Do-it-yourself repair of a fresh cement floor screed. Do-it-yourself floor screed repair, from small to major

29.08.2019

A simple calculation of the usual cement-sand screed M150, shows its suitability for modern flooring. For example, piece parquet riveting with dimensions of 40×250 mm, laid on a screed, must transfer a static pressure of 15 tons to it, so that the screed under it falls apart. And in order for the screed to be squeezed through by a female stiletto heel, a woman must weigh 150 kg and at the same time stand on one leg, relying only on the heel.

If your apartment is still in Soviet times a cement-sand or expanded clay concrete screed was made and at the moment it is in good condition, then you don’t need to touch it: it is quite suitable for modern flooring. The maximum that needs to be done with it is to align it to “zero” and even then not always. Dusting of the upper layer of screeds is not a sign of its destruction, it is natural process release of calcined particles - it is eliminated by priming, and not by replacing the screed.

However, it must be taken into account that, despite static calculations, destruction from stiletto heels in M150 ties made in the last century is really possible. Even graceful dancing women can easily damage a screed of such strength with stiletto heels if, for example, linoleum or carpet is laid on it. A hairpin is a terrible weapon! If it is not customary to walk in shoes in the house, then in this case the screed is knocked out when moving heavy furniture. For the same reason, on uneven screeds, parquet rivets are knocked out of the tongue-and-groove locks and the riveting is pressed into the screed. Therefore, it is better to lay floor coverings of all types on M150 screeds through a substrate that redistributes stress. It is not necessary to lay a substrate under ceramic tiles.

To determine the safety of the existing screed, debris, residues of adhesives, paint and other contaminants are first carefully removed from it. In the process of cleaning the screed, it is visually inspected. Ideally, the screed should have an even, uniform light gray color. Inspection reveals cracks and delamination of the screed. Then the screed is tapped with the end of a wooden bar. The sound from blows should be the same over the entire area of the screed - hard and ringing. If in some places the screed “blows” - the sound is deaf (hollow), then there are delaminations of the screed from the floor slabs.

First of all, the "bumping" of the screed is eliminated. There are several ways to eliminate screed peeling, but all of them will be inaccessible to the home builder, so the only option for you is to determine the “bump” border by tapping and cut the screed to overlap with a scarpel and a hammer, or a rotary hammer switched to “blow”. If the screed "blows" over large areas, then it must be completely removed and discarded. A screed that has peeled off from the base, even if it is still holding on, will surely sag over time, occupy the void formed under it and pull the floor covering with it. In other words, a floor covering mounted on a “floating” screed will please you a little with its beauty, and then, sooner or later, it will fail.

Screeds that are small in area can be repaired (Fig. 32). To do this, the screed is broken at the place of its delamination from the ceiling. Then pieces of the screed are removed from the broken hole, the hole is swept and dusted. Before applying the repair mortar into the hole, the boundaries of the hole and the exposed surface of the floor slab must be primed. Priming can be done in several ways: with water, cement milk or primers.

Rice. 32. Repair of individual screed points

When priming with water, the entire surface of the pit is wetted with a large amount of water, but without the formation of puddles. Priming with water aims to wet the mortar of the old screed around the hole and the concrete of the floor slab in order to saturate their open pores with water. Otherwise, these materials will “suck out” the water from the repair mortar laid in the hole. Water, instead of participating in the process of setting the repair mortar, will go away for other purposes. In addition, priming with water washes away dust from the pit that was not removed by a vacuum cleaner (if the vacuum cleaner is a pity, you can only do with priming with water).

Priming with cement laitance saturates the pores with water and binds dust. Cement milk is diluted from cement and water in a ratio of 1:2. When priming with water or cement laitance, the repair mortar is applied immediately after the primer, without waiting for it to dry (wet on wet method). Priming with cement laitance is preferable to priming with water. With this method, the cement in the primer is combined with both the repair mortar and the old screed.

Priming with special primers has a slightly different character. These primers are kind of adhesives that react at the molecular level with both the old coating and the patch. For example, some primers penetrate into the pores of the old screed and into the pores of the floor slab and crystallize there, thus stopping the suction of water from the patch. The primer that does not get into the pores remains on top and also crystallizes, covering the surface on which it is applied with differently directed scales.

The modern construction market offers a large assortment primers. They are divided into primers for absorbent, slightly absorbent and non-absorbent substrates. Cement screed and top reinforced concrete slab overlappings belong to the slightly absorbent bases. And on the labels of many primers it is written: "for concrete surfaces, plasters and screeds."

It does not make sense to use expensive dry mixes with high strengths for patching, since the screed itself was made from a solution of M150. You can mix the mortar yourself from sand and cement or use inexpensive domestic ready-made dry mixes. For a patch, it is better not to use "Universal dry mix M150", because, reading specifications mixture (of some manufacturers), we see: it gains strength of 10 MPa (100 kg / cm²), which does not meet the requirements of SNiP. It is better to buy a dry mix M300 (Pescoconcrete) - after hardening, its strength is also not very high, but it is intended specifically for screeds and is produced according to the corresponding GOST. It is necessary to dilute the dry mixture exactly according to the instructions written on the bag, that is, if the manufacturer writes that the amount of water needed for mixing is about 0.15–0.2 liters per 1 kg of the mixture, then so much water must be poured in, not more and nothing less.

