How to make your floor strong and level

A floor is a building structure on which human activities are carried out or production processes take place. The floors can also be called highways and building areas. The comfort and aesthetics of a particular interior room largely depend on the quality of the base underfoot, that is, on the well-being of those very roads and squares. To stand firmly on your feet, the floor must be at least firm and level.

The design of the floor must be carried out taking into account the degree of influence of external factors on the future overlap. There are many of them. We will not list everything on the pages of our publication, however, we note that in addition to mechanical loads and the effect of water on the future floor, builders are interested in such seemingly insignificant parameters as climatic conditions during construction.

However, an ordinary man in the street, without delving into the intricacies of the construction business, usually subdivides the floor into household and industrial. Of course, each of them has different requirements. The so-called household floors must be durable, wear-resistant, resilient, smooth (but not slippery), have low heat absorption, be easy to clean from dirt, have an aesthetic appearance.

Industrial floors are subject to increased requirements for resistance to mechanical stress (abrasion, impact), for some industries, chemical resistance, heat resistance and other parameters of the base are fundamental. Any floor, regardless of type, is a multi-layer structure. Industrial floors, the main task of which is to take the load from moving machinery, equipment and an aggressive environment, can consist of many layers: waterproofing, thermal insulation, sound insulation, screed and topcoat. Household floors are like a simpler “layer cake”, the components of which are limited to: waterproofing, screed and flooring.

In our reviews, we often talk about different types of floor coverings: ceramic tiles, natural stone, parquet, laminate, PVC and cork coverings, so we won’t dwell on them in this material, let’s just say that all types of finishing materials are united by one important requirement – the base under them should be as flat as possible. Otherwise, the whole repair is worthless..

A very solid foundation … concrete

The builders assign the responsibility for leveling the floor surface to the screed. It is this layer of the “three-layer” floor, according to the opinion of the builders, which makes it possible to achieve an ideal flat surface. It just so happened that the slabs, which serve as the basis for the floor in serial houses, are produced smooth only on one side – the one that will become the ceiling of the apartment on the floor below. The side that is supposed to become the floor is always uneven, with bumps and depressions, often the ends of the metal reinforcement rods stick out from it. And floor level drops in an apartment can reach 10 cm.Of course, laying even the cheapest coating on such a surface is a senseless undertaking.

However, having a “bare” concrete slab has its advantages. If you start work on the flooring “from scratch”, then the chances of getting a better floor covering in the end are significantly increased.
Because often a previously made screed does not meet the requirements, both in strength characteristics and in the laying technology.

There are several options for preparing the base: the device of a cement-sand screed, the use of self-leveling systems for leveling the floors, the use of gypsum plasterboards, the device “rough” plank floors. But, before giving preference to one of them, it is necessary to carefully study the available concrete slab.
The quality of the base is evaluated according to the following main parameters: evenness, strength of the top layer, moisture. Additional criteria are defined as necessary (porosity, cracks, expansion joints, etc.).
As we have already said, the evenness of a concrete slab in serial houses, as, indeed, in custom-designed houses, is far from perfect. In addition to the negligent attitude towards the manufactured products, this is also explained by objective reasons: low plasticity of cement-sand mixtures, their tendency to significant shrinkage and the appearance of cracks, as well as the use of imperfect means of geodetic control.

The requirement for the strength of the base is set by the architect when designing the building and is determined by the purpose of the premises and the conditions of its operation. But, unfortunately, mortar or concrete of an undefined brand is often brought to construction sites. Even if the mortar is prepared on site under close control, it is possible to obtain a low grade due to poor quality cement and a violation of the water-cement ratio for this type of construction. All these features of nation-building do not in the best way affect the strength of the foundation..

