A house made from a material such as aerated concrete has many differences from houses built using foam concrete or brick. Aerated concrete is lightweight artificial stone, which has a porous structure and high thermal insulation properties, which indicates that the plaster used for aerated concrete is not ordinary.

So what kind of plaster should be used for the exterior finishing of houses made of aerated concrete blocks? What kind of solution should this be, and why can’t you use regular mixtures?

As you may have guessed, to perform external protection walls, you cannot use ordinary cement-sand plaster mortar. The reason for this ban is that ordinary plaster has lower vapor protection parameters than the aerated concrete blocks that make up the building.

There is an unspoken principle that any multi-layer breathable wall structure must be built using such a method that each subsequent layer has greater vapor permeability than the previous one. The closer to the street, the greater the permeability.

As an exception, it is possible for all layers to have this indicator of the same level, but this is not encouraged.

For work with aerated concrete blocks You should use exclusively special facade plaster for aerated concrete, which is called that.

How to plaster aerated concrete

Plastering walls made of aerated concrete is done as follows: apply facade plaster for aerated concrete blocks to the walls. This material is a special porous plaster mixture that has high vapor-permeable properties.

It is advisable to apply the plaster on the mesh so that it does not crack or fall off when it dries.

Plaster that is used for finishing buildings made of aerated concrete must have the following necessary qualities:

• bulk weight – about 0.8 kg/dm³;
• fraction within 2 – 4 mm;
• it should be a light plaster mortar belonging to plasters of group P I;
• resistance to compression pressure – class CS I;
• low water absorption coefficient;
• non-flammability - class A1.

The plaster mixture used to finish the façade of aerated concrete houses must have good ductility, it must be easy to process and should be applied on top of the base. This plaster can be applied in a layer whose thickness does not exceed 1.5 cm at a time.

Once hardened, this plaster should have good water-repellent properties.

However, nevertheless, it must implement good throughput in relation to water vapor, and in addition, it must easily cope with the harmful effects of adverse weather conditions.

How to plaster aerated concrete video

It’s worth saying right away that plastering work on aerated concrete is neither simple nor cheap.

If you have already firmly decided to carry out plastering work in a house made of aerated concrete, then use only suitable materials. Don’t forget, this is the guarantee that the work you perform will be of high quality, and the plaster will delight your eye for many years.

Aerated concrete is increasingly used in private construction, competing with traditional brick. Such houses are much warmer, and less time is required for construction. By technical specifications aerated concrete differs markedly from other materials, and these differences must be taken into account when choosing exterior finishing for walls. The most popular option is plastering, and in order for the coating to best match the base material, you need to choose the right composition.

Let's take a closer look at the types of facade plasters for aerated concrete and the right technology their application.

Aerated concrete has a cellular structure with open pores, which not only provides thermal insulation properties, but also high vapor permeability. Thanks to this quality, an optimal microclimate is created inside the house, the accumulation of condensation is eliminated, and the risk of mold development is minimized.

But there is also a downside: open pores increase the hygroscopicity of the material, and absorbed water destroys the cells when freezing. For this reason, the exterior finish must be waterproof in order to reliably protect the walls from moisture, and have a vapor permeability no lower than that of aerated concrete, so as not to prevent the escape of fumes.

Important! According to the standards prescribed in SP 50.13330.2012, in heated houses, the vapor permeability of materials should increase from internal to external layers. Only under such conditions is normal functioning possible load-bearing structures. Since for aerated concrete this parameter varies within the range of 0.11-0.23 mg/(m h Pa), then plaster composition you need to choose one with a vapor permeability of at least 0.12 mg/(m h Pa).

Additionally, facade plaster must have the following qualities:

• high adhesion to the base material;
• frost resistance (minimum 35 cycles);
• increased compressive strength;
• resistance to atmospheric influences;
• decorativeness.

In principle, aerated concrete surfaces can be used without protective coating, but after a few years the external attractiveness will disappear: the blocks will darken, peeling will appear, and mold may develop. So it's better to do it right away facade finishing and then only periodically update the coating by painting.

