The main points to consider when building a house from aerated concrete. Crack in hay from aerated concrete blocks Cracks under windows in aerated concrete house

During construction work, various unpleasant situations may arise, from which no one is insured. One of them is the crack in.

There are several reasons why cracks may appear in this usually happens due to the subsidence of the foundation or due to a violation of the technology for the production of blocks.

There is another reason that arises when creating a ventilated facade, when the wind load is transmitted through the frame to the walls of the house.

Violation of manufacturing technology

Some manufacturers, during the creation of blocks, may experiment with the composition of the mixture and violate the technology of their manufacture.

This may be the use of inappropriate additives, when they begin to set earlier and the gas-forming processes do not have time to complete, there may be no hardening accelerators, additives that ensure the uniformity of the structure.

Violations of the technology for the production of foam blocks lead to the deterioration of the operational characteristics of the material.

In this case, cracks usually appear almost immediately or 1-2 weeks after.
It will not be possible to fix the indicated drawback., since the structure of the building material has been changed, therefore the way out of the situation is to dismantle the walls and use normal foam blocks.

It is imperative to carry out high-quality waterproofing, since foam concrete absorbs moisture well and this can cause cracks.

If you plan to install a ventilated facade with additional insulation, then it is necessary to use blocks of grade D600 and higher, otherwise they may not withstand the wind load, which is transmitted from the cladding to the walls.

With the wrong creation of the rafter system, the load is unevenly distributed, which can cause damage to the walls of the foam blocks.

To compensate for the forces created by the rafter system, it is necessary to install puffs (a beam connecting the rafters at the Mauerlat level) and use the installation scheme with inclined legs.

Construction errors

Often, the cause of cracks is associated with a violation of the technology for creating both the foundation and the walls of the building:

• during the installation of the foundation, the characteristics of the soil were not taken into account and as a result of the action of the heaving forces, the soil layers are displaced, which destroy the concrete base of the house;
• not performed, this must be done every 3-4 rows, due to which the stiffness of the wall decreases, and cracks may appear on it;
• homemade solution is used, in which the recommended proportions are not observed or there are impurities that reduce the strength of the seams.

Unlike brick walls, foam blocks must be properly and reliably protected from precipitation, wind, sunlight, it is best to do this by creating a wet facade.

What to do if a block burst

It is necessary to ensure that the cracks that appear on the foam blocks are not transmitted to the finish; this can be achieved in several ways:

1. the cracks are sealed with putty, at the same time, the facade is leveled, and only then the topcoat is mounted;
2. at , it is recommended to use fiberglass mesh due to which the surface is reinforced, this prevents the appearance of cracks on the finishing material;
3. use of decorative plaster with wear-resistant fillers, such as basalt or granite chips.

These methods do not eliminate the formation of cracks, they make it possible to hide them and prevent them from appearing on the facade cladding.

Strengthening

In order to prevent further formation of cracks on the walls of foam blocks, it is necessary:

• reinforce the foundation;
• install an additional armopoyas;
• change the scheme of the rafter system in order to reduce horizontal loads on the walls.

For additional protection of a foam concrete house, experts recommend making a drainage system and a blind area around its perimeter.

Stormwater drainage or will allow to divert ground, flood and melt water from the walls, which will not increase the moisture content of the soil, so the foundation and walls will not absorb it.

How to repair the crack

To fix the crack, you will need:

1. vacuum cleaner;
2. glue;
3. water;
4. cement;
5. grout;
6. putty knife;
7. primer;
8. iron mesh.

First, the place where the crack appears is well cleaned and the destroyed material is removed, then it is washed with water or cleaned with a vacuum cleaner.

A primer is applied to a dry and clean surface and the crack is closed.... Depending on the size of the crack, it can be repaired with a solution of crushed stone or glue.

The selected composition is used to fill the crack, do this with a spatula and grout, after which it is closed with a sheet of plywood, which is attached to the wall with self-tapping screws.

If a large crack or hole has formed, then it is reinforced with an iron mesh, which is attached with self-tapping screws, and then filled with mortar.

Output

To avoid the occurrence of cracks in the walls of foam concrete, it is necessary to buy high-quality building material, make the foundation correctly, prevent violations and create a rafter system.
If you do everything right, then you can build a reliable, durable and comfortable home on your own.