Simple domestic mixtures, in addition to a major advantage - a low price, have an equally major drawback - they lack polymer additives. And this means that, having closed the mixture in its original form with the amount of water recommended by the manufacturer, you will get a hard, hard-to-place mixture, which, moreover, will also set in the screed for almost a whole month (28 days). Therefore, a plasticizer and a hardening accelerator must also be bought to the mixture. It is not entirely necessary to buy a plasticizer for patching, since the area for repairing the screed is small, and with some effort, you can lay an unworkable mixture, but buying a hardening accelerator is required. Otherwise, the humidity of the patch will exceed the values required for floor coverings for a long time. You can, of course, neglect the hardeners and dry the patch with heaters, but this will disrupt the normal setting of the mortar. Solution hardeners do not accelerate the setting time, they only form a crust on the surface, allowing further work to be carried out, and the setting itself is “driven into the material” and continues there for the prescribed time. Artificial drying of the material removes water from the material, which becomes insufficient for normal chemical reaction setting. In the process of caring for a patch, on the contrary, it must be covered with polyethylene that does not allow premature evaporation of water and periodically sprayed with water from a spray bottle.

The simplest and most affordable setting accelerator is liquid glass(stationary glue). However, this set accelerator makes a hard mortar even more rigid and shortens its "life" to 1-2 minutes. For high-quality work, it is better to purchase a branded setting accelerator, for example, Plitonit-Active Accelerator, which has plasticizing properties, that is, it will not only speed up the setting and hardening of the mortar, but also make the hard mortar workable.

If the screed being restored is made with fillers, for example, the screed is made of expanded clay concrete, then expanded clay balls must be added to the sand concrete. The ratio of dry mix to expanded clay is 1:2. To prevent expanded clay from floating up, load the patch with a sheet of tin.

After installing patches on the screed, we proceed to eliminate cracks. If the entire screed is riddled with numerous cracks, then it is better not to repair it, but to completely remove it. If there are few cracks and the screed does not fall apart, then it can be repaired. The technology for repairing cracks is almost the same as the technology for installing patches on the “bubbling” sections of the screed.

Cracks along their entire length are expanded (expanded with a scarpel or perforator), debris is removed from them and they are primed. Then the repair mortar is stirred and applied to the cracks. By the way, patching cracks with a scarpel or a perforator will immediately show the condition of the screed. On a reliable screed, work with percussion instruments will only chip off the places that are hit, and a bad screed will split in large pieces.

After installing patches and repairing cracks, we wait 9 days. Next, we carry out a geodetic check of the screed. We check its evenness with the “clearance rule” and slopes with a laser or ordinary level. If the screed is even, and the gaps are normal, then you can do nothing with the screed, it is suitable for all types of parquets, laminates, massive boards, laid in a "floating way", linoleums and carpets. However, all of them must be mounted on a substrate, since old screeds made in Soviet times do not pass the strength of modern floor coverings. Under tiled floors, the repaired screed is suitable in the state in which it is - no underlayment is needed.

If the screed is not horizontal or has gaps more than normal, it must be leveled. Geodetic checking with a laser level should show the unevenness of the screed, and the result of the check is recorded directly on the screed. By comparing the difference in elevation between the hillocks and the pits, you must decide how to level the screed.

The screed can be leveled with coarse levelers laid in a layer of 10 to 50–80 mm, or finishing levelers (“self-spreading”), as dry mixes are called, laid in a layer of 1 to 10–20 mm.

If it is written on the bag with the mixture that it is used for screeds with a thickness of 10 to 50 mm, then the screed from them must be made of exactly these sizes, that is, this screed cannot be pulled “to zero”: the thickness of its thinnest part must be at least 10 mm, and the thickest is not more than 50 mm. If the inscription contains the addition “and pits up to 80 mm high”, then this addition must be taken literally, that is, the height of the screed must be at least 10 and not more than 50 mm high, but deeper pits up to 80 mm high are allowed in it, but this height is only permissible, but the main one is still 50 mm. The same is true for the finish liners.

The difference between rough levelers and finish ones is in the size of the filler grains, in the finish ones they are finer. Coarse levelers are thicker; when laying, they need to be “pulled out” by the rule, setting the thickness of the screed along the beacons or guide rails. With the skill of these screeds, you can create a floor slope. Finishing levelers - liquid, approximately like syrup or kefir, they are stretched without beacons and slats - set the thickness of the screed with a wide spatula. This kind of material is quite fluid and on an uneven basis can leak into a low corner. Under the finishing rover in the base there should be no holes.

Based on the results of a geodetic check of the existing repaired screed, you must decide which of the "levelers" you will use for leveling: rough or finishing, or both mixtures in turn. In most cases, only the finishing mixture should be used, since a rough mixture will take 30-50 mm from the height of the room. However, the finish mixture has a rather strict limitation on the height of the screed. Therefore, high bumps must be removed from the old screed mechanical method. This can be done in two ways: old-fashioned - weld an ax to thick reinforcement or steel scrap and clean off the bumps; buy a grinder, abrasive wheels for it and grind off the bumps.

After removing the bumps, we clean the entire upper layer(old cement "milk") to the screed filler. Practice shows that the best adhesion (sticking) of the upper layer to the lower one is given by a rough surface. First, on a rough surface, the adhesion area increases. Secondly, when grinding the old screed, cement particles are removed and the aggregate (particles of sand, expanded clay, small gravel) is exposed. Thus, the closed cement of the upper screed adheres not only to its aggregate, but also to the aggregate of the lower screed. Thirdly, the lower screed needs to be freed from dirt, which is possible only by grinding (removing the top layer) of the surface. If a marriage was made during the installation of the screed and the top layer of the screed peels off, then, of course, it must also be knocked down.

After sanding, the screed must be swept and vacuumed. Next, we treat it with cement-cement primers for weakly absorbent surfaces, or with universal primers. For a cement screed, it is better to use a cement-containing "self-spreading", if we use gypsum, then we buy a separating primer of the "cement-gypsum" type, for example, "Grunt 2" (Plitonite). Priming of the old screed is best done double. The screed has been lying on the floor for a long time and most likely it is dry, the first layer of primer such a screed will simply “suck” into itself, leaving no trace on the surface. Therefore, when the first primer crystallizes in the screed, it must be covered with a second coat of primer. The time between the first and second priming, read in the instructions for the primer, as some primer manufacturers require the first coat to dry completely, others allow wet-on-wet primer.

