The need to install a screed for underfloor heating
To provide the floor with a solid foundation that can withstand heavy loads from both furniture and people moving around, a warm screed should be done. This element will ensure a perfectly flat surface of the coating, which will ultimately increase the attractiveness of the interior.
The following tools will be required for the work:
According to the standards, the installation of screed is made after the installation of pipes. It is necessary to meet the main requirement. lay the pipes in such a way that the outlet of each pipe is located slightly higher than the intended level of the screed.
After completing the installation of pipes the free space between them is filled with mortar. Most often it is a standard mixture, thanks to which you can significantly reduce the consumption of cement. The filler can be regular sand. Other, coarse fractions, such as gravel or crushed stone, are added to this mixture to obtain concrete.
The standard mortar used when installing the screed for this floor system consists of 3 parts of sand and 1 part of cement with the addition of water.
You can also use other reliable mixes that have the same properties. Specialists recommend the purchase of an already prepared mixture if the work is carried out in rooms with a very large area. The high quality of such compositions is ensured by the fact that they are mixed evenly and fully ready for use. The only necessary procedure is periodic hydrogenation by means of a mixer.
Often the composition of ready mixes contains additional components, such as plasticizers, which increase the plasticity of the mortar. This property allows the mortar to penetrate into the most inaccessible places. At the same time there is no risk of voids when pouring. The self-levelling compositions are particularly popular. The mixture spreads itself over the area, which makes the entire work process much easier.
Plasticizer. a special additive designed to interact with cement mortar and to increase its fluidity and plasticity
Laying a warm water floor
One of the key components of the system pipes and their fixing system. There are two technologies:
Dry polystyrene and wood. On the system of foamed polystyrene mats or wooden plates are placed metal strips with molded channels for laying pipes. They are necessary for a more even distribution of heat. The pipes are inserted into the notches. On top are laid rigid material plywood, OSB, GFB, etc.д. Soft flooring can be laid on this subfloor. laying tiles on tile adhesive, parquet or laminate flooring is possible.
Both systems are not ideal, but it is cheaper to lay pipes in a screed. Although it has a lot of disadvantages, it is the one, due to its lower cost, that is more popular.
What system to choose
In terms of cost, dry systems are more expensive: their components (if you take prefabricated, factory-made) cost more. But they weigh much less and are quicker to put into operation. There are a number of reasons why they are worth using.
First: The heavy weight of the screed. Not all foundations and floors of houses can withstand the load created by a water-heated floor in a concrete screed. Over the surface of the pipes there must be a layer of concrete of at least 3 cm. If we consider that the outer diameter of the pipe is also about 3 cm, the total thickness of the screed is 6 cm. The weight is more than significant. And the top is often even tiles on a layer of glue. It’s good if the foundation is designed with a reserve it will hold, but if not. problems will begin. If there is a suspicion that the ceiling or foundation can not withstand the load, it is better to do wooden or polystyrene system.
Second: the low maintainability of the system in the screed. Although when installing underfloor heating circuits it is recommended to install only whole coils of pipes without connections, occasionally pipes get damaged. Either a drill has hit it during repair, or it breaks because of a defect. The place of damage can be identified by a wet spot, but it is difficult to repair: you have to break the screed. In doing so, you can damage the neighboring hinges, so that the damage zone becomes larger. Even if you managed to do it neatly, you have to make two seams, and they are the potential places of the next damage.
The process of installing water heating
Third: the commissioning of the floor heating in the screed is possible only after the concrete gains 100% resource strength. This takes at least 28 days. You cannot turn on the underfloor heating before this time.
Fourth: You have made a wooden floor. The tie itself on the wooden floor is not the best idea, and even a screed with high temperature. The wood will quickly collapse, collapsing the entire system.
The reasons are serious. Therefore, in some cases, it is more appropriate to use dry technology. Especially since the wooden water heated floor with their own hands is not that expensive. The most expensive component is metal plates, but they can also be made of thin sheet metal and better aluminum. It is important to know how to bend by shaping grooves for the pipes.
Polystyrene heating system variant without a screed is shown in the video.
Installation of water heated floor in the concrete screed
Experts have proven that a large part of heat loss in private homes. about 20%. is due to the floor. Houses in apartment buildings with their iced ceilings in winter are not in a particularly advantageous situation either. Therefore, one of the best solutions to this problem over the past couple of decades have been well-insulated underfloor heating (UI) systems, often water-based. For example, in a private home, the water underfloor heating is often used for additional (comfort) heating or as an alternative heat source. In apartments, the TP is able to independently provide heating for homes and businesses. However, in order to get an effective heating system with minimal losses, you should perform its correct calculation and installation.
