Aerated concrete is an excellent building material, the main advantage of which is heat preservation. But at the same time, aerated concrete is quite fragile, which makes it less versatile.

A house made of aerated concrete must be built exactly according to technology, and then it will be warm, comfortable and will last 100 years. But if some stages of the construction technology are violated, cracks will appear in the aerated concrete.

And it is precisely about cracks in aerated concrete that we will talk about in this article. So, the cracks can be small shrinkage cracks, which in principle is not scary, but they can be fundamental.

Causes of cracks in aerated concrete:

1. Laying blocks on mortar.
2. Do not level the surface of the aerated concrete with a float.
3. Absence or improper reinforcement of masonry.
4. Incorrect or missing jumpers.
5. Lack of armored belt.
6. Poor quality aerated concrete.
7. Savings on foundation, cushion, drainage.
8. Application of low density aerated concrete.

Laying an aerated block on the mortar is not allowed, since mortar joint will not be able to properly fasten gas blocks. The thing is that aerated concrete very quickly draws water out of an ordinary solution, and as a result, the cement does not have time to react with water. That is cement mortar It does not hold gas blocks together very well, so glue is needed.

The only place where gas blocks need to be laid on mortar is the first row for waterproofing.

Between themselves, the blocks must be laid on a special glue, which ensures a thin seam and excellent bonding of the blocks.

You can read more about the composition of adhesive for aerated concrete in our previous article - composition of adhesive for aerated concrete.

Also recently there has been a special polyurethane foam for masonry, which is also an excellent material.

Although aerated concrete blocks are geometrically accurate, there is still an error of 1-2 mm. And during laying, this error must be removed using a grater. The plane of the gas blocks must be perfectly flat.

The thing is that aerated concrete adhesive has a very strong shrinkage, about 1.5 times. It follows from this that if the difference between the blocks is several millimeters, a void will form under one of the blocks, and as the walls grow, tension will be created in this place, which will create a crack along the entire wall.

It is necessary to level the plane of the blocks with a float. It is strictly forbidden to use the thickness of the glue to level the blocks.

Reinforcement aerated concrete masonry is also an important part of the technology, without which a crack in the wall is ensured. The reinforcement works in tension, and ensures the rigidity of the walls and resistance to cracks.

The first and every fourth row are reinforced. Two reinforcement rods with a diameter of 8 mm are used per row, although 10 mm can be used. The overlap of the reinforcement must be at least 200 mm, with mandatory bends at the corners. The distance from the edges of the block to the reinforcement must be at least 690 mm. Places under need to be reinforced window openings, under the jumpers.

We described reinforcement in more detail in the article at the link, be sure to read it, it contains very important information!

The lintels over windows and doorways must be rigid and must not bend. For such rigidity, there are two solutions: buy ready-made aerated concrete lintels, or pour the lintel yourself. In order for a homemade lintel to be of high quality, you need to use four reinforcement bars with a diameter of 8-10 mm for reinforcement, and also use grade 300 concrete.

The lintels must rest on blocks of at least 300 mm on each side. Also, do not forget about insulating the jumpers with polystyrene foam to avoid cold bridges.

Armored belt required reinforced concrete structure, which creates a monolithic ring around the perimeter of the walls. The armored belt significantly strengthens the walls of the house, and also evenly distributes the load from the floors and rafter system.

Low-quality (garage) aerated concrete has different densities and sizes, which affects overall quality masonry Moreover, the garage gas block shrinks differently, which can cause cracks.

Other causes of cracks

A house made of aerated concrete requires a reliable and rigid foundation. We also note that the lower the density of aerated blocks, the greater the likelihood of cracks occurring in the walls.

It is also advisable to protect aerated concrete from getting wet, because if frost hits, microcracks in the blocks are possible, although in most cases, aerated concrete does not collapse in the cold.

As a result of this article, we will say that aerated concrete is a good building material, but it requires full compliance with technology. Build wisely and don't skimp on quality.

The appearance of cracks in aerated concrete walls structures may be caused by mechanical loads on the masonry (constant and variable) and/or technology deviations in the manufacture of blocks.

The size and time of occurrence of damage can suggest the causes and methods of repair, reducing external influences on the structure of the walls and the entire building as a whole.