We dilute the leveling mixture according to the instructions (“self-spreading”). When mixing the mixture, it is better to pour the mixture into water (80% of the total volume) and mix, then lumps will not form, and in the process of mixing, add the rest of the water. If you work with a drill with a mixing attachment, do not turn on the drill at high speeds, stir the mixture at medium speeds, otherwise the mixer blades will capture air and bring it into the solution.

Rice. 33. Leveling the screed with a finishing leveler (leveling compounds)

We begin to fill the screed (Fig. 33) from the far corner of the room with stripes along the far wall, moving back to front door. We install a temporary threshold in the doorway. Two people work, since the screed must be poured in one go over the entire area. One closes the mixture, the other pours and levels with a spatula. When laying the mixture, do not walk on a fresh screed, disperse it with a spatula to the side and towards you, but not under your feet. After pouring a strip of screed (width - so that your hands reach out), roll it with a spiked roller or poke it with a rake or a stiff brush to release air trapped in the solution.

After pouring, leave the screed for a few hours (recommended by the manufacturer). After this time, walking on the screed to care for it is allowed. Courtship lies in covering her plastic wrap so that it does not dry out ahead of time. When pouring the screed and in the process of caring for it, a stable room temperature must be maintained in the room and there should be no drafts, that is, the windows must be closed. Courting the screed usually does not exceed three days, read on the bag, from different manufacturers different term gripping screeds.

In rooms whose area exceeds 20 m² or one of the sides of the screed is longer than 8 m, expansion joints must be left in the screed. The fact is that when the dry mixture closed and laid on the floor is set, internal stresses arise in the solution that can break the screed. To do this, a room of a large area is divided in half or into four parts and wooden slats are laid in these places. In fact, not one, but two or four screeds are poured into the room. When the screeds grab and it becomes possible to walk on them, the boards are removed and you can fill in the places from which the boards were taken out. If for some reason you forgot to leave expansion joints, then they can still be done as soon as the screed allows you to walk on it. In this case, only the top layer becomes strong in the screed, while inside it is still soft. Jointing, an old file or other similar tool, you need to cut the top layer of the screed to a depth of the old screed. In fact, create artificial cracks on the screed and relieve internal stress in it. If this is not done or not in time with the creation of expansion joints, then the screed will make them itself, that is, it will crack. Needless to say, the cracks will not be where we would have made them ourselves. After setting and hardening of the inner layer of the screed, the internal stresses in it subside and scratched cracks can be puttied.

After the leveling compound has hardened, the screed is ready for all types of floor coverings, both with and without underlayment. The strength of self-leveling compounds is usually not less than 20–25 MPa (200–250 kg/cm²), which is in line with international standards.

Repairing concrete floors with your own hands is by no means a simple “lubrication” with cement mortar. Such a "blamba" will not stop the destruction of concrete, will not level the floor and will not block access to fumes through it.

The thing is that concrete, even having gained structural strength, lives its complex physical and chemical life for decades: it changes its structure, gains strength, and then weakens a little until it stabilizes. In fresh concrete, a number of indicators, including the shrinkage rate and the coefficient of thermal expansion, differ significantly from cured concrete. For the repair of the old floor to be successful, you need to somehow coordinate the properties of the old and new concrete. One of the best ways for minor self-repair is to give fresh cement mortar thixotropic and rheological properties.

Thixotropy and rheology

Thixotropy is the ability of a medium to succumb, to reduce its viscosity with a small but constant impact. A good example of a thixotropic substance is common construction bitumen. If you move your finger along it with pressure, then at first roughness is felt, and then the movement is facilitated and a hollow remains behind the finger. By the way, continental plates move across the face of the Earth due to the fact that the substance of the upper mantle is thixotropic.

Rheology is nothing but superfluidity. This phenomenon is by no means a privilege of ultralow temperature physics. Any housewife who forgot to tightly close the vessel with sunflower oil. However, if liquid helium-II is 100% superfluid, then vegetable oils- units and fractions of percent. But this is enough for the dish to turn out to be all sticky after a while, and kitchen furniture was spoiled.

Under normal conditions, thixotropy and rheology are inextricably linked. Builders, when they say "thixotropy", immediately mean rheology. When repairing a concrete floor, rheology ensures that the smallest irregularities are filled with a repair compound, and thanks to thixotropy, the new concrete mass, figuratively speaking, does not rest against the previous one, but plays along with it.

A wide range of thixotropic-rheological mixtures for repairing concrete floors based on epoxy resin and polyurethane is available in hardware stores. However, to repair an apartment floor, which is in relatively stable conditions and lightly loaded, a cheap thixotropic composition can be prepared independently:

To do this, PVA glue or bustilat is diluted with water three to five times, and a cement-sand mortar is kneaded on the resulting suspension in a ratio of 1: 3. If the amount of work is large enough, you can immediately buy PVA putty. This is the same highly diluted glue, but the minimum package is 5 liters.

PVA-suppension is not suitable for sealing deep deformation cracks; here you will have to buy a branded thixotropic primer for concrete and a repair compound. In this case, you should focus solely on the price: the apartment floor is a light object, and the exclusive quality of the compositions is not required.

Mixer and rule

All repair compounds for concrete must be kneaded: ready-made on water; homemade - on PVA suspension. It is impossible to mix manually: the finished solution should be as “dry” as possible, i.e. water or suspension is added in a minimal amount. A very viscous mixture will have to be “pounded” for too long to the desired uniformity, and irreversible changes will begin in it, worsening the quality of work.

For mixing small amounts of repair construction compounds I use an electric drill or a hammer drill at low speeds with a special nozzle - a mixer. The principle of its operation is no different from a cocktail mixer.

