What will happen if the screed is made 2.5 cm. How to make a floor screed: characteristics of the types of screeds, do the screed with your own hands in stages

The screed is an intermediate layer between the subfloor and the finished floor covering. It is designed to level the subfloor. Without pouring this layer, major repairs in a private house or apartment will be of poor quality. If you need to know how a floor screed is made, the technology will be presented below.

The laying of the presented layer should be done only after you decide on its type. The screed can be classified as follows:

By production method:

1. Wet. For its manufacture requires a cement mortar with the addition of sand. You can cook it yourself or buy a ready-made mixture. In this case, the layer must be further strengthened with a reinforcing mesh. The optimal thickness of the screed is about 10 cm;
2. Dry. It can be produced using special large-format sheets, 1.5-3 cm thick.

By type of connection:

1. floating. It is usually laid if a waterproofing film is used during the repair. This screed is about 3.5 cm thick or more;
2. Solid. It is firmly fixed on the base.

According to the materials of manufacture:

1. cement layer. It can be used both in an apartment and in a private house. The most optimal mixing ratio of cement and sand is 1:3;
2. Sand concrete screed. Laying is done using a ready-made mixture, which can be purchased at a hardware store. The biggest disadvantage of this floor leveling method is the rapid shrinkage of the material. While working with the mixture, you need to monitor the thickness of the screed, as well as the uniform distribution of the solution. To maintain the integrity of the layer, it is necessary to strengthen it with reinforcement or fiberglass. To achieve maximum quality, the filling must be sprayed with water for 2 weeks. It will take at least 20 days to completely dry the layer;
3. Gypsum floor screed in the apartment. In installation, it is very simple, does not allow shrinkage, has good plasticity. A layer of small thickness is laid. At the same time, the plaster dries very quickly. The only drawback of this material is the impossibility of its installation in those rooms where high humidity is observed;
4. Screed using concrete mix. It is laid in the same way as cement. But a cellular concrete solution is added to the finished mixture;
5. . Since it is not difficult to make a screed of this type, it is becoming increasingly popular, especially in a private house. This layer is from 0.5 to 3 cm thick. But if the horizontal differences in the base are very large, then to use the mixture, you need to additionally make a rough screed (you can use a concrete mortar);
6. Plasterboard. In this case, rectangular sheets are used, which are laid with a slight overlap. Please note that such a screed does not require a long time to dry, and is equipped quite simply.

What will be needed for work?

The most common and frequently used material for pouring is concrete mortar. Before you make a floor screed, you need to collect all the necessary fixtures and materials. You will need:

• Container for mixing concrete.
• Drill with a special nozzle or construction mixer.
• Hydraulic level.
• Rule.
• Master OK.
• Roulette and marker for marking the area.

Some tools needed for pouring floor screed

Features of the preparation of the base

The floor screed device is not a very complicated process that you can handle on your own. However, first you need to prepare the foundation. First, the old floor covering is dismantled. If the subfloor has already been filled with a cement or concrete screed, then it should be carefully examined. If there is no significant damage, then you can apply for pouring.

Small flaws are eliminated with a cement or concrete mixture. Convexity is better to grind off with a grinder or perforator. Further, the base should be cleaned of debris, remnants of the adhesive substance of the concrete mixture.

Priming improves adhesion between the screed and the floor surface. It is carried out in two layers with a primer for highly absorbent surfaces.

The thickness of the screed is important not only in the apartment, but also in a private house, especially if you decide to insulate. This indicative may vary depending on the selected materials and parameters of the room. However, it must also be borne in mind that a screed with an incorrectly selected thickness may be of poor quality.

Installation of lighthouses

Before you make a floor screed in a private house or apartment, beacons must be set. They will help to pour the solution as evenly as possible. Their installation involves the following actions:

1. Determination of the highest point of the floor using a hydraulic level. Please note that a small horizontal difference can be "winned" without additional pouring of a layer of concrete mortar. If it is too large and exceeds 8 cm, then an additional screed will only increase the load on the floors.
2. . Most often, for this purpose, a metal profile is used in a private house or apartment, although there is another option - oak slats;
3. Installation of elements. The distance between them depends on the width of the rule with which you will level the solution. The alignment of the beacons must be constantly monitored with a level. Further, the elements are fixed with a small amount of solution;

Please note that even if an additional substrate is needed under the profile, wooden bars cannot be used, as they are able to change shape under the influence of moisture. The following video will tell you in more detail and clearly about this stage:

Features of the preparation of the solution

If you use, then the mixture is prepared very simply. Combine 1 part cement grade M400 and above with 3 parts sand. You can also add expanded clay, which will achieve additional insulation. Next, all the ingredients are well mixed with a construction mixer. Water is added gradually. In this case, the mixture must continue to stir so that no lumps remain. The liquid is added as needed, that is, the solution should not spread quickly or be very thick.

