickness

What could be the thinnest screed over the underfloor heating pipes? It depends on some factors. Suppose that the SNiP indicates a thickness of 20 mm, but this is the case when using a metal-cement composition when installing the base. How to deal with other solutions, sand concrete, or semi-dry material, nothing is said in the document. However, another norm is prescribed in SNiP, which determines that the minimum layer of screed over the pipe communications laid in the floor (applies to cement mortars, such as classic concrete or semi-dry sand concrete) should be at least 4 centimeters. If you add to this the cross section of the pipe, you get 6-7 centimeters. That is what the optimal foundation should be, according to the requirements of SNiP. In practice, it is of this thickness that the finishing screed over the pipes is made. How this happens, you can watch the next video

When watching a video, you can notice that the screed is of uniform thickness (visually - about 6 cm) over the entire area of \u200b\u200bthe room.

Now, sometimes, the upper base of a warm floor cake is made using self-leveling solutions with increased strength. When using such materials, the screed is minimized, that is, so that it slightly covers the pipe communications. Typically, this method is used if tile is assumed as a floor material. The tile laid on a layer of tile adhesive gives additional strength to the floor surface.

The thickness of the layer above the electric underfloor heating system is determined in a completely different way. A heating cable is much stronger than pipes used in water circuits, because the top layer of the coupler in this case has a much smaller protective function. Moreover, the heated floor, made with electric cable or mats, in most cases is used for subsequent tile laying. For these reasons, the thickness of the screed with the device for electric floor heating does not exceed 1.5 centimeters.

Important! No matter what the thickness of the finishing base, you should leave a deformation gap between it and the wall, where to place the damper tape. For large pouring areas, expansion joints must be additionally made.

Maximum thickness of the finishing base

About how many centimeters there can be a maximum layer above the underfloor heating system, nothing is said in SNiP. Strongly exceed the optimum thickness of the screed in residential premises (house or apartment) there is no point. This will lead to such negative points:

cost overruns, therefore, the cost of activities associated with the installation of warm water floors;
increasing the inertia of the surface heating process;
decrease in usable living space.

Usually, an increase in the layer is associated with the need to level the surface or create a floor at the same level in adjacent rooms. This is best done with a rough screed. The upper base of different thicknesses will lead to uneven floor heating. Although this situation will not have a significant effect on energy costs, since the screed is floating, that is, independent of other structures. So she will give off as much heat as she receives from heating pipes. The unevenness of the thickness will only affect the inertia of the heating of the floating floor base.

Important! Significantly exceed the layer of finish screed over the pipes for underfloor water heating in those rooms where the floor load can be significantly increased (garages, other technical buildings). When installing the base in living rooms, you should strive to create a uniform layer of optimal thickness.