And finally, humidity. Determination of the residual moisture content of the substrate is an important factor when choosing a particular coating. When installing, for example, a cement screed, one of the components of the finished mixture is water, which is necessary to create the mobility of the solution and the formation of a cement stone.
One sq.m. a base 20 cm thick contains 30 liters of water, which will evaporate gradually over 2-2.5 years. In this case, the drying of the base is uneven in depth. The top coat dries quickly and gives the illusion of a finished base. The solution to this problem for accelerated construction is the separation of the base layers. Another solution to the problem is the use of fast-setting cements. Specially developed formulations bind water in concrete and prevent it from evaporating. After 3-5 days, the coating can be laid on such bases. Only taking measurements for three main indicators allows you to choose the laying technology, calculate the required amount of materials and determine the timing of work.

Cement sand tradition

So, you can make a high-quality screed using various technologies and materials, the most common of them in our country is a screed made of dry concrete mixtures. The main components of such a screed are cement and sand. So, on the square. m. mortar grade M 150 accounts for approximately 320-340 kg of cement grade M 400 and 950-1020 kg of sand. In this case, the composition of the solution should include only dry sand with a density of 1.6-1.8 t / m3. The use of wet sand leads to a deterioration in the quality of the solution.

As a binder in cement screeds, Portland cements are mainly used, the raw material for which is natural clays with the addition of ground limestone. Under tight deadlines, aluminate cements are used in construction, less often pozzollan cements are used. Sand or gravel is added to the binder as a filler in the required amount. The ratio of elements depends on the requirements for the strength of the screed. Cement screeds are connected hydraulically – with water. Cement for hydration requires 10 – 25% of water (by weight of cement), and taking into account evaporation, 28 – 30%. About 20% of water binds within a month.

When curing, it is necessary to protect the screed from uneven or too fast drying, so that the required amount of water does not evaporate before complete hardening. The strength of cement slurries depends on the water-cement ratio. But since a mixture of concrete with sand in any proportion is not the most durable material, adhesive substances are often added to it.

But before laying the screed, the surface of the concrete slab is cleaned of dust and dirt. A poorly prepared foundation will certainly affect the final result. The concrete surface is treated with a metal brush or a roughing machine to remove weak, non-bearing particles. Garbage and dust are carefully swept away with a stiff brush and removed with a vacuum cleaner. But it is impossible to perfectly clean the concrete, so then the surface is primed with binders. The primed surface ensures good adhesion to the screed. This is important for any floor, but especially for ceramic tiles. If the screed under the tile has poorly grasped the surface of the slab, then when walking on such a tile, a characteristic knock will be heard, and over time the floor will become uneven and the tile will begin to separate from the base and fly out.

A primer is necessary to normalize the porosity of the base and secure adhesion of the screed to the base, while for each type of base there is its own primer composition. On porous and very porous substrates, it is recommended to use a water-thinnable primer. On dense, non-porous substrates, use a primer without adding water. The primer is applied to the substrate with a roller or brush in 1 layer at a time. Before making a choice in favor of this or that composition, experts recommend carefully reading the instructions for the primer, which contains recommendations for using the composition.

It is convenient to knead the cement-sand mortar in a metal container (for example, a trough) with a shovel. The solution is leveled with a trowel and a rule – any bar with smooth edges convenient for this. The minimum thickness of the screed without reinforcement is recommended to be at least 25-30 mm. If significant loads on the base are expected, the thickness of the screed should be increased to 45-100 mm and reinforced with a metal mesh.

If the finishing coatings of the floors in different rooms of the apartment are of different types, the thickness of the screed must be made different depending on the thickness of the coatings so that the level of flooring in the entire apartment is the same.

In order to smooth out the unevenness of the floor slab or old screed and get a horizontal floor without a slope and holes, you will need beacons, which, using a rack level, will need to be set in one horizontal plane. Mortar beacons are performed as follows: a solution (preferably gypsum) is applied with tubercles no more than the thickness of the screed. The gypsum solution grabs after about 20-30 minutes, so it is better to knead a small amount of solution each time. Then you need to insert a pole into the tubercle, which is made from various available materials (for example, wood). The rack level is necessary so that the tops of the poles are at the same mark.