If you choose a ready-made dry mix for work in a private house, then it is prepared in accordance with the description drawn up by the manufacturer. However, the standard preparation procedure involves the following actions:

• Pour water into a large container at the rate of 1 liter per 5 kg of the mixture.
• Pour the purchased material into a bucket and mix thoroughly. If you pour liquid into the mixture, you are unlikely to achieve a high quality solution.
• Leave the resulting substance for a few minutes to infuse, and then mix thoroughly again.

Foundation pouring technology

The main stages of arranging a single-layer cement-sand screed for lighthouses

After all the preparatory work, you can proceed to the most important thing - pouring. How to make a screed step by step:

1. Start work from the far corner, gradually moving towards the doorway.
2. The mixture just needs to be poured onto the area that is enclosed between the two beacons. At the same time, constantly try to control the level of the layer. At this point, the rule is applied.
3. After processing by the rule, the surface is rubbed with a trowel. Please note that the movements should be light, circular.

Note! The screed should be poured so that the work is completed in 1 day.

1 - Preparation of the base; 2 - Installation of beacons and damper tape; 3 - Preparation of the solution; 4, 5, 6 - Filling and distribution of the mixture; 7 - Removal of beacons from the screed layer; 8 - Filling voids with mortar; 9 - Finished floor screed

Naturally, after the completion of the pouring of the solution, it must be given time to dry. At a temperature of + 20 ° C, the mixture will be solid after 24 hours. However, this does not mean that it is ready for operation. In the first few days of drying, the concrete must be periodically moistened with water so that its surface does not crack. Lighthouses can be removed already on the third day. In this case, the formed pits are filled with a solution prepared in advance.

Now lay cellophane on the resulting base, pour sand on it, and water it periodically for 14 days. Then the film is removed, and the base is again wetted with liquid. The surface must then dry completely. That is, it will be ready for loading in a week.

Now you know how to make a floor screed. This process requires special attention and patience. Many factors must be taken into account, in particular the thickness of the layer. Leave your opinion about the article in the comments or share your experience of installing a screed in your home. And finally, a couple of very useful videos.

When repairing an apartment or building a house from scratch, it is important to think through all the nuances so that the final result is not only beautiful, but also of high quality. Much attention should be paid to preparatory work, including manufacturing. It is necessary so that the base under the feet is strong and reliable, as well as for arranging the finishing floor. And its long service life can be ensured only by properly manufacturing it. What is the minimum thickness of the floor screed? After all, making it is not a cheap pleasure, and a small consumption of materials would allow achieving a certain degree of savings.

The screed is an important and even the main element of almost any room. It must be made in any case, since without it it is impossible to properly lay a fine floor covering. Also, the screed performs additional functions of heat and waterproofing, and will provide a good level of noise insulation, if done correctly. But its main function is just in leveling the rough base and the correct distribution of the load on the floors.

In order to level the base, that is, the implementation of the first function of the screed, it is possible in certain situations to make a very thin layer in thickness. So, sometimes it is enough to make a screed with a thickness of about 5 mm. But in order to achieve the correct distribution of the load on the base, which will depend primarily on the thickness of the layer, sometimes it is necessary to fill in a much thicker layer.

On a note! The screed layer must calmly withstand a compressive load of 15 MPa. Moreover, the slope of the base should be minimal and not more than 0.2%.

Thus, the screed must be strong, reliable, not cracked, and even. The better this building element is made, the more likely it is to get floors that, as a result, will last without complaints for many years.

What affects layer thickness?

The thickness of the concrete screed layer depends on the influence of many factors. Let's consider the main ones:

• the state of the base, that is, the floors. This is one of the main factors affecting the final thickness of the screed layer. So, the greater the height difference of the rough base, the thicker the screed will turn out. Otherwise, it will simply not work to achieve even floors. Plus, the base can be covered with cracks, have some kind of protrusions - all this will affect the final thickness. That is, for example, if the base has very slight flaws, then the thickness of the concrete layer in the screed, according to SNiP, can be only 4 cm. If the height differences are too large, then you should prepare for the fact that the consumption of materials will increase - get off with a minimum layer will not work;

Important! A screed that is too thin can quickly collapse, even if it is filled in correctly. Therefore, when pouring a layer of minimum thickness, reinforcing elements will have to be used as a supplement. If they are not used, then the minimum layer should be at least 4 cm.

