Dry floor screed is one of the main technologies used in modern construction for carrying out construction and repair work aimed at leveling the floor. Along with the “dry floor screed” method, which demonstrates a modern approach, there are more traditional version, called wet or cement screed.
Idea wet screed has been known for a long time and involves the use of such building materials, like concrete or cement-sand mortar. Taking into account modern development construction technologies, this approach turns out to be irrational due to its economic impracticality. In addition, the use of a wet screed, in contrast to the “dry floor” technology, is associated with a number of inconveniences and can cause undesirable consequences. These disadvantages are associated with the peculiarities of the processes for preparing and carrying out measures for the use of cement screed, as well as with some of its tactical and technical characteristics. The work itself of using a wet screed can be characterized as time- and labor-intensive, as well as dangerous from the point of view of sanitary and epidemiological standards.
Dry floor screed, being a modern development, is devoid of all the disadvantages that we described for wet screed. In addition, dry screed has a number of additional advantages and positive characteristics, which will be appreciated by both the builders themselves and their clients.
Dry backfill for floors (dry floor)
The process of making floors where dry screed is used is carried out in accordance with certain rules, including the following steps:
Surface preparation includes removing old floor structures (if any), clearing floors of debris, eliminating gaps, recesses and cracks.
The construction of a moisture-proofing layer involves the use of polyethylene film, glassine, batuminized paper, etc. waterproofing materials. This procedure is mandatory when using dry floor technology, as it protects it from moisture and steam, which can cause it to swell and deform.
For sound insulation, a special tape made of polyethylene foam, mineral or glass wool, as well as other similar materials. To install it, a small gap of up to ten millimeters is left along the entire perimeter at the base along the walls, in which the soundproofing tape is installed.
The use of backfill is a necessary step when installing floors based on dry screed. This process involves the use of bulk material that creates a flat surface for installing the flooring, and also acts as additional sound and heat insulation. For this purpose, materials are used that are characterized by properties such as low shrinkage and hygroscopicity, increased flowability and porosity. Quartz and silica sand, expanded perlite sand, screenings from expanded clay production, fine-grained slag, etc. are often used as backfill. Dry backfill must be done on a film and leveled. As for the thickness of the backfill, this parameter is selected depending on the conditions for laying the dry floor backfill, the condition of the base, height differences, etc.
The final stage of installing a floor using dry screed technology is laying gypsum fiber board. At the same time, they can be used as stacked sheets as asbestos cement sheets, and chipboard, OSB, as well as waterproof plywood, etc. The sheets themselves are laid in one or two layers. The sheets are fastened to each other using self-tapping screws and special glue.
As a result, we get a finished floor using dry screed technology. Further manipulations with the dry screed directly depend on the coating under which the floor is being prepared. So, in the case of using linoleum coating, it is necessary to carry out the operations of puttying the seams and grinding the surface. If you choose a laminate, you will not have to subject the dry screed to any further processing.
Is it possible to finish screeding the floors in one day and begin laying the finishing coating the next day? Not so long ago it seemed unrealistic, because “wet” cement strainer requires at least 28 days for final drying. But about 15 years ago, the revolutionary technology of Knauf loose floors appeared, which changed the understanding of this process. One of the names assigned to it for this reason is “superfloor Knauf”.
Today, there is probably no person, one way or another connected with the construction industry, who has not heard about this company, which produces a variety of finishing and building materials, as well as paint and varnish products, system components suspended ceilings, hydro, heat and sound insulating materials, fasteners, various tools.
But most of all, this company is known for its plasterboard technology, perfected to the smallest detail. facing materials, being its ancestor. Founded by the two Knauf brothers in 1932 as a manufacturer of gypsum building mixtures, already in the 50s the company began producing the first plasterboard materials, soon becoming the undisputed leader of this technology. And today we can confidently say that “Knauf” and drywall are two inextricably linked concepts.
The Knauf method of bulk floors is essentially a long-known technology of semi-dry or dry prefabricated screeds, when the floors are fastened together on a substrate made of a thin layer of finely dispersed bulk material. sheet panels rough coating. The soft and seemingly loose backfill pressed by them becomes strong and hard, capable of withstanding quite large loads.
