Old buildings of houses or apartments require competent and professional repairs, especially for floors. Usually in such houses the floor is uneven and has many cracks, as well as all kinds of errors. To make its base even and smooth, it is necessary to screed the floor. The concept of screed includes the distance between the base of the floor and its covering. Now there are coatings that cannot be laid without preparing the floor in advance. Thanks to the screed, your floor will not only look beautiful, but will also serve you for several decades. Floor screeds are poured in one or several layers. This speaks for itself.
The base is laid in one layer with one type of solution at a time. And multilayer includes several types of solution and spherical layers between them. There are several types of screeds, differing in materials and installation technology. Let's consider several options for such floor preparation. First you need to understand their functional meaning. In addition to the fact that your floor will be perfectly flat and smooth, it will also become much stronger and stronger. The level of the floor itself will also increase slightly. When laying the floor covering, the load on it will be distributed evenly.
In order to decide what kind of flooring to make in the apartment, as well as to choose the right materials for this work, you should consider possible types.
It has only one drawback: it takes too long to dry. But it also has advantages because it is made on the basis of environmentally friendly material.
But it's very fragile construction material and you cannot lay a heavy floor covering on top of it, or you simply need to correctly distribute the entire load over it.
Remember that screeding in an apartment is carried out within one day and only with one type of mortar. Only high quality laid screed will give the floor good strength and level the surface. Install only on floors that have been cleared of old coating. If there is already another screed on the floor, then you need to examine it for strength. It should not crumble or fall out. This is the main condition for a new coating. Seal all cracks and holes on the floor. Then decide on the height of the floor and start doing the main work.
After cleaning all the garbage and dust in the apartment, it is necessary to install beacons using water or building level so that the surface is of the same thickness. This level will show even the smallest error in filling the floor. The thickness should be at least 3 cm. Then you can put it on different coating without worrying about its operation. The floor screed creates a real air cushion, thanks to which the floor is leveled. Beacons are pre-installed, which are used for cement screed.
The lighthouses are located at an equal distance from each other, approximately one meter. They are fastened on the basis of ready-made cement mortar thickly placed on them. The next point of implementation is the high-quality preparation of concrete - cement mortar. Here all proportions must be strictly observed. It's better to buy at hardware store already prepared mixture and simply dilute it with water. When the solution is ready, we fill it. We pour cement mortar between the beacons. Simply pour the self-leveling solution onto the floor and level it towards you from the corner of the room.
Now you need to wait a certain time for the solution to dry thoroughly. This will take approximately two weeks. When you are sure that the floor in the apartment is completely dry, take out the beacons and carefully seal the remaining cracks.
The cracks are sealed with the same cement mortar, which is what they poured. Beacons begin to rust very quickly and can harm your work. Therefore, they must be removed immediately after drying. After this, wait a little more time and the floor screed is ready. Then you can continue the repair and lay the covering you like on the floor. Now you will have a beautiful and smooth floor that will delight you for many years. The types of screeds are varied. Which one to make for the floor in the apartment is up to its owner to choose.
Screed is done with the purpose of leveling or stiffening the surface, ensuring heat absorption of the floor, and creating a slope in the floor on the floors. Pipelines are covered with screeds.
Screeds are made as the final surface or as an intermediate layer on which the final coating is laid.
Considering the design, couplers are:
Screeds made of cement-sand mortar are a thing of the past because such work took a lot of time. While the solution gained strength and dried, more than one week passed. If finishing coat laid on a solution that was not completely dry - the quality of the work decreased.
Modern quick-setting cement-sand mixtures with polymer additives simplified the process of screed formation. Instead of several months, it now takes only a couple of days for the fill to reach the required humidity for laying parquet. Modern screed- This is a 2-layer construction. The first layer is leveling, rough, the second is thin, finishing.
When choosing material for two-layer screeds, you need to be interested in what the astringent base of these mixtures is. Modern dry mixes are produced using the following binders:
An important factor is the compatibility of materials. For example, if rude screed leveling layer is made from dry mixtures on a cement binder, the final layer is made from dry mixtures on a gypsum binder, then a primer layer must be laid between these layers. The reason lies in the fact that cement binders promote a mild alkaline reaction, while gypsum binders promote an almost neutral reaction. The result of using dissimilar materials in two layers of one screed is gypsum leaching. You can put gypsum on the cement layer of the screed, having first applied a primer, but cement will not work on the gypsum layer, because gypsum, even hardened, will not withstand moisture, raw cement will turn it into mush. Most the best option when for multilayer screed they use materials based on one binder component, because even the use of a primer entails extra costs and loss of time.