• type of solution used. Some materials allow you to achieve a strong, but very thin base. So the mixture used to fill the screed will also affect its thickness. The minimum consumption will be indicated on the package. This point applies to all modern mixtures. Using the usual time-tested compositions or making a dry screed, one should expect that its minimum thickness in some cases can reach 8-15 cm. screeds and consumption of concrete mix;

• the presence of insulating layers for various purposes also affects the thickness of the screed layer. So, for example, a screed can be poured directly onto the floors, if their condition allows it. And in this case, sometimes 2 cm of the mixture is enough. But if there are layers, the screed will have to be made thicker. Even if only waterproofing is used.

It is important to remember that too thick a layer is not the best option. Excessiveness in this case can cause a decrease in the space between the ceiling and the floor, the material will dry for a long time, and if used, it will take much more energy to warm the base than with the optimal or minimum layer. Also, do not forget about the increase in the mass of floors and the load on the floors. In some cases, a heavy thick screed is completely prohibited.

By the way, if you plan to equip a warm floor, this should also be taken into account when creating a screed. It must completely cover all heat sources. For example, if the diameter of pipes for underfloor heating is 2.5 cm, then the thickness of the screed should vary between 5-7 cm. Experts note that sometimes 4 cm of thickness is enough. Too thick a screed is not an option, as a lot of thermal energy will be spent on heating the concrete itself.

SNiP 2.03.13-88. Floors. Download file (click on the link to open the PDF file in a new window).

Video - Screed thickness with underfloor heating

What is the screed?

It was mentioned above that the thickness of the screed is also influenced by what it can be made of. Let's get acquainted with the main types of screed.

Table. Screed types.

Type	Description	Minimum Thickness
	Classic. Such a screed has been used in construction for decades and does not lose its relevance due to its reliability. However, it is quite heavy, and it can not be used in all buildings. It is made independently from cement, sand and water.	4-5 cm or less. In the latter case, it is important to use additional reinforcement. When mounted on concrete slabs, its thickness is at least 5 cm. In the absence of reinforcement, at least 7 cm.
	In this case, the screed is made from special compounds that can spread on the floor on their own with a little help. You can achieve the thinnest screed layer. Often used as a finishing coat of screed before laying the final floor. Here the screed is very even relative to the horizon.	From a few millimeters to 2 cm.
	Ready-made mixtures are very convenient to use, but they are not cheap. Often, this option takes much more money than the creation of a conventional concrete one. But the bases from ready-made mixtures dry faster, and the layer usually requires a much smaller thickness.	In this case, all recommendations on the thickness of the layer should be looked at on the packaging - they are given by the manufacturer, the indicators for different mixtures may differ.
	In this case, the screed is made of expanded clay, special plates and a number of other elements. It is lightweight and easy to style, does not need to dry and can sometimes be used immediately after styling.	The thickness can be approximately 10-15 cm. And the minimum figure is 3.5 cm, provided that the thickness of the plates forming the surface is 2 cm.

In some cases, the thickness of the concrete screed can reach 15 cm. This is a monolithic heavy thick floor, inside which reinforcement is necessarily used or for additional strengthening of the floors. In ordinary city apartments, this option is not used due to the fact that a significant load is created on the interfloor floors. But in a private house, this screed can itself become both a foundation and a floor at the same time.

The minimum thickness of the screed layer will also increase if backfilling is applied. It can be crushed stone or expanded clay, poured onto the ground or a rough base, and concrete mixture is already poured on top or laid. The thickness of the concrete layer cannot be less than 10 cm in this case.

Can the strap be made thinner?

In fact, it is not worth deviating from the minimum indicators of screed thickness recommended by experts, even in order to save money. This will be unjustified, since a thin layer will be unreliable, and all the same, over time, everything will have to be redone. Of course, no one forbids saving on materials, but too thin a layer can:

• cause rapid cracking of the screed;
• serve an extremely short period of time;
• be damaged when a heavy object falls to the floor;
• cause improper heat distribution when installing underfloor heating.

On a note! Sometimes you can still get out of the situation - to make a thin screed. But a decrease in thickness is allowed only if any plasticizer is added to the mixture - for example, lime, detergent, PVA, etc. There are a number of professional products that can be bought in stores.