In method Knauf company Expanded clay sand is used for this very small fraction with a granule size not exceeding the standard 4 mm. After leveling the backfill according to the “beacon” rule, it is covered with sheets of gypsum fiber material. The backfill thickness should be in the range from 30 to 100 mm.
Gypsum fiber sheets (GVL) differ from plasterboard in the absence of a top paper coating and are a uniform mixture of gypsum and cellulose fibers reinforcing it. Possessing high strength and fire resistance, they are also quite environmentally friendly and chemically safe.
Structural elements of the Knauf superfloor are produced in the form of panels glued together from two GVL sheets with dimensions of 1200 × 600 × 10 mm, offset relative to each other to form folds 50 mm wide along the perimeter, along which they are fastened when laid together using adhesive mastic and self-tapping screws . The total thickness of the resulting superfloor coating is 20 mm.
If we talk about the disadvantages of Knauf technology, then there are practically none, although many here call this material “phobia of water”, but leaks and flooding can thoroughly ruin any type of flooring. Even if the consequences of such accidents do not appear immediately, after some time they will certainly make themselves felt in the form of fungus, mold and rot. But the ease of dismantling Knauf floors allows you to replace them with the least labor costs compared to other types of coatings.
Many homeowners and master installers, for reasons of economy, believe that on the upper floors of buildings and structures, laying a moisture-proof film under the base of a dry screed can be neglected. This blunder, since moisture can enter through the floor slabs from adjacent rooms. In addition, such a film also serves as a vapor barrier, protecting materials from condensation.
In the simplest method of constructive technology of dry screed discussed here, which has the designation “Alpha” in Knauf company terminology, a single-layer installation of gypsum fiber board is used, but there are other options that involve a more complex “pie” using additional layers of polystyrene foam or porous fiber acoustic and thermal insulation materials from this company.
To significantly increase the strength of the coating, you can lay a second layer of gypsum fiber board panels by changing the laying direction perpendicular to the sheets of the first layer.
Knauf superfloor technology is perfectly suited for systems so popular today warm floors. And the high thermal insulation properties of bulk floors significantly reduce the heat loss of the room through its base, which significantly increases the energy efficiency of any heating systems. We can confidently say that the cost of installing Knauf loose floors with good general thermal insulation the houses will pay for themselves within 2–3 years due to savings on heating costs.
The popular expression “A good floor is half a repair” eloquently speaks of the fact that installing a floor screed is one of the most important and critical stages of repair. The service life of the floor covering, the heat and sound insulation of the room, the arrangement of furniture, and in some cases even the possibility of using certain engineering systems depend on how this work is performed.
We understand well how important the quality of the screed is from the point of view of physical and performance characteristics. Having created the universal self-leveling floor KNAUF-Tribon, the company’s specialists took into account everything important criteria, determining its quality, reliability and availability.
The KNAUF-Tribon universal self-leveling floor is a material that significantly simplifies the screed technology. It is a dry mixture based on a mixed (complex) binder (building gypsum and Portland cement), special modifying additives and quartz sand as a filler
Indoors with dry and normal humidity conditions on load-bearing bases to create self-leveling leveling screeds 10-60 mm thick for subsequent finishing coatings.
In new construction and renovation on concrete and wooden foundations.
To increase the soundproofing properties of the ceiling and reduce the level of impact noise.
In heated floor systems
Used if there is a strong supporting base, if necessary minimum thicknesses(from 10 mm).
It is used when there are difficulties in preparing the base (poor strength, contamination, etc.).
It is used to increase the thermal insulation properties of the ceiling, as well as to reduce the level of impact noise. In addition, it allows, if necessary, to raise the floor level to the design value. As an insulating layer, it is recommended to use insulating materials based on foamed polystyrene, such as KNAUF Therm® PolPRO and KNAUF Therm® Perimeter. If there are significant differences in the load-bearing base and it is necessary to install a screed along laid communications (pipes, cables, etc.), it is recommended to use a KNAUF-Ubo screed as an insulating layer.
Used to create heated floors. The thickness of the screed is calculated based on the condition that the minimum height of the screed above the heating element is at least 35 mm. In this case, the recommended thickness of the screed should not exceed 60 mm. This will help avoid increasing energy consumption for heating the screed and reduce heat loss.