Choosing screed material, The following nuance is also taken into account: screeds based on cement binders are shrinkage. In other words, cracking is possible during setting. To prevent cracking from occurring, add polymer additives. Screeds based on gypsum binder do not shrink, are more environmentally friendly and are vapor permeable. The latter quality means that the screeds absorb excess moisture from the air, and release it in a dry room. If the floor is wooden, then it is better to make gypsum, since such screeds are only suitable for dry rooms. Cement screeds are suitable for various premises. If polymers are added to the gypsum, then the screed will become more tolerant of moisture, and it can be used in rooms where the humidity is moderate.
According to the method of adhesion to the floor, there are the following *types and types of screeds*:
Rice. 1. Types of screeds according to the method of adhesion to the floor
Tied ties are those that are tightly coupled to the base. In other words, there are no separating layers between the base and the screed. This type Screeds can withstand heavy loads, but the shrinkage of tied screeds is uneven and can often result in cracks. And the humidity of such screeds depends on how saturated the ceiling is with moisture. Prevent screed adhesion The use of screeds on the separating layer will help with the overlap. The role of the separating layer is usually performed by the following materials:
In order for such a screed to be strong enough, its thickness should be at least 30 mm. If special waterproofing is required, then a screed is applied to the separating layer.
On the insulating layer they do not bond to the base. This is an independent building structure. The layer - bedding between the floor concrete and the “floating” screed is made of the following heat and sound insulating materials:
The smallest thickness of the “floating” screed is 50 mm. The use of screed on the insulating layer increases the thermal and sound insulation of the floor. In addition, the moisture contained in the screed will not depend in any way on the concrete floor. But this design scheme has low compressive strength and also has increased thickness. In this type of screed, in most cases it is necessary upper layer additionally reinforce.
Rice. 2. Reinforced screed
Prefabricated screeds- these are elements that are ready for installation and are designed to be joined with seams. Installation is made from large-sized sheets, as well as boards - plywood, chipboard, fiberboard, gypsum fiber (GVL) sheets. The elements of prefabricated screeds are not heavy, so even one person can easily install them. There are no “wet” processes when working with prefabricated screeds, which makes it possible to lay face coverings immediately after installation. It should be noted that prefabricated screeds cannot be used for every face covering.
Rice. 3. Dry screed diagram
Different types and types of screeds imply individual characteristics installation work.
Manufacturers of screeds indicate the degree of strength of the coating in the instructions for their products. But the manufacturer does not do the installation itself, so the warranty only applies to the material. As a result, the packaging often overstates the strength of the original screed. There is a conflict of interest. The manufacturer is interested in having the material he produces laid on super hard screed, the buyer wants to buy a quality product at an affordable price. If the buyer fulfills the requirements of the flooring manufacturer and makes the screed with a strength of up to 300-400 kg/cm², he will retain the guarantee. If he does everything according to the requirements of SNiP, then he can be sure that everything was done correctly and reliably. The conditions of SNiP 2.03.13-88 “Floors” are as follows:
1) Screed strength based on cement binder for all types floor coverings should not be less than 150 kg/cm²;
2) If necessary leveling the screed self-leveling mixtures - at least 200 kg/cm²;
3) The strength of gypsum screed for all types of floor coverings should not be lower than 100 kg/cm²;
4) For polymer “self-leveling” - no less than 200 kg/cm².
Screed for self-leveling mixtures is usually made the strongest because “self-flowing” sets the fastest, which contributes to the development of high internal stress. There will be no cracks, but a weak bottom tie may be “pulled” and torn from the base.
It is also necessary to take into account that complete replacement or installation of a new screed will press with all its weight on reinforced concrete slabs floors. Reinforced concrete floors in old houses they have restrictions on load-bearing capacity, which is equal to 400 kg/m² - permanent load and plus 150 kg/m² - temporary load. For example, every centimeter of screed, volume weight which 1800 kg/m³ will press on the ceiling with a weight of 18 kg/m². If the screed is 5 cm thick, then each square meter of flooring will receive a load of 90 kg. These figures prove that such a screed will take 25% of the entire load-bearing capacity of the floor.