Screed installation: general rules

Knowing all aspects of the device and installation of the screed, you can start working. However, it is worth remembering a few rules that must be observed during this process. And they are relevant for absolutely any type of screed.

1. Always waterproofing. Otherwise, during the pouring of the cement screed, you can flood the neighbors. And in the future, pipe leaks are not ruled out. In this case, a neighbor's repair will again save the waterproofing layer. Also, in some cases, it allows you to get rid of adhesion, which is not always necessary when pouring the screed.
2. The installation of a damper tape must be mandatory. The bottom line is that the screed changes its physical parameters during the drying process and can either crack itself or damage the walls. And in any case, it will soften the pressure of the poured base on the walls of the room. It is better to install the damper tape before laying the waterproofing layer.

Modern decoration makes high demands on the correct geometry of all surfaces of your home, especially the floor. In order for the finish coating on the floor (tile, linoleum, laminate, parquet board, etc.) to be of high quality and look great, it is necessary that the base of the floor - the screed - be done professionally. The screed, of course, can be made independently, if you know exactly what type of screed you want to use specifically in the house, but for this you need to know the technology and features of the screeds. In this note, we will analyze the device of the most common - cement-sand screeds of the DSP.

The very first stage in carrying out work on the screed device is surface preparation. How long your screed will last depends on the quality of this stage. It is necessary to understand once and for all - the surface under the screed must be thoroughly cleaned of dust, dirt, various layers, etc. Ideally, of course, it is necessary to use an industrial vacuum cleaner that will collect the smallest debris from the surface, but in the absence of such equipment, you can use an old vacuum cleaner or carefully sweep the entire surface for 2-3 times. It is necessary to clean the slab to concrete, try to knock down all the uneven bumps.

The next preparatory step is primer. It is advisable for the first time to go through a deep penetration primer for floors, which will reliably remove dust from the surface and create a film. After two hours, the primer will dry and it is necessary to apply a second layer of primer on it - Betonkontakt, which includes quartz sand and other binders that will create a strong rough surface that can ideally interact with the screed, creating a monolithic structure tightly bonded to the slab. If, when cleaning the slab, you find cracks, they must first be repaired with the composition from which the screed will be. Naturally, cracks should be sealed along the primed surface.

Next stage - level detection future screed. This stage requires the use of special tools - a hydraulic level, or better, a laser level. If the area of ​​​​the room is small up to 20 square meters. m - you can use a hydraulic level, the level itself is accurate, but when marking reference points on the walls, the participation of two people is necessary - and here the notorious human factor interferes with the accuracy of the method, which always leads to an error that the laser level is deprived of.

To determine the level of the future screed, you need the so-called "zero level", i.e. a line drawn at an arbitrary height (1-1.5 from the level of the plate prepared for the screed). To apply the zero level, you need to mark a random point anywhere in the room on any section of the wall, and with the help of a laser level, this mark is transferred to all the walls of your house. All marks applied in this way on the walls must be connected with one solid line, which will be the same zero level for all rooms where the future screed will be cast. This level will be the same relative to the horizon, and not relative to the surfaces prepared for the screed - and this is what you need to determine the height of the future screed.

Next stage - thickness height determination screeds. In all rooms where there will be a screed, it is necessary to measure the distance from the zero level to various points on the floor surface - this is necessary to determine the highest point on the floor, the more measurements there are, the more accurate the result will be. On the walls it will be necessary to record the results of all measurements. The smallest height value from zero level to the floor will mean the highest point of the surface in this room, and the largest height value, on the contrary, will mean the lowest point on the floor surface. Summing up all these values ​​- the largest and smallest - and, getting the difference, you will have an idea of ​​​​the height difference and, accordingly, the ability to calculate the thickness of the future screed and, most importantly, the consumption of materials.

If you are planning different coatings in different rooms of your house or apartment - somewhere tile, somewhere laminate or parquet board, somewhere linoleum, then you will need to calculate the height of the screed for each coating, this is necessary in order for your future the floor, consisting of different types of coatings, was perfectly flat. After all, if you cast the floor throughout the house at the same level, and then put tiles in the hallway, and parquet in the hall, then the height difference between these coatings will be visible to the naked eye and you can’t compensate for this difference with any sills, and you can knock down your legs very easily . Therefore, decide in advance what specific floor coverings will be in each room and, based on this, calculate the thickness of the screed for each floor so that the height difference in the floor coverings is compensated by the different thickness of the screed.