Manufacturing factors for cracking

Shrinkage of the foundation after the walls are erected often leads to cracking of the walls

• lack/absence of hardening accelerators for uniform setting of the foam mass (soda ash, Na, Al sulfates, Na, K chlorides);
• the use of one and a half aqueous gypsum instead of dihydrate leads to too rapid setting (5 minutes) and does not allow gas-forming processes to complete;
• lack of NaOH causes the formation of an uneven structure of aerated concrete.

Defects in aerated concrete due to manufacturing defects appear immediately or within the first 2 weeks. It is impossible to eliminate them locally; you have to complete replacement wall materials.

Choosing the right brand

Aerated concrete - brittle material

Not every product can be used in a load-bearing wall with the same result. The low bending strength of aerated concrete makes it a rather fragile material.

By increasing the mechanical resistance of the monolith, the thermal insulation properties are reduced.

Manufacturers take these features into account and produce blocks of different brands according to their purpose:

When designing ventilated walls, choose concrete grade D600 - D1000 for construction. Using smaller values ​​will result in cracks due to low bearing capacity material.

Causes of appearance and methods of elimination in structures

Excess moisture can also cause defects

The use in wall construction is constantly growing and reaches 1/3 of the market, second only to brick (51%).

According to statistics, the economic effect from using this material is obtained in 95% of cases. In this case, a crack appears in the masonry with 100% result.

The reason is that aerated concrete needs reliable protection from aggressive influence environment and destructive forces:

• mechanical damage;
• precipitation;
• ultraviolet;
• lifting moisture through foundation groundwater;
• weathering. For more information about the formation of cracks in walls, watch this video:

The porous material is capable of intensively absorbing moisture, which, expanding when heated or freezing into ice, breaks the structure. The means of protection will be waterproofing the base, covering with a layer of plaster (outside and inside the building), and installing external thermal insulation.

An independently completed project for the construction of a building may not take into account the maximum values ​​of forces determined by the geology of the site, building density, climate zone, the effects of snow, wind loads, man-made influences. As a result of the created structure, it is necessary to redistribute constant and variable loads to materials for which they may be excessive.

1. Roof. The installation of a rafter system with your own hands may not correspond to the fastening scheme required in this case. Thus, the absence of a tie beam at the bottom hanging rafters gives horizontal forces to the upper rows of masonry and pushes the gables apart. It is recommended to compensate for the recognition effect by applying puffs; the horizontal cracks that appear should be sealed with the same adhesive composition that was used in the masonry seams.
2. Foundation. Aerated concrete walls will react to the movement of the supporting foundation in the following cases: the weight of the entire building exceeds the bearing capacity of the soil (subsidence); heaving forces exceed the reaction of the foundation and cause its displacement; the reinforcing belt is not installed (or broken), the rigidity of the base is reduced; low-quality mortar was used for the masonry, the seams do not fully perform their function, there are foreign impurities and harder inclusions.

Drain groundwater away from the foundation

Eliminating comments on the foundation is a rather labor-intensive process (increasing rigidity and load-bearing capacity). Reduce the impact of geological and climatic factors can manufacture drainage around the perimeter of the house, storm system, wide insulated blind area.

Preventing groundwater from accessing the foundation and preventing soil freezing near the building’s support zone will reduce the risk of developing cracks that appear on the walls, which should be repaired with finishing putties for exterior work. If necessary, the wall surface can be reinforced with fiberglass.

The formation of small, insignificant cracks on the surface of the block indicates the need to protect it from the environment and does not create a danger of destruction of the entire structure. In this case, apply coating with one of protective layers: putty, plaster, painting. To learn how to get rid of cracks in the walls of your house, watch this video:

Excessive cracking may occur with the onset of a thaw. Humidity changes and temperature changes work here. In severe winters, in addition to the finishing coating, it is recommended to cover it with a layer of insulation - aerated concrete not only quickly gains temperature, but cools down at the same speed.

Most developers prefer to use aerated concrete blocks in construction, but the advantages of the chosen material hide the obvious problems that the owner will have to face.

These include, perhaps the most unpleasant of all, the appearance of cracks of varying lengths and depths in the walls of a built house. In most cases, this happens after construction is completed, so you need to know how to deal with them.

“Treatment” begins with identifying the negative factors that destroy the walls and eliminating them.