The distance between adjacent poles should not exceed 1500-2000 mm. This distance is due to the fact that to check the horizontal position it is necessary to reach with the level of two adjacent poles. It is preferable to fill the cement mortar in strips, since this method increases labor productivity. For this purpose, it is necessary to expose lighthouse strips, which will limit the spreading of the solution and at the same time serve as formwork when pouring the screed. As lighthouse rails, you can use wooden bars or metal pipes, the main thing is that their height (or diameter) corresponds to the thickness of the screed being arranged.
The strips should be poured through one. After waiting for the first stage to solidify, you can fill in the second, not forgetting to first remove the no longer needed guides. The strip width of 1000 mm is optimal for the installation of a cement-sand screed in an apartment. The unevenness of the screed laying can be eliminated by remembering a simple rule: where the screed solution is lighter, there is a bump, and where the cement milk accumulates, there is a depression. The hillock should be leveled with the rule, and the solution should be added to the cavity.

Before the floor covering is laid on the screed, it must dry. Long drying times are required depending on the layer thickness. The set of strength occurs gradually, within 28 days (while the average time required for complete drying is 45 days), unevenly in depth. Ironing is often used (grouting with cement “milk” to give the screed a presentation). This layer must be removed before applying the coating. After the screed has dried, a waterproofing coating is applied to it, and on top – sheets of moisture-resistant plywood, 12 mm thick. Plywood will not hurt in any case, but it is especially necessary under parquet, otherwise high humidity (with water leaks or just in early autumn days, when the weather is damp and the central heating is not yet turned on) can destroy the most beautiful and expensive parquet.

The main signs of cement screeds are: gray color, rough surface, seams in door areas or when the cross-section is narrowed, expansion joints over an area of ​​more than 40 square meters and a length of either side of more than 8 m, frequent formation of convex places on seams and edges, low sensitivity to moisture.

A strong and even cement-sand base is the most durable and reliable. The main disadvantage is the difficulty of obtaining a perfectly smooth surface, the impossibility of using traditional mortar screeds at low thicknesses and a long waiting time for such a screed to completely dry..

However, there is one more problem, not very noticeable at first glance. According to experts, it is not an easy task to get a strong screed that will not crack later. For a reliable result, it is necessary to combine many factors: the correct ratio of sand and cement; lack of harmful impurities; strictly defined amount of water; correctly selected granulometric composition of sand; type and brand of cement. Also, in order to make the cement-sand mortar easier to lay, the water-cement ratio is often overestimated. This leads to a decrease in the strength of the screed and strong shrinkage and an increase in the drying time. It is for this reason that many builders and customers do not want to risk it, to create a cement-sand screed in a domestic environment, they use a ready-made dry mixture.

The dry mixture must be dry

To simplify and significantly accelerate the screed device, both cement-based and gypsum-based mixtures are used. Immediately it is necessary to make a reservation that the concept of a dry mixture includes completely different materials. It is often used to designate dry mixes such as “self-leveling floor”, and among professional builders, this concept is used by binders for the manufacture of bases. In this section, we will talk about the last.

Before proceeding with laying the dry mix on a concrete base, it is necessary to clean with a metal brush from various particles, remove dust from it. Then, as we already know from the example of a traditional cement-sand screed, it must be primed. Then comes the most crucial moment – preparing the dry mixture for use..

It should be noted that when working with dry mixes, this is perhaps the most difficult stage of work. The fact is that, when preparing a dry mixture for use, it is very important to correctly observe the amount of water recommended by the manufacturer. Excess water in the finished mixture will speed up and facilitate the installation process, but will significantly reduce the performance of the dried screed. On average, a bag weighing 50 kg requires about 7-8 liters of water (each manufacturer indicates the exact number of liters on the label). With this ratio, a tough mixture is often obtained, which is rather difficult to stack. In most cases, workers, without further ado, add more water to the solution to make the mixture more malleable. This leads to the formation of shrinkage cracks and delamination of the screed from the base. It is possible to avoid unpleasant consequences and facilitate the laying process by adding not water to the solution, but special plasticizers, which make the mixture more flexible when applied, ensure uniform drying and significantly increase the resistance to cracks of the dried mixture, increase the impact strength and abrasion resistance of the finished composition.