Next stage - wall preparation. To ensure that the screed does not come into contact with walls and partitions, they must be waterproofed. A plastic film is best suited for this, which is fixed along the perimeter of the walls with a stop of 10-15 cm above the level of the screed and under the screed.

Now you can proceed directly to the screed device. It must be said that the screed can be cement-sand and dry. Their differences, of course, are in the different amounts of water used. There are also ties monolithic and floating. Monolithic, of course, is poured directly onto the prepared base and is in close contact with it, and the floating screed is used if it is necessary to insulate or soundproof the floor, i.e. the floating screed is poured onto the pre-laid material and does not come into contact with the floor slab and walls.

If we consider the classic cement-sand screed (CPS), then it consists of a solution consisting of a mixture of sand and cement (3: 1), mixed with water and a metal mesh that acts as reinforcement, a kind of reinforced concrete structure is obtained. The thickness of the classic DSP should be at least 50 mm (40 mm ties and 10 mm reinforcement) - these parameters are suitable for domestic use, i.e. for our apartments and houses. When such a layer is not enough or heat and sound insulation is required, expanded clay is used. The required thickness is covered with a mixture of expanded clay and cement. First, expanded clay is evenly poured, leveled and spilled with cement milk - this is necessary for a strong adhesion of expanded clay between themselves and a monolithic slab. In modern conditions, as a heat and sound insulating material, extruded polystyrene foam, which is lighter than expanded clay and more convenient to use.

After the expanded clay pillow is ready, it is necessary to lay metal mesh , which reliably reinforces the screed. It is desirable that the mesh cell be 10x10 cm in size and it must be laid with an overlap of 15-20 cm, and the meshes should also be tied together with a knitting wire. An important condition is the location of the mesh inside the screed - it must be right in the middle poured solution, only in this case the mesh will fulfill its reinforcing function. To do this, plastic supports or pieces of ceramic tiles are placed under the grid, but not wood. In places where the highest load is expected, a metal bar can be laid by tying it to the mesh.

The same mesh installation steps apply to extruded polystyrene foam. The expanded polystyrene itself must be primed with Betonkontakt before laying - it will give the best adhesion of the material to the future screed. If the slab is very bumpy and there are a lot of irregularities, you can level the bay with a screed and pass the problem areas as a rule, then the surface will be more even. All foam polystyrene mats must be securely fixed to the floor with the help of "fungi" - special fasteners for this material. There should not be any backlash when walking on polystyrene foam - this is a prerequisite.

Then you can proceed to the next stage of work on the screed device - the installation of beacons. This is a very crucial moment, since your screed will be smooth or not depends on the quality installation of the beacons. As lighthouses, a beacon profile made of galvanized metal with perforated edges 10 mm high is most often used.

Beacons are installed on the same solution from which the screed will be. Along the entire length of the lighthouse, small piles of mortar are laid out at a distance of 20 cm, the lighthouse is laid on them, the distances between the piles are filled with excess mortar, and the lighthouse lies completely on the track from the solution. The distance between adjacent beacons should be 30-40 cm less than the rule by which the solution will be leveled. The optimal distance between the beacons is 2 m. But if you work together on leveling, you can also use a 4-meter rule.

It is most convenient to lay a beacon on a gypsum mortar, since there is time for its complete alignment to a given height, and complete filling of the space between the beacon and the floor with a mixture will provide the necessary hardness and strength of the beacon profile. You don’t have to listen to craftsmen who suggest using metal pipes or drywall profiles instead of a special profile - this will affect the quality of the screed, it’s better not to be too lazy and buy beacon profiles specially designed for leveling the screed. Special lighthouses can not be removed after pouring, especially if a finishing coating (self-leveling floor) is subsequently applied, which will create a perfectly flat surface (this requires experience).

There is another way to set beacons through metal string, which can be stretched between two dowel-nails to any length (width), and fill the distance between the string and the slab with a screed mortar or gypsum mixture to create a solid guide structure. This method will give the most even surface over the entire area (experience is also required for the installation of such beacons).

After setting the beacons and solidifying them, it is the turn of the screed device itself. The prepared solution is placed between two beacon guides, completely filling the space between them and is leveled with the help of a straightedge sliding along two parallel beacons. It is advisable to work with three of us - two on mixing and a tray of the finished solution, and one is directly involved in leveling the screed.

