Underfloor heating screed mix: All You Need To Know About Screeding & Underfloor Heating

All You Need To Know About Screeding & Underfloor Heating

Underfloor heating has never been more popular, having become a luxury addition to rooms which might usually require tile flooring, such as bathrooms and kitchens. Not only that, but it is highly compatible with condensing boiler systems, offering greater energy efficiency where insulation has been adequately implemented.

What people don’t consider though, is the screeding which needs to be laid over the underfloor heating and how the two interact. Screed is the word used to describe the thin, top layer of sand and cement mixture poured on the top of structural concrete or insulation.

The screeding and the heating elements are often laid separately and can cause trouble further down the line. To help you plan your underfloor heating project and get you up to speed, we’ve put together a short guide on the main things you should know about screeding and underfloor heating.

The Layers of Underfloor Heating

You can’t just lay heating and spread concrete over it. You need to first think about the layers. There are usually four key layers to the process which will help to make your heating both efficient and long lasting.

The Subfloor – The subfloor is the section at the very bottom and is usually a simple concrete or slab substrate.

The Insulation – In order to maximise the heat in your room there is an insulation board put on the subfloor, helping to push the heat upwards into the room rather than it draining through the substrate.

Heating Pipework – The heating pipework is the next layer, this can either be fitted on a track or it might simply be secured down.

The Screed – This is the layer which will go over your heating elements, giving you a smooth, level surface on which to lay your choice of flooring materials.

Heating & Cooling: Make Room For Expansion

Whenever you’re dealing with heating and cooling, there is bound to be some expansion and contraction. For this reason, it’s important that your screed has expansion joints and perimeters which are tailored specifically to the size and shape of the room.

Expansion joints are in place between the screed in places to allow the screed some movement when heated. Perimeter foam should be in place at the heating element level to prevent damage to the perimeter of the room.

The Finish & Load of Underfloor Heating

Most people will be thinking about the finish of the flooring when anticipating having underfloor heating installed, and while the finish should be even, smooth and level, there is a greater issue to be factored in: the load.

The primary function of your floor is to hold your anticipated load. Whether this means being able to simply hold the weight of a filled bathtub in a home, or the weight of machinery in a commercial setting, due consideration should be given to the screed specification and the thickness in order to avoid damage under duress.

Why Should You Consider Both?

There is a temptation to simply consider the underfloor heating or the screed, thinking of each as separate components, but the truth is that if you rush the plans and the process then you risk having to make changes and complete the job again further down the line. Cracks in the screed and the failure of the heating are often blamed on the screed layers, but it is the careless planning and a lack of foresight when it comes to the combination of both which causes problems.

Here at EasyMix Concrete we offer premier screed and concrete floor laying services. Simply contact our professional team today to find out how our screed can be utilised in combination with underfloor heating.

Underfloor Heating Screeding | Free Flowing Screed

IS IT RIGHT FOR THE JOB?

Underfloor Heating Screeding

Traditional Screed

Traditional sand and cement screed is mixed in the ratio of 1:3-4.5 with water and polypropylene fibres which reduces surface micro-cracking within the screed and generally applied to a depth of 75mm.  The screed is mixed semi dry to an earthy consistency and the snowball test is the simplest and most effective way of judging the correct quantity of water.  The snowball test consists of creating a snowball like ball of screed and if it holds together without evidence of excess water this is deemed to be of the correct proportion.   If the snowball does not hold together then more water should be added to the mix.

Traditional cement sand screeds are suitable for all manner of construction methods ranging from bonded, unbonded, floating and heated floors.

Fast Drying Screeds

Fast drying screeds: These are enhanced screeds with accelerated drying times, and are generally recommended as the ideal screed systems for underfloor heating. These screeds yield the best results when applied using forced action mixers such as screed pumps or pan mixers. These types of screeds have additives mixed along with the cement sand mixture to improve their drying time.

Fast drying accelerated screeds are now very much in preference because of the quick drying time they offer. Many fast drying floor screeds allow foot traffic to proceed as early as 12 hours and facilitate the early installation of the final floor finish, allowing the heating system to be used much earlier. Proprietary screeds are highly recommended fast drying screed systems that perform well when used over underfloor heating.

Free Flowing Screeds

These screeds have the advantage of being easy to install as the liquid can be poured quickly to cover a larger area. However the drawback is that they cannot be used in wet areas and have long drying times. Some flowing screeds cannot be used in wet areas and cannot be laid to falls.