It is impractical to apply the mixture in a layer less than 50 mm. With a smaller thickness, it is difficult to provide sufficient strength and crack resistance of the base. The prepared mass is distributed over the surface, carefully monitoring to ensure horizontal alignment. When applying, any convenient method is used. Often the most convenient is a long metal trowel, or stretching along the guides as a rule.

To get a strong and non-spreading screed, it is necessary not only to correctly observe the proportions, but also to take care of the freshly laid mixture. After 6 – 12 hours, when the mixture gains its initial strength (you can gently walk through the mixture without leaving footprints), it is necessary to spray the surface of the screed with water (the surface is moistened as for wet cleaning).

Then, during the first 3 to 4 days, it is necessary to protect the screed in every possible way, maintaining constant humidity and temperature. The presence of drafts, the inclusion of fan heaters is unacceptable. Any sudden changes in temperature and humidity can lead to uneven shrinkage, cracks and delamination. Subsequently, the procedure for wetting the surface must be repeated regularly as the surface layer dries out (once a day or even more often, the frequency of wetting depends on the ambient temperature, humidity, etc. factors).

To obtain a guaranteed high quality screed without special care, it is recommended to use special coating polymer compounds. These compounds are applied under the dried screed (after about 4-8 hours). The coating composition forms a transparent vapor-permeable film on the surface. It protects the screed from excessive drying out and quick drying, ensures normal, even drying. Subsequently, this composition does not affect the laying of finishing or leveling layers, it will act as a primer.

What the market offers?

Optirok has been known as a leading manufacturer of modern, reliable and cost-effective dry mixes and expanded clay concrete products for 100 years. Optirok is part of the Optirok Group, which has factories in more than ten countries, as well as dealers and retailers around the world..

Optirok offers a wide range of products that meet specific conditions and tasks of repair and decoration. Under the Vetonit trademark, mortars, concretes, putties, materials for tiling, as well as leveling mixtures for floors are produced.

For example, Vetonit 5000 for the initial leveling of concrete floors. It is a hand-applied, quick-setting, quick-drying, cement-based mortar for leveling concrete substrates. Vetonit 5000 is suitable for leveling concrete floors indoors: in residential buildings, offices and public buildings. Due to its good sealing, Vetonit 5000 is suitable for use in electric or water floor heating systems. This compound can also be used to fill sloped surfaces..
The leveled surface can be further covered with ceramic and stone tiles, PVC or textile carpets, linoleum, floating parquet or cork. Plywood is used under block parquet glued to the base due to the presence of moisture stress in the wood.
Before applying the mixture, loose and weak concrete, adhesives, oils, as well as water-soluble leveling compounds must be removed. The holes in the base and the places of possible leaks are sealed. Places where drain wells are located are protected and separated with a special stopper.
The base is vacuumed and primed with Vetonit MD 16 dispersion in accordance with the instructions on the package. The dispersion treatment improves the adhesion of the leveling compound to the base, prevents the formation of air bubbles and also too fast absorption of water from the leveling compound into the base. The dispersion also improves the flow of the leveling compound. Dry and highly absorbent substrates (monolithic concrete floors) are treated 2 times. If the leveling is done in several layers, dispersion treatment is performed before each leveling layer..

“Vetonit Light Floor” is a lightweight and easy-to-apply mixture based on expanded clay gravel and cement for application to concrete and wood floors. Due to its ease of use and quick setting and drying, it is well suited for repairing floors, as well as for creating floors in new construction, when, due to large irregularities or curvature of the base surface, a thick layer of the mixture is required. Layer thickness – not less than 30 mm.