The design of a water underfloor heating
The water underfloor heating includes:
The control system of a warm water floor includes a pump, since without forced circulation to achieve an even flow of coolant is simply impossible. In addition, this device helps to maintain a constant temperature in the system.
For a warm water floor only centrifugal type pumps are used. They are designed for different modes of operation, respectively, to change the temperature of the coolant device with different speed pushes the water in the circuit.
The boiler is needed to heat the coolant, but if the floor is connected to the central hot water supply, it is not necessary. It is usually installed for autonomy.
Its distinctive feature is the operating temperature, which does not exceed 45 ° C. This fact is worth paying attention to if the system operates with a gas boiler.
Circuits, boiler, pump and other elements of the control unit are connected to each other using fittings. This way there are several contacts, joints and joints. The risk of leaks will depend precisely on their number. In order to minimize the chances of a gap, they use a manifold. It consists of two combs, each represented by a pipe with holes. Their diameter varies from 8 to 12. The first pipe is designed for distribution of hot liquid in the circuits, and the second to collect the cooled coolant.
The water heating system rarely consists of a single circuit. Each is regulated separately. Servo drives and thermostats allow the system to be controlled automatically. As a result the user can save up to 30% of the energy consumed.
In addition, it is often put thermostats with a sensor or remote control. They have full functionality. They are often used in “smart home” systems.
information about the insulation of pipes in the horizontal floor can be studied in the standards SP 41-102-98.
Corrugators or shells are used to maintain a certain temperature in the pipeline. At the sites. With cold liquid sometimes accumulates condensate, and thermal insulation helps to significantly reduce the risk of excesses.
In the arrangement of the concrete screed is most often used corrugated. As a result the pipes are additionally protected against mortar pressure. On sale it is possible to find materials in blue and red colors.
If the height of the screed exceeds 10 centimeters, a rigid corrugation is used. If you additionally put a shell, the layer height can be up to 7 cm. Double protection helps to cope not only with the pressure of the concrete screed, but also with the subsequent loads.
Screed for underfloor heating: options, thickness and mortars
Floor screed is a layer in the construction of the floor, the main purpose of which is to distribute the load evenly on the floor of the building. An additional task of the screed to level the floor base.
Underfloor heating screed performs the task of a heat exchanger, which first takes the heat from the underfloor heating system, and then evenly releases it into the room. It is for this reason, the screed for warm floors is made by special rules, somewhat different from the usual screed.
Installation for electric heating
Take into account the minimum thickness of the screed, which is located over the heating cable (and under it). There are several methods of installation. It is necessary to prepare the mortar, and only after this to deal with the pouring of the surface.
Careful implementation of all rules will help to avoid cracking coating, and heating will be the same throughout the room, and the system will serve for a long time.
Underfloor heating in the screed: pros and cons
The difference between underfloor heating and other types of space heating is the location of heating elements under the floor covering. This type of heating gets rid of radiators on the walls, which should be placed two or more in each room, and gives a uniform heating throughout the room, if the floor heating is arranged in a private home.
Arrangement of the screed under the water heated floor
Experienced finishers for the organization of a warm floor prefer to use the traditional pouring of screed with concrete. Semi-dry screed technology allows you to significantly reduce the period of delivery of the base under the finishing trim, which is a plus, but this type of floor alignment has significant disadvantages compared to conventional concreting:
- Even with the most thorough compaction of the dry mixture in the layer thickness remain air s, which are an obstacle to the passage of heat waves from the heater. As a result, the efficiency of underfloor heating decreases dramatically;
- Especially noticeable losses, if the semi-dry screed is performed on the first floor. In this case, the coefficient of performance is 0.5.
A denser structure of the concrete base allows heat waves to pass without interference, respectively, to obtain the specified parameters of heating the air in the room will need much less energy than when functioning in a semi-dry screed.
Necessary materials and tools
Before you start laying a warm water floor in the screed with your own hands, you will need to buy the following materials:
- pipes with a cross-section of 16-25 mm of plastic, ceramic metal or copper;
- collector for the estimated number of outlets;
- Styrofoam pad with the markings for installation;
- polyethylene film;
- connecting fittings;
- Fiberglass reinforcing mesh, recommended mesh size of 3 mm;
- clamps for fixing the pipes to the base;
- damping tape;
- Cement, it is best to choose the brand M500;
- quarry sand;
- rails for screeds;
- plasticizer for concrete.
For the work you will need the following tools:
- container for the preparation of the mixture;
- hand mixer;
- laser level;
- construction knife;
- measuring tape;
- PVA glue;
Instructions for the device wet screed
In carrying out the work should adhere to a certain technology:
- Before starting work, the surface must be free of dust and dirt.
- In order to ensure waterproofing of the floor, the surface is covered with a polyethylene film. The film is laid overlapping, the joints are glued with scotch tape, the film rises 150 mm near the walls.