Prices for aluminum stairs

Aluminum ladder

Types of plasters for aerated concrete

The most common and most inexpensive plaster for exterior work is cement-sand. But since its vapor permeability is only 0.09 mg/(m h Pa), it is not at all suitable for aerated concrete structures. Other types of plaster mixtures, such as mineral, silicate and silicone, have the necessary parameters. Let's look at the characteristics of each of them in more detail.

Mineral

Mineral based plaster refers to inexpensive materials and it’s easy to do it yourself. The main disadvantage is the limited range of colors, but since this coating is highly paintable, this is not so big problem. Ready-made mixtures contain lime, white cement, marble chips and other fillers, as well as some additives that improve the quality of the plaster. Homemade mixtures are most often made from cement, lime paste and sand, or only from sand and lime. It is worth noting that sand-lime mortars have low water resistance, and direct exposure to precipitation is detrimental to them.

Silicate

In silicate plaster, liquid potassium glass plays the role of a binder. Such compositions are more convenient to apply, are not afraid of moisture and are highly permeable to evaporation, which allows them to be successfully used for finishing aerated concrete walls as a finishing coating.

Silicate plaster - photo

The color range is quite limited, but, again, this drawback is easily eliminated by painting. Silicate plaster goes on sale in a ready-to-use form, and the cost is slightly higher than dry mineral mixtures.

Silicone

The basis of silicone plaster is silicon-organic polymers. She has best characteristics compared to other types of plasters: does not absorb water, is easy to apply, resistant to atmospheric influences, vapor permeable and does not lose its visual appeal for a very long time. In addition, such a coating remains elastic and does not develop cracks when aerated concrete blocks shrink. Silicone plasters are also sold ready-to-use and have many color options. Thanks to the availability special fillers, silicone plasters make it possible to create a varied coating texture. The only negative is the high price of the material, so not everyone can afford such finishing.

Acrylic

But acrylic plasters for aerated concrete can only be used if there is enhanced waterproofing on the inside of the walls and high-quality ventilation of the premises. This is due to the low vapor permeability of the material, which is closer to cement-sand compositions. If you do not provide sufficient protection internal surfaces, water vapor will begin to accumulate in the thickness of the walls and provoke peeling of the finishing layer.

Popular types of plaster mixtures for aerated concrete blocks

Name	Characteristics
	Dry mixture on a mineral basis. It is distinguished by its plasticity and ease of application. The prepared solution should be used within an hour. Application thickness – from 3 to 30 mm. After drying, the coating can withstand temperatures from -50 to +70°C, and at least 100 freezing cycles. The dry mixture consumption per m2 is about 14 kg when applied 10 mm thick. The coating can be painted 7 days after application.
	Cement-lime dry mixture. It has good resistance to shrinkage, adheres firmly to the base, and is not afraid of moisture. Applied in thicknesses from 5 to 30 cm, consumption - 14 kg with a layer thickness of 10 mm. The prepared solution must be used within 3 hours. Frost resistance of the coating is 50 cycles, can be used in the temperature range from -50°C to +65°C
	Ready-made mixture based on silicone resins. Very plastic, firmly adheres to the base, forms a strong coating with dirt- and water-repellent properties. The palette includes about 200 colors and shades. Consumption is 2.5-3.9 kg/m2, depending on the thickness of application
	Plaster composition based on silicone emulsion, ready for use. It has different grain sizes - from 1.5 to 3 mm, and is tinted in more than 200 colors and shades. The coating is moisture resistant. Pollution, exposure to ultraviolet radiation and temperature changes. Consumption is 2.4-4.7 kg/m2
	Ready-to-use silicate plaster. It has a grain size from 1.5 to 3 mm and 200 tinting options. Forms a dense coating with high vapor permeability and moisture resistance. Approximate consumption 2.5-4.2 kg/m2
	Acrylic composition with mineral filler. Can be used for exterior finishing of aerated concrete blocks if there is internal waterproofing and ventilation of the premises. Forms a thin but durable coating, resistant to negative influences. Has frost resistance up to 100 cycles, consumption is 4.5-5.2 kg/m2

Prices for various types of decorative plaster

Decorative plaster

Technology for plastering aerated concrete facades

Conditions for work

It is possible to plaster a façade made of aerated concrete only after all “wet” processes inside the room have been completed and the surfaces have completely dried. This applies not only to plastered and painted walls, but also to floor screeds, from which moisture evaporates very actively. The blocks themselves must also be dry - the maximum permissible humidity is 27%. If you plaster wet walls, intense release of water vapor will cause peeling of the coating.

