Plaster for aerated concrete - the choice of solution.

Cellular types of concrete are now very popular. It is caused by the fact that this building material is almost twice as light as a traditional brick or cinder block, due to which there is no need to build a strong foundation. In addition, this material has high performance. But the wrong plaster of the house of aerated concrete, can negate all these qualities. Therefore, finishing work should be given special attention.

What is the difference between cellular concrete?

Cellular concretes, this is a product of new building technologies, initially they were developed as insulation materials, but over time they became the main ones.

The block does not include crushed stone, this explains their lightness.

• The production technology is based on the principle of yeast dough.. In addition to the traditional components and special additives in the composition of such concretes necessarily includes baking powder. In particular, aluminum powder is used for aerated concrete. Having risen, such a composition freezes and is subsequently cut into blocks of regular shape.
• Visually, foam and aerated concrete are almost the same, but their similarity ends there.. The surface of aerated concrete is vapor-permeable, speaking easier breathing, thanks to this quality it is valued. But there is a significant minus, aerated strongly absorbs moisture. Therefore, aerated concrete plaster has its own subtleties.

Tip: to distinguish the gas block from the foam block, it is enough to immerse a piece of material in water. The foam block, unlike the gas block will remain dry.

Subtleties plastering

The first and biggest mistake in the construction of aerated concrete houses with their own hands is the use of traditional cement-sand mixtures. As is well known in the usual cement mortar a large percentage of water, and aerated concrete is afraid of high humidity. As a result, the blocks get wet and lose their characteristics by at least 50%.

Tip: both laying and plaster on aerated concrete should be made in the warm season, optimally from late spring to early fall. In private construction it is quite realistic, since the buildings of cellular blocks are built quickly.

The choice of plaster

As mentioned earlier, gas blocks are taken because of their vapor permeability, Hence the first rule, plaster for aerated concrete blocks must also be vapor permeable. Otherwise, you can lock the moisture inside the wall, as a result, after a couple of seasons the house will become damp and cold. (See also the article Heater for concrete: features.)

Experts recommend choosing from 3 main types: mineral, silicate or silicone plaster.

1. Mineral compositions are based on the use of conventional cement, but instead of sand, mineral aggregate acts as a filler. Plus, to improve performance, you need to add special additives. The price of the mineral composition is average, the negative point is that the color range of the coating is quite limited.
2. Silicate plasters can be called the most popular. The price here is closer to the budget. Potassium glass is used instead of cement, which ensures good vapor permeability. Plus, the composition has zero electrostaticity and does not attract dust. The disadvantage is that only fiberglass or stainless steel can be used as a reinforcing mesh.
3. Silicone plaster for aerated concrete blocks can rightfully be considered the highest quality. It has the widest color palette, completely vapor-permeable, keeps well on the surface, you can choose the texture and most importantly, it has a high elasticity. What is very important when shrinking a new house. The only negative is the high price.

Surface preparation

• Initially, it should be noted that all the compositions used in the lining process must be highly specialized, that is, designed for aerated concrete.
• Unlike brickwork, cellular blocks are large, so the lining will not be held only by gaps between the blocks. There are 2 ways to fix this problem.
• On the wall you can apply a grid of even cuts up to 5 mm deep. Cutting reinforced concrete with diamond circles or diamond drilling of holes in concrete is not needed here, the material is soft and fairly ordinary chainsaw. But having processed, thus, the average private house, the cutting chain should be discarded. The method is economical, but dusty.

• The second method is more clean; here the instruction is also not very complex. Reinforced mesh is stuffed on the wall. For the silicate mixture, only glass fiber mesh can be used. For other compositions, except fiberglass, you can fill a galvanized mesh with a small link.
• Mesh is fastened with wood screws with large diameter washers. Or you can use nails of 120 mm. Nails are hammered on 2/3 and bent.
• The plaster of aerated concrete blocks begins with covering the wall with a special primer. And in the case of applying a mesh chainsaw, the surface is primed after the work. And if you decide to fill the reinforcing mesh, the primer should be applied before mounting the mesh.

Plastering technology

Important: plaster house of aerated concrete has one feature. The internal and external thickness of the plaster layer is very different. Inside the layer should be twice as thick as the outside. Otherwise, the moisture will be locked and the walls will be damp.

• The first plaster layer is the thickest, it is applied by spraying, if you have the opportunity to use a plastering machine, then this will be ideal. After application, the solution should be allowed to set well, but not completely dry. Align it is not worth it. Thickness depends on the climatic zone, the colder, the thicker the layer.
• The composition for the second layer is made on the basis of crushed blast-furnace slag, it has a porous structure, high vapor permeability and does not absorb moisture at all. It is applied with a construction trowel or trowel. It is not necessary to level perfectly, but there should be no large height differences or defects. The thickness of the layer varies within 5 mm.
• The last finishing layer is mixed on the basis of the fine fraction of the sifted quartz sand. Its thickness is minimal, about 3, maximum 5 mm. It’s certainly possible to do the composition with your own hands, but without experience it’s easy to make a mistake. Therefore, it is better to buy a ready-made mixture. Currently on the market a wide choice of such material. It is not necessary to take expensive imported plaster, domestic manufacturers in this niche have achieved great success.
• Internal and external plaster of aerated concrete differ only in the thickness of the applied layer, the technology of deposition remains the same.

Important: the waterproofing composition of the facade can be covered no earlier than 1 - 2 years. Moisture remaining in the walls after plastering should erode. It is also desirable that shrinkage processes are over.

• Another important point to consider when finishing the house. The outer lining of the aerated concrete facade of the building begins only after all the wet work inside the house has been completed. Initially, the plaster screed fixes and everything else from the inside. And only after everything is dry, you can proceed to the facade.

The video in this article is a master class in facing aerated concrete.

Conclusion

Summing up, we want to remind once again that aerated concrete blocks have a high hygroscopicity. Therefore, they need to be laid exclusively on a special glue, plus at the end of construction you should not be delayed with plastering. Because if you leave the box to spend the winter, it is saturated with moisture and all those properties, because of which you chose aerated concrete, can, to a large extent, be lost.