In tool stores you can find a wide selection of different mixers, sometimes in completely bizarre configurations. But a mixer that is in no way inferior to them is obtained from an even rod 8-10 mm in diameter and half a meter long, the end of which is bent into a ring or simply folded in half.

The kneading lasts 3-5 minutes. When kneading in a bucket, the tool is driven in a circular motion; in the trough - transverse zigzag. A bucket of water should be at hand - after kneading, the mixer must be rinsed immediately, lowered into water and given more speed. When mixing with a perforator, in no case should you turn on the impact mechanism: the whole room and you will immediately find yourself concreted with a thin layer.

In addition to the mixer, to repair the concrete floor, you will need a rule - a meter wide spatula. The plaster trowel will not work: it will not smooth the concrete properly, but it will be erased on it. The rule, on the contrary, is to purchase a factory one, and you should not save on it, especially since it is inexpensive. Concrete is a good abrasive, and if the middle of the rule turns out to be “eaten up”, then the floor will turn out to be humpbacked.

Types of concrete floor repair

There are four different types of concrete floor repair:

Elimination of defects - bulges, potholes, seams from markers and formwork, cracks in the screed.
Seal gaping cracks.
Overhaul of the floor screed for polishing concrete, laying a finishing coating or underfloor heating with insulation and waterproofing.
Dedusting.

Each type of repair is carried out according to a special technology. The most time-consuming and costly repair of the screed under a clean floor. For its overhaul, you will additionally need a metal roller with a width of at least 0.5 m and a weight of at least 10 kg with a carrier handle.

After all types of repairs, except for dust removal, the floor must be kept for at least 20 days before continuing work, spraying it with water every day or wiping it with a richly moistened cloth. It is impossible to fill the floor or wet it more often: the set concrete absorbs a certain amount of water and slowly. "Drinking" will hurt him.

Recommendations on mandatory exposure of 40 or more days, covering concrete with wet burlap, etc. are intended for concreting on outdoors. In relatively stable conditions of a residential or utility room, 20 days of exposure is more than enough.

Room preparation

Preparation for the repair of the concrete floor comes down to the release of the premises and thorough cleaning. Large debris is raked with a shovel, then the floor is thoroughly swept two or three times with a wet broom with spraying. Potholes and cracks after drying the floor after each sweeping are blown with a household vacuum cleaner.

If it is possible to use an industrial vacuum cleaner, floor preparation can be done in an hour: they suck the floor, blow through potholes with cracks, suck it again - and that's it, the preparation is over.

Concrete floor repair procedure

Repair of the floor in the apartment begins with its inspection and assessment of the condition. Before dismantling the old finishing flooring and cleaning, it is impossible to correctly assess the required degree of repair. The following cases are possible:

The floor is generally level, but dusty, and in places there are potholes, clearly defined small protrusions, or thin, serpentine cracks. Self repair possible and inexpensive.
There are gaping cracks no longer than half of the short side of the floor, tending to the perimeter or longitudinal-transverse. Self-repair is possible using branded thixotropic compounds.
The floor is "all humpbacked": small bumps and depressions alternate relatively regularly. Self-repair "on concrete" is possible in a private house or outbuildings.
In a multi-apartment building, there are long gaping cracks on the floor on the floor screed, generally located diagonally or crosswise. It is only possible to overhaul the screed with a preliminary professional assessment of the state of the ceiling.

Note to point 3: leveling a carelessly poured screed is possible either with a milling machine or with a liquid leveler after repairing the cracks. Leveling the floor with a hardening compound is the subject of a separate discussion, and a milling machine cannot be used in an apartment building: it is very dusty, and the presence of cement dust in the air of residential premises is strictly prohibited sanitary standards. In addition to the “gratitude” of neighbors, one can also fall under serious legislative sanctions, up to and including imprisonment. For example, if a resident is hospitalized with an exacerbation of asthma or a lung disease during or after your work, this is a moderate or severe health hazard. Terms - see the Criminal Code.

Minor patching

Potholes are filed with a grinder with a diamond wheel in a rectangle with a grip of at least 20 mm to the sides. Cutting depth - to the depth of the pothole plus 10-20 mm. Less - if the floor is dense; more - if dusty. The protrusions are knocked down with a puncher or manually to the hollow.
A puncher with a chisel for concrete chooses a rectangular recess in place of the pothole. Small dents can be removed by hand with a 200 g hammer and carbide-tipped chisel. It is impossible to beat with all your might on a dull metalwork chisel: a crack may occur.
The recess is blown with a vacuum cleaner, then the remaining dust is sucked out with it.
Lubricate the recess with one layer of any primer on concrete. Choice - by price; case is not responsible.
After the primer dries, the recess is filled with a thixotropic compound, home-made or purchased, leveled with the rule and left for aging - sealed.

Notes:

Branded repair compounds are kneaded only on sifted quartz sand. It can be purchased from the same store. Proportion - according to the instructions on the package. Thixotropic mixtures in small packages are sometimes sold in a set with sand packaging in the right amount.

Sawing work should be done in a respirator, goggles, earplugs, gloves and tightly buttoned clothes, with windows wide open, tightly closed door and as quickly as possible. Unlike a hypothetical asthmatic neighbor, you will certainly find yourself in the very center of a cloud of cement dust. Headphones in this case protect more from it than from noise.

Repair of small cracks

Small cracks are first sawn through with a grinder along the length to a depth of 20-50 mm and a width of 10-20 mm. As in the previous case, the minimum / maximum depth and width of the cut is determined by the condition of the floor. The cut is also blown and sucked.

How to fix cracks in the floor? If the floor itself is not dusty, and the circle is a little tight, then a home-made repair mixture will fit perfectly. If sawing is easy, and the angle grinder sometimes even slips, you definitely need a good branded primer and thixotrope. But if the dust during sawing is so thick that the tool in the hands is hard to see, and / or streams of sand are thrown out from under the circle, you need to close it up in full, like gaping cracks.

