Screed on a warm water floor: a choice of thickness and popular methods of installation

Evgenia Kravchenko
Checked by a specialist: Evgenia Kravchenko
Author: Antonina Turyeva
Last update: April 2019

Comfort in a house, apartment or cottage depends on the correct arrangement of communications, an important element of which are underfloor heating. Their functioning completely depends on whether the screed is correctly made on a warm water floor.

And it doesn’t matter how the work will proceed - with the involvement of the brigade or on their own. The main thing is that all processes are carried out correctly and in accordance with applicable standards.

What can be a screed?

Pipes with water or other coolant used to equip heating are hidden inside the floor structure. Water floor heating collected, like pie, from several layers, among which there is a screed designed to protect the line from mechanical damage and to ensure uniform heating of the entire surface.

Application Methods

Depending on the consistency of the substance used for the arrangement, a wet, dry and semi-dry screed is isolated. The first option is made of available materials - most often it is sand and cement. Moreover, you can try to implement it yourself - you need to work out a bit and make an effort.

The peculiarity lies in the correct preparation of the mixture and its uniform distribution. The consistency will be fluid, which facilitates application and alignment.

Wet screed option is good for tiles
The wet version of the screed is ideally suited for decoration with marble, ceramic or other decorative coating. The layer conducts heat well and transfers to natural stone, which gives it to the room as much as possible, providing heating

The dry method is quite simple to install and can be implemented on its own. All components can be bought - manufacturers offer dry backfill from composite materials and finished gypsum boards. The filler will be placed over the entire surface and cover the top of the GVL, which is fixed with screws.

To perform the third type of screed, you will need additional equipment. It is a pneumosupercharger and other automatic devices.In order to evenly distribute a semi-dry mixture, you need experience in performing such work.

Equipment can be rented - construction organizations present it for rent. True, without skills to cope with the work will be difficult. It is better to buy the mixture ready-made - independent production will be difficult due to the inaccessibility of individual components. And manufacturers are not in a hurry to share the right recipe.

The choice of arrangement depends on the characteristics of the premises, skills and budget. In any case, deciding to make the floors warm, you can not save on quality. Even the best material can ruin your crooked hands.

Moreover, the system is being built for more than one decade - the expenses are justified and will pay for themselves in the coming years. If you invite cheap co-workers and do not control every process that they perform, you can end up paying a double price.

The difference in the material of manufacture

To perform the screed can be used in various mixtures and materials. You can prepare the solution yourself, buy a dry mixture and knead it using the manufacturer's recommendations, or order the finished material that will be delivered at the specified time.

The most commonly used options are:

  • concrete - it can be ordered or made;
  • a solution of sand, cement and additional additives to improve the properties of future coatings;
  • ready-mixed cement with mineral fillers such as Ceresit CN 85 and others.

When choosing finished materials for the installation of screeds, you should carefully monitor that they are designed for underfloor heating and strictly follow the recommendations of the manufacturers.

Not all ready mixes can be used in the bathroom
Especially it is necessary to observe the requirements regarding the thickness of the arranged coating - as a rule, this figure should not exceed 10 mm. This mixture dries quickly, but can not be used in wet rooms and outside the building

For screed over floor heating in the bathroom more suitable concrete or sand-cement composition, made in appropriate proportions. Moreover, his recipe can be improved by creating a more plastic mixture, which is most suitable for arranging a floating screed.

To do this, you have to buy a special liquid - a plasticizer for concrete. This substance is added in the proportions indicated by the manufacturer on the label. It allows you to get a plastic solution that is resistant to damage after drying.

You will also need polypropylene fiber - this is the filler used to reinforce the mixture. With its help, it is possible to create a composition that is maximally resistant to cracking.

Solution preparation
To prepare the solution, it is better to take cement of the M300, or M400 brand. In an extreme case, the M200 is suitable, but no less. Sand should be chosen clean, not containing large fractions.

It is important to remember that any mixture, except dry, should be used immediately. Its storage is unacceptable - the solidification process will begin. And this can happen after 2-4 hours, unless otherwise specified in the manufacturer's recommendations.