Useful video

How to repair a wall crack in an apartment with your own hands, video:

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Hello everyone, Happy New Year and Merry Christmas.
The story is this:
In 2013, the foundation was poured - a 25 cm slab.
In 2014, we delivered a box of aerated concrete house 600X400X250 (D600). + roof, every 3rd row is reinforced + reinforcement under the windows. + 2 armored belts above each floor. The plinth is made of concrete blocks, the lintels above the openings are made as follows - outside there are two corners on which there is an aerated concrete block, about 15 cm thick, the rest of the space is filled with concrete with reinforcement.
In 2015 we installed windows
Partial heating was launched in 2016
In 2017, the walls were plastered (mostly with rotband) and plastered inside, full heating was launched.

Recently noticed two types of cracks:
1) Above window openings, in the area of ​​lintels
2) Cracks of unknown origin in the bay window of the house.

More information on cracks from p. 1. (cracks are very thin, less than a millimeter) the lintels in front of the plaster were treated with concrete contact. My guess is that cracks could appear as a result of uneven shrinkage of the plaster (however, then they would appear at the stage of plastering, it seems to me, and not at the stage of plastering), or they appeared due to the fact that concrete and aerated concrete have different thermal expansion.
According to item 2. (cracks are very thin, less than a millimeter) Divided into 2 groups, under the windows - vertical. It can be seen that they go along the seam in the block, but not in full length - that is, the crack hides a little behind the battery and stops there. The second group - horizontal - go from the opening to the perpendicular wall. They don't seem to go deep into the block. My guess is that these cracks may be the result of the same sandwich made of different materials that have different extensions. There is metal (bay window pillars) and concrete in the lintel of the bay window and aerated concrete, in general, a whole set. In addition, it seemed to me that the cracks appeared after I sharply cooled the room from 21 degrees to 2 degrees, with the help of ventilation. (the last plastering work was carried out a long time ago, the plaster should have already completely dried)
Outside, the house is not finished and not insulated, and on the day when I decided to ventilate, there was a very cold and strong wind.
Then there are a number of photos with comments to better understand the situation.

I would like some comments from experts, why these cracks could appear, how they can be repaired, and solutions for interior decoration, with different scenarios (initially I wanted to paint most of the walls)

1) Blocks used in construction

2) An example of a lintel device (an external gas block is exposed to 2 corners, the rest of the space will be filled with concrete with reinforcement)

3) The design of the bay window. In the gas block, the hole is filled with concrete, in which there is a metal embedded part, to which the pillars are welded.

4) A lintel above the window before pouring concrete

5) Formwork on top of the bay window, outside and inside 50mm EPS, the middle will be filled with concrete. This is all part of the armopoyas.

6) Filled ereker of the 1st floor. On the second floor, a similar structure

7) View of the lintel inside - concrete treated with concrete contact before plastering

Sorry, the problem is in the high moisture absorption of gas silicate. When you started heating the house, the silicate began to dry and shrink, as a result of cracks in the masonry. And on the corner cracks there is a complex of reasons, the first has already been voiced, the second you yourself have voiced (different materials with different coefficients of linear expansion, well, apparently, when plastering at the corners, they did not do additional reinforcement of the plaster (as should be done in the upper and lower corners of windows). , but until the load-bearing wall is covered with cladding and completely dries up (and this is after facade work 2-3 autumn-winter seasons with strong heating in order to squeeze moisture out of the wall by the difference in partial pressure) all your efforts will be in vain. !

The building material popular today, aerated concrete, has several disadvantages. One of them is the appearance of cracks. Let's talk about the possible causes of this problem, preventive measures and ways to deal with cracks.

The building material popular today, aerated concrete, has several disadvantages. One of them is the appearance of cracks. Let's talk about the possible causes of this problem, preventive measures and ways to deal with cracks that have already appeared in the walls and partitions made of aerated concrete.

We described in detail the properties, pros and cons of aerated concrete, mentioning separately that about 20% of all blocks used in the construction of a house crack. Of course, most often the cracks are very small, not critical, and you don't really need to do anything with them.

External small cracks are perfectly hidden, for example, under plaster or siding, without violating the thermal insulation of the house and the bearing capacity of the walls. From the inside, such small flaws in aerated concrete blocks are also usually hidden by the finish and do not lead to serious problems.

But what if the crack goes through several blocks and is visible even from afar? If it formed on the most important section of the wall, for example, at a corner and threatens to expand over time?

Cracks are of two types: caused by shrinkage of the house, exposure to moisture and temperature, as well as mechanical, associated with the applied load.