The sealing of small cracks is reduced to coating with a primer and filling with a thixotrope, as well as recesses.

Advice: if possible, two to six months before the repair, stick paper strips on the cracks every half a meter. If the paper is not torn for repair - the crack is shrinkage, it will not go further, and you can close it on hastily as described. If at least one piece of paper is torn, the crack is deformational and needs to be repaired in full.

Seal gaping cracks

A gaping crack is considered to be more than 2 mm wide, but this criterion is very relative. Greater value has the dynamics of the process: will the crack go further or not. You can independently evaluate the dynamics, without having building experience, using the “paper” method described above or by turning on a laser level with a sensor or reflector on the opposite wall for several days. If, for example, the light spot has gone by an average of 0.01 mm per day, then for the year it will be 3.65 mm - the situation is emergency, and you need to think about the overhaul of the entire building.

If the condition of the building as a whole does not cause concern, then the repair of gaping cracks is carried out as follows (see figure):

The crack is sawn 50-60 mm deep and 20-30 mm wide.
The edges of the cut are knocked down to form a triangular hollow.
The cut is carefully blown and sucked.
The hollow is treated with a primer.
After the primer dries, markers are inserted into the cut in turn. Holding the next marker vertically with your hand, the hollow is covered with a thixotropic compound, leveling it with a rule. Homemade thixotrope in this case can not be used!
When the thixotrope sets, the markers are removed, and the seam is cut through the holes from them to the previous width.
A damper cord of the Viloterm type or similar is placed in the seam. Clotheslines, synthetic ropes, etc. are not suitable.
The seam is finally sealed with silicone or polyurethane sealant; in no case with mounting foam, epoxy or other fully hardening compounds.

Note: markers - thin smooth metal bars. Excellent markers are obtained from bicycle spokes. To make it easier to remove later, markers can be lubricated with grease before installation.

Overhaul of the screed

Overhaul of the screed means, in fact, its replacement. This is an extreme measure, costly and time-consuming. They go to it if it is supposed to be laid or finished, and the moisture test gave an unfavorable result.

More about formation various kinds floor screeds from scratch can be read at the links below:

Screed thickness calculation

If repairs are made in a room adjacent to others, then the floors should be on the same level. And in any case, the finished floor should not be higher than the threshold of the door. Therefore, the calculation of the thickness of the screed is carried out from the bottom up with a margin upwards. In this case, the level of the base floor will be lower, but this can be compensated by increasing the thickness of the plywood bedding or the height of the logs. The thickness of the solution layer above the reinforcing mesh must be taken at least 8 mm.

Calculation example: from bare ceiling to door threshold 80 mm. Initial data:

Waterproofing - 1 mm.
Expanded clay bedding in one layer - 25 mm.
Reinforcing mesh - 6 mm.
The concrete layer above the grid is 8 mm.
Layer of mastic - 1 mm.
Plywood - 8 mm.
Adhesive layer - 1 mm.
Laminate - 16 mm.

The total is 66 mm. You can improve thermal insulation by pouring one and a half layers of expanded clay or taking thicker plywood. However, laying the floor on the logs will not work, except perhaps to abandon expanded clay thermal insulation, but such a floor will be colder and more sensitive to dampness.

Screed markers

The screed is leveled with pin or plaster lath markers. Both of them are immured with a small amount of cement-sand mortar (see the figure below):

Pins - in the corners and along the walls in half a meter or less.
Plaster markers - parallel to the short wall. The first is 25-30 cm from her; further - half the width of the rule from each other.

Pins can be made from improvised materials, and plaster markers will have to be bought, and expanded clay will need to be rolled very carefully. But even an experienced craftsman is unlikely to be able to withstand the horizontal surface better than 3 mm / m using the pins, since as a rule you will have to work without additional support.

The height marks on the pins are made with a taut cord and bubble level, starting from the corner closest to the door diagonally. Then, the second diagonal is beaten off along the primary cord, the cords are pulled around the perimeter and marks are made on the wall markers. To speed up the beating of heights, you can use a laser level, but this will not improve the accuracy and smoothness of the floor, see above.

Screed overhaul procedure

Lay waterproofing ( plastic film) with an overlap of 0.5 m and an overlap on the walls of 10-15 cm. The joints along the entire length are glued with adhesive tape.
Expanded clay is poured and leveled with a rolling roller. Under the draft floor, it is permissible to use a manual rammer, wooden or metal.
A reinforcing mesh is laid with an overlap of 1-2 cells and with an indent from the walls of 30-40 mm.
Priming markers.
If pin markers are used, after the curing is set, the heights are marked.
Knead in portions of 10-20 liters of a viscous cement-sand mortar (1: 3); thixotropic additives are optional. At the end of the kneading, the next portion is dumped between the markers next to the previous one.
Each portion of the solution is leveled with a rule, starting from the far wall: along a cord or with the support of the rule on two adjacent markers. The rule is held obliquely so that excess solution falls into an empty cell.
The kneading of the next portion is started after leveling the previous one.
After the solution hardens, the markers are removed and the grooves are sealed with a solution.
Excess waterproofing is not touched; they are cut off after installing the plinth.

Note: under the draft floor, instead of plaster markers, you can use wooden logs-lighthouses, even and of the same height.

Video: an example of pouring a screed

Dedusting

Quite serviceable, but dusty due to surface wear, the concrete floor can be quickly repaired with special compounds:

Draft floor and floors in outbuildings - domestic Neomer-LP, Elakor-PU or imported Ashford formula, etc. They give a layer of 150 microns.
Finished concrete floor in living quarters, garage, workshop - GruntElast-PU, Elakor-ED, Retroplate. Layer - 250 microns.

In terms of quality and cost, these compositions are approximately equivalent.