When mixing the finished mixture, it is necessary to strictly adhere to the manufacturer's instructions for the amount of addition of water and the mixture itself. If the proportions are not met, for example, there is too much water, then cracks will definitely appear, after drying and the effect of a "stone". i.e. the solidity of the screed will be lost. It is very important to remember that when the mixture is leveled, excess air remains in it, which must be helped to come to the surface; for this, special needle rollers or thin steel wire knitting needles are used to pierce the leveled surfaces.

Currently, when installing screeds in apartments and houses, only special modified building mixtures are used for rough and final leveling of surfaces. The classic DSP is now poured only during construction, and when the owners of the purchased apartments begin to make repairs, such a screed, which eventually turned into a bumpy and uneven surface, is usually removed and thrown away.

In special mixtures, the composition is selected in such a way that when mixed with water and subsequent drying, as a result of chemical reactions, the formation of monolithic stone effect designs. Such a screed dries within 24-48 hours, does not require soaking with water and cracks do not form on it. The only thing that is required is to cover the new screed with a thick plastic film, which will prevent it from getting dusty and protect it from excessive abrasion during further repairs and will allow it to "survive" to the finishing floor coverings, so to speak, in the best possible way.

I would like to draw attention to one more important point. When a screed is made, several goals are pursued: leveling, soundproofing, waterproofing. We all want us not to hear the "life activity" of our neighbors and, accordingly, so that the neighbors do not hear us. If the goal is to qualitatively soundproof your home, then in the screed you should apply unleashing the structure and absorption. You can use expanded polystyrene, low density mineral wool. For decoupling, materials of different density are used, the so-called low-density pads, which exclude the contact of dense materials with each other, respectively, the sound is lost in these decouplings.

Ideally improved sound insulation the design looks like this:

wooden crate installed on polyethylene foam pads under the logs

the crate is filled with low density mineral wool

a thick layer of high-density mineral wool is laid on top of the crate

on top of the mineral wool, a dense insulation is laid in one layer

a cement-sand screed is laid on the insulation

It is worth noting that when soundproofing the floor, one should not forget about the walls, since the sound, meeting an obstacle in the floor, spreads further and goes into the walls.

It is also worth mentioning the weight of the screed. In general, the floor slab itself is designed for a weight load in the range of 350-400 kg / sq.m (can be specified in the project). If you have a concrete or DSP screed 5-6 cm thick for thermal insulation with a finishing floor covering of tiles, then the weight of a square meter of such a "pie" will be 130-150 kg.

And in conclusion. If you are not indifferent to what kind of foundation will be under your floor covering, from what materials and what technology it is laid with, then you should familiarize yourself with the building codes and rules that were developed in construction laboratories by specialists in construction chemistry and physics. The results of the work of these people should not be neglected. SNiPs and GOSTs are documents in which all technological subtleties and rules are described in the most detailed way. As for the screeds themselves, it would not be superfluous to look at such documents as SNiP 2.03.13-88 "Floors", SNiP 3.04.01-87 "Insulating and finishing coatings", SNiP 3.03.01-87 "Bearing and enclosing structures" which are active.

The floor screed is the part of the base that is located between the ceiling and the finishing coating. Without it, it is impossible to make the floors perfectly even - such that even the most demanding finishing material in terms of installation conditions can be safely laid on them. You can’t do without it when building a house and even during a major overhaul, but how to make a floor screed is a very difficult question for many. Let's try to figure out how to create it with your own hands.

The screed is not only a structural element of the floor, responsible for its leveling. It performs other equally important functions - for example, it takes over and redistributes all the loads experienced by the floor covering. But still, the most important function of the screed is precisely the alignment of the base. It is necessary in order to lay the floor covering without problems and correctly, some types of which are quite demanding on the evenness of the subfloor. For example, ceramic tiles, parquet and other materials will quickly become unusable if they are used lying on an uneven floor. They will begin to break and collapse, and when moving along the coating, it will emit an unpleasant creak.

Another function that the screed performs is increasing the heat, sound and waterproofing properties of floors. Also, due to it, it is easy to raise the level of the base to the required level if necessary.

What is the screed?

The floor screed can be divided according to several criteria into different types. For example, depending on the manufacturing method, it can be dry, wet, combined.

Table. The main types of screeds.