The most common causes of cracks:

• Possible movement of the soil, and with it the foundation, which can become a real disaster and lead to colossal material costs to eliminate the problem. Most often this happens due to untimely or improper insulation of the foundation. As a rule, the foundation is built at the beginning of the construction season and there is no rush to make an insulated blind area, which at the end of the season during frosts leads to “frost heaving” of the soil on one side of the foundation and a large through crack.
• Changes temperature regime at high humidity with poor foundation waterproofing, which will cause saturation wall materials water and their destruction when water freezes in the pores of the blocks.
• Also relevant is the occurrence of defects when the aerated concrete production technology is violated, namely, incorrect supply of a particular amount of components in the mixture for blocks and technological failures in the operation of the autoclave. There have been cases of defective batches of blocks from good factories, so a thorough check of suppliers or dealers is recommended when purchasing building materials, because such a manufacturing defect can cause too much damage to the builder.

The main problems of aerated concrete, the consequences of ignoring them

The main problems of concrete include excessive fragility, as well as inelasticity of the material, the presence of a loose structure, even when ideally correct operating conditions are provided. Even with perfect correct installation, compliance with all requirements established by building codes, minor cracks may appear on the walls over time, which certainly risk “damaging” the layer of plaster. This is the first moment when such small cracks appear on the surface of the plaster, the owner urgently needs to pay attention to the condition of the aerated concrete and take measures to eliminate the problem.

Important! The situation in which they occur on the surface large cracks aerated concrete, looks slightly different. This is a sign that the problems are not so much with external influences, but with a violation of the condition of the soil, its movements. Such cracks can also be dealt with very well, for which you can use improvised means.

What to do if cracks form, how to deal with it?

Many experienced builders recommend dealing with this situation in the following way: simply drain individual areas earth located around the house, thus diverting liquid from the foundation. With this approach, it is possible to prevent the formation of cracks in aerated concrete if the material is covered with the cheapest and most practical glass wallpaper.

Carrying out work in stages

So, let's get down to the work itself. First, you should definitely clean the surface of the aerated concrete, remove various accumulations of dirt and remnants of the destroyed layer from it. After completing this part of the work, the object is removed from dust using a vacuum cleaner. In this case, you can use it without any problems plain water, or an aqueous solution, you don’t have to do this, using dry cleaning methods. This is the very first set of work to be done to rid the structure of cracks.

At the second stage, it is important to prime the surface, for which it is customary to use a PVA dispersion of aqueous composition (50%). An alternative is also a latex mixture under the brand name SKS-65GP, which is diluted in a ratio of 1:3 with ordinary water. The solution is specially prepared taking into account all current requirements and compliance technological process, thanks to which the structure acquires additional strength and reliability during use.

Important! Compliance with all the above proportions guarantees excellent result and will protect you from negative consequences, destruction of the structure in further work.

At the next stage, it is important to carry out the actual sealing of the formed cracks, which are assessed depending on the number and size of existing damage. If the cracks have a width of about 0.4 mm, they need to be expanded to a value of 10 mm, after which they must be sealed with any available solution. For example, you can take high-quality cement mortar, or regular glue for working with aerated concrete. The solution itself will acquire additional quality characteristics, if in the future you simply add standard, fine crumbs of aerated concrete composition to it.

If the cracks are within 10 millimeters wide, to eliminate them it is also necessary to widen them to 15 mm, after which a special glue with a porous structure is used. In the case of more wide cracks, an adhesive composition or high-quality cement must be applied to the cleaned surface. In order for the material to set better, you will need to apply grooves or special notches to the surface, which will stand out against the background of the other structure and will not allow it to separate during subsequent use.

Restoration of large cracks

For large cracks, it is recommended to use a regular flat trowel and a standard plywood board. After the damaged structure or crack has been filled with a restoration solution, it will need to be stabilized for approximately 5 hours until it has completely hardened. This is done using standard plywood, secured with screws opposite the seam, which allows restoration of the damaged structure with minimal effort and expense on the part of the owner. Otherwise, if this operation is not performed, the concrete may not only crack, but also collapse.

If part of the aerated concrete wall has already collapsed, then it is necessary to thoroughly clean the edges, after which it is necessary to reinforce it with a metal mesh and high-quality galvanized nails, the length of which is 200 millimeters. Such nails are located at a distance of 15 centimeters from each other, after which metal fragments of the mesh are put on them. After this, we install the formwork from panels or boards and completely fill it with glue with pieces of aerated concrete. A wall restored in this way will have the same parameters as an unrestored one.