Outcome

Do-it-yourself concrete floor repairs can be as simple, quick, and cheap as they can be complex, difficult, and expensive. The need for repair of one degree or another, in addition to the presence of gaping cracks, can be determined independently. In any case, it is definitely beneficial for self-fulfillment only dedusting worn from the surface of the floor.

Most craftsmen say that a narrow, small crack is allowed in the floor screed in new apartment and you don't have to do anything about it. In most cases, this is not the case. The question arises, what is the reason that it cracked? Such a defect may occur due to improper pouring or a weak foundation, and if, without eliminating these defects, a new screed is poured or cracks are repaired on the old one, the foundation will continue to collapse. The next step will begin to crumble concrete along the edges of the crack, then the finishing layer will begin to warp, then the plinth. And you will have to do all the repairs again. Therefore, it is necessary first of all to find out why the floor screed cracked in the new building and what to do so that the cracks do not go further?

Like it or not, the floor screed is the best, and sometimes almost the only way leveling the base for finishing. She makes a smooth and even coating for the flooring of the finishing layer, hiding communications or any defects in the base under her thickness. But when pouring it, some people face such minor difficulties as preparing the right mixture or putting the wrong beacons for the floor screed. Just the same, these little things lead to unwanted cracks when the screed dries. But don't despair! Sometimes sealing cracks in the floor screed is not such a difficult task. Let's take a look at the reasons why the screed can burst and how to avoid it. And if it was not possible to avoid this, we will analyze specific example how to repair cracks in floor screed.

Causes of cracks

Broken manufacturing technology
Incorrect mixing ratio of ingredients
Poor quality or low amount of cement in the mixture
No expansion joint
Wrong reinforcement

Mixing proportion not correct

This is the most common cause of cracks in the floor screed. This is usually found in ready-made mixtures. First of all, those who decide to do this for the first time, go to the store and purchase a ready-made dry mix, fall into the risk group. Manufacturers of dry mixes in production calculate the exact amount of necessary additives, which, dissolving in water, are uniformly distributed among themselves.

You probably know that the liquid solution is better applied to the floor, and beginners will probably be tempted to add a little water. Such a move in the end result will only make the quality of the mixture worse. What the manufacturer writes on the pack of the mixture must be strictly observed according to the instructions.

Mixing the solution by hand is not recommended, a construction mixer is most suitable for this purpose, and if you don’t want to fork out for this expensive miracle of technology, you can buy a simple nozzle for an electric drill and make a uniform batch at low speeds.

For reference!

For a high-quality screed, it is recommended to take medium-grained sand mined in a quarry and not river sand, which is more affordable. The optimal brand of cement will be M-400. First of all, the sand is sifted from lumps of clay and pebbles. Water is added by eye until the mixture has sufficient viscosity and plasticity.

If this minimum condition is not met, cracks are more likely to appear.

Lots of water in solution

Lots of water in concrete subject it to shrinkage or deformation. In this case, the screed is also likely to crack. Flood concrete mix also reduces the strength of the finished product (screed). In simple words the screed will not be strong enough and the surface will be loose.

In this case, the screed will need to be covered with a deep penetration primer in order to avoid dusting and sweeping after the topcoat is laid. And this is again an extra cost.

Material difference

The second common mistake is different and the screed itself. Gypsum-based plaster will rarely shrink after drying, which cannot be said about the cement-sand mixture. And since not much time passes between the installation of the beacons and the pouring of the screed, either depressions or bumps will be obtained on the surface of the screed.

They arise not only because of different compositions gypsum mixture beacons and cement-sand screed., but also differences in plasticity, coefficient of linear expansion and adhesion. And in those places where cement mortar adjoins gypsum beacons, cracks may occur in the floor screed, so what to do. We'll have to fix everything.

No expansion joint

Another rough cause of a crack in the screed is the incorrect location of the expansion joints or their complete absence. Namely wall seam and intermediate seams on the floor.

The wall expansion joint must be filled with an elastic material (polypropylene, polystyrene), pass through the entire thickness of the screed, thereby separating it from the influence of the deformation loads of the walls. Some craftsmen also recommend laying an expansion joint around columns, built-in interior items and stairs.

Intermediate expansion joints, per turn, do not pass through the entire thickness of the screed, but only half. They divide the screed into equal shares, preventing it from cracking after shrinkage. The width of such seams is selected depending on the thickness, and the presence of a warm floor. Do not forget to make special marks in the area of \u200b\u200bthe reinforcing mesh if your screed is reinforced.

Expansion joints are provided in all types of screeds in rooms with an area of more than 30 m². Accordingly, the maximum area of the fields into which the screed must be divided is the same 30 m². The sides of the area should not be more than 6 m. At one time, intermediate expansion joints should be cut in the corridors, and the distance between these types of joints should be less than six meters.

If the top coat is selected ceramic tile or porcelain stoneware, then the notches from the expansion joints should be comparable between the tile joints.

Indoors, we leave the seams unfilled, but it is recommended to seal the seams on the street site with silicone or waterproof glue in order to avoid water getting into them and not to break your screed at sub-zero temperatures.

Wall joints can usually be left empty. In the event that you decide to repair them, it is recommended to use only soft materials.

Reinforcement

Another of the common mistakes in which the screed cracks is incorrect, poor-quality reinforcement. If you decide to purchase reinforcement and make a high-quality foundation, then it should be in the body of concrete and not lie under the thickness of the screed. It is not recommended to use a reinforcing mesh here, and there is simply no need to transfer so much money for nothing, but fiber reinforcement will be very effective. The reinforcement must be in the body of the concrete, but not under the screed. By by and large the use of reinforced mesh is meaningless. Much cheaper and more efficient.

Before renovation

It does not matter if the screed is cracked, but the beginning of resuscitation work should carry out a number of procedures to simplify and speed up work to eliminate the crack.

First of all, determine for what reason they were formed. If the screed was not performed, you will determine the presence of expansion joints and how the floor was poured.

