2023 Author: Philip Bishop | [email protected]. Last modified: 2023-08-25 07:54
- Ordinary solution or not?
- Screed functions
- Preparatory work
- "Pie" and screed thickness
- Laying heating elements
- Temperature sensor and thermostat
- Possible solution compositions
- Benefits of ready-mix
- Filling the underfloor heating system with a screed
Cable electric underfloor heating requires the obligatory device of a concrete screed for underfloor heating, which performs a certain list of functions. But first it is worth leveling the surface so that the heating elements fit well. In the process of pouring the screed on your own, you should pay attention to the exact adherence to the technology. Otherwise, the efficiency of heating the air in the room will be minimized. It is important to understand not only the screed itself and the construction of the "pie" of the warm floor, but also to clarify all the subtleties associated with the working solution.
Ordinary solution or not?
Often, when using a conventional cement-sand mortar on top of underfloor heating elements, one question arises - why did cracks begin to appear? Several very weighty reasons are distinguished here at once, contributing to such a defect.
- Lack of damper tape along the perimeter walls in the room. In the process of mortar shrinkage, cracks begin to appear.
- After pouring, the solution gains strength for a certain time and dries. A certain level of room temperature should be maintained here. Air humidity will also play a significant role.
- Using too liquid solution in the work.
- The alignment layer has reached a height too different from the optimal value.
- The need to create expansion joints in rooms with a large area.
- Drying took place using various heating systems, and not independently.
- The proportions were not observed when preparing the solution.
Filling the solution in stages. To achieve the desired result, the surface must be filled with mortar in one moment, without distractions.
All proportions of the preparation of the solution must be exactly observed. Everything is said about this even on the packaging from the mixture. In addition, experts recommend using ready-made dry mixes, in which all that remains is to add a certain amount of water. With them, many troubles when pouring a warm floor will remain aside. Mixtures can be purchased not only for finishing the underfloor heating system, but also for rough alignment for heating elements. Everything will depend on the specific characteristics and cost of the products, which will tell you which floor heating screed will be the most optimal and of high quality.
A concrete screed under a warm floor performs a certain list of functions, among which the following are the main ones:
- Surface leveling, as well as possible elimination of defects. Any differences in base height will be eliminated and the load will be evenly distributed. The leveling layer is most often a rough version for a warm floor.
- Creates a protective layer for underfloor heating elements. They will not be afraid of external mechanical influences.
- Thermal insulation. That is, keeping heat and not passing it into the base from the heating elements.
- Creates a level and smooth surface for subsequent application of the selected flooring option.
Uniform heat transfer from the underfloor heating system to the interior of the room to warm up the air.
When performing concrete pouring of a warm floor yourself, you should remember that air cavities should be avoided inside. This will prevent the base from receiving the same temperature level during system operation. The efficiency of electrical heating will not be as good as needed.
Before starting the installation of underfloor heating elements, several very important steps should be performed sequentially:
Determination of the place where the thermostat is located. It attaches like a conventional switch. The most optimal distance from the floor is 30 cm. There is no point in installing it below. In addition to drilling a hole in the wall for the thermostat, a hole is also made from it perpendicular to the base of the floor, where the power wire and other wires in the corrugation will be placed.
Sub-floor preparation. All debris and dust is removed, a thorough leveling of the surface is performed. There should not be any pits or drops. When leveling, the thickness of the screed for electric underfloor heating is at least 30 mm. Otherwise, the screed will begin to crack. Apply a layer of primer before spreading the solution over the surface. In addition, the areas where the furniture will be located are marked, as well as indents from the walls to the heating elements, which must be at least 50 mm.
- Insulation layer. It can reduce heat loss by about 30%. Insulation can be laid not only vertically, but also horizontally. For vertical insulation, a damper tape is used, as well as polystyrene sheets, the width of which is 15-20 cm. Heat losses will be reduced through the outer walls in the room. As for the horizontal distribution, here it is laid on a prepared concrete base. The thickness of the sheets is usually at least 20 mm.
If there is a room with a high level of humidity, a waterproofing layer is additionally arranged.
Before laying the underfloor heating elements, fill the rough screed. Usually, a cement-sand screed is taken. This layer will prevent overheating of the heating cable. In addition, the base will become much stronger for the subsequent creation of the entire "pie" of the warm floor. If it is not possible to create a preliminary screed, a metal mesh is laid on top of the heat-insulating layer, to which the underfloor heating element is attached.
With subsequent pouring, the screed is strong and uniform.
As soon as the cement-sand screed for an electric underfloor heating gains the necessary strength, you can cover it with foil thermal insulation, which is the mounting foil. It covers the entire base of the floor, the concrete surface. In this case, it is worth remembering that laying should be done with a margin. The edges and joints should be glued together with foil tape. These actions are carried out in order to prevent the thermal insulation from twisting during the installation of the heating cable.
The foil screen is created with one main purpose - uniform heat distribution during the operation of the electric floor under the screed.
To ensure that the subfloor heating cable is securely fixed, mounting tape is most often used. It is laid on the surface in 50 cm increments.
Subsequently, the final fixation is carried out using self-tapping screws or ordinary nails.
The cable must be properly fixed to the mounting tape. For this, special brackets are used, which are located at the same distance from each other. Typically this distance is about 25 mm. In addition, the brackets allow you to select the required step of laying the heating element and observe it during the installation process.
"Pie" and screed thickness
As standard, the underfloor heating system is installed over an old concrete base. It is enough to lay a heat insulator on it, which can be penofol. This material additionally performs a soundproofing function.
After that, the heating cable is arranged over the surface. At the end, the concrete screed is poured. The result of all this is a "cake" of a warm electric floor.
