Dry Screed Floor With Sheets On Expanded Clay, Technology And Installation Rules

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Video: Dry Screed Floor With Sheets On Expanded Clay, Technology And Installation Rules

Video: Dry Screed Floor With Sheets On Expanded Clay, Technology And Installation Rules
Video: How to floor screed with sand and cement - Beginners guide- plastering Guru 2023, September
Dry Screed Floor With Sheets On Expanded Clay, Technology And Installation Rules
Dry Screed Floor With Sheets On Expanded Clay, Technology And Installation Rules
  • Varieties of floor screeds and their features
  • Tools and materials
  • Dry screed technology
  • Preparatory stage of work
  • Markup
  • Expanded clay insulation device
  • Leveling the surface of the insulation
  • Installation of GVL plates from Knauf
  • Positive and negative qualities of dry screed
  • Cost of dry screed Knauf
  • Dry floor videos

Recently, the construction industry has undergone significant changes. New materials and advanced technologies have appeared. This also affected the performance of flooring works. Since 2000, such technology as a dry floor screed from the German company Knauf has come to the market of the CIS countries. It is now widely used in multi-storey residential buildings, cottage-type houses and in various office establishments. The main advantage of the dry screed GVL floor is the speed of installation. It can be installed in one day and is immediately ready for use, unlike cement screed, which takes 28 days to fully cure. Also, an important point is the complete absence of water during installation and rather low dust formation.

Varieties of floor screeds and their features

During construction or renovation, an important element is the provision of a durable sub-surface of the screed, on which a decorative covering such as laminate, parquet, linoleum or ceramic floor tiles will then be laid. Today there are several types of screeds. It is a classic cement or concrete screed and is applied wet. There is also a semi-dry screed using a minimum amount of water. There is a so-called self-leveling floor, which serves to level the surface of the subfloor. And finally, such a type as a dry screed, which is mounted from GVL boards on a layer of expanded clay backfill without using water.

advantages of dry screed
advantages of dry screed

Tools and materials

For the high-quality performance of work on the installation of bulk from expanded clay and gvl sheets, you will need the necessary set of tools:

  • tape measure and marker;
  • laser level;
  • normal building quality level;
  • puncher;
  • screwdriver with nozzles;
  • jigsaw;
  • drywall knife;
  • square or metal ruler;
  • roughing plane for edges;
  • construction stapler;
  • guides for beacons made of aluminum or galvanized profiles;
  • rule or leveling rod;
  • bucket and shovel;
  • vacuum cleaner;

For the installation of a dry floor from gvl, materials will be needed that must be purchased in advance and delivered to the site. For the screed you will need:

  • 80 micron polyethylene film for vapor barrier;
  • edging tape 100 mm wide;
  • PVA glue;
  • self-tapping screws for drywall 19 mm long;
  • Expanded clay backfill Kompavit with granule sizes 1-4 mm;
  • sheets of dry screed Knauf;
  • putty Knauf

The amount of material required is calculated based on the floor area of the room and the thickness of the backfill. Everyone can easily perform all these calculations for his apartment himself, knowing the length and width of the rooms and the corridor. It is worth noting that the material must be purchased with a small margin, based on the fact that during the installation process there will be necessary trimming of the plates and the thickness of the screed at different points may differ.

Dry screed technology

Knauf's screed flooring technology is quite simple, but even it requires sufficient experience and skills. Therefore, in order to do the job quickly, efficiently and not spoil expensive material, it is better to contact qualified specialists. The coordinates of such craftsmen can always be found in building supermarkets or on specialized sites, where you can also find customer reviews.

The whole process of installing a dry screed can be conditionally divided into several stages:

  • preparatory stage;
  • markup;
  • vapor barrier device;
  • expanded clay backfill device;
  • installation of sheets of dry screed knauf.

Let's consider in more detail each stage separately.

Preparatory stage of work

Before starting work on the screed, it is necessary to disassemble the old existing floor covering - it can be parquet, wooden floor, old tiles. If it is an overlap, it is necessary to seal large dents and holes with mortar or putty. After the solution has dried, it is necessary to vacuum the floor surface, remove all construction debris, in some cases it is necessary to prime the surface. By this time, all materials must be purchased and delivered to the site. After that, you can proceed to the vapor barrier device.


Before the installation of a loose screed, it is first necessary to measure all rooms using a laser level, applying horizontal plane marks to all walls of the rooms. At the same time, it will be easy to determine the difference in basement levels in different rooms. Usually it does not happen more than two or three cm. However, if a significant difference in elevation is found, then this must be taken into account when filling a layer of insulation from expanded clay sand. After measurements of all rooms, it is possible to finally determine the thickness of the backfill and, therefore, with its amount in each room or room.

floor markings
floor markings

Expanded clay insulation device

After completing all the preparatory operations, proceed to the installation of a vapor barrier made of polyethylene film. For this, a film with a thickness of 80 microns is used. Lay in such a way that the film overlaps the walls by 10 cm. When using a film smaller than the area of the room, it is laid with an overlap of 150 mm and all joints are glued with tape. The vapor barrier will not allow moisture to penetrate the floor and damage the structure of the dry screed. All work must be performed at a temperature not lower than 10 degrees Celsius and a substrate humidity of not more than 65%. After installing the vapor barrier around the perimeter of the room, an edge tape 100 mm wide is attached to the walls. It can be secured with a construction stapler.