Base strength assessment
You can evaluate the strength of the base using any sharp object (for example, a nail, a screw, etc.). You need to draw four parallel lines. Then, at an angle of 45° to the first lines, draw parallel lines intersecting them (at least four). The distance between the lines should be from 1 to 1.5 cm.
Solid base– no chips at the intersection points of the lines, a clear diamond pattern, the edges of the lines without obvious nicks or damage.
Unstable foundation– the presence of chips at the points of intersection of lines, a blurry diamond pattern, the edges of the lines have frequent jagged edges and destruction.
If the supporting base is fragile, you should abandon the contact method of pouring the floor in favor of structures on a separating or insulating layer.
Before attaching the edge tape, it is necessary to prime the surface of the supporting base. For this purpose, KNAUF-Multigrund or KNAUF-Mittelgrund primer is used.
Primers must be applied in two stages:
KNAUF-Mittelgrund: dilute the primer with water in a ratio of 1:2 and apply the first layer to the surface.
KNAUF-Multigrund: apply the first coat without thinning and after drying (at least 6 hours) apply the second coat.
Along the perimeter of the room and around load-bearing elements buildings (supports, columns, etc.) it is necessary to install and secure the edge tape. It serves to reduce acoustic noise, ensures free deformation of the screed and protects against leakage of the mixture into other rooms through possible cracks at the junction of the wall and floor.
After attaching the edge tape, the apron is folded back and special KNAUF lining paper is laid. The overlap of adjacent sheets of paper must be at least 80 mm. The edges of the paper do not extend onto the wall and are adjacent to the edge tape on top of the apron.
First, polystyrene foam boards are laid on the base, after which an edge strip is attached to the upper level of the insulating layer and the apron is folded back. The lining paper is laid on top of the insulating layer and the apron. If the base is uneven and the height difference is more than 10 mm, then before laying insulating material Pre-leveling with the same KNAUF-Tribon mixture is recommended. And only after the leveling screed has dried, the insulating layer and lining paper are laid.
An edge strip is first installed around the perimeter of the room. If the base is uneven and the height difference is more than 10 mm, then before laying the insulating material and the heated floor system, preliminary leveling with a KNAUF-Tribon mixture is necessary. After the leveling layer has dried, proceed to laying the insulating layer and underfloor heating system. When laying underfloor heating systems, it is necessary to strictly follow the recommendations of the system manufacturer for its installation and fastening. In this case, the system must be tested and designed for use with this type of screed, and the methods for attaching the heating elements must ensure that they do not float up during pouring. The installed heating element system must be checked for reliability before pouring the floor.
The time for using the finished composition is 60 minutes, after which the work must be completed. If due to large sizes area and thickness of the fill, this cannot be done, then the room must be divided into zones using dividing structures and then poured one after another - an hour for each.
Treat the surface using a lath and (or) special brush For self-leveling screeds for the purpose of final leveling and removing air bubbles. When finished, remove the beacons. After 6 hours the surface can be walked on, and after 24 hours it can be loaded
At construction work or during the operation of the floor covering, flaws arise that subsequently have to be eliminated. Faced with the need to take action in case of uneven foundations, you have to consider options and look for the most acceptable ones in terms of installation method and financial capabilities. For experienced craftsmen and for beginners, we recommend the Knauf dry floor, which has some disadvantages, but they are so insignificant that this method increasingly preferred.
Modern construction market rich in materials that can cope with the problems that arise. Professional craftsmen use different methods, using new products that help correct coating defects even for a novice in the field of repair. Weather conditions do not always allow for work with liquid mixtures that require compliance temperature regime and sufficient time for the base to dry.
Increasingly, the attention of builders is attracted by the opportunity to use dry mixes as a worthy alternative, including the Knauf dry floor, which guarantees high-quality coatings in a short period of time without extra financial costs. high level. This material can be used regardless of the time of year.
To achieve flawlessly flat surface buyers choose Knauf dry flooring. This prefabricated structure from a German manufacturer is the only one in the world where wet processes are excluded. It allows you to use the coating on the second day, and not on the 28th, as with What does the base consist of?