It is recommended to plaster external walls at a temperature of +5...+30 °C, while relative humidity air should not exceed 80%. If for some reason it is not possible to complete the exterior finishing before the onset of frost, you need to treat the entire area with a deep penetration primer. The best option– primer Ceresit ST-17, applied in 2 layers. This protection will be sufficient until spring, when weather conditions allow plastering to begin.

Advice. Do not apply plaster compositions in hot weather, when strong wind and under the influence of straight walls sun rays. These factors contribute to the rapid drying of the solution, and it does not have time to firmly adhere to the base. As a result, many small cracks appear and the plaster peels off.

Prices for deep penetration primer

Deep penetration primer

Surface preparation

As a rule, walls made of aerated concrete blocks are quite even and smooth, so there is no need to specially level them. If there are deep chips or dents, you need to repair them with the glue that was used when laying the blocks.

To do this, mix a little glue (you can mix it with the dust formed when sawing blocks), scoop it up with a narrow spatula and fill the recesses. Remove excess and allow the solution to dry. Empty seams between blocks are sealed in the same way. When the glue dries, the walls need to be rubbed down to remove minor flaws. Use a metal flat grater for this. Finally, sweep away dust from the entire surface with a brush.

Padding

For priming aerated concrete walls under plaster, deep penetration compounds with strengthening properties are used. They create a very strong elastic film that allows water vapor to pass through, but does not allow the material to absorb water. Additionally, such primers increase the adhesion of the base and finishing layer. Popular products: Knauf Grundiermittel, Siltek E-110, Aerated concrete-contact-1.

The primer is applied in 1-3 layers, depending on climatic conditions terrain. For example, in dry and warm regions one layer of primer is sufficient, but in areas with a damp climate, coastal areas, three layers are needed. To apply the composition, use a roller or a wide paint brush. Prime with a continuous layer, evenly distributing the composition over the base. Use a narrow brush in corners and hard-to-reach places to avoid dry areas.

Plastering and reinforcement

It is not necessary to reinforce a layer of plaster up to 10 mm thick if the walls are properly primed. For larger thicknesses, reinforcement is indispensable, and for this purpose a fiberglass mesh with cell sizes of 3x3 mm is used. The mesh must be alkali-resistant - this will ensure high durability and strength of the finishing layer. This information is indicated on the packaging, so when purchasing a mesh, pay attention to this point.

Step 1. Prepare the plaster solution. The proportions of water and dry mixture are in the manufacturer's instructions, so read it carefully before starting work. To knead, take a clean container and pour the specified volume of water at a temperature of +15…+20 °C. Pour in the dry ingredients and stir with a construction mixer at a speed of 400-800 rpm. Let the solution sit for 5-7 minutes and stir again.

Construction mixer price

Construction mixer

Step 2. Take a wide metal spatula, apply the solution to the edge and apply it to the wall in an even strip. The spatula should be held at an angle to the surface and not pressed too hard, so the composition will be distributed most evenly. The layer thickness should not exceed 5 mm.

Step 3. A mesh is placed on top of the mortar, straightened, and then carefully deepened into the plaster, rubbing it forcefully over the surface with a spatula. If necessary, add the solution in small portions and rub thoroughly again. Having secured the mesh, apply the solution to the next area and repeat all over again. The mesh must be overlapped by 40-50 mm to avoid cracks at the border of adjacent areas.

Step 4. Special perforated profiles with a mesh attached at the edges are attached in the corners. To do this, apply the solution to the very corner, level it in height with a spatula, and apply corner profile and press gently. Then, like the mesh, it is deepened into the plaster and the surface is smoothed with a spatula. They are placed not only on external and internal corners, but also around the perimeter of window and door openings.