If necessary increase screed thickness or replace the screed material with one that is heavier, you will have to coordinate everything with bearing capacity overlap, which means it must be approved by local authorities.
Hello! To ensure that your floor in the apartment is level, concrete floors, which are the foundation of the entire floor, it is necessary to make a screed. But a floor screed not only levels the floor, but also solves a number of other problems. Depending on the tasks and types of floor subfloors, screeds are divided according to their design, adhesive components and method of adhesion to the floor. This is all I want to talk about in this article.
In addition to leveling the base floor, the screed gives the surface the necessary rigidity. In addition, the floor screed, laid on heat and sound insulation layers, creates normalized values for heat absorption and sound insulation of the floor. Under the screed you can hide electrical wiring in pipes or corrugation, electric and water heating elements of a heated floor. Screeds can be the finishing surface or an intermediate layer for laying the final layers of the floor.
Floor screeds are divided according to the binding components included in the mixture, according to the method of adhesion to the floor surface and walls, and according to constructive solution screeds. In addition, screeds can be divided into “wet”, “semi-dry” and “dry”, according to the presence of water and fillers in the screed.
According to the method of adhesion to the base, screeds are divided into
By the very name of a bonded screed, it is clear that the screed is chemically bonded to the base. There are no separating layers between the screed and the base. This screed can withstand heavy loads, but has a number of features. This type of screed refers to “wet” screeds and the solution for this screed includes a large number of water. When drying, the screed shrinks greatly. The “sticking” of the screed to the base “stretches” the screed. Combined with uneven drying, this often leads to cracking of the screed. And the humidity of such a screed directly depends on the humidity of the ceiling.
To eliminate dependence on the humidity of the floor, screeds are made with a moisture-proofing or waterproofing separating layer.
To reduce adhesion (adhesion-adhesion of liquid and solid contacting surfaces) of screeds to the floor of an apartment, moisture-proofing separating substrates are used. For such substrates, glassine, roofing felt, bitumen paper and, of course, polyethylene film are used. The thickness of these ties must be at least 30 mm. This will ensure the required strength of the screed. Screeds on a separating substrate are indispensable if waterproofing of the room where the screed is made is required.
A "floating" screed represents an untied building structure made on the floor of the room. A moisture-proofing layer is laid on the ceiling, heat-insulating and soundproofing materials, on top of which a “wet” screed with a thickness of at least 50 mm is made. When reinforced with mesh, the thickness can be reduced to 40 mm.
In operation, such a screed shows excellent heat and sound insulation qualities. Unfortunately, such screeds have low compressive strength. Therefore, “floating” screeds require additional reinforcement. To top it off, “floating” screeds have a greater overall thickness from the floor of the room.
The screed designs are also different. According to their design, screeds are divided into solid and prefabricated.
Solid screeds are screeds that contain water in the solution. If a continuous screed is made in one layer, it is called single-layer. If the screed is poured in several layers, it is a multilayer screed. The layers are laid sequentially, and each subsequent layer is laid on the completely dry previous one and must have good adhesion to it.
The classic version of a continuous screed is a “wet” cement-sand screed. The main disadvantage of this screed is the long time it takes for the screed to dry until it reaches the required strength. Until completely dry cement-sand screed At least 21-28 days must pass, and for laying parquet, all 60 days. When drying, you need to take care of the screed: cover it with polyethylene to dry evenly, and spill it with water for the first week. This will avoid uneven drying of the screed and the appearance of cracks during drying.
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To reduce the amount of water in the solution, various modifiers are added to the “wet” screed. Modifiers are otherwise called plasticizers. Essentially these are regulators of shrinkage and hardening of the screed. They allow you to reduce the amount of water in the solution without losing quality and avoid shrinkage upon drying.
Cement-sand screeds have been replaced by quick-drying mixtures. These are the so-called self-leveling floors and leveling mixtures. Typically, such screeds are made in two layers. The first layer of rough leveling and the second thin layer of finishing leveling.