This is a prefabricated floor made from:
Created using a dry mixture, it will last a long time only if all stages of installation are followed and carried out correctly. preparatory stage works Building materials are used in indoors with good ventilation, preventing moisture from entering the structure.
An undoubted advantage of a bulk foundation is the reduction in time spent on leveling the surface, but not every room is suitable for this option for organizing a rough covering. You should carefully consider the use of the material, because in addition to its advantages, the Knauf dry floor has disadvantages that should not be ignored. Easily absorbing moisture, the mixture becomes unusable. You need to listen to the recommendations of experts:
1. It is strictly forbidden to lay the floor in damp basements, V ground floors where there is a high level of humidity. It is not recommended to use this coating in bathrooms and toilets - this can lead to undesirable consequences, fraught with new repair work and financial costs.
2. Dry screed is appropriate in domestic premises with low traffic. Bulky massive furniture in the room is undesirable. The base in a private house, apartment, or quiet office is ideal for leveling using products from a German manufacturer.
3. Minimum height the bulk layer should not be less than 6 cm, and better - 8-10 cm. This condition is not always acceptable in a room with low ceilings. This aspect must be taken into account by the owners, because this is only the height of the rough coating, and the presence of a decorative one is also assumed.
4. If moisture gets on a dry floor, the only way out in this situation is to dismantle the coating. But the appearance of destructive mold is possible if the foundation laying technology is violated.
5. The cost of Knauf products as a bulk screed is considered a disadvantage, because for many owners it is unacceptable. But this is a controversial issue, because one should take into account the absence of dirt and a long wait until the base dries, as with “wet” work.
The correct installation of a Knauf dry floor is carried out precisely following the technology. It is worth taking a responsible approach to preparing the base for the screed floor. To do this, the old coating is dismantled and the surface is cleaned of dirt, debris, and dust. Existing cracks must be sealed cement mortar which must dry. For vapor and waterproofing, a polyethylene film is laid. Without this protective coating in the future, there is a risk of exposing the dry mixture to unwanted moisture.
It is better to lay the film overlapping, and its edges are placed on the walls to the marked level, determining the height where the floor structure ends. The overlap must be at least 20 cm. Care should be taken to securely fix the film. An edge strip is laid between the screed and the width of which corresponds to the height of the bulk layer.
Having prepared the coating, it is necessary to install beacons along which the expanded clay chips are pulled together and leveled. The slats are attached to the floor. Having made marks for the height of the future covering, a profile is installed. You can stretch the thread or fishing line at the height of the beacons. The rail is fixed along the room from the door to the window, and the fishing line is fixed across the room, from wall to wall.
We scatter the mixture in heaps, but not all of it, but only to the width of the rule that aligns the strip. The dry Knauf floor is poured and laid sequentially, in several squares, because it is necessary to cover the compacted mixture with GVL sheets so as not to walk on the leveled layer. The internal fold is pre-cut from the side adjacent to the wall.
Expanded clay sand is added in parts and immediately pulled along the beacons. When applying the second sheet, the joints are coated with glue. Installation of slabs occurs according to the principle brickwork, therefore, in the next row the number of whole sheets is determined, and the panel remaining from trimming will need to start the next strip. As you progress, the supports and profile are removed, and the resulting voids are filled up.
Dry Knauf floors do not require special professional skills when installing. Feedback from craftsmen about the design is positive, but it is necessary to follow the technology and listen to their recommendations in order to avoid mistakes.
When installing a rough foundation, Knauf dry flooring is increasingly being used, the disadvantages of which pale in comparison to its advantages noted by builders.
Owners of living space where products from a German manufacturer were used to level the base note:
· this is the most quick way eliminating differences and irregularities;
· Even a beginner can handle the installation, you just need to follow the instructions;
· communications are easily masked;
· work is carried out cleanly, without dirt and at any time of the year;
· laid floors do not creak, do not deform over time, provide coolness in summer and warmth in winter;
· tiles, carpet, laminate are laid on the created structure, parquet board or linoleum;
· the coating has excellent sound insulation properties.