Free flowing screeds are gypsum based liquid screeds that can be applied at reduced depths compared to the traditional screeds. Ideal for screeding over large areas. But the major drawbacks are, these screeds are not suitable for wet areas and are generally not compatible with cementitious adhesives. The surface usually requires sanding and priming, before a bonded finish can be applied.  Proprietary screeds are highly recommended fast drying screed systems that perform well when used over underfloor heating, some of the commonly recommended free flowing screeds are Tarmac, Breedon, Cemfloor, Longflow.

SCREED CONSTRUCTION FOR

Under Floor Heating

The heating elements for the underfloor heating are usually encased in a layer of screed before the installation of the final floor covering. In the case of hydronic underfloor heating, the heating pipes are usually secured to insulation panels on the floor slab fitted with moisture barriers, and the screed layer is laid over this to provide a level surface for installing the final floor finish.

Though traditional sand, cement screeds are generally used for screeding over underfloor heating, this can be quite time consuming as the screeds require a long time period for drying sufficiently to take on the final floor covering. However, though an obvious option, the underfloor heating system cannot be utilised to accelerate the drying process as it can result in the cracking of screed due to quick drying.

Fast Drying Floor screeds help to overcome this issue, drying much faster than traditional screeds while allowing the screed mix to hydrate fully. They act as capillary pumps, removing excess water and locking in the rest of the water by crystallisation, thus preventing the cracking of screed. An example for Fast Drying screed is Isocrete K-Screed fast drying floor screeds. The different types of screed laid over underfloor heating are:

Underfloor heating(UFH) is a highly efficient form of space heating that generates heat through electric or hydronic heating elements embedded beneath the surface of the floor. The heating elements are typically secured to insulation panels on the floor slab and the screed layer is installed over the heating elements before laying the final floor finish.

Apart from serving as a level surface for taking on the final floor finish, a good screed plays the important role of conducting the heat evenly across the surface of the floor, without producing any hot or cold spots. A good quality screed, laid to the right depth helps to retain the heat for longer hours, reducing the energy required at the source and improving the energy efficiency of the UFH system. A wide range of screeding options are now available for underfloor heating systems:

 

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CSC Screeding were engaged by Berkeley Group to carry out Calcium Carbide testing, on anhydrite screed with underfloor heating, throughout their development at Prince of Wales Drive.

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CSC Screeding are members of Constructionline, CHAS and Builders Profile where a predefined Health & Safety questionnaire is pre-completed and our clients have direct access to the information. Documents contained in the pre-qualification system are updated throughout the year, ensuring continued compliance. We have focused on developing the business through constant innovation, implementation and collaboration.

We were an early adopter of FORS – gaining Bronze accreditation – as we recognised this would become more widely requested on construction sites.

We are now ready for the business to grow with the increasing demand.

screed composition, mortar for underfloor heating, dry mix, concrete, proportions for pouring, mortar brand

Content:

Types of screeds
Wet screed
How to mix
Semi-dry screed
Types of plasticizers
Dry screed for underfloor heating
Video

In most cases, the heating element of the “warm floor” system is located in the thickness of the cement screed, while the cement layer has a considerable thickness. This can be explained as follows: firstly, the heaters as part of the warm floor receive protection from mechanical stress, and secondly, the screed accumulates heat. These factors make it possible to use a warm floor as the only source of heat. At the same time, even a slight heating temperature can heat the entire volume of the room.

It is possible to lay the “warm floor” system only on a perfectly even base; in the presence of significant differences, a leveling rough screed is performed. Installation work begins only after the complete drying of this layer. Failure to comply with this rule may result in failure of the heating cable or film membrane. In particular, when laying the heating element on an uneven surface, air pockets can form, which cause overheating.

In addition, the screed can also turn out to be uneven, which will lead to uneven heating of individual sections of the floor. As a result, due to different temperatures, the screed can simply burst, but significant cracks can damage the cable or membrane. Therefore, the alignment of the base under the heating elements should be approached very responsibly.

Tie types

For the “warm floor” system, several types of screed are used: wet, semi-dry and dry mix for underfloor heating.

Wet screed

This option can be called traditional, it is often used to level the floor surface. In most cases, a solution is prepared from cement, sand and water.

The proportions of cement and sand in concrete for underfloor heating should be 1: 3, while the cement should be M400 or M500. It is not recommended to add gypsum powder to the solution, as in this case the hygroscopicity of the composition increases. As a result, even a slight decrease in floor temperature can cause condensation to form on its surface. In addition, gypsum is characterized by high thermal insulation properties, which is not entirely necessary for a warm floor.