If cracks in the floor screed look like segments scattered over the entire base, they are repaired with epoxy adhesives using the “forced closure” technology.

If cracks in the underfloor heating screed appeared due to the absence of an expansion joint between rooms or along the walls, they should not be repaired without making this very joint.

Necessarily!

Before the start of the repair work the cause of the cracks must first be identified. Otherwise, after a few months, they will again make themselves felt, and not only in old, but also in new places.

Before repairing cracks in the floor screed, you will need to see what the degree of damage is and highlight the areas that need to be repaired.

You can easily find visible cracks. But you will have to look for hidden voids by tapping the whole base with a wooden mallet.

If during this procedure you hear a ringing sound, then you have found one of these voids. Found hidden flaws should be marked and at the end of the work, calculate the area that needs repair.

Important!

If, as a result, it turned out that 30% of the area of the room or more is needed to be repaired, it is recommended to dismantle the old base and fill in a new coating.

Repairing small cracks

Minor cracks in the floor screed are recommended to be cut with a grinder up to 20 mm. Remove debris after processing with a conventional vacuum cleaner and wipe the remaining dust with a damp cloth and allow the surface to dry before repairing. After drying, the surface is ready for repair.

Cunning! If the premises are non-residential, it is recommended to check the cracks for possible subsequent deformation. To do this, cracks in the floor screed are sealed over with sheets of paper and left for a while. If the sheet is torn, the resulting crack continues to expand and repairs require a more difficult approach.

Repairing large cracks

It is not for nothing that a crack is one of the most severe damage to a screed, so repairing cracks in a floor screed must be done here and now. If you do not pay attention to this in time, then most likely it will grow, which will lead to the impossibility of repair and you will have to make a new screed.

In order to eliminate cracks in the floor screed, it is necessary to make quite a few costs, both financial and physical. Therefore, we recommend that you follow all the technologies described above and strictly follow them, then the repaired floor will serve you for a long time and you will not have to undertake its repair again.

Conclusion

To avoid repair work after drying, it is enough just to follow the technology of laying the screed. To summarize: First of all, we observe the proportions of the mixture. Excess water 100% will give us cracks on the dried floor. Ground preparation also plays a big role. If it absorbs moisture, the screed will need to be reinforced anyway.

And the most important thing! No need to speed up the drying of the solution by artificial drafts or warming up the room. With such actions, moisture evaporates unevenly and quickly, cracks will also appear from this.

Remember!

The screed on the floor should dry itself, gradually and at an equal temperature. If the weather outside is hot or, on the contrary, windy, it will need to be moistened, thereby protecting it from rapid drying. For the implementation of this process, wet burlap is mainly used.

By following these simple rules when pouring screed cracks on your floor will never be

Video instruction

A cracked or crumbling screed is not only an uneven and uncomfortable floor, but also an undistributed load on the floor slabs in the house. If you can more or less put up with the first moment, then things are a little different with the second - excessive loads on the floors, despite the fact that they have a fair margin of safety, can be disastrous, especially when it comes to old houses. The screed must be kept in order - in the event of a major overhaul, change or at least repair. In this article from the website, we will deal with the question of how to repair a floor screed with your own hands?

Repair of cement floor screed photo

Floor screed repair: about its feasibility

Before embarking on a direct solution to the question of how to repair the floor screed with your own hands, first you need to figure out its expediency - perhaps things are so that it makes no sense, and you need not to restore the surface, but its complete replacement. In what situations does it become necessary to install a new floor screed? There are not so many signs that indicate that the screed has outlived its time.

By and large, there are no specific criteria according to which it is necessary to completely change the floor screed. There are simply prescriptions and common sense, which suggests that new surface better than the old one. She can serve for a long time, and if you intend to live in an apartment or house long time, then it would be best to completely replace this surface - naturally, if we are talking about overhaul. It is better to spend money on a new screed once than to repair an old floor screed with enviable regularity. Restoration is primarily a temporary measure that resolves the issue for a short period of time.

Repair of cement floor screed: preparatory work

Preparing an old screed for repair is a simple matter, and in most cases comes down to just two steps.

You can not wait for the second layer of primer to dry - while you prepare the solution, it will be absorbed into the old screed and this will be enough. Such repair of cracks in the floor screed (or rather, the preparatory work associated with its implementation) will give you a guarantee that the floor base will last at least another ten years.

How to repair a floor screed: the main stage of work

This stage (as, in general, preparatory) can be conditionally divided into two sub-stages - fastening the split fragments of the floor and finishing leveling the base. These are two different technologies that should be dealt with separately.

Bonding or sealing cracks. This is a fairly simple stage of work, for the implementation of which it is necessary to prepare a solution of a rare consistency. One thing should be understood here - too rare a solution can leak to neighbors on the ceiling. We need a moderately rare mixture that can flow into all cracks and recesses, but at the same time not leak onto the neighbors' heads. In general, all the knocked-out sections of the floor are poured with such a solution. After the repair of the concrete floor screed is completed, you should wait for the complete drying of the repaired areas. After this happens, the repaired floor must be cleaned of dust and dirt and qualitatively opened with a primer, paying particular attention to fresh patches. They need to be opened twice.
How to repair a floor screed photo
Finishing leveling is at the same time the surface bonding of the floor. To solve this problem, the so-called is used - in the people it is called a self-leveling floor screed, to create which a mass level is used. It is filled with a layer of 3mm (plus or minus). The process is quite simple, but there are many nuances - you can read more about it in another article on our website (). Briefly describe this technology, it can be represented as follows. The mixture prepared in the container using the mixture is poured onto the floor and spread with a notched trowel. Then it rolls out with a plastic roller with spikes, after which it is left to dry. The next day, such a screed is gaining primary strength (it is already possible to walk on it). The full operation of the floor is possible only after complete drying - this is at least 3 days (can be determined by the color of the floor). The finished surface of such a floor can be finished with any decorative materials, including, and.
Floor screed repair photo

In principle, this is the entire repair of the floor screed. It seems to be not difficult, but there are plenty of nuances - they are not obvious. We can say that the subtleties are almost all individual. For example, depending on the degree of destruction of the old floor screed, reinforcement may be needed - naturally, it is better to change such a floor covering as a whole, but the situations are different, and even with large damage, repair may be appropriate.