“Vetonit light floor” is used for leveling floors, as well as for sealing large floor irregularities inside premises in residential buildings, offices and public buildings. Also suitable for filling sloped floors, e.g. in bathrooms.

The leveled surface is suitable for walking after 12 hours at a room temperature of + 20C. The hardened surface can be cleaned / sanded one day after applying the mixture. This reduces material consumption and improves the final result..

Henkel Bautechnik has been producing high quality building materials for nearly 100 years. The company has developed and produced whole systems of materials that allow performing complex work in various areas of construction, in particular, for the repair and decoration of premises, insulation of facades, waterproofing and refurbishment of basements, waterproofing of pools and reservoirs, repair of reinforced concrete structures and buildings. To create even floors, Henkel Bautechnik produces a binder for subfloors with Ceresit CN 85 floors.

Ceresit CN 85 is intended for the installation of monolithic substrates that are rapidly gaining strength under textile flooring, ceramic cladding and parquet. Ceresit CN 85 can also be used in the manufacture of underfloor heating for pouring heating elements (pipes, pipelines), subject to the general rules of the heating system manufacturer. In the manufacture of foundations on floors, the thickness of the base must be at least 10 mm. When manufacturing floating floors laid on a vapor barrier, the thickness of the base must be at least 35 mm. Ceresit CN 85 must not be used for outdoor work and in damp rooms.

The mixture is quick-hardening, ready for use in 3 hours. Laying of coatings is possible in 24 hours, which significantly reduces the time of work. Has a low shrinkage. Cannot be used as final coating.
Ceresit CN 85 is a mixture of cement with mineral fillers and modifiers. Bulk density: about 1.2 kg / dm3. Mixing ratio: 100 – 125 mineral aggregate and 8.0 – 12 liters of water (depending on the moisture content of the aggregate) per 25 kg of dry mix. Consumption time: up to 40 minutes.

25 kg of Ceresit CN 85 should be mixed in a concrete mixer with 100-125 kg of mineral aggregate and the prepared mixture should be mixed with 8-12 liters of clean cold water. The amount of mixing water is determined by the moisture content of the filler. The above composition of the mixture is designed to obtain a finished solution with a volume of 0.1 m3 and a compressive strength of 25 MPa at an “age” of one day. The use of finer granular aggregate results in lower grade slurries. Do not add other astringent and modifying additives to the solution. The prepared portion of the solution should be consumed within 40 minutes from the moment of mixing. Under normal conditions, after 3 hours you can walk on the laid base, and after a day you can lay the floor on it. Fresh mortar residues can be washed off with water, while hardened ones are removed only mechanically.

Work should be carried out at a substrate temperature between + 5 ° C and + 30 ° C. All the above recommendations are valid at an ambient temperature of + 20 ° C and a relative humidity of 60%. In other conditions, it is possible to change the setting time and strength gain. Ceresit CN 85 contains cement and, when interacting with water, gives an alkaline reaction, therefore, when working with it, you must protect your eyes and skin.

The Polish company Kerakoll offers builders and designers a wide range of technologically advanced products designed for a comprehensive solution to all problems associated with the preparation of substrates.
Keracem is a high-tech, professional binder for underfloor heating substrates and heating panels, with normal bonding, fast-drying, shrinkage-compensated and high thermal conductivity, intended for gluing ceramic tiles, porcelain and marble chips, natural stone, parquet and floor coverings. It guarantees the achievement of the condition and stability of the applied layer within 24 hours, the residual moisture content of 2% is reached after 120 hours. For indoor and outdoor use.

Keracem Pronto is a ready-to-use, water-based binder for rough screeds with normal adhesion and fast drying. To create abutting or overlapping screeds. Suitable for laying ceramics, natural stone, terracotta, parquet, roll coverings. Ideal for underfloor heating. It guarantees the achievement of the condition and stability of the applied layer in 24 hours, a residual moisture of 2% is reached after 120 hours.

