Facing aerated concrete: how to avoid mistakes

Gusevsky Andrey Anatolyevich

Facing a house made of aerated concrete with brick

Aerated concrete brick lining is the only type of exterior wall decoration that is performed only in the process of their construction. This technology has many nuances that must be taken into account in the process of construction and decoration of such a house.
When facing walls made of other structural materials, many of them are simply irrelevant. This is primarily due to the characteristics of aerated concrete.
We hope that our instructions, as well as the video on installation and cladding of blocks, will help you avoid many mistakes and build a durable and warm house.

Information for consideration

When starting the construction of a house from aerated concrete, you must clearly understand what its properties will have to face. Concretes of this type differ from other types of structural building materials in their porous structure.
If we talk specifically about gas silicate blocks, then their pores are open, like a sponge, and this is clearly visible in the photo below.

• You do not need to be a professional to understand that the presence of open pores means that moisture is absorbed instantly into such a surface. And here is the first task that you need to solve.
  Walls of aerated concrete in the process of finishing, it is desirable to protect from all wet processes.

Gas silicate block

• Many manufacturers claim that plastering is the best type of finish for the reason that the putty layer seals open pores. But practice, unfortunately, shows the opposite: both cement and gypsum screeds crack on such a basis, and no soil helps.
• Only fiberglass glued to the surface as a reinforcing layer can save the situation, but at the same time, both the price and the complexity of the process increase. The main advantage of cellular concrete is its heat-insulating properties, which it just gets due to pores filled with air.
• By acquiring one valuable quality, the material loses another, more important property of concrete - strength. This is the second task requiring a responsible and correct solution. Aerated concrete blocks were originally created as a heat-insulating material.
• In multi-story construction, it is used constructively in only one case: in frame houses - as filling spans between columns and crossbars. This applies to load-bearing walls.
  But for the construction of all kinds of partitions and parapets, gas silicate blocks are just perfect.

Frame building with a filling of aerated concrete blocks

• In such a house, all load-bearing loads take on the elements of the frame, and the block masonry actually performs only enclosing functions, and works mainly for its intended purpose - as a heater. In a similar construction of the house, the value of aerated concrete blocks is difficult to overestimate.
• For multi-story buildings, the fact that they are light enough is especially important. In comparison, a cubic meter of masonry made of red building bricks weighs about a ton, masonry made of silicate brick is almost twice as large, and the mass of 1 m3 of a wall made of aerated concrete blocks is only 560 kg.
  The figure speaks for itself: the load on the foundation is significantly reduced in the house.
• Advertising of this material has led to an increase in the popularity of cellular concrete blocks in private construction. But the problem is that in order to save money, citizens try to do without a project, which, of course, costs money - and also, they try to do everything with their own hands.
  This is commendable, but lack of knowledge often leads to errors that are difficult, and sometimes impossible to correct.

Beam ceiling for aerated concrete house

• One of the common mistakes is the installation in the house of gas silicate blocks of concrete floors. Cellular blocks are not able to withstand their weight, under its influence, cracks appear in the masonry, through which cold air penetrates deep into the room.
  Even if during the construction process, aerated concrete is lined with brick (seeAerated Concrete Finishing: Material Overview), this will not change anything, because the overlap does not rest on the cladding. In addition, the brick wall is connected with the block masonry, although rigidly, but not monolithically.
• Therefore, for a house, the walls of which are built from cellular blocks, the most correct constructive solution is the installation of beam ceilings. In the photo above you see exactly this option.
  Details of its arrangement you can easily find on the Internet, including on our website. Believe me, with proper installation, such an overlap will not create problems, and its elements can be used even for internal design.
• As for the exterior decoration, whether it is plaster or a ventilated facade, it should be done only in the summer, and only after all the internal work is completed. Facing walls of aerated concrete with brick is an exception, since, as we have already said, it is produced during the construction process.

Facing of gas silicate blocks

• To build any building, it is necessary to make a thermal engineering calculation of the walls. Designers do this, but most private builders do not apply to them.
  They prefer to believe advertisements of the type: “laying of gas-silicate blocks 30 cm thick will replace a meter-long brick wall”. If everything was so simple, then the brick, as a building material, would cease to exist.
• The thickness of the walls is always designed with a margin, so those who are independently engaged in construction should consider this golden rule. In any case, if the walls are supposed to be simply plastered, without additional insulation.
  Brick cladding Aerated concrete walls are good in that it protects them from blowing, gives rigidity, and gives the opportunity for additional insulation.