If the screed is planned in several layers (multilayer), it is necessary to take into account the separation of the screeds according to the binder components included in the dry mixtures for the mortar.
Based on the binding components, dry mixtures are divided into cement, cement-polymer, gypsum and gypsum-polymer. This must be taken into account when making multilayer screeds.
Important! Gypsum screed can be laid on a cement screed only through a layer of primer. Cement screed cannot be laid on gypsum screed. Hardened plaster is afraid of water and a “wet” layer of cement screed will turn the plaster into mush.
Therefore, when constructing a multilayer screed, it is necessary to use mixtures with the same binder component. Even better than one manufacturer.
One more thing should be noted here. It is better to lay wooden floors on gypsum screeds. They are non-shrinking and vapor-tight. But gypsum screeds are afraid of moisture and are not suitable for damp rooms. Cement screeds are suitable for all types of premises.
Another type of screed is prefabricated screed.
Prefabricated screeds are classified as “dry” screeds. A striking example is Knauf - superfloor, the full name is “Prefabricated floor base”. This screed consists of prefabricated elements ready for installation. The elements are connected by seams. The elements are assembled from large-sized sheets of gypsum fiber (GVL), plywood, chipboard and fiberboard. Prefabricated screeds are lightweight and after laying such a screed, you can immediately begin laying the finishing coating on the floor. But prefabricated screeds are not applicable for all types of premises.
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What is floor screed? The design performs several functions in your apartment. It is installed primarily to level the floor, but in frequent cases, a layer of floor insulation, electric or water heated floors and other communications are hidden in the “depths”. Based on this, we note the types of floor screeds:
According to their design, they are also divided into groups: solid and prefabricated.
Solid options, in turn, are further divided by the number of layers:
Prefabricated screed - set components, ready for installation or almost ready, with minor modifications.
Now let's look at each type of leveling layer separately.
The materials used for the device are varied. This is a traditional cement-sand mixture (CSM), with or without special additives, gypsum, polymer mixtures or sheet leveling materials on support logs, stands or loose substrates.
This is, in most cases, a continuous layer of material in contact with the base of the floor (interfloor ceiling).
During Soviet times, builders used time-tested technology of traditional cement-sand screed. The method, I must say, is inexpensive compared to other options, but long-term.
The period for complete drying of the DSP is 4 weeks and to this you need to add the time for the device and further care behind the covering, otherwise many days of work will turn into dust. Without proper care concrete screed the floor dries unevenly - and this at least leads to the appearance of cracks on the surface.
Modern mixtures contain polymer additives to speed up drying. Chemical processes, thanks to which the CPS becomes hard and strong, are completed in such a mixture after a few days. A striking example of this type of foundation device is a semi-dry floor screed.
However, the moisture level of the finished surface will not allow the installation of some types of wood finishes. That's why traditional version additionally coated with polymer self-leveling mixtures, which, in addition to their main purpose (surface leveling), also act as a barrier to moisture and increase the strength of the screed. This “pie” is called a two-layer floor screed.
When choosing a building material for a two-layer coating, start by specifying binder as part of the mixture, because some of them are incompatible.
Dry mixtures are made on the basis of cement, gypsum, cement-polymer, gypsum-polymer binders.
We do not recommend combining layers of different compositions without additional treatment with a primer. For example, the first layer of CPS covered with a thin layer of gypsum will lose strength over time, since different materials have a chemical effect on each other.
When the cement dries, it gives a light alkaline reaction. Gypsum is almost neutral. After some time, leaching of this layer will occur. The consequence of such a process, as mentioned above, will be a loss of strength and subsequent destruction.
Pouring the floor in reverse order– cement on gypsum is completely impossible. The gypsum layer, when interacting with the wet composition of the mixture, will turn into a porridge-like substance.
Adding polymer additives and additives to gypsum makes it less susceptible to moisture, but still use compositions based on a single binder for the multi-layer version. This will at least save you time and money.
This type is laid out on a pre-laid separating layer made of waterproof materials. These materials prevent adhesion of the base to the screed and act as a waterproofing layer in the floor covering structure. By the way, waterproofing is also laid on the walls, to the height of the planned layer.
Coating building materials or roll materials, such as roofing felt, glassine, bituminous paper or polyethylene film, can be used as floor waterproofing. The thickness of the finished base, which provides the necessary strength for laying the finishing coating, must be at least 20 mm.