The corners and mesh should not protrude above the plane of the wall anywhere. The surface must be flat, smooth, without visible defects. Now you need to let the solution dry thoroughly. Drying time depends on the composition of the mixture and weather conditions, on average ranges from 3 to 7 days.

Finishing layer

Mix the solution for the finishing layer and apply it to the surface with a wide spatula. The thickness of this layer varies between 4-10 mm. Special care is required here, since all defects will remain visible. When plastering adjacent squares, the formation of stripes along the edges should be avoided; all excess should be removed immediately with a spatula.

When the plaster has set sufficiently, but has not yet hardened completely, begin grouting the walls. For this, it is most convenient to use a polyurethane grater, but a metal one will also work. The grater must be applied flat to the surface, pressed, and smoothed in a circular motion. plaster layer. Do not press too hard to avoid leaving scratches and dents.

After grouting, you need to wait until the plaster is completely dry, and only then proceed to the final stage - painting. You can also use decorative structural plaster, applying it in a thin layer to the prepared base.

Video - Facade plaster for aerated concrete

Blocks made of aerated concrete, foam concrete and gas silicate differ in their structure, so the approach to plastering walls built from these building materials may be different.

You need to know this about gas silicate, aerated concrete and foam blocks

A special feature of aerated concrete blocks is that their structure contains individual microscopic pores closed type. They are evenly distributed throughout the entire volume and provide the necessary degree of vapor permeability and thermal protection of the walls.

Foam concrete, like aerated concrete, contains closed pores that provide the required amount of waterproofing, as well as the thermal insulation properties of the material. Taking into account the technology of its production from sand, cement, water and foaming agent, we end up with a material with smooth walls and a porous internal structure.

Gas silicate blocks are made from lime, sand, water and additives that ensure the formation of pores in the volume of the material. The peculiarity of this material is that the pores are often not isolated, which is the reason for the increased hygroscopicity of gas silicate products.

Almost all properties of building materials have a downside. Thus, foam concrete blocks have a closed porous structure, which allows them to better resist moisture. On the other hand, the surface of such blocks is quite smooth, which complicates the process of plastering the walls. In turn, gas silicate blocks quickly absorb moisture, and in order to prevent this process, you need to either prime the walls or moisten them generously with water before applying plaster. Of all three types of blocks, the most unpretentious for finishing is aerated concrete.

Basics of technology for finishing facades with plaster

Wall decoration with plaster looks like this:

• cleaning the base from dust and removing deformed sections of blocks;
• priming the wall surface to increase the adhesion of the plaster mixture;
• applying a base layer of plaster with the introduction of fiberglass mesh to reinforce the coating. The mesh must withstand exposure to an alkaline environment, otherwise it will simply dissolve over time;
• applying the final layer of plaster, leveling the base

We will need the following as tools: a duster (it is convenient to clean the walls from dust and apply primer), large and small spatulas, a steel trowel, a hammer drill with a stirrer attachment.

A good master class on applying thin-layer plaster. After watching the video, you will learn how to finish smooth walls from foam blocks.

Cost of materials and labor

High prices for finishers are a powerful incentive to pick up a trowel and spatula yourself. So, the cost of plastering 1 sq. m. of wall can vary from 300 to 600 rubles. And that's without taking into account necessary materials! With approximate prices for primer and finished plaster mixtures you can see in the following two tables.

Primer for pre-treatment of walls

Name	Type	Packing, l	Approximate cost
Ceresit CT 19	Water-dispersive, for treating foam concrete walls	15	730 rub.
Litokol PRIMER C-m	Deep penetration for interior work	10	720 rub.
Thomsit R 777	Strengthening for absorbent substrates inside buildings	10	860 rub.
Putzgrund RD313	Acrylic dilutable for interior and exterior use	10	800 rub.
Terragrunt		20	1620 rub.
LAKRA Universal primer with deep penetration	With anti-mold additives	10	440 rub.
Tikkurila Gravel Strong	Water-borne acrylic primer of deep penetration with a sanitizing and strengthening effect, facade	10	1400 rub.