View	Description and characteristics
	This option is made without the use of heavy mortars. The technology is used to level floors with very large height differences (up to 11 cm), as well as in rooms where floors cannot experience significant load. In this case, a dry screed can be laid along the logs and be made of plywood or chipboard, or it can be made of sheets of gypsum fiber, which is laid on expanded clay bedding. The thickness of the screed can be quite large. Dry screed is easy to perform, does not require drying after production, is very light, does not exert a load on the floors and foundation of the building.
	This screed can also be called concrete or cement. The most familiar and most commonly used way of leveling and raising the floor. As a rule, it is used for the initial stage of leveling floors or subfloors. It is made on the basis of cement with the addition of fillers, it is laid in a layer of 3 cm or more. Difficult to work with, takes a long time to dry, but very strong and durable. Unfortunately, it exerts significant non-overlapping pressure due to its considerable weight, and therefore cannot be applied to all types of buildings. For 1 sq.m. accounts for at least 100-120 kg of mortar - the mass is quite impressive.
	This type of screed combines the main advantages and, in some way, the technology of wet and self-leveling screeds.
	This method is good because there is no need to use beacons and somehow monitor the evenness of the finished base. The fact is that special mixtures are used for manufacturing, which tend to self-level on the surface of the subfloor. Such compounds are quite expensive, and they can be filled with floors with irregularities up to 2 cm. Often, due to this method, you can additionally level the usual cement screed.

Also, screeds are divided into different types depending on the number of layers. Thus, they are single layer(poured immediately at a time to the required thickness) and multilayer. The latter have the so-called rough and finish surfaces. As a rule, the rough base has a thickness of 2 cm or more, and the finishing one - 3-20 mm.

According to the type of connection with overlappings, screeds can be divided into solid and floating. The first has a reliable connection with the draft base, the second has no hitch with anything. For installation, hydro- and heat-insulating materials are used.

What can be used to create a screed?

Depending on the type of screed, they can be made of various materials. So, to create a wet screed, cement, water and sand are used. Cement in this case acts as a binding material, and sand becomes a filler. To improve the quality of building mixtures, various components can be added to them to improve strength and reduce drying time.

On a note! To prepare such a mixture, it is necessary to mix 1 part of cement with 3 parts of sand. The required amount of water is added to them. This is a fairly economical option.

To create a wet screed, ready-made sand concrete sold in stores can also be used. Its main disadvantage is the high shrinkage rate. Because of this, the thickness of the screed layer cannot be less than 3 cm, otherwise it will quickly become covered with cracks.

Advice! To reduce the risk of cracking of the screed, fiber fibers are added to the raw composition, or layers of reinforcing mesh are laid on the rough base.

Gypsum-based mixtures are used for wooden floors. This material can be laid in a thin layer, as it practically does not shrink. Drying time is also attractive - only 1-2 days. The only exception in terms of the use of such compounds is high humidity in the premises.

Self-levelling or usually used for the final leveling of conventional wet screed. The reason is the rather high cost of the material. Such a composition is used for leveling floors with an unevenness of 2-7 mm.

For the manufacture, sheet materials such as drywall will be required, as well as expanded clay of medium and fine fractions for backfilling the base. The joints of individual sheets of material are treated with adhesives.

How to make a floor screed

Work on the installation of floor screed invariably raises questions from beginners. Below are instructions for creating a dry, wet and semi-dry screed. However, no matter which option is chosen by the masters, in any case, before starting work, it is important to prepare a rough foundation.

Features of the preparation of the base

To begin with, if the house was not built from scratch, you will need to get rid of the old floor finish. Moreover, you will have to remove the old screed up to the overlap. It is especially important to repair any flaws on the base. It can be cracks, chips, any gaps. All this must be sealed with a sealant or cement composition after preliminary priming in order to avoid too much consumption of mixtures (relative to a wet screed) and to increase the adhesion of the compositions to the base.

Preparing the base for the screed - photo

On a note! Sometimes a new screed is poured directly on top of the old one, but this is only acceptable if the previous version of the base is strong enough. However, only an experienced specialist will be able to assess the condition of the old screed. Sometimes it is even enough to use just self-leveling compounds to make the old base perfectly even.

You can clean the floor from the old screed using a jackhammer. Further, the base is cleared of construction waste, which is placed in strong bags and taken to a landfill.

Small protrusions on the old screed can be removed with a grinder. After preparation, it is important to prime the base in order to increase adhesion.

Making a wet screed

Step 1. The first step is to prepare all the necessary tools and materials. This is a building level, slats that will act as beacons, self-tapping screws and dowels, building mixtures, sand and cement, as a rule, a perforator.