Record Pronto is a ready-to-use water-based screed binder. Ultra-fast curing and drying. For laying ceramics, natural stone, terracotta, parquet, roll coverings. Ideal for underfloor heating. Ensures a highly stable subfloor with a significant reduction in waiting time before laying floors.

And finally, Keralevel professional leveling mortar for leveling uneven absorbent surfaces is ideal for leveling uneven walls and uneven screeds, including heated ones; for subsequent facing with ceramic tiles or coatings with other types of coatings. The thickness of the applied layer is from 1 to 10 mm. Keralevel technology introduces alkaline resistant thixotropic polymers to provide perfect thixotropic equilibrium for fast and reliable leveling of walls and floors.

Keralevel technology allows you to extend the shelf life of the solution for professional repair of large areas, including in extreme weather conditions. The use of high-dispersion flow-enhancing polymers and surface tension regulators prevents the product from sticking to tools, provides a smooth and appropriately matched base, ideal for laying ceramic tiles, porcelain and marble gres, natural stone, parquet and floor coverings.

Atlas was founded in 1991. Over the course of ten years, it has grown from a small business to the powerful Atlas group. It has seven modern factories and its own mines, which supply raw materials for the production of some products. Atlas Group is based on 100% Polish capital. The Atlas group includes a number of large and small businesses throughout Poland. Today the Atlas group offers its customers an assortment of over 50 products. In all production sites of the Atlas group in Lodz, Piotrkow Tribunalski, Bydgoszcz, Nyvnice and Dбbrowa Gornicza, the production process is fully computerized, and well-equipped laboratories monitor detailed quality control.

Atlas’s main products are adhesives for ceramic tiles, although building mixes, thermal insulation systems for exterior walls of buildings, underlays, plasters and paints are also very popular. Atlas exports its products to Russia, Lithuania, Latvia, Belarus, Estonia, Czech Republic, Slovakia, etc..

The Atlas group offers the Atlas cement mix for flooring and cementitious underlays using traditional methods..

It can be used for making floors or underlays in the following types: bonded to an existing base (min. Layer thickness -20 mm), on a release layer (min. Layer thickness -35 mm), “floating” (min. Layer thickness -40 mm) or in heating systems with underfloor heating (minimum layer thickness above the heating element -25 mm).

Atlas floor cement mix is ​​a ready-made, dry mix of cements, mineral aggregates, and modifying agents, thanks to which a material with improved technical parameters is obtained (compared to typical cement mixes). It is characterized by good adhesion, high ductility and increased flexural strength, making it a universal product. The simplicity of preparation of the mass, as well as its operating parameters, make it very easy to use, convenient and economical. Optimally matched setting time (up to approx. 3 hours) and the rapid achievement of the initial strength enables the floor to be used earlier and shortens the construction cycle. Cement mix for Atlas floor frost and water resistant.

The mass is prepared by pouring the dry mixture into a container with a measured amount of water (in a proportion of 2.4 – 4.5 liters of water per pack of 30 kg) and stirring until a homogeneous consistency is obtained. This is best done with a drill with a stirrer, continuous feed mixer or concrete mixer. The mass is ready for use immediately after stirring and should be used within 1 hour. The proportions of added water are adjusted empirically, guided by the desired consistency of the solution, the type of base and atmospheric conditions. The use of the wrong amount of water for the preparation of the mass leads to a decrease in the strength parameters of the floor or sublayer.

But, despite all the efforts, using a cement-sand mixture is quite difficult to get a perfectly flat base. The fact is that in order to ensure strength and normal resistance to cracks, such mixtures must have a coarse aggregate (grains of sand up to 2-3 mm and even more). Such a composition will always have a rough surface upon drying. Accordingly, it is not recommended to glue linoleum, carpet, or lay parquet on such a screed..

A conscientious foreman, knowing these features of “rough” screeds, must offer the customer a more complex, combined option. In which on the primary screed is a concrete mixture, a second layer of European self-leveling mixtures is placed.

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