- Damper tape is installed on PVA glue on the bottom of the walls. Using a laser level on the surface of the walls is applied a horizontal marker at a height of 1200 mm from the floor. After that the maximum point is found. Calculation of the floor layers is carried out from this mark, it is necessary to take into account the thickness of polystyrene foam base or foil substrate, pipe cross-section, the height of the reinforcing grid and the minimum thickness of the filling. This determines the height of the screed over the water underfloor heating.
- Place a thermal insulator on the surface to prevent the heat from escaping into the thickness of the floor slab.
- Then a grid is laid that serves as a reinforcement for the screed.
- At a distance of 50 mm from the wall mount the first row of pipes, then spiral untwisted with a gap between the adjacent pipes at least 120 mm.
- The pipes are fastened in the grid with clamps.
- Pour the mortar on the ready basement at once, without interruptions, so a large container or a few people, who will be constantly preparing new portions, are required for preparation of the mortar. For screed it is recommended to use cement and sand in proportion of 1 to 3, for each cubic meter of mortar it is necessary to add 800-900 grams of fiberglass, which is poured into the mixture in small portions. The volume of water is equal to approximately the volume of cement, but the optimal amount is selected on the basis of plasticity of the ready mixture.
- The mortar is ready, you can pour the base. The work starts at the far corner and gradually, smoothing the surface with a rule on the screeds, reach the doorway.
- Within two weeks it is necessary to sprinkle the fresh screed with water every day to prevent the surface from cracking. After wetting, lay a polyethylene film on the floor.
- When the base is cured, trim off the excess polyethylene foil and the damping tape from the wall. At the same time it is necessary to remove the beacons, seal the recesses with mortar.
What can fill the floor
For pouring a warm floor there are three options. semi-dry screed, concrete screed and screed from self-levelling mixtures. All three methods have a simple technology and are largely similar, although each of them has its own characteristics. To determine which type of screed to choose, you need to familiarize yourself with the main advantages and disadvantages of each option.
The classic option. pouring the floor with a cement-sand screed. But since the screed will be constantly exposed to significant variations in temperature, it must have a high strength. The strength largely depends on the filler, so the sand is replaced by sift and receive a concrete screed solution. According to construction regulations, a quality solution for pouring a warm floor must contain:
Sift provides better and more reliable adhesion, unlike sand. Cement of low grades will not give the concrete the necessary strength, and the surface will certainly crack when heated. Softener is needed to ensure that the screed under the influence of temperature fluctuations does not crumble. In addition, the use of plasticizer makes it possible to reduce the thickness of the screed from 50 to 30 mm.
Mix the mortar in the following proportions:
- cement. 1 part;
- sift. 6 parts;
- plasticizer. 0.35 liters per 1 bag of cement;
- Water. until a pasty homogeneous mixture is formed.
Installing your own radiant heat tubing in a concrete slab. (DIY METHOD)
If you pour the floor complex configuration or area of more than 40 square meters, it is recommended to add fiberglass in the solution. This contributes to a better distribution of the mixture and eliminates the need to lay a reinforcing mesh.
When properly poured, the screed is strong, durable, provides uniform heating of the surface. The disadvantages of concrete screed include its heavy weight and long drying period. If time is pressing, it is better to pay attention to the second method. laying semi-dry screed.
The main difference of this type of screed is the lesser amount of water. The mortar must contain polymer additives and fiberglass. You can buy ready-made dry mixes for the manufacture of screed, but also to prepare a solution yourself is not difficult.
Mix for semi-dry screed with polypropylene fibers
Technology of production and laying of semi-dry screed
Water is added in small quantities, thoroughly mixing all components. You can easily check if there is enough water in the screed: put a small amount of mixture in your hand and squeeze hard. If the water flowed, it means its overabundance, if the mixture crumbles, you need to add more water, but if the solution after compression holds shape well, does not crumble and does not smear in the palm, it is ready.
Pluses semidry screed more weighty: dries faster than concrete, the strength is higher, gives less shrinkage, almost does not crack. Temperature fluctuations also do not have a noticeable effect on the screed. As for the disadvantages: the mixture has less plasticity, and therefore more effort is required in making the mortar. For the same reason, the compaction of the layer on the floor is not always uniform, and voids are formed in the thickness of the screed. Layer needs to be protected from moisture after drying.
By their properties self-leveling compositions similar to the standard cement-sand mixture, but they have some advantages. They are more plastic and do not require careful leveling, since they flow out under their own weight. They also dry faster. Self-leveling mixes are divided into a rough and finishing; for the filling of the warm floor only rough is used, as the finishing is not designed for a thick layer. In turn, rough smoothers are available on the basis of gypsum and cement, both of which are excellent for casting a warm floor.