Types of ties: 1) adhesive screed, in contact with a concrete slab. The screed is laid directly on the floor slab and adheres to it. For such a screed, the thickness can be small, from 2 cm, but adhesion to the base plays an exceptionally important role. In the production of such screeds, it is important to vacuum the surface well, use a good primer, ideally Betokontakt, and ensure that the base does not become dusty during the work. 2) Screed on the separating layer. The solution is laid on a thin separating material: polyethylene film, roofing material or waterproofing. 3) floating screed. It is laid on a layer of heat and sound insulating material. It can be ordinary or extruded foam plastic, dense mineral wool, polyethylene foam roll, including foil, expanded clay bedding. Each type of screed has its own advantages and disadvantages. The disadvantage of the adhesive screed is poor sound insulation. The advantage is the smallest possible screed layer and the possibility of combined leveling using finishing smoothers in areas with a thin layer. At the same time, there is practically no danger of cracks at the junction of materials. The screed on the separating layer, while curing, is protected from moisture by the overlap and improves the waterproofing properties, but at the same time it should not be less than 3 cm thick, and requires reinforcement. The floating screed also cannot be thinner than 3 cm, and the optimal layer is 5 cm and must be reinforced. Pros: good noise and heat insulation, the ability to equalize large differences without increasing the load on the floors. Cons: Significant rise in price and large thickness. When choosing a pouring method, it is necessary to take into account the unevenness of the base, and remember that the weight of the screed is 20 kg per cm of thickness per square meter, i.e. a layer of 5 cm weighs 100 kg/sq.m. The mesh is laid on supports so that after pouring the mesh is in the center of the layer. Grids are stacked overlapping and tied with wire. When installing cable underfloor heating, it is convenient to fasten the cable to the grid with wire or electrical ties.

2) Fiberglass mesh. I myself have not used it, but I know that it is cheaper, lighter and more durable than metal, it is a pity that it is practically not represented at the bases of building materials

3) Metal fiber, polypropylene, basalt or fiberglass. This reinforcement method is good, but only if the fibers are evenly distributed when the solution is mixed. As a rule, fiber is added to the automixer when leaving the concrete plant. During the journey to the object, the fibers have time to be well distributed throughout the volume of the solution. At home, such uniformity is difficult to obtain.

Even under the condition of reinforcement, the screed, in the process of curing, has shrinkage, and it is "pulled together", which leads to the formation of shrinkage cracks over large areas. To prevent this from happening, expansion joints are made. In apartments, it is better to place seams in the area of ​​​​doorways and at the junctions of different floor materials. The expansion joint can be laid during pouring with any thin separating material, or cut through after pouring in a still fresh solution that has not gained strength. Reinforcement at the seams is interrupted

A little about lighthouses. Lighthouses are made so that the floor level is perfectly even. For a high quality screed, the deviation should not exceed 2 mm at a 2 meter level applied at any point on the floor. These are the requirements of any manufacturer of laminate and parquet boards. For laying tiles, this is also an excellent base. I won’t tell you much about how lighthouses are made, I’ll only say that you shouldn’t use gypsum compositions for their manufacture. Especially if the floor is tiled. The fact is that gypsum, with increasing humidity, increases in volume, which can lead to cracks on the surface of the tile.

The screed should not come into contact with walls and columns, therefore, before starting work, a separation tape made of polyethylene foam or its equivalent is laid along the wall. One of the important points in the screed device is the water-cement (W/C) ratio. The more water in the solution, the stronger the subsequent shrinkage of the screed. It is possible to reduce W / C by adding a plasticizer to the solution, as well as using the “semi-dry screed” method, when the cement-sand mixture is mixed with a small amount of water. The solution turns out to be crumbly and if it is left in the container for several minutes, no moisture is released on its surface. To prepare such a solution, one cannot do without a powerful mixer, since it is very dense and non-plastic.

To level the solution, use the blunt side of the rule and pour the material in the right places. Also for leveling, it is convenient to use a yellow styrofoam grater

A significant advantage of the semi-dry method is the rapid drying time and the acquisition of primary strength. You can make mortar beacons and level the floor on the same day. You can immediately walk on a freshly laid screed in special shoes with a wide sole, similar to snowshoes. In ordinary shoes, you can walk after 6-12 hours. Tiles can be laid on such a floor every other day, and laminate and parquet board after 5-10 days, depending on the thickness of the layer and the readings of the moisture meter. In order for the screed to gain strength correctly, on the first day it should be protected from drafts and covered with a film, and for the next 2-3 days, periodically moistened. In industrial premises and wherever floors are used without coating, they are rubbed with special trowels to strengthen the top layer.