When screeding, you can not only perfectly level the surface, but also improve the heat and sound insulation properties of the coating. One of the options for such an integrated approach can be leveling the floor using expanded clay. Due to its low cost, simple technology of application and high operational characteristics, this material is in demand by developers and owners of new apartments.
Pros and cons of expanded clay for screed
Expanded clay used as insulation and soundproofing is oval granules from 1 to 20 mm in size. Expanded clay stones of a larger size, before use for insulation, are subject to grinding in special mill drums. Like any building material, expanded clay has a number of advantages and certain disadvantages. TO positive qualities of expanded clay should include:
- high mechanical strength of the granules, allowing the use of this bulk material as the main filler of concrete mixtures;
- low thermal conductivity and ability to absorb sound vibrations;
- chemical inertness and resistance to acid and alkaline conditions;
- low specific gravity;
- frost resistance;
- incombustibility;
- affordable cost;
- the ability to do dry or expanded clay concrete floor screed with your own hands.
Rodents, insects do not settle in this building material, mold and fungus do not start.
At the same time, it is impossible not to say about such significant shortcomings as the ability to absorb moisture and the ascent to the surface of the concrete mixture with an increased water content in its composition. The latter factor leads to the formation of a corrugated surface. As a result, it is necessary to level it with an additional layer of cement mortar or to perform mechanical grinding of the surface.
In which cases it is recommended to use expanded clay
The device screed floor with expanded clay is not always appropriate. Moreover, there are options when the use of this material is impossible according to the technical conditions of the work. However, its use will be effective in case of:
- creating a support pillow on the ground in the absence of a cellar and basement;
- the need to compensate for the large difference in height on the floor surface and reduce material costs for the acquisition of materials;
- weak overlap or wooden boards as a basis;
- hidden laying of utility networks or underfloor heating in the screed layer.
The use of expanded clay, first of all, allows to provide a variant of the screed device with the lowest possible costs of insulation, sound insulation and the creation of a layer of large thickness.
Types of screeds using expanded clay and their features
When leveling and warming floors, apply three technologies for screeding with expanded clay:
- wet filling with expanded clay concrete;
- dry screed;
- combined (semi-dry) version with the device of a filling layer.
Each method has the pros and cons of floor screed with expanded clay. The choice depends on the specific conditions and condition of the surface to be coated.
Wet screed
Monolithic filling of floors with expanded clay concrete is used only in the most extreme cases, when the creation of a bulk layer of insulation or the use of a dry screed will be impossible for any important reasons. Preparation of concrete mix is performed in the following sequence:
- initially expanded clay granules must be poured into a tray and filled with water to soak;
- to knead the working mixture, load cement, sand and expanded clay into a concrete mixer in a ratio of 1: 3: 4;
- install beacons from the metal profile on the floor surface at a distance from each other of 1.2-1.5 meters;
- leveling the layer when pouring concrete, make the plaster rule or a flat metal rail;
- during the setting period of the concrete mixture, the surface must be periodically moistened with water to avoid cracking.
If floating granules will be visible on top of the floor, then after concrete has hardened, they must be sanded or additional floors should be poured with a thin layer of a self-leveling mixture.
Dry screed
This is the simplest and most effective technology for screed using expanded clay. Insulation granules are simply poured onto the floor and leveled. After that, fiberboard, plywood or gypsum plaster sheets are laid on the backfill and poured with a mortar of a mixture of sand and cement with the addition of plasticizer or liquid soap.
The thickness of the poured dry expanded clay layer is equal to the difference in which 25 mm of the cement mortar layer and the thickness of the sheet material should be taken away from the total thickness of the screed. This method is quite accessible even to a novice builder.
Combined method
This technology resembles a dry floor screed, but without the use of sheet materials for intermediate coatings. The dry method allows you to significantly reduce the cost of financial expenses, but requires certain construction skills and work experience.
Its essence lies in the fact that the surface of the bulk expanded clay layer is leveled, but not covered with sheets, but spilled with cement "milk" - a liquid mixture of cement and sand in a ratio of 1: 2.
After setting pouring, expanded clay 2-4 cm forms a solid layer, which allows final alignment with ordinary mortar on beacons. Instead of a cement mixture, it is allowed to fill with sand concrete if its thickness is 30-50 mm.
Expanded clay requirements for screed
Concrete mix, dry backfill or material for combined technology can be any fraction. However, it should be understood that small granules or crushed expanded clay will provide a denser filling and better thermal insulation. Therefore, the solution to the question of which expanded clay to use for screeding depends on the tasks that you want to solve by leveling and warming the floors.
By the size of the fractions, expanded clay is divided into:
- expanded clay sand with particles up to 5 mm;
- sand and gravel mixture up to 10 mm;
- crushed stone with granules of 5-10 mm;
- gravel of two categories 10-20 and 20-40 mm.
In addition, what fraction of expanded clay is needed for screed, you need to consider the category of bulk density in the range of 450-600 kg / m3 and a strength grade from P75 to P125 MPa according to the results of mechanical pressure tests.
Determining the amount of expanded clay for screed
Calculation of the required material depends on the accepted technology of the work, the size of the granules, the requirements for the strength of the coating and the brand of cement used. The brand of expanded clay is determined by the volume ratio of cement M400, sand and expanded clay, which should be:
- for concrete M150 - 1.0: 3.2: 5.0;
- M200 - 1.0: 2.5: 4.2;
- M250 - 1.0: 1.9: 3.4;
- M300 - 1.0: 1.7: 3.2;
- M400 - 1.0: 1.1: 2.4.
To determine how much expanded clay is needed for a dry screed, simply calculate the volume of the bulk layer and multiply its thickness by the area of the room.