This is important for any plastering works Oh:
— the cellular building material used is initially characterized by some humidity, which exceeds the operational values. Therefore, plastering of walls begins only 6 or more months after the construction of the house;
— first comes the interior finishing, and then the exterior. If the sequence is reversed, there is a possibility of “locking” moisture inside the blocks with subsequent condensation of steam at the junction of the block and the outer layer of plaster. Usually there are no questions with this requirement, because for most people it is important to quickly create comfortable conditions inside the building, and only then deal with its appearance;
— if there are wide seams, it makes sense to pre-seal them. This will avoid a number of inconveniences when plastering walls;
- because blocks made of cellular concrete are vapor-permeable, plaster should also have this quality. For this reason you should not use cement plaster for finishing facades. Lime and lime-cement mixtures are suitable for these purposes. The exception is interior work, when the condition for increasing the vapor permeability of the layers of the wall from the inside to the outside is satisfied;
— when using reinforcing mesh, the material is laid with an overlap of at least 100 mm, which ensures the required closeness of the layer. The mesh must be exactly recessed into the layer of solution, otherwise there is no guarantee that it will work as it should. For example, there is a higher probability that the finishing layer will soon simply fall off the wall

Options for ready-made mixtures for plastering walls

Name	Type	Packaging, kg	Approximate cost
Baumit GrundPutz Leicht	Light lime-cement	25	300 rub.
WIN - Aegis TM-35 I		30	245 rub.
Pobedit-Aegis TM-35 ELITE			280 rub.
TM-22 will win	Facade cement	50	260 rub.
Wins - Aegis XI-S-42		25	220 rub.
REAL RT29	Cement-lime for external and internal work	25	200 rub.
Quick-mix LP 18	Cement-lime with polystyrene (for external and internal work)	30	450 rub.
Ceresit CT 24	Cement, for facade and interior work	25	335 rub.
Hercules	Cement-sand for work inside and outside	25	150 rub.
Glims Velor		15	210 rub.
Bonolit	Gypsum for interior work	30	315 rub.

The video below shows an example of plastering walls made of gas silicate. cement-sand mortar inside the house. In this case, the plaster has less vapor permeability than the wall material. But if the condition of increasing vapor permeability in the wall pie from the inside to the outside is met, then such a solution has a right to life.

Plastering aerated concrete walls with lime-cement mortar

We invite you to try economical option plastering walls made of aerated concrete or gas silicate blocks - using lime- cement mortar. To prepare it you will need slaked lime(150-220 rubles per 25 kg bag), sand (sifted through a sieve with a mesh size of no more than 5x5 mm), water, grade 500 cement. The step-by-step process looks something like this:

• saturating the surface to be finished with water. To do this, you can use a spray bottle, a spray bottle, a broom, water from a hose, the main thing is that the wall stops absorbing moisture. Otherwise, moisture will quickly leave the plaster applied to the wall, which will lead to the appearance of cracks in the finishing layer;
• splash or spray. It is a kind of ersatz primer, which allows you to increase the adhesion of the plaster to the gas silicate surface. Naturally, the choice is determined solely by economy. Spraying is carried out using a broom with a liquid lime-cement mortar, reminiscent of kefir (in thickness), diluted 2 times with water. The proportions of lime, sand and cement, which we will discuss below, remain the same. But several times more water is added to achieve the required viscosity. The solution applied in this way is not smoothed over;
• leveling layer of plaster. For one batch you will need a bucket of lime, a bucket of water, 5 buckets of sand, ½ bucket of cement. The solution is prepared as follows: add lime to water, mix using a hammer drill with a special attachment (the required consistency, brought with water, is thick sour cream), then add sand and cement, again mix everything thoroughly. Plaster with beacons or without them - it all depends on the quality of the wall surface. If the differences are serious, then they set up beacons; if not, they limit themselves to puttying;
• grout. The main goal of this stage is the final leveling of the surface. They resort to it if, as a result of applying the base layer, there are sagging, unevenness, gouges, etc. In some cases