When renovating a room, quite often you have to deal with the fact that under the old flooring there is a screed on which various kinds of defects appeared in the form of cracks, potholes or swelling. Many masters believe that in this case it is necessary to completely remove the old material and re-align.

However, if the total area of damage does not exceed 30%, then it is possible to repair the floor screed, which will help save a lot of money and time.

Types of damage and their elimination

First of all, it should be noted that each individual defect requires special attention and requires its own unique way of elimination. At the same time, they can be used completely different materials and installation technology.

Cracks and potholes

The main problem with old cement floors, a manual on how to repair a floor screed, considers the presence of small cracks or small chips. Such damage often occurs during prolonged use, and indicates the use of poor-quality mortar, in which there is too much sand or water.
To work, it is first recommended to find all the problem areas and outline them with chalk.
Then, using a chisel and a hammer, expand the crack or pothole by at least 1 cm on all sides. Also, this area needs to be deepened a little.
At the next stage, using a vacuum cleaner, remove all debris from the surface.

Next, it is necessary to treat the cleaned area with a deep-penetrating primer in several layers with an application interval of 4 hours. This will significantly increase the adhesion of the material and give it strength.
After that, you need to prepare a cement mortar with proportions of 1 to 3. In this case, it is desirable to add a plasticizer to the composition. Many craftsmen, when repairing floor screeds with small potholes or small cracks, prefer to use glue-cement or quick-hardening leveling mixtures, which are diluted to a mushy state.
The finished composition is filled with a cut place, leveling with the surface.
After the solution has hardened, the place of work is polished.

Advice!
If the old screed is shallow, then it is better to embroider damaged areas and cracks to its entire depth.
This will prevent further breakage and ensure good adhesion to the surface.

deep cracks

This type of defect appears as a result of installation errors associated with preparatory work and the quality of the solution.

To eliminate such damage, you first need to embroider them to the full depth.. At the same time, the repair manual recommends using a hammer drill and a circular saw for concrete. The fact is that with an ordinary chisel and hammer it is impossible to go deep for a long distance without expanding the area of \u200b\u200bthe place of work.

After cutting the crack, a strobe is made perpendicular to it with a depth of several centimeters so that it crosses the recess, going beyond it by 5-6 cm. Further, recesses of 2-3 cm are drilled at the ends of the strobe.

The next step is to remove the debris with a vacuum cleaner..

Then the primer is poured into the resulting recesses and left to dry completely..

To produce quality repair cracks in the floor screed, you need to prepare a cement mortar in a ratio of 1 to 3. In this case, the filling will be carried out in several stages, the first of which involves the use of a liquid mixture.

First, pour a small amount of liquid solution into the place where the crack was.. Its consistency should resemble sour cream, and it will allow the material to leak even into the most inaccessible and inconspicuous places.

At the next stage, we prepare a normal cement mortar and pour it into the crack to the level of the passage of a perpendicular strobe. After that, it is necessary to withstand the time until the mixture solidifies completely.

Then it is necessary to make a bracket from a piece of reinforcement or thick wire, which is installed in the strobe so that its pins fit into the drilled grooves.

After that, everyone is covered with a solution, in which a little plasticizer can be added and leveled with the surface.

At the final stage, the repair of the old floor screed involves. It is done in order to remove the excess solution and disorder the place of work.

Advice!
To facilitate installation, it is best to first make a bracket, and only then prepare a seat for it.

Bloating

Defects of this kind occur in cases where, before installing the screed, debris was not removed from the surface. You can find swelling with a hammer or a metal rod. They tap the surface, and where the sound is deaf, there will be a peeling of the coating from the surface.

Some masters believe that such damage must be opened and done, or at home again. However, if this defect does not affect the evenness of the surface, and at the same time there are no cracks and chips on it, then a cheaper method can be used, which will save a lot of time.

First you need to determine the area of \u200b\u200bdamage with a hammer. After that, it is outlined with chalk or a marker.

Then you need to take a drill, on which a drill bit for concrete with a diameter of 16 mm is installed. With its help, holes must be made in the surface of the swelling area to the entire depth of the screed. In this case, the distance between them should be about 240 cm.

Further do-it-yourself repair of a floor screed, which has damage in the form of swelling, involves a primer. In this case, the material must be poured into the holes made so that it flows throughout the cavity. You can use a hair dryer to speed up drying.

The next step is to decide on the fill material. The fact is that the installation method involves the use of a construction syringe or a plunger pump. Therefore, the finished mixture must be plastic, have good fluidity and not contain lumps.

Glue-cement or a special mixture for leveling ceilings with large differences is best suited for these purposes. These materials have almost the same qualities and can be used in this type of repair. However, it is worth noting that the price of adhesive cement is much lower, which gives it an additional advantage.

It is necessary to fill the cavity gradually so that the material inside can flow and fill the entire space. In this case, this process must be carried out until the solution completely fills the holes.

Drying of the filler takes from 12 to 24 hours. During this time, you can put a load on the surface.

After the allotted time has passed, the injection sites of the solution are polished.

Advice!
It should be noted that after any repair, the screed over the entire plane must be cleaned of debris and treated with a primer.
This will bind the top layer and protect it from shedding.

Conclusion

In the presented video in this article you will find additional information on this topic. Also, based on the text presented above, we can conclude that when repairing the screed, it is necessary to detect and eliminate all small damages on its surface. Moreover, each individual defect requires its own method of restoration.