Silicate blocks with front decor

• Instead of bricks, aerated concrete blocks with cladding can be used for this purpose. They come from the conveyor with a ready-made front finish, and can serve as an excellent option: both for decorating the exterior walls, and for their additional insulation.

Advice! Whatever the advertisement may convince you to, you should not use such blocks as the main structural material.

They are mounted as a decorative wall, similar to a front brick. About some of the subtleties of this process, we will tell in the next chapter.

The nuances of building a block wall with brick cladding

A decorative brick wall is being erected simultaneously with a load-bearing wall for the simple reason that a cladding with such a solid weight should also rest on the foundation. Moreover, its width should be designed so that a place is provided for laying the insulation, as well as a ventilation gap of at least three centimeters.
So:

• In order to avoid condensation, the facade of any building must be ventilated under the skin. For aerated concrete walls, this is doubly relevant, since excess moisture will be absorbed into the open pores of the blocks, and, in the process of repeated freezing and thawing, gradually destroy their structure.

Hydrophobic impregnation "Aquasol"

• To prevent this from happening, wall decoration from aerated concrete with brick, it is made only after treatment with hydrophobic impregnation, specially designed for the porous surface of cellular concrete, for example, “Aquasol”.It is important to note that the installation of the blocks is not done on ordinary cement-sand mortar, on special glue, which should be coated not only on the spoon sides, but also on the ends.
• The masonry performance depends on how carefully the joints between the blocks are sealed. Block and brick walls are not laid out at the same level.
  First, several rows of masonry, or an entire floor, are erected around the entire perimeter of the house, and the surface of the blocks is immediately treated with impregnation. Then, a series of insulation is mounted.
• If this is mineral wool, then on top of it you will have to make another layer - a windproof membrane, which at the same time will serve as a vapor barrier. Only after this, you can start the construction of the front brick wall. This procedure allows priming the surface of blocks without interference.
• To simplify the task will help the right choice of insulation material. Minvata, by virtue of its organic origin, can become wet during the operation of the facade, and, consequently, decay with time.

Brick walls aerated concrete

• For the filling of a multilayer wall, this is not the best option. Experts recommend the use of foam glass for such structures, which is devoid of all the shortcomings inherent in soft insulation. Bulk insulation is also an ideal option for a well wall.
• Polystyrene granules, expanded vermiculite, expanded clay - just fall asleep in the sinuses formed by two walls. Regardless of the choice of insulation, the need for hydrophobic impregnation of aerated concrete is not eliminated.
• The supporting and decorative wall should be tightly interconnected, but technological fixation options are different. The decision is made by the master, based on the thickness and configuration of the walls, the sizes of the used blocks and bricks.
• One option is steel mesh anchoring. It is mainly produced during the construction of walls from various types of blocks: ceramic, expanded clay, cellular.
  In this case, both walls are brought to the same level, and the strip of mesh is laid so that it is monolithic in the horizontal seams of both the masonry.

Steel Mesh Anchoring

• Another way: for rigid fixation, stainless steel anchors are used, which are laid in the joints between the blocks during the construction of the load-bearing wall. The free end of the anchor is passed through a hole made in the insulation, and then, monolith in the brickwork. In the photo below it is clearly visible.
• Instead of steel anchors, polymer bonds can also be used. Their flexible end is monolithic, on the contrary, in brickwork, and the rigid steel tip is clogged into the load-bearing wall.
  But this option is not so good for working with cellular concrete blocks, since even a dowel-nail hammered into the cellular surface does not hold very securely in the socket.

Anchored and insulated wall, prepared for brick facing

• The aesthetics of the building is certainly important, but the main task of the brick cladding is to stiffen the load-bearing walls. In addition, such a cladding will protect the house from blowing out even if, as a result of shrinkage processes, cracks appear in the walls.
  So, we advise you to choose this particular method of decorating the facade for a house from aerated concrete.

And finally: before undertaking any work, it is best to watch a master class from professionals. This will not hurt even those who have some knowledge in construction, and even if an amateur is taken up, and even more so!