The next stage is the installation of expanded clay insulation. The best example for this is the Compavit prefabricated floor dry backfill, which has been certified by Knauf. Until recently, it was the only backfill that met all the requirements. However, other backfills have now begun to be produced, including Knauf's backfill. Expanded clay insulation Compevit is characterized by high quality in terms of granulation composition, as well as the absence of dust, which is a very important indicator when working in residential premises. The thickness of the insulation layer can be from 20 to 100 mm. Usually this is determined at the very beginning and by this thickness and by area the volume of purchased material is calculated.

After the device of the vapor barrier and the installation of the edging tape, they begin to fill in dry expanded clay for prefabricated floors, while approximately determining how much should be filled in a particular room. Next, it is necessary to compact and level the surface of the insulation, while ensuring the required thickness.

expanded clay backfill for dry screed
expanded clay backfill for dry screed

Leveling the surface of the insulation

Leveling the surface is carried out using two beacon guides and one leveling rail. The guides are laid parallel to each other on the width of the leveling rail. The guides are installed on a layer of expanded clay, and the installation level is checked along the entire length using a laser level. In this case, the installation accuracy should be as high as possible. After the guides are exposed, expanded clay backfill is poured between them. With the help of a leveling rail or a rule, the level of expanded clay is leveled under the level of the guides. In this case, if necessary, add the missing or remove the excess expanded clay. After the strip between the guides is aligned, they are rearranged further and the process is repeated. The result should be a flat surface of the insulation.

Guide for the arrangement of gvl floors
Guide for the arrangement of gvl floors

Installation of GVL plates from Knauf

The next stage is the direct laying of dry screed plates. Sizes of sheets of gvl for dry floors are: 1500x800x12.5 mm; 1200x600x20 mm; 2500х1200х12 mm, there are other sizes. Usually GVL boards are made by gluing together two gypsum fiber boards. Installation of slabs usually begins from the doorway from left to right. In the first slab, adjacent to the wall, cut out the extreme joining quarter with a jigsaw. The second plate is laid on the first one after the docking quarter is coated with PVA glue. The third and fourth are laid in the same way. All sides that are adjacent to the walls are trimmed from the docking quarters. The last slab in the first row is cut to fit the remaining size. The second row starts with the trimmed tiles left over from the first row. In this way, maximum savings are achieved, and the seams of adjacent rows are offset by at least 250 mm. After laying three rows, all connecting joints are fastened with self-tapping screws using a screwdriver with a pitch of about 300 mm.

gvl floor screwing
gvl floor screwing

Self-tapping screws are screwed strictly vertically with a slight recession of the cap by about 1 mm. If the self-tapping screw has entered obliquely, it must be unscrewed and a new one must be screwed in next to it.

After all the plates are laid and fixed with self-tapping screws, dust and debris are removed with a vacuum cleaner. Depending on the type of finishing decorative coating such as linoleum or carpet, all joints and recesses from self-tapping screws are sealed with Knauf putty. After that, it is advisable to let the dry screed stand for about a day and you can start to clean the floor. You can use a knife to cut off the protruding edges of the plastic wrap and edging around the room.

Positive and negative qualities of dry screed

The Knauf dry screed has become very popular due to its obvious advantages, which include the following:

  • the screed is laid without water in an absolutely dry way, which allows it to be carried out in residential buildings without fear of leakage to the lower floors;
  • the speed on the device of the knauf bulk floor is the highest in comparison with other types of screeds;
  • after installing the dry screed, you can start laying the decorative floor covering, almost immediately;
  • the weight of a dry floor screed from gvl is much less than a similar cement screed;
  • work on the device of a dry floor from gvl can be performed at any time of the year;
  • knauf bulk floor has high heat-insulating and sound-insulating characteristics;
  • the design of the dry screed allows you to hide various utilities and floor heating elements;
  • Considering that laying a knauf bulk floor does not require special qualifications, all work can be performed by anyone who knows how to use a power tool.

Despite the large number of advantages, knauf bulk floor has disadvantages that can be found among customer reviews:

  • dry prefabricated knauf floors do not like moisture very much, and can deform in case of flooding, this applies to the corridor next to the bathroom;
  • it is not recommended to arrange such a floor in damp rooms, bathroom, toilet;
  • a high-quality gvl plate is expensive, so such a screed cannot be called cheap;
  • if the screed is arranged in low rooms, then structurally it steals up to 100 mm of the height of the room.

Cost of dry screed Knauf

The cost of Knauf bulk floor is determined by counting the amount of materials taking into account their price, and the cost of the work is added. The price of a screed with a thickness of about 80 mm will be approximately $ 15-16 per square meter. Of these, $ 9-10 is the cost of materials, the rest is the salary of hired workers. Now, to calculate the cost of materials on the sites there are built-in calculators by which it is easy to determine the total cost of the entire screed. Approximate price for materials:

  • the cost of GVL boards is about $ 3.3-3.5 / m2;
  • bag of expanded clay backfill $ 14.5 with a bag weight of 24 kg;
  • polyethylene film $ 0.2 per lin. m;
  • $ 1.9 edging tape per 20m roll;
  • self-tapping screws $ 1.8 per package.

In the event that all work is carried out independently, the cost of the screed is determined only by the cost of materials.

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