Features of the choice of layer thickness

One of the key points is to choose the thickness of the screed for arrangement of water underfloor heating. Here too bad value is too small, and vice versa. In the first case, the coating will quickly crack over the entire surface and simply fail. Yes, and uniform heating does not work.

Optimal screed layer
Too thin a layer will not allow the heat to evenly distribute, so it should be at least 30 mm. If heat passes through a rather thick layer of concrete, it will take a long time to reach the surface

In the second - too high a layer above the pipe with a coolant will warm for a long time.

In addition, the user will additionally receive the following disadvantages:

  • uneven heating - heat strips alternate with cold, especially if the bottom of the pipe with a diameter of 16 mm;
  • high consumption of materials, which turns into an unnecessary waste;
  • long time for arrangement - a thick layer will dry for more than 1.5 months, which is not always acceptable;
  • a substantial rise in floor level will reduce the overall height of the room.

It turns out that the choice of the optimal thickness should be approached responsibly. Moreover, if you look at the recommendations of manufacturers of equipment and materials for arranging a warm floor system, they advise making a layer of screed on average 40-45 mm above the level of the pipe.

The following factors directly influence the choice of thickness:

  • laying step;
  • diameter itself floor heating pipes;
  • the type of mixture to be poured onto the surface;
  • ceiling height in the room;
  • floor strength.

With the features of calculations of water heat-insulated floors and determining the optimal step of laying next article, which we highly recommend reading.

Given the initial data, it is necessary to determine the parameters of the future layer. Moreover, less than 30-35 mm can not be taken, and the maximum limit is 100-120 mm. These are the recommended restrictions for living rooms.

Screed device
When installing the screed, it is often performed in 2 stages - first the pipes are poured, covering at the same level with them. Then apply the second layer of the desired height (+)

In the case of production facilities, the approach will be radically different - it all depends on their purpose and the loads that must be met - whether visitors will dance, if it's a cafe, or forklift trucks when it comes to a supermarket warehouse. We are talking about a thickness of 200 mm.

A more popular material for arranging a screed is concrete or a cement-sand mortar, applied wet. It is important not to forget about the need to perform expansion joints, which will provide a high-quality integral layer above the pipes with water.

For this procedure, use a 10 mm wide polystyrene foam gasket - damper. It allows you to get a floating floor that is not connected with the walls of the room, so it does not have any effect on them when heating or cooling.

The rules for performing expansion joints depend on the characteristics of the room. The most basic requirement is to lay a damping tape of elastic material around the perimeter of the room. It is important to do this before laying the screed.

Wet type screed

On your own, you can perform a screed of sand-cement mortar. It is not difficult to cook it at home. Moreover, the purchase of additional inclusions will improve the strength and ductility characteristics of the mixture, making it look like concrete.

The recipe for preparing a wet working mass is simple: you need to take 3 parts of sand, add 1 part of cement to it. To improve the properties that contribute to a better distribution of the mixture, you need to pour in a plasticizer, and for reinforcement, you need to introduce fiber.

Before preparing the composition, it is necessary to determine how many layers to couple in two or one? The volume of the mixture that will need to be prepared will depend on this.

First, you can pour laid on insulation layer pipes, having received at the outlet the surface flush with their placement. The second layer, which will be above them, will be done after the first one has dried. Or immediately form a layer of the desired height. For the self-taught master, the second option is simpler and more convenient.

For its implementation, you will need to mark the height of the future layer in the room. Here you need to use the laser level and metal guides, called beacons.

The lighthouse option is the surest assistant in getting the right screed surface. Moreover, the damper tape at this stage should already be glued around the perimeter and in all places where you want to make a deformation seam. Without it, even the best styling technology will not justify itself - the surface will be covered with cracks.

A day after the installation of beacons, using a wet solution, you can continue to work. Pouring mixture to the pipe.

Similarly, you have to fill in all areas of the room, gradually moving to the exit. It is important to complete the work before the mixture has lost its properties. We are waiting for the complete hardening of the laid layer. This will take at least 28 days, unless otherwise specified in the instructions.

