Roof insulation with expanded clay

Roof insulation

Roof insulation; how to use expanded clay? Use expanded clay for roof insulation, its properties, advantages and disadvantages, and various types of roof insulation technology. Roof insulation with expanded clay is the home’s oldest and most commonly used thermal insulation method. Life’s comfort depends on the roof’s reliability, and this material helps to ensure this reliability for a long time. Today we will tell you how to use expanded clay for roofing.

Properties of roof insulation with expanded clay

Expanded clay is a porous insulating material of dark brown color, obtained by firing clay for 30-45 minutes at a temperature of +1200 degrees. The raw material is crushed and placed in a special oven that can rotate at a certain speed. By moving in it, the clay sticks together in crumbs, and the rotation of the kiln gives them a rounded shape. The size of the grains and their quality are controlled by the speed of course of the device and the temperature of the hot air in it.

The production process results in environmentally friendly, fireproof, frost-resistant bulk insulation with excellent thermal and acoustic properties. It is of three types:

  • Expanded clay gravel … The particles have a smooth oval shape and a size of 5 to 40 mm. The material is used to insulate foundations and close structures with a required thickness of insulative fill more significant than 50 mm.
  • Expanded clay crushed stone … It has a rectangular shape with sharp corners, is obtained by crushing a piece of sintered clay, and is used as a heater.
  • Expanded clay sand … The size of the grains is between 14-50 mm. It makes it possible to perform insulating filling with a thickness of less than 50-60 mm. The sand can be used as a filler for mortar.

Because sand weighs a lot and crushed stone has unpleasant jagged edges, gravel is more suitable for thermal insulation of the roof. They can fill all cavities and create a reliable insulating layer. To insulate ceilings, you can use expanded clay with several fragments simultaneously and add foam crumb to enhance the effect.

In terms of thermal insulation properties, a layer of expanded clay 10 cm thick is comparable to a 250 mm wooden beam or a meter-long masonry. Can achieve the maximum effect of insulation with a layer of expanded clay 15 cm wide. In addition, this method of saving heat is three times more economical than using wood and brick – 10 times. It does not require special skills from the performer; it can use to insulate the roof cheaply, quickly, and efficiently.

Expanded clay insulation for the roof is used only in the form of a dry loose layer of a certain thickness. Adding aggregate to concrete or cement concrete has no particular effect. Because expanded clay is open, its use is best on flat roofs or with up to a 5% slope.

The quality of roof insulation made with expanded clay depends on suitable materials, including waterproofing, roof slope, and structure under load calculation.

Advantages and disadvantages of roof insulation with expanded clay

Since expanded clay is built on a natural foundation, it competes in many ways with synthetic insulation. The structure of expanded clay must not be disturbed by temperature drop, moisture, or decay.

In addition, roof insulation with this material has several other advantages:

  • Bulk insulation does not require connection and fixing.
  • The roof, insulated with expanded clay, does not emit harmful fumes into space.
  • It is highly inedible to living creatures.
  • Expanded clay, a refractory material, cannot become a source of fire on the roof.
  • The amount of insulation increases the thermal and acoustic properties of the upper floor of the building. Heating with high-quality expanded clay with thermal conductivity of 0.07-0.16 W / m reduces heat loss by 70-80%.

The disadvantage of expanded clay insulation can be called a significant load of the material on the roof, despite the low weight of the porous grains. After all, the mass of the backfill layer with a thickness of 100-400 mm is very significant. Another disadvantage of insulation is excessive moisture absorption. Soaking material loses its quality. Therefore, when insulating the roof with expanded clay, a protective waterproof film should be laid on it.

Roof insulation technology with expanded clay

Since all roof insulation is done outside, weather conditions have some limitations. For example, carrying out the technological process in atmospheric precipitation is unacceptable to avoid wetting the expanded clay. Therefore, it is necessary to keep the waterproofing of the roll ready before starting work. In addition, in the future, you will need a bucket and a shovel, a vapor barrier membrane and a sharp knife, a rule for leveling the backfill, and a rammer to compact it.

Preparation for work

The roof needs to be repaired for insulation if it is old. From a smooth concrete surface, it is enough to remove the peeled insulation, remove debris, seal holes and cracks revealed during inspection with a cement mixture, and fill in a new abrasive if necessary. With a wooden roof, the situation is more complicated. In addition to reviewing and replacing its structural elements, you should pay attention to the strength of the roof structure, as the weight of the insulation can make it impossible to use. In any case, a calculation is required here.

If the roof is not strong enough, it can be strengthened using a beam or pole of a more extensive section, other posts, and crossbars. In addition, it is necessary to support the elements of the inner roofing on additional rods connected to the rafters with bolted fasteners. After you have ascertained the strength of all the main structural components of the roof, you can proceed to its insulation.

Roof insulation
Roof insulation

Thermal insulation of a flat roof.

The horizontal plan of the upper floor allows you to realize all the advantages of insulation in bulk without unnecessary problems. The proposed roofing cake with expanded clay should have several alternately stacked layers.

The first is a vapor barrier that can be applied to the prepared surface in two layers for strength. It will protect the insulation from moisture coming from the room under the roof. This material can be a membrane or polyethylene film, which should stretch the sheets during installation and overlap by 10-15 cm. The joints of the sheets must be glued with double-sided tape. If the foundation is concrete, a vapor barrier is not required.

After the substrate is installed, you can fill the insulation again. It will be correct if the calculation of its thickness for the weather conditions of a particular area is carried out in advance. It is simple and is determined by the formula: P = R * k, where k = 0.16 W / m (thermal conductivity coefficient of expanded clay), and R is the thermal resistance of the structure, which can find in SNiP.

But usually, the thickness of the filling is determined approximately in the range of 25 to 40 cm. Suppose it is not enough after winter. In that case, it will be possible to carry out additional insulation of the air inside with rock wool or foam boards. When the roof is filled with expanded clay, do not forget the permissible load the structure can withstand. The choice of the “golden mean” in this case is critical.

Expanded clay laid on the roof must be leveled with a rule and then compacted to reduce voids between the grains of the material. Packing the fill using an electric vibrator on the platform is convenient, or manually rolling the surface with a log.

Then, to move to the roof for maintenance purposes, the insulation needs to be protected with a cement-sand coat. By performing grinding on the top covered with expanded clay, it must be reinforced with a metal mesh.

The final stage of work is a tool for rolling waterproofing in 1-2 layers. Roofing or similar material must be glued to the dried deformation using a gas burner for work. Installation of such insulation is done gradually as the rolls are rolled out. To give the roof an aesthetic appearance, it is recommended to decorate it with a coating. Can paint it on profiled sheets, shingles, and even lawn, which can sow on a prepared layer of black soil.

Heated insulation on the roof

It is more difficult to insulate a pitched roof with expanded clay. The main thing here is to achieve an even distribution of the insulation layer in the cavity between the rafters. If the roof slope is more than 5 °, then must fill this space according to the internal filling of frame walls in small doses with seam structures level by level.

For the expanded clay grains not to roll down the slope, the cavities between the roof supporting beams must be separated by joists. Then the cells filled alternately with insulation should be closed with tapes from the outside.

After you have filled all the free space between the rafters of the crate, you need to fix a waterproofing film and install the roof covering. From inside the attic, vapor barrier material should be attached to the inner lining of the roof slopes. Overlapping panels must fix all insulation with joint sealing with tape.


In short, it should say that although work is not entirely comfortable, it is pretty versatile. Its simple laying technology makes it possible to carry out thermal insulation on flat roofs and pitched roofs with expanded clay with equal success.

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