This floor screed is suitable for rooms with high levels of humidity and (or) in which there is running water.
Waterproofing and heat and sound insulating building materials are installed between the reinforced concrete base and the leveling layer. This floor screed significantly insulates the surface and reduces the noise level coming from neighbors below.
The minimum thickness of the layer should be 40 mm, which ensures the necessary strength of the structure. A smaller thickness will require reinforcement with steel or plastic mesh. If you add up the thickness of the entire “pie” and add the finishing coating, you get a considerable figure that is not suitable for every apartment.
The components for this option are large-sized sheets of plywood or OSB (oriented strand board), GVL (gypsum fiber sheet), gypsum board ( plasterboard sheet), fiberboard (fibreboard), chipboard (chipboard), SML (glass-magnesium sheet), which are laid out on a prepared and leveled base. (Description of all types sheet materials you can find on the pages of our website).
The basis, in turn, is wooden or plastic slats, rigidly attached to a reinforced concrete base or bulk materials, aligned with beacons.
Particularly successful in this type of screeds Knauf company. Their screed flooring has become very popular in Lately on Russian market building materials.
The minimum distance between the surface of the prefabricated structure and the subfloor is 40 mm. Heat and sound insulating building materials are laid in the spaces between the slats (lags).
Dry floor screed completely eliminates “wet” processes and upon completion of installation, you can immediately lay the finishing touches. A significant disadvantage is absolute intolerance to moisture.
Manufacturers of flooring, insuring themselves against liability for legal costs, declare deliberately inflated requirements for the strength properties of the floor base when laying their products.
The manufacturer wants his products to be placed on a super-hard base, and the consumer wants to save money. It turns out to be some kind of conflict.
If you want to receive a guarantee from the manufacturer of the floor covering in case of damage, you should comply with the requirements by arranging a screed with a strength characteristic of 300–400 kg/cm². But this figure exceeds the approved standard twice.
According to SNiP 2.03.13-88 “Floors”, the strength indicators of screed on cement binder for all known species finishing should not be lower than 150 kg/cm². The floor screed, also covered with a leveling mixture, using the same binder, must have a strength of at least 200 kg/cm².
Likewise plaster screed– 100 kg/cm², and polymer-gypsum 200 kg/cm².
All types of floor screed in an apartment are good in their own way. Which one is suitable for a particular room is up to you to decide.
Having weighed all the pros and cons, and perhaps agreed with the relevant licensing authorities, proceed to implement your plans. I would like to hope that the floor screed will serve you for a long time.
For anyone who even remotely has an idea about floor finishing, the concept of screed is familiar. The principle of surface leveling is known, and there is enough information about the materials used. But it will be quite difficult for a non-professional to immediately answer the question of which screed is better, dry or wet. In this matter, it should be understood that builders pursue the main goal - to level the surface, but the method of this preparation will depend on further work.
First, we will try to answer this question by classifying the types and highlighting the advantages of each of them. The following list will help us understand the question of which screed is better or wet.
Be that as it may, no matter how many advantages this or that screed has, sometimes you have to choose taking into account the situation. For example, what kind of screed is best to make in an apartment when you have a short deadline for finishing the floor? It is clear that we will give preference to dry or semi-dry. On a substrate made of mineral materials We lay OSB sheets and compact the surface as much as possible. Next, remove the sheets and allow time to dry.
Nowadays, heated floors are already commonplace. Many people prefer this method of heating their home, and here it is quite logical to ask the question about choosing a screed. When we want to be extra safe and, in case of urgent need, to gain access to heating coils, it is quite logical to give preference to the bulk option. And this is exactly the way they go in most cases.
However, there are customers who prioritize the strength of structures. In such a situation, you should choose wet screed. There is a whole pie of layers here: first, a film for waterproofing is laid, insulation and rolled foil are laid on it, then the reinforcing mesh and pipes to it heating system. And on top of all these layers the screed mixture is laid. It is mandatory to place a seam of insulation around the perimeter to maintain temperature. That is why it will be quite difficult for a non-professional to find the answer to the question of which floor screed is best, and it is worth first telling the builders your plans for further finishing of the floor and stipulating the time frame for the work.
