Ceramsite screed: how it is done

For insulation of floors, especially on the ground floors (above the basement), or in situations where the floor is generally located practically on the ground, it is often done claydite-concrete screed with their own hands for thermal insulation. However, there are other, more powerful insulation, for example, the same extruded polystyrene foam, but its cost is too high compared to expanded clay, therefore, most often resort to the budget and, moreover, very convenient option.

Below we will talk with you about how this is applied in practice, and as a supplement we will watch a video in this article on the same topic.

Strainer из керамзитобетона в процессе производства

How it's done

What is claydite

Different fractions of expanded clay
  • Expanded clay is obtained by firing clay or shale, producing light porous building material, which may be in the form of crushed stone, but more often it is oval granules, which can range from 350kg / m3 up to 600kg / m3. Керамзитовый песок с фракцией до 5 мм имеет самую высокую объёмную массу - up to 600kg / m3, fraction from 5 mm to 10 mm - 450kg / m3, from 10 mm to 20 mm - 400 kg / m3 and from 20 mm to 40 mm - 350 kg / m3.
  • It should be noted that this material with very high density has excellent thermal insulation and noise absorbing qualities, has excellent frost resistance, is refractory, and its price is the lowest among all possible thermal insulators for the floor. In this situation, it can be used both as a bedding and as a filler for expanded clay.

  Note. It should be noted that the claydite absorbs water very quickly, but gives it away for a long time, so the instruction recommends storing it in a dry, covered place where water does not flow. The moisture content of the material will further affect the amount of water added to the solution.


Ground planning

In order to pour a layer of concrete screed with expanded clay, we need a smooth base, and if this is a RC floor slab, then we can say that the preparation has already been done before us, but most often such fillings are made on the ground.

That is why, before we do floor screed, we will have to lay out the base - there is no need for a mirror surface at all, but just a flat platform, onto which sand and rubble can be filled. But after planning, the ground should be compacted compulsorily, and if there are indentations, then fill them in so that the pillow lies evenly.

Now about the pillow - in this case, you will need sand with rubble or the same expanded clay, but if we are talking about lightweight concrete for warming, then, of course, it would be more logical if clay as well, but not rubble or gravel.

Now about the cut-off waterproofing - some recommend laying it on top of the pillow, but judge for yourself, the wet bedding holds the cold very well, so it’s better to cut the bed from the ground, not just the screed.

  • Consequently, we will get this kind of cake - on the ground (if it is stony, then it needs to be leveled with sand so as not to damage the waterproofing) the film is laid (vapor permeable or just dense cellophane, roofing material in two layers).
  • Then a layer of sand is not less than 20-30 mm thick, and then a layer of expanded clay (crushed stone), which also should not be less than 30-50 mm. The last layer can be poured at least a meter high - with this level you have to level the rough base, on which, actually, the concrete screed with a specific size of expanded clay will be poured.
The minimum thickness of lightweight aggregate is determined by beacons
  • Right above the backfill, beacons are mounted, but sometimes, to give the solution greater strength, a plaster net is laid on the floor, as in the top photo, or the sheathing is simply made from pieces of reinforcement, wire, and sometimes even from wooden slats..

Of course, the minimum layer thickness will also depend on the fraction size, but for the smallest (5-10 mm) or even for sand, the pouring thickness is not recommended to be less than 30 mm, but this, as an extreme option, is better to stick to a minimum of 40-50 mm .

The proportions of claydite for screed depend on its fraction

Прежде чем приступить к изготовлению раствора, следует определить пропорции стяжки из керамзитобетона, но здесь точные цифры сказать затруднительно - всё зависит от предстоящей нагрузки и от величины фракции (см.также статью «Утепление дома из газобетона: практические советы по оптимальному монтажу»).

Но, тем не менее, определиться как-то нужно, поэтому, здесь можно ориентироваться по общепринятым соотношениям для жилых зданий - 1/3/4, то есть, на одну часть cementа М400 пойдёт 3 части песка и 4 части керамзита.

The proportions of lightweight aggregate can be determined by other ratios - at 30 kg of the finished solution (1cement/3cement M400) add 25 kg of expanded clay of the middle fraction. It is important to achieve a normal consistency of the solution, since the thick mixture is poorly smoothed by the rule, and in a rare mixture - expanded clay floats up and it is almost impossible to make a mirror.

It is impossible to say how much water you will need for the best consistency, as this will depend on the humidity of the sand and expanded clay.

Excess concrete is cut off by the rule.

Если с консистенцией у вас всё в порядке, то когда вы будете стягивать раствор по маякам правилом, то у вас будет получаться почти зеркальная поверхность и кусочков керамзита практически не будет заметно (читайте также статью «Грунтовка для бетона - виды, особенности, правила применения»).

Просто cementно0песочный раствор будет обтягивать их, как плёнкой, так что вам останется просто затереть стяжку на следующий день тёркой или полутёром, исправив возможные погрешности.

Note. It should be noted that cutting of reinforced concrete with diamond circles (reinforced claydite) and diamond drilling of holes in concrete is performed on a level with heavy concrete, since claydite is a fairly dense material.


The entire consumption of materials for the lightweight aggregate will depend on the thickness of the layer itself, as well as the height of the pillow poured under it. It is quite easy to count each component separately - for this you just need to calculate the fill volume and then divide the resulting cubic meters by the amount of material provided for 1m3.

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