How to mix

To prepare a high-quality concrete solution, it is better to take coarse-grained sand. Small grains of sand contribute to the formation of cracks in the screed under the influence of constantly changing temperatures. Such a defect is practically beyond repair, while the heat transfer of the system decreases and the temperature in the room decreases.

In order for the screed to be of high quality, it is necessary to properly prepare the solution. To do this, it is necessary to combine sand and cement in a dry form, mix them thoroughly, and then add water. The liquid is added to the dry mix for underfloor heating screed in small portions, mixing the composition well after each addition. The amount of water depends on what consistency the solution is required. It is very important that it does not spread over the floor surface, but has sufficient plasticity. It is possible to start pouring the screed only after reaching the necessary plasticity and uniformity of the solution.

Wet screed is popular with private and professional builders. During operation, not only the advantages of such a solution for underfloor heating screed, but also its disadvantages began to be revealed. In particular, the following became known:

• The screed dries for a very long time, complete drying is achieved in 28 days. This is because the solution contains a large amount of water.
• In the process of pouring the screed, the formation of voids is not excluded, which is practically impossible to remove, since the heating elements of the warm floor can be damaged during compaction.
• Drying of the screed is always accompanied by the formation of cracks. Reinforcement with a metal or polymer mesh helps to partially solve the problem. However, small cracks are always present on the surface.
• Leveling the screed is a labor-intensive process, for this it is necessary to install beacons and use the rule. After the mortar for the warm water floor screed dries a little, it is necessary to wipe the recesses and cut off the excess solution. See also: “How to calculate the floor screed – how much material is needed.”

Semi-dry screed

To reduce the number of shortcomings of the concrete screed, it is necessary to introduce plasticizers and additives into the screed for underfloor heating. Due to this, the properties of the solution change and the drying time is reduced. In addition, additives allow the use of less water, so the screed is called semi-dry.

The use of such a screed has several advantages:

• Short drying time due to small amount of liquid.
• Get a smoother surface.
• Improving the water resistance of concrete, which is especially important for the floor in the bath, bathroom and kitchen. See also: “How and how to treat the floor in the bath – choosing the right impregnation.”
• Plasticity retention for a long time, which allows you to mix a larger amount of mortar.
• Plastic mixture for pouring underfloor heating is laid more densely, filling voids as much as possible. As a result, the screed is characterized by uniformity and higher heat transfer.
• Cracks do not appear during the maturation of the screed, since there is practically no shrinkage.
• The surface can be used after 12 hours.
• In most cases, the top coat can be laid after 28 days, and with the introduction of certain additives into the solution, after 7 days. See also: “What to make the floor in the kitchen – options for flooring.”

Tip: Use our construction calculators online and you will calculate building materials or structures quickly and accurately.

This method also has disadvantages, among them are the following:

• Higher cost of some underfloor heating mixtures.
• Significant vapor permeability.
• Long initial mortar setting. In this case, the problem can be solved with a special hardening accelerator.

For a semi-dry screed, you can use a ready-made mixture for underfloor heating, to which it is enough to add a certain amount of liquid in accordance with the instructions on the package. In addition, you can purchase plasticizers separately and add to the solution at your discretion. All dry mixes for underfloor heating screed contain certain components, so you should follow the manufacturer’s recommendations for preparing a solution for a semi-dry screed.

One of the modern methods of reinforcing a concrete screed underfloor heating can be called the addition of fiber to the solution. As a result, the strength of concrete is significantly increased, and its water permeability, on the contrary, decreases, and the formation of cracks is also prevented. The effectiveness of the additive is quite high, so damage to the heating elements is completely excluded. In addition, a smoother and more attractive surface is noted.

The use of fiber is carried out according to a certain scheme. If the solution is prepared in a concrete mixer, then the additive is introduced a few minutes before readiness. With manual kneading, the component is added to the dry ingredients and the mixture is brought to homogeneity. After that, start pouring water in small portions. For a quality screed, 9 is enough00 grams of additive per cubic meter of the finished solution. Despite the high cost of fiberglass, its addition significantly increases the heat transfer of the surface.

If there is no possibility of using fiber, then the quality of the screed is increased by laying a metal or polymer reinforcing mesh. The choice of material depends on the type of underfloor heating: for water floors it is recommended to use a metal mesh, for electric floors – from polymeric materials. Also, sometimes they make a dry warm floor, which eliminates the use of various solutions.

Types of plasticizers

To give the cement-sand mortar certain properties, special additives are used – plasticizers, which have a different composition and shape.