The reasons for the appearance of cracks in aerated concrete masonry can be:

• Low-quality aerated concrete. Simply defective material, which has no chances to calmly "survive" the coming winter. We strongly recommend purchasing aerated concrete blocks exclusively from trusted suppliers, from manufacturers already known on the market, and not from "bushes";
• Wrong choice of block class. Recall that for load-bearing walls, you should choose aerated concrete of the D500 modification, or better D600 and with a density of B2.5, B3.5–5. Otherwise, the material will simply not be adapted to high loads and will begin to crack;
• Foundation problems. Yes, aerated concrete is a relatively light material, especially in comparison with hyper-pressed bricks or good old cinder blocks. However, you cannot save on the foundation! It must be reinforced, hydro- and heat-insulated, otherwise frost heaving and uneven subsidence will lead to the appearance of very serious cracks;
• Laying aerated concrete on a poor-quality mortar or adhesive mixture. It is better to purchase a special glue recommended by the manufacturers of aerated concrete blocks to prevent problems.

So, in order to prevent the appearance of cracks in aerated concrete as much as possible, it is necessary:

1. Choose quality material.
2. Use material of the correct grade and density.
3. Purchase high-quality adhesive.
4. Take care of a reliable foundation, its heat and waterproofing.

That is, in fact, observe the technology of building houses from aerated concrete blocks, paying attention to all the details. There is no guarantee that even in this case there will be no cracks at all, but serious problems will definitely not appear.

Based on the causes of cracks in aerated concrete blocks, there are several options for eliminating them. For example, in case of problems with the foundation, most often it is necessary to first strengthen it, insulate it, waterproof it, and only then deal with the cracks themselves.

The crack itself should be fought like this:

• clean this place from dust, wet with water;
• prime;
• cover cracks with putty;
• use a reinforcing material on top, for example, fiberglass, which will then disappear under the finish.

Important! Most of the cracks in aerated concrete are formed during the cold season. There is a high risk of large cracks if the house has already been built, but not finished and no one lives in it, that is, there is no heating.

We advise, if the crack is very deep, and the reasons for its occurrence are unclear, contact a specialist. In this case, self-repair of the wall can only aggravate the situation.published by

If you have any questions on this topic, ask the experts and readers of our project.

Gas blocks are considered one of the most effective and cheapest wall materials that are used in private construction. The advantages of such products are obvious - they are sufficient strength, good heat and sound insulation, resistance to high temperatures, mold and mildew, and the price of such materials is quite affordable.

Some builders who used aerated concrete for the construction of walls could notice the appearance of various defects on the walls, especially after wintering. Many are looking for an answer to the question: why do cracks appear in aerated concrete? Some attribute this phenomenon to wall shrinkage, but in fact, this is not the only reason. Let's take a closer look at the answer.

Causes of cracks in aerated concrete

• use of defective products. Cracks on the walls can occur as a result of improper production technology. In the manufacture of blocks, an insufficient amount of binder may be included in the raw mixture or the proportions of the main components may be violated. Experienced craftsmen recommend buying autoclaved aerated concrete;
• the possibility of foundation subsidence. This phenomenon usually leads to the formation of long transverse cracks. It is known that up to 25% of the cost of the cost of the entire house falls on the arrangement of the base. It should be noted that the structure under consideration perceives loads from all sides, therefore, when designing the foundation, it is necessary to take into account not only the applied forces, but also the characteristics of the soil;
• wrong choice of finishing material. For example, for the device of a ventilated facade, a crate is required, which will be attached to the outer wall. The frame itself experiences various loads (wind pressure, etc.), which can lead to cracks on the wall surface. In this regard, the installation of supporting structures is carried out using gas blocks of the D600 and higher grade;
• the next reason for the appearance of cracks on aerated concrete walls is considered to be incorrect masonry technology, poor waterproofing or lack of insulation.

How to repair cracks in aerated concrete walls

We figured out the reasons for the appearance of cracks, and now we will get acquainted with the technology of masking them and ensuring the solidity of the wall.

The affected area must be cleaned of dirt, dust removed with a vacuum cleaner or spilled with water. Next, the crack is primed, and when the liquid is completely dry, it is sealed with cement mortar. With a significant width of damage, the dirt is removed, the crack is cleaned and primed, and then it is filled with a solution with aerated concrete particles.

I am increasingly asked the question - "Have cracks appeared in your walls?" However, I think they want to ask another question - "How to build a house from aerated concrete, so that the walls are not covered with cracks."

I will say right away that I am not a builder or even a specialist in gas blocks, but on the other hand, I managed to build the walls of my house without experience and with my own hands and I still have not found a single crack, although I examined my walls with great passion, especially after the opinion of many people that aerated concrete is under-material.

To prevent the walls from cracking, you need to follow a few rules. At the same time, failure to comply with one of these rules at first may not lead to cracks, which is used by unscrupulous builders who build a house in violation of technology, take payment from the client, and then change the SIM card in the phone. What are these rules?