The reasons for the occurrence of cracks in aerated concrete walls do not differ radically in different cases - most often, this is mechanical stress in the wall masonry, or technological errors in the selection/production of blocks.

To understand the reasons for their appearance and suitable repair methods, you need to assess the scale of what is happening: measure the size of such cracks and determine the period of time when this happened. After this, it will become clear whether this is a consequence of errors during construction, finishing or further operation of the building, or whether production factors are to blame.

The main reasons for the appearance of cracks in walls made of aerated blocks or on the finishing layer may be the following:

• Shrinkage of the foundation due to the appearance of loads in the form of blocks;
• Seasonal shifts in certain parts of the structure due to the fact that it is not rigid enough;
• Too much influence of wind or dynamic loads, due to which the stress in the wall reaches a critical level, significantly exceeding calculated values;
• Incorrect installation;
• Incorrect insulation type or device;
• Incorrectly selected fittings;
• Type of gas blocks not suitable for these conditions;
• Violation of technology during construction.

Irregularities during block production

Aerated concrete blocks consist of cement and sand, with the use of additives that change the characteristics and composition of the mixture. The density of the product is regulated by proportions, and the brand of aerated concrete is determined by it. One of the features of this material is its fragility, compared, for example, with “traditional” brick. However, this is precisely due to the fact that when the material is compacted, its thermal insulation properties.

Some manufacturers, especially small ones, may change the composition to reduce the cost of the production process. In the worst cases, this leads to the destruction of masonry, deformation of walls and the risk of structural collapse if this is combined with other factors - for example, problems with the foundation. We will not open America if we say that it is safer to buy an aerated block from the manufacturer directly than to rely on luck. In most cases, prices will be the most favorable.

Incorrect selection of material

According to GOST, brands of aerated concrete differ in medium density from D200 to D1200. The fragility of the material decreases with increasing numbers in the designation. For example, the D250 is absolutely not suitable for the construction load-bearing walls, and D1000 is not able to provide sufficient thermal insulation.

Table of types of aerated concrete blocks by grade, according to GOST

Depending on the brand, the following types of blocks are distinguished:

• D200 (d200)–D350, thermal insulation blocks
• D400–D600 (d600), structural and thermal insulation
• D700–D1200, structural gas blocks

When choosing aerated blocks for construction, do not hesitate to contact specialists who can tell you what type of material will be needed for the construction of walls and partitions. Incorrectly made independent decisions, or the results of the work of non-professionals, can later result in very serious expenses, or even lead to accidents.

Reasons for and ways to remove cracks in structures

Wall blocks made of aerated concrete today are considered one of the most advantageous materials for private construction, construction apartment buildings and commercial buildings. However, despite all its advantages, it is important not to forget about the need to protect aerated concrete from negative external influences: wind and moisture, ultraviolet radiation, snow and mechanical damage.

The porous material absorbs water well, and it, increasing in volume when freezing, causes cracks to appear. At the same time, you should not only insulate the surface of the blocks, but also avoid making mistakes in waterproofing the foundation. In addition, improper installation of the thermal insulation layer can also lead to the appearance of moisture at the junction of materials and its further penetration into the aerated concrete.

Violation of the geometry of the building frame

If you are building according to individual project, then all calculations related to the terrain: geology, climate, snow and wind load, etc., must be made specifically for your conditions. In the case when they turn out to be incorrect, or are not taken into account at all in the project, the erected building may experience additional loads, leading to a change in its geometry. The consequence of this, of course, will be the occurrence of cracks and related problems.

Errors when constructing a roof

It is quite common to hire workers from seasonal crews for roofing work. They are not always professionals and may not take into account the choice of rafter system as applied to this material walls This can further lead to deformation and damage to the blocks.

When choosing hanging rafters, there will be no tension beam in their lower part, which would help remove the forces pushing the gables apart and acting on the upper rows of gas blocks. To avoid the appearance of cracks, tie downs are used to hold the rafters and neutralize horizontal forces. If cracks do appear, they are filled with the same glue that was used for the seams in the main masonry.