Plasticizers are available in dry or liquid form. Liquid additives are supplied to commercial enterprises in canisters, the volume of which can be completely different. Before use, such a plasticizer must be thoroughly shaken and added to the dry mixture along with the liquid. In most cases, about 1.5 liters of additive is taken per 100 kg of cement.

If a dry plasticizer is purchased for work, then immediately before it is added to the concrete for a warm floor, it should be diluted with water. The proportions of water and additives are indicated on the package, in most cases, masters take one part of the dry component and two parts of water. The diluted mixture must be left for several hours to infuse. After a certain time, the composition is mixed and added to concrete for underfloor heating screed.

It is important to understand that a solution for underfloor heating screed with the addition of a plasticizer is prepared using a small amount of liquid. Therefore, the cooking process should be approached very responsibly and carefully read the instructions on the packaging from the manufacturer.

Each additive in the composition of the underfloor screed mortar is designed to improve certain properties, however, most of the additives are introduced to more completely dissolve the cement particles. This allows you to get a more uniform and durable composition. Some additives make concrete waterproof, this quality is especially important for the floor surface in rooms with high humidity. There are also additives, thanks to which it is possible to reduce the amount of cement in the solution by up to 20% while maintaining the strength characteristics of the concrete screed for underfloor heating.

When choosing a plasticizer, special attention should be paid to the quality of the additive and carefully study the scope of its application. In particular, the additive must be compatible with underfloor heating.

As for the cost, different brands of mortar for underfloor heating cost differently. It cannot be said that the price is too high, since the plasticizer consumption is negligible.

Dry screed for underfloor heating

Not always and not everyone has the opportunity to mix the components, choose and add plasticizers. In this case, a ready-made mixture for underfloor heating comes to the rescue, which is designed specifically for this case. In this composition, all components are measured in a certain proportion and mixed to the desired consistency. It is only necessary to pour in water, mix and achieve uniformity of the solution.

The advantage of dry mixes for a warm water floor is the ability to choose the composition for a specific floor covering. Their disadvantage lies in the rather high cost compared to similar self-preparation materials. Therefore, with a sufficient budget, you can purchase a dry mix, if you want to save money, you can knead the solution yourself. However, in any case, it is recommended to use a dry screed as a finishing leveling layer.

The “warm floor” system requires the mandatory presence of a cement screed. What solution is needed for underfloor heating – this issue can be decided at your own discretion and depending on financial capabilities.

Concrete screed for underfloor heating

Content:

1. types of screeds for underfloor heating
2. what is a wet screed?
3. semi-dry
4. which brand of concrete for floor screed is better?
5. concrete composition
6. cement for underfloor heating
7. what to use as placeholder?
8. Are plasticizers needed, and which ones?
9. concrete mixture proportions for underfloor heating
10. how to mix concrete and pour screed?
11. basic requirements for underfloor heating screed

Different technologies are used for arranging underfloor heating in apartments and cottages. Most often, systems of water pipes or electric cables are installed, which heat up respectively due to the circulation of hot water or electric current, and then transfer the heat to the floor covering. According to building codes, pipes and cables are poured with concrete or cement-sand mortar, which, after hardening, forms the basis for the installation of floor coverings.

Finishing screed for underfloor heating

Installation of water and electric underfloor heating is a multi-stage process, including preparing the base, laying an insulating layer if necessary, directly installing heating systems and finishing screed from concrete mortar. The result is a multi-layered “pie” with a clear structure.

Finishing screed over underfloor heating performs several functions:

• protects heating elements from deformation and damage;
• redistributes the load created by furniture and people’s movements;
• serves as a heat-conducting and heat-distributing layer;
• creates a level surface suitable for the subsequent laying of flooring: laminate, tiles, etc.

In practice, two types of finishing screed are used: wet and dry. Each of them has its own advantages and disadvantages.

Wet screed

It is ordinary concrete, which should not be confused with cement-sand mortar (CSM). The difference is that large aggregates such as crushed stone or gravel are always present in the concrete mix. Concrete mortars, in comparison with CPR, have greater strength and are used not only for interior work, but also in construction.

Key benefits of underfloor heating concrete screed:

• optimal ratio of cost and characteristics of the material;
• flat surface;
• the minimum probability of cracking during shrinkage, which is critical for the efficient operation of a warm floor;
• high heat transfer prefabricated.