To date Knauf system– the only one in the whole world where wet processes are not used. But the most main drawback concrete screed- absolutely all its types - is that you can start living in a room with such floors only on the 28th day, and not earlier. While prefabricated floors are ready for use on the second day. Like this interesting technology offered to the whole world by a German manufacturer. You can easily master it!
So, KNAUF OP 13 floors are hollow-core and easily installed dry-assembled structures intended for installation in public and residential buildings where there are:
Moreover, Knauf floors can be installed on both concrete and wooden surfaces. But they also have their own requirements for premises according to SNiPs:
Also, the Knauf superfloor is officially allowed to be installed in wet areas, like showers and bathrooms, but only with proper waterproofing. In this case, lay Knauf or Flechendichtband waterproofing tape at the junction of the floor and the walls, and cover the entire surface with waterproofing.
All prefabricated subfloors according to KNAUF technologies are divided into the following types: Alpha, Beta, Vega and Gamma. Let's take a closer look at their differences:
But remember the main thing: Knauf floors are intended for use in rooms where the temperature is not lower than 10°C and the humidity is about 60-70%.
If you are just planning to screed the floor and want to learn more about different kinds materials and methods of carrying out work, we advise you to read a short educational program on making screeds with your own hands:
Here are the main advantages of “super floor” from Knauf:
So, just one square centimeter of Knauf flooring can withstand up to 360 kg of weight. But such a coating is not allowed in a garage - heavy moving equipment can move and break the sheets.
So, first of all, let's prepare the old base. Knauf can also be installed under floor elements plumbing communications- but only before filling the expanded clay.
Before making a Knauf floor, you must carefully prepare concrete surface. So, all cracks and gaps between the slabs must be sealed with M500 cement mortar, and then the entire area must be thoroughly cleaned of debris.
If such a floor has minor unevenness up to 5 mm, then such floors must be leveled with the same corrugated cardboard. But it is better to fill local unevenness up to 20 mm with special “repair” mixtures. For example, Vetonit 4000 has proven itself well.
You need to check the level, but you don’t have a level, and you don’t want to buy an expensive tool for one-time use? We'll tell you how to make a laser level with your own hands from inexpensive and accessible parts: .
If there are even larger potholes, then it is better to fill them with fine-grained expanded clay. You can also use it to level the slope of the base, if there is one. But, if you are going to insulate the floors with polystyrene foam boards before installing a dry screed, then you need to level them with putty or a sand-cement mixture.
After preparing the floor, it is necessary to lay waterproofing layer– after all, expanded clay does not like to come into contact with humidity. Therefore, cover the prepared base with plastic film with an overlap of at least 20 cm over the adjacent strips. At the walls, the edges of the film should be at least 2 cm higher than the future prefabricated floor. This is important to ensure vapor barrier. Instead of film, you can also use corrugated or waxed paper, glassine, or the modern Svetofol vapor barrier.
For concrete base film is more suitable, but for wooden coverings– only lining paper, overlapped. If you have communications laid along the base in corrugated pipes or pipes, then also place a film under them so that there are no empty cavities left.
The expanded clay itself, which is used in the prefabricated screed, is wonderful thermal insulation material. It must be taken in a small fraction, 2-4 mm, but you cannot take backfill from a large fraction - such floors will sag.
Before laying expanded clay sand, install beacons according to laser level, after which you can use the trapezoidal rule.
It is important that the dry screed does not come into contact with the walls, and therefore a contour insulating tape 10 cm wide and 10 mm thick is also laid along the perimeter of the walls. mineral wool or polymer at least 8 mm thick. Edge tape will have to compensate for deformation expansions.
Simply pour the fill-in insulation onto the floor and level it with a lath along the beacons - as in the photo instructions. Start from the wall opposite the entrance. Expanded clay must be compacted manually.
To get a perfectly flat floor, various beacons are used when leveling. Read more about this in the analysis of all possible options for any screed: .
Let's immediately figure out how gypsum boards differ from gypsum boards. It's about about two materials that are successfully used today.
So, gypsum board is plasterboard sheet. All its edges are lined with cardboard, except for the end part. To make such a material strong enough, binders are added to the gypsum. And the cardboard itself is bonded to the gypsum thanks to special adhesive additives. It cuts and bends well. Although it is used much less frequently in prefabricated floors than other types.