Foundation

The formation of cracks in aerated concrete walls is understandable if:

• the weight of the structure will be greater than the soil’s ability to withstand long-term loads;
• heaving forces will shift the foundation, as they will exceed its reactions;
• the reinforcing belt will not be applied or will be damaged;
• the base rigidity will be less than the required one;
• a poor mortar was used in the masonry;
• the stitches do not work as they should;
• there are unnecessary and harmful impurities.

Fixing foundation problems is not that easy. We will have to increase its rigidity and ability to withstand high loads. Can help prevent negative effects from the influence of the external environment drainage systems and proper drainage of storm water, as well as an insulated wide blind area. Thus, the likelihood of cracks occurring will be significantly reduced. And the existing ones are sealed with putty. If necessary, the wall can also be reinforced with fiberglass.

If the cracks are small in size, then this is not critical for the structure - however, it is important to provide the gas blocks with protection from further impact. In this case, there is no danger of destruction. The material coating is made with one of three layers: painting, plaster or putty.

Large quantity cracks may appear when there is a thaw. This occurs due to changes in humidity and temperature. If the winter is harsh, then insulation will help very well - aerated concrete heats up and cools down easily and quickly.

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 do not become covered with cracks.”

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

To prevent walls from cracking, you need to follow several rules. At the same time, failure to follow one of these rules at first may not lead to cracks, which is taken advantage of 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?

Laying aerated concrete using glue only

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

The aerated block is laid using a special glue or, more recently, foam is used.

I can guess why some masons put gas block on masonry mortar. Because they think that an aerated block is a big brick, so they use the same masonry mixture, as for brick or they simply don’t want to level each row with a plane. Instead, when horizontally aligned, they want to play with masonry joint. You can’t really play with glue, because the thickness of the glue is about 2-3 millimeters.

This photo shows an almost ideal 2mm thick seam for an aerated block. If you make such seams, your wall will have virtually no cold bridges. Once you have placed the block on the glue, it is almost impossible to break it in this place. The blocks are very firmly bonded with glue.

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

Aligning layers

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

The figure shows the reasons why cracks form.

If you have a step in the horizontal plane and you simply increase 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 there will be a void and the upper blocks will partially overhang. Pressure upper layers may simply break overhanging blocks with the appearance of a crack. Moreover, the crack may not be limited only to these blocks.

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

Masonry reinforcement

Here you can see two grooves in which reinforcement 8 mm thick 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 groove close to the edge of the block. Thin when wet or frozen outer layer It may simply break off or crack.

I made my grooves at a distance of 9 cm from the edge.

Window and door openings

Be sure to reinforce the first row and window sill spaces.

The reinforcement passes here, and it extends beyond the line where the window opening ends by about 1 meter. Moreover, to strengthen it, I reinforced not only bottom layer blocks, but also the top one.

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

Upper armored belt

My armored belt is a rather impressive product. I have already shown how to make it with your own hands.

The armored belt runs along the perimeter of all walls and partitions and is a mandatory structural element for supporting heavy structures. In my case it's empty reinforced concrete slabs. An armored belt is needed even if you use wooden beams ceilings

Protect walls from moisture

The gas block absorbs moisture well. If you let it get wet on top, it will absorb water like a sponge. After this, it is enough to be hit by frost and the gas block will collapse, like any material that gets wet and freezes.

Quality of aerated block

There are a lot now different manufacturers including private owners who do it in garages. As a rule, such a gas block has different densities, structures and even sizes. If you buy a gas block from a decent factory that monitors quality, then you will not face these troubles.

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

The foundation must be strong

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

The most important paradox

And perhaps the most important paradox. Most often I hear that aerated block is a bad material from professional masons. And at the same time, I know quite a few cases when such professionals built people a house whose walls within six months or a year were covered with finger-thick cracks. Maybe gas block really is such a bad material? Before the construction of my house began, I simply couldn’t find a place for myself - “and the right material I chose for the walls? "You may be interested, but I have never regretted that I built my house from aerated block. And I’m not the only one so lucky. Two of my friends and two neighbors built their own houses from the same aerated block. Maybe we have problems with our eyes since we can’t find cracks? But I think that eyes and luck have nothing to do with it. Before building our house from aerated concrete, I took free courses organized by the Sibit plant, where everything is. The aspects of construction were explained to us in detail within three hours.

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

If possible, take courses and learn more additional information.