Disadvantages include:

• the weight of the structure is rather large, therefore, before pouring the screed in multi-storey buildings, it is necessary to make sure that the floors are strong and reliable;
• time-consuming and messy pouring process;
• long period of curing of concrete (up to 1 month).

Wet screed concrete is recommended to be ordered from the factory. Concrete from a concrete mixer will cost more than self-prepared. But the cash costs are compensated by saving time, effort, wages of auxiliary workers, especially if a large amount of material is required for a large object, and work is carried out in a high-rise building.

In addition, it is difficult to prepare mixtures with ideal proportions on your own, and inconsistency with the recipe leads to cracking of the screed during the curing process and a deterioration in the strength characteristics of the concrete structure.

Semi-dry screed

For a semi-dry screed, a mixture of sand, cement with the addition of a minimum amount of water and plasticizers is used. Typically, such compounds are sold ready-made and delivered to the facility using pneumatic blowers. After laying, the surface is treated with trowels. The result is an even base, which is completely ready for installation of the floor covering in 3-5 days.

It is almost impossible to thoroughly mix the ingredients of a semi-dry screed by hand without a concrete mixer. It is also quite difficult to lay such a mass on your own – you need special machines and experience working with them. In addition, semi-dry compositions are more expensive than concrete and cement-sand mixtures. Therefore, it is better to avoid such technology if you plan to do the work on your own without involving a construction team.

In various sources, you can find references to the so-called dry screed. In fact, it is a mixture of bulk materials (expanded clay). It is leveled after falling asleep, covered with chipboard sheets, on which the flooring is then attached. This technology is not suitable for arranging underfloor heating screeds. The fact is that expanded clay is a material with low thermal conductivity, so heat transfer from heaters will be inefficient.

What brands of concrete are used for underfloor heating screed

The choice of brand of concrete for pouring the concrete floor screed depends on a number of factors: the area and purpose of the room, the expected loads on the future concrete structure. Most often, concretes of the following grades are used for this purpose:

• B10 (M150) – an inexpensive material with a low cement content. It is not resistant to high loads, therefore it is used limitedly, mainly for small areas, for example, bathrooms and utility rooms.
• B15 (M200) – the optimal brand of concrete for pouring underfloor heating in most living quarters of an apartment or a private house.

Concrete grade not lower than M150-M200 – optimal in terms of quality-price ratio and the most used materials for finishing pouring underfloor heating. They give an almost perfect surface, which is dust-free and meets the requirements of flooring manufacturers for the quality of the base.

It is advisable to use heavy dense concrete of high grades B20 (M250) and B22.5 (M300) for arranging floors only if they will be subjected to significant loads in the range of 500-600 kg / cm ² : garages, hangars, production halls. This grade has outstanding performance and is commonly used for building foundations and highways.

The use of concrete B22.5 for screed is also complicated by its low elasticity and poor workability. For this reason, it is difficult to achieve a thorough compaction with conventional methods, and intensive tamping can lead to damage to the underfloor heating structural elements.

Concrete composition

The concrete mixture contains 4 main components in certain proportions: binder, fine and coarse fraction aggregate, water (mixer).

Cement

The binder is responsible for the setting process of the mixture. As a rule, two types of Portland cement are used in concrete mixtures, depending on the type of room and the expected loads:

• CEM I 32.5 N (mark M400) – for living rooms;
• CEM I 42.5 N (mark M500) – for outbuildings, garages, basements.

Sometimes cement is replaced with lime or gypsum, but this composition is not optimal for underfloor heating, because it has a shorter life and gives a surface with less strength.

Cement retains optimal characteristics for 2 months from the date of manufacture, then setting reactions begin to develop in it, and this material is not suitable for concrete mixes. When preparing concrete yourself, try to buy the material immediately before starting work, pay attention to the date of its production, do not use caked cement.

Filler

Serpentinite, amphibolite, granite or marble crushed stone with a particle size of 5-10 mm is ideal as a coarse aggregate for pouring concrete in residential premises and domestic buildings. Chipped gravel is also suitable – a material obtained by crushing river pebbles.

Do not use natural gravel – it contains a large percentage of inclusions of weak rocks and clay impurities, which significantly reduces the strength of the screed. Also, expanded clay is not suitable as a filler for a concrete screed of a warm field. Firstly, it is a fragile material, and it is impossible to obtain concrete with high characteristics on its basis. Secondly, as already mentioned, expanded clay has a low thermal conductivity, that is, such a floor will warm up poorly and unevenly.