In the presence of elevations, you can take the average between the minimum and maximum values or summarize several volumes in individual sections.
When preparing a mortar or concrete mixture with expanded clay as one of the fillers, it is necessary to take into account the brand of insulation in bulk density from M250 to M800 kg / m3. At the minimum value, the test strength of the hardened layer will be at least 0.6 MPa, and at the maximum - more than 4.5 MPa.
Tools and equipment for work
Work on the installation of floor screed using expanded clay is carried out in several stages. Each of them will require a howling set of construction tools and equipment.
To prepare the base for laying layers, you must have:
- hammer drill or hammer drill;
- a shovel or a large scoop;
- construction mixer;
- buckets and spatula.
In addition to this, the installation of beacons will be required;
- durable cord or matte fishing line;
- bubble, hydraulic or laser level;
- plaster rule and tape measure;
- construction trowel;
- pencil or marker;
- grinder for cutting profile.
When performing a dry screed, additionally prepare a screwdriver and a sheet cutting tool. For the preparation of expanded clay concrete, a concrete mixer for a batch, shovel and bayonet shovel will also be required. In the case of combined technology, the possibility of working with a reinforcing mesh should be considered.
Preparatory work
The quality of the base surface for the installation of expanded clay screed directly depends on its quality, strength and durability.
A full range of preparatory work may include the following steps:
- cleaning of garbage and the remains of old materials;
- hydraulic and thermal isolation device;
- installation of beacons;
- fixing the damper tape around the perimeter of the walls.
After garbage collection, it is necessary to fix weak boards on wooden floors and replace rotten ones. Level and compact the soil in the absence of an old coating. In concrete floors, fill holes and large cracks with cement mortar and only then proceed to the next stage of work.
Hydraulic isolation and additional insulation
Due to the hydrophobic properties of expanded clay, a waterproofing device is a prerequisite for any screed technology. A waterproofing layer of rolled material can be laid under a expanded clay layer, on top of it or simultaneously on both sides.
As insulation, roofing material, hydroisol, liquid rubber or bituminous soils are used. The choice of material depends on the requirements for moisture protection and financial capabilities.
It is recommended to use additional thermal insulation for rooms on the ground floor or when performing expanded clay screed on the ground. Insulation of the floor will reduce heat loss and will save you money on heating your home. The best materials for this purpose are sheet foams and polystyrene foam. Their use simplifies the execution of work and provides effective protection.
Installing beacons and attaching damping tape
The presence of correctly installed beacons greatly simplifies the process of leveling the screed to obtain a perfectly flat horizontal surface. When doing this work:
- By measuring, the design level of the floor is determined, which is applied as a solid line to the wall;
- depending on the width of the poured strips, the required number of beacons is calculated;
- the profile rails are fixed in the required position.
The process of installing beacons when installing a screed is described here.
With a dry screed, the beacons after the start of the setting of the mortar should be removed, in other cases they can remain inside the filled layer.
The damper tape is fixed in such a way that a strip of 15-20 mm peeks out above the field level. It is necessary to compensate for the temperature expansion of the bulk layer and to prevent the formation of cracks.
Detailed instructions for determining the zero floor level are presented here.
Device instruction
Combined screed with expanded clay As mentioned above, this technology provides for a dry layer of bulk material at the bottom and wet cement pouring at the top. The device of a semi-dry floor screed with expanded clay with your own hands must be performed in the following order:cover a clean prepared surface with roll waterproofing or cover with a layer of bitumen soil;fill in a layer of expanded clay with a fraction size of 5-20 mm, 30-40 mm below the future level of screed;tamp the bulk material well and level with the rule;make cement milk and spill the surface with it;after setting, which will occur in a day, install beacons on the frozen surface that correspond to the level of screed;prepare a cement mortar in the ratio with sand 1: 3 or 1: 4;pour the solution between the beacons in strips and level it with the plaster rule;the top layer of the screed must be punctured with a thin rod with a pitch between the holes of not more than 100 mm;over the next two days, the surface must be periodically wetted with water.The full readiness of the screed is determined at the rate of 5-7 days for each centimeter of the cement layer. After that, you can proceed to laying the finishing flooring.Wet screeds with expanded clay
“Wet” screed - filling the base with expanded clay concrete followed by leveling the surface. The concrete layer is laid in the following sequence:
- pour dry expanded clay into a tray or other container and fill it with water for 10-12 hours to soak;
- install beacons on the base surface that will determine the horizontal level of the future floor;
- pour wet expanded clay (4 parts) into the concrete mixer, then add some water and cement (1 part);
- after a short stirring, pour sand (3 parts). The mixing time of the mixture until ready - at least 4 minutes. If necessary, add water during the mixing process (requires constant sour cream);
- to level the surface, use the plaster rule, which must be pulled along the beacons with transverse movements of the tool.
If surfaced granules of expanded clay are visible after setting the screed, they must be sanded with a power tool. With a large number of such granules, an additional layer of self-leveling mixture will have to be laid on top. The full drying period is 28 days.
Dry couplers with expanded clay
To install a dry screed, it is necessary to purchase expanded clay small fractions or crushed granules, sheet material such as chipboard or plywood, sand, cement and plasticizer. The order of work is as follows:
- fill the surface of the base with dry expanded clay and level the surface with a flat rail. When laying a building bubble level on a rail, periodically check the horizontal level of the layer;
- remove the beacons;
- lay sheet material on expanded clay so that it covers the entire surface;
- check the horizontal position of the sheets with a level;
- cover the second row of sheet material in the same way. The only thing that needs to be foreseen is the shift of the seams of the second layer relative to the first should not be less than 20 cm.
After that, you can start laying the finish coating.
Visually and in more detail about the device expanded clay screed can be seen in the video presented.