Since the laying of the entire structure is performed on a relatively soft base, it will not be possible to say about extra strength. This indicates the need to make a hole in every square meter of the applied heat insulator. Additionally, a distance of 10-15 cm should be left along the walls in the room, so that the upper tie rests on the lower base. This cannot be done without it in those rooms that have an insignificant area.
It is worth dwelling a little on the screed itself. Its usual thickness is 30-50 mm. This guarantees an even heating of the subfloor over the entire surface. In this case, they will not collide with areas (stripes) of warm and hot air. In exceptional cases, it is possible to arrange the correct underfloor heating screed up to 30 mm. But in this case, you should think about adding additional plasticizer to the solution in the required amount. Every 100 kg of the finished mixture will require about 1 liter of additive.
Laying heating elements
When you have a plan for laying the heating elements on your hands, you can start all the actions. Particular attention should be paid to the styling step. Before unwinding the cable, check its resistance. These data are recorded in the warranty card. It is worth noting that they must fully comply with the data on the label. The difference in indicators is allowed, but not more than 10 percent.
The cold end of the heating cable should be placed in the corrugation, and then installed in the made strobe. The beginning of the cable should be fixed to the mounting tape on the base of the floor. It is from this section that the cable laying will begin. Subsequently, the coupling must be completely covered with a concrete screed.
All heating cable lines must not be connected or crossed with each other. Throughout the entire area of the room, the laying step must be maintained, which is previously selected. In those areas where it is necessary to bend the cable, its radius should be more than 50 mm. The installed thermostat must have both subfloor heating cables attached.
Temperature sensor and thermostat
After that, the temperature sensor is installed. It is placed in a corrugated pipe, making installation together with the supply end of the heating cable. To prevent the solution from entering the tube with the thermostat during the pouring process, a special plug is made. In this case, there will be no problems with replacing the sensor during operation and its failure.
The sensor is laid on the base of the floor so that it does not cross the heating cable lines. The best fixing option is in the middle of the cable lines, directly on the mounting tape.
Installation of the thermostat can only be carried out when three main cables are routed to the junction box:
- The wire of the temperature sensor itself.
- The mains wire has a voltage of 220 V.
- Heating cable wire.
If the room has a high level of humidity, then it is forbidden to install a thermostat in it. This is contrary to all safety requirements.
When all the above steps are completed, you can think about preparing a solution and pouring a concrete screed, which has its own characteristics and subtleties of installation.
Possible solution compositions
It is difficult to point out exactly what the composition of the solution should be when installing an electric floor heating. Everything will depend on the supporting structure of the floor. So, a concrete base is capable of withstanding a load of 230-250 kg for each square meter of the premises. Reinforced concrete slab is capable of withstanding loads of up to 1.3 tons. If we take into account the standard thickness of the screed, then it creates a load in the range of up to 180 kg per square meter.
The compositions can be of the following form:
- Concrete mix.
- Cement-sand mortar.
- Semi-dry composition.
The preparation of the solution should be carried out in compliance with the following proportions:
The grade of cement for the leveling layer is taken at least M400. Here you can take the proportions of sand and cement, like 3 to 1. In addition, the sand must have a fine fraction. Instead of reinforcement or as additional reinforcement, microfiber acts, which has even better qualities and properties. The addition of plasticizers helps to protect the concrete solution from the effects of elevated temperatures.
All possible dry ingredients are mixed with each other within five minutes. The plasticizer is mixed separately with water. Each bag of cement used requires the use of about 5-6 liters of water. In this case, additives will need about 200 grams. In the future, you just need to add all dry ingredients to the water.
The concrete solution, which is poured onto the heating elements, has slightly different components and proportions: for 2 parts of sand, 3.8 parts of crushed stone will need to be added. All this is mixed with one part of cement grade not lower than M300.
Benefits of ready-mix
In order not to waste time preparing the solution, you can purchase ready-made dry mixes. They have a number of positive qualities, among which it is worth highlighting:
- No need to comply with the proportions of all components.
- The package displays detailed instructions for preparing the mixture and subsequent pouring.
The weight of the finished mixture is slightly lower than self-preparation of the solution.
This reduces the cost of transportation and installation work.
- Technologies allow you to choose the most optimal composition of ready-made mixtures. They can be suitable for any room where a warm floor is installed, as well as for any type of floor covering. There are no restrictions here.
- Dry mixes are lighter in weight, which reduces the pressure on the floor slabs.
- The thickness of the screed can also be made in a thin layer from 5 to 30 mm.
- When self-executing a screed for a warm electric floor, it is best to use ready-made dry mixes, which save not only time, but also, to some extent, money.
Filling the underfloor heating system with a screed
Before mixing the solution and distributing it over the entire surface of the floor in the room, make sure that the warm floor is fully functional. It is turned on for a certain period of time. A photograph or sketch of the placement of all elements of the electric floor heating is included in the warranty card.
The most optimal solution is prepared from specially designed mixtures. There should be no questions about what kind of screed to make for a warm floor. In some cases, the solution can be prepared independently, strictly observing the proportions. Pour the screed under the warm floor evenly and carefully. The cable insulation must not be damaged. The most important thing is that there are no air pockets here that reduce the efficiency of the warm floor.
In this case, the thickness of the screed should be between 30-50 mm. Complete drying of the solution is 4 weeks. During this time, the underfloor heating system cannot be activated so as not to face negative manifestations. As soon as the screed hardens, you can begin to cut off the protruding parts of the insulation layer and damper tape. In the end, the flooring of the selected flooring option is made.
Consider the options, which lightweight warm screed is the most economical and which fillers for underfloor heating screed are the best. Using polystyrene concrete for pouring into the floor in the room
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