Gas block laying only on glue

One of the main violations occurs when laying a gas block on a masonry mortar. I don’t know where such masons are still taken from, because this is a direct violation of technology.

The gas block is laid on special glue or, more recently, foam has been used.

I guess why some bricklayers put the gas block on the masonry mortar. Because they think that the gas block is a large brick, so they use the same masonry mixture as for the brick, or they simply do not want to level each row with a plane. Instead, when leveling horizontally, they want to play with a masonry seam. You can't really play with glue, because the thickness of the glue is about 2-3 millimeters.

This photo shows an almost ideal 2 mm seam for an aerated block. If you make such seams, then your wall will be practically without cold bridges. After you put the block on the glue, it is almost impossible to break it in this place. The blocks adhere very firmly with glue.

Somehow I didn't have enough glue and I used masonry mixture. Arriving the next day, I easily tore the block away from another block. The reason for this is the property of the aerated block to quickly absorb moisture, so an ordinary masonry mortar simply will not have time to grab without water and the blocks will remain not glued. Therefore, I highly recommend using glue.

Aligning layers

Leveling the layers should be done with a float, and not by increasing the thickness of the glue.

The figure shows the reasons for the formation of cracks.

If you have a step in the horizontal plane and you simply increased this step by increasing the thickness of the glue, then the following thing will happen. The glue shrinks very well, about one and a half times. Therefore, in the place where the step will appear, a void will appear and the upper blocks will partially overhang. The pressure of the upper layers can simply break the overhanging blocks, creating a crack. Moreover, the crack may not be limited only to these blocks.

Therefore, all unevenness of the layer must be leveled with a plane, i.e. do not be lazy to use a grater.

Reinforcement of masonry

Here you can see two grooves in which reinforcement with a thickness of 8 mm is embedded.

I used 8mm ribbed reinforcement and reinforced every 4th row.

I often see a mistake that even professional builders make. They make a strobe close to the edge of the block. When wet or freezing, the thin outer layer can simply break off or crack.

I made my grooves retreating from the edge of 9 cm.

Window and door openings

Be sure to reinforce the first row and sill spaces.

Here the reinforcement passes, and it goes beyond the line where the window opening ends by about 1 meter. And to strengthen it, I reinforced not only the bottom layer of the blocks, but also the top one.

I often see that instead of a lintel, builders use metal corners in window and door openings. Even a thick metal corner can bend. And if you have a gas block on top of such a bent jumper, it will surely crack. To prevent this from happening, I used factory-made concrete reinforced lintels plus a reliable armored belt, which is also a lintel.

Upper armopoyas

My armopoyas is a pretty impressive product. I have already shown how to make it with your own hands.

Armopoyas runs along the perimeter of all walls and partitions and is an obligatory structural element for supporting heavy structures. In my case, these are hollow reinforced concrete slabs. Armopoyas is needed even if you use wooden floor beams.

Protect walls from moisture

The gas block absorbs moisture well. If you allow it to get wet from above, then it will absorb water like a sponge. After that, it is enough to hit the frost and the gas block will collapse, as indeed any material that gets wet and freezes.

Gas block quality

Now there are many different manufacturers, including private traders, who make it in garages. As a rule, such a gas block has a different density, structure and even dimensions. If you buy a gas block from a decent factory that monitors quality, then these troubles will not threaten you.

I decided that I would not risk it and therefore I used a gas block with a density of D600.

The foundation must be solid

I think that in half of the cases when the walls of gas blocks cracked, because the owners or builders decided to save money on the foundation. I have heard many times that people say that a gas block is 3-4 times lighter than a brick, which means that you can save on the foundation. No, friends, it won't work that way. A gas block structure requires a very reliable foundation.

The most important paradox

And perhaps the most important paradox. Most often I hear that the gas block is a bad material from professional masons. And at the same time, I know quite a few cases when such professionals built a house for people whose walls, after six months or a year, were covered with finger-thick cracks. Maybe the gas block is really such a bad material? Before starting the construction of my house, I simply could not find a place for myself - "did I choose the right material for the walls?" Perhaps you will be interested, but I have never regretted that I built my house from a gas block. And I was not the only one who was so lucky. Two of my friends and two neighbors built their own houses from the same gas block with their own hands. Maybe our eyes are bad since we cannot find the cracks? But I think that eyes and luck have nothing to do with it. Before building my house from aerated concrete, I and all my friends took free courses organized by the Sibit plant, where all the moments of construction in three hours were explained to us in detail.

If you decide to build a house from a gas block, then there can be no amateur performance!

If possible, go to courses and study more additional information.