If you used a mixture purchased from one of the manufacturers and designed to cover underfloor heating pipes, the waiting time may vary. Here you have to adhere to the recommendations of the specific manufacturer whose brand of solution was used.

The surface is ready for tile laying. But for linoleum or laminate, a grind is required. To do this, pour screed with water, take a polisher and rub it thoroughly. The procedure allows you to get perfect evenness at the output.

Such a result may not please every beginner performing a screed for the first time. Here, a self-leveling mixture will come to the rescue, which is designed to remove all differences. It is used as prescribed in the manufacturer's recommendations.

After application, it will remain to wait for it to dry and no grout will have to be done - as a result, a flat and smooth surface, ready for decorative finish.

The nuances of verification

When arranging a wet type screed from concrete or a cement-sand mixture by a hired team, you should not rush and immediately pay for their services. It is necessary to wait until the artificial stone solidifies completely. Moreover, the first 2 weeks the surface is covered with a film, periodically moistened with water in order to maximize nourish moisture.

Then you need to wait time, and this is about a month, so that the composition, which covered the pipes of the warm floor, crystallizes. The term depends on the thickness of the layer - this is an individual indicator for each case.

As soon as the allotted time for hardening has expired, it is possible to carry out an audit of the surface, the arrangement of which the hired team engaged. There are some nuances that should be checked when taking their work.

Screed Cracks
First of all, time should be carefully examined the surface - the presence of cracks clearly indicates the mistakes made. Such work cannot be accepted

During the inspection, it is necessary to pay attention to each section of the screed in all rooms - the presence of shine is undesirable, the top layer should be even, evenly gray, without chips and cracks.

Then the evenness of the surface is checked with a two-meter rail - the rule. It is applied in several places to the screed. Norm, if the gap does not exceed 4 mm. This is SNIP 3.04.01-87, table 25.

Checking the quality of the screed on the warm floor
You should check the horizontal slope - permissible for a length of 4 meters, the deviation from the horizontal is not more than 0.2 percent. It turns out that in this case the permissible slope level is 8 mm

For tapping, it is better to take not a hammer, but a wooden block and tap the butt. The entire surface is checked - the sound is the same, ringing. If deaf, then there are detachments of the screed from the base.

If the surface has passed the test with honor, the work can be accepted and paid to the team honestly earned money. If this is the result of independent work, then you can be proud of it.

Now it remains to conduct thermal tests. It is important to remember that they are launched in a month, not earlier. Start at 25 with a daily increase in temperature of 5 degrees until it reaches the design value, not forgetting to monitor the pressure loss.

Rules and examples of calculations of a water floor heating system given here. We recommend that you familiarize yourself with useful, systematic information.

Conclusions and useful video on the topic

Technology for screed laying in the video:

A detailed video with explanations of the minimum and maximum allowable screed thickness for a water floor heating:

About the choice of the type of mixture and the rules for its manufacture for the installation of screed:

Existing methods for creating a screed for underfloor heating pipes allow you to choose the most suitable option for your room.

Engage in these works independently or invite a team - the decision depends on the chosen method and the characteristics of the premises to be equipped. In any case, knowledge of the nuances is useful to check the quality of the surface at the end of the work.

Want to talk about how you made a screed for your floor heating system? Do you have useful information for site visitors on the production of work? Please leave comments in the block below, post a photo on the topic of the article, ask questions.

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Visitors Comments
  1. For a long time already I plan to make a “warm floor” in the apartment. But there were many obscure questions, so I put off this question “for later” until I figure it out. I did not even imagine that when choosing the thickness of the screed underfloor heating, so many factors must be taken into account. And if you ignore them, then in the future, the construction of “warm floor” can bring a lot of trouble. And it’s better not to save on additional materials, so as not to redo them later.

  2. Alexander

    It is very useful to become for beginners ... I began to make repairs at home, but after watching reviews and a bunch of articles on this topic, I decided for myself to contact an experienced company and order a screed from them.