The best and most affordable fine concrete aggregate is quarry washed sand with a particle size of 2-3 mm. Due to the rough surface, the grains of sand adhere well to other components of the mixture and do not settle into the lower layers, which ensures a uniform concrete density throughout the entire depth of the slab. The sand should be as dry as possible.

Plasticizers (additives)

There are different types of plasticizers that are designed to improve the quality of the material in one way or another. First of all, additives are introduced to increase the elasticity of the mixture. When poured, it lays down better, levels out easier, fills all cracks, dries out in an optimal time period, gives a smoother surface.

The screed tends to expand when exposed to heat from the heating elements. As a result, cracks appear in it, which cause deformation of the floor covering. Therefore, additives that counteract the thermal expansion of the material are necessarily added to the DSP for underfloor heating.

Proportions of concrete mixtures for underfloor heating

When self-preparation of concrete mixtures, special attention must be paid to respect for proportional composition. This directly affects the strength and durability of the structure. It is more convenient to measure the ingredients in containers of the same volume, for example, a regular 10-liter bucket or shovel.

Table 1. Proportions of concrete mixtures for underfloor heating screed

Cement grade	Concrete class	Average composition of dry ingredients by volume
		cement	sand	crushed stone	water
CEM I 32. 5 (M400)	B10	1	3.5	5.7	0.45-0.55
	B15	1	2.8	4.8	0.45-0.55
	B20	1	2.1	3.9	0.45-0.55
	B22.5	1	1.9	3.7	0.45-0.55
CEM I 42.5 (M500)	B10	1	4.5	6. 6	0.45-0.55
	B15	1	3.5	5.6	0.45-0.55
	B20	1	2.6	4.5	0.45-0.55
	B22.5	1	2.4	4.3	0.45-0.55

By increasing the volume fraction of cement and decreasing the amount of water, a composition is obtained that can theoretically provide a higher strength concrete structure. But in this case, plasticity decreases, which means that it will be more difficult to lay such a mixture.

Rules for mixing concrete and pouring screed

For manual mixing, dry ingredients (cement and sand) are mixed in a building trough or similar until a homogeneous, evenly colored mixture is obtained. Then water is added to it in small portions, the composition is thoroughly mixed for 5-6 minutes. The volume fraction of water in the recipe is given approximately, since it depends on the moisture content of the sand. In general, the less liquid, the less cracks will be in the screed when it dries.

Plasticizers are added according to the material manufacturer’s instructions. The result should be a PCS with the consistency of thick sour cream. If concrete is needed, crushed stone is added as the last component to the finished sand-cement mixture. The mass is thoroughly mixed again. The entire coarse fraction must be covered with a solution.

Visually check the consistency of the solution. Scoop up the finished mixture with a shovel – it should drain for a fee. If the mass does not lag behind well, this does not indicate its low plasticity, it will be difficult to fill in such a composition. Sand and cement must be added to a mixture that is too fluid, but there is a risk of violating the correct proportions of the composition.

The concrete setting reaction starts after mixing the dry components with water. The solution retains plasticity for no more than 1-2 hours, depending on the composition, the presence of plasticizers, and environmental conditions. During this time, it is necessary to complete the planned amount of work and completely use up the prepared concrete.

Filling the screed is the last stage of arranging a warm floor. Before this, a series of preparatory work is carried out, a rough screed is being equipped, a waterproofing layer is being equipped, and a floor heating system is being installed. Please note that the pouring of the screed on the water floor is carried out with the pipes filled, otherwise they will bend under the pressure of concrete.

The mortar is carefully tamped to achieve maximum filling of all internal voids. It is best to use a deep vibrator. A bayonet shovel for this purpose must be used very carefully so as not to damage the cables or pipes.

Requirements for underfloor heating screed

Underfloor heating systems are becoming more and more popular. According to the laws of physics, warm air is understood upwards from the heated floor, which means that such space heating is more economical and efficient than a centralized system. The arrangement of a warm floor in many cases allows you to completely abandon the batteries.

In order for the system to work correctly, it is necessary to carry out careful calculations, strictly follow the installation process, use materials that meet the conditions. The thickness of the finishing screed has a great influence on the efficiency of the underfloor heating system. The optimal parameter is 3-5 cm, but not more than 10 cm. The choice of thickness in each specific case depends on the type and height of the substrate under the heating systems, the composition of the concrete or PCS.

A screed that is too low will cause excessive overheating of the floor covering. An overly thick layer of concrete will negate the efficiency of the system: the lion’s share of the energy released by the heaters will go to warm up the screed, and the heat reaches the upper layers weakly and unevenly.