But GVL is a gypsum fiber sheet, absolutely homogeneous in its composition. It is considered stronger than gypsum plasterboard and more suitable for arranging a prefabricated floor. Unlike gypsum plasterboard, gypsum plasterboard is not produced by pressing gypsum, but through reinforcement with cellulose from crushed waste paper, and with special additives. This material is stronger and more fire resistant. But gypsum board will cost you less.
The manufacturer itself currently offers only two sheet formats for prefabricated floors: EP, because floor elements measuring 1200x600x20 and small-format GVLV sheets. The first type consists of two moisture-resistant gypsum fiber sheets glued together with folds and a thickness of as much as 2 cm. But GVLV is a small-format, high-quality and environmentally friendly pure material for rooms with high requirements on sound, thermal insulation and fire safety. It is much more convenient to work with such light weight sheets, and for home use I can't think of anything better.
And - this is a new product from the KNAUF company. This material is also impregnated with a water-repellent hydrophobic substance, which protects well from steam and water. Distinctive feature such sheets - green color. Therefore, if you are making a dry screed where there is a risk of water getting in, take this material:
The good news is that the surface of such floors is absolutely suitable for everyone existing species floor coverings. You can even install a heated floor system. But it is better to put only water heated floors on GVL slabs.
There are different types of Knauf sheets along the edges - straight, PC, and folded FC. You can understand what exactly you are buying by special markings on the back side: the type of sheet, type of edge, standard and parameters are indicated.
Knauf sheets are treated with a water repellent, well sanded and impregnated from chalking. When installing such sheets, the manufacturer himself advises to place the material in advance in the room where the floor will be filled. And for convenience you can cut it. And when making a seam, be sure to chamfer the sheets - 1/3 of the sheet thickness.
Now let’s clarify in more detail how exactly they are attached GVL sheets. Thus, the first layer is laid from the doors, with a gap at the joints of no more than 1 mm. But if you use thermal insulation boards, then - from the opposite wall, with a joint offset of at least 20 cm.
Now we cover the entire first layer with adhesive. Apply glue sequentially to each sheet without skipping. In total you will need about 400g/m2.
Lay the second layer across the first one, with a gap of no more than 1 mm. It is important that the top sheets cover the cross-shaped joints of the bottom ones. Remove any glue protruding from the seams with a spatula. Each sheet of the 2nd layer is also secured as it is laid with special screws for gypsum fiber board. Use screws with anti-corrosion coating.
But please note: for gypsum plasterboard sheets there are some screws, and for gypsum board sheets - completely different ones. The latter have a double thread and a device for self-countersinking, which helps the screw to penetrate 12 mm into the sheet and not be unscrewed from there anymore due to some unexpected operating loads.
After laying the superfloor, trim off excess film and tape.
The minimum thickness of the leveling layer should be about 2 cm. And usually the floors in the room using this technology are raised by only 4-5 cm.
Check how level the floor is using a level and a two-meter control strip. In total, you need to make at least 5 such measurements.
An example of a strength test:
So why, with all the advantages of this floor design, have not all builders switched to it? Because there are often rumors that such a floor sagged, sagged and generally collapsed after a couple of years. Like, it’s all about the central vibration-impact load, while there is almost none near the walls. And supposedly then a noticeable “swelling” appears, because expanded clay is like bulk material Over time it will still be compacted.
But even those who have been professionally involved in prefabricated floors for quite a long time still do not recommend laying on prefabricated floors ceramic tiles or install a heavy cast iron bathtub. But, at the same time, such people categorically do not accept the comparison of Knauf floors with a conventional screed - the former should be used where appropriate, and ordinary concrete they will not be replaced with all their advantages in strength.
In addition, if there were no technological violations during the laying of Knauf floors, then neither sagging nor coiling will occur even after twenty years. Here, for example, is a rather subtle point: if you use expanded clay backfill of the wrong calibration, then, of course, subsidence can occur. That’s why stories about someone’s Knauf floors sagging somewhere are just evidence of that the laying technology was violated. After all, expanded clay, like any bulk base, must not just be thrown in with a shovel, but compacted and compacted, just as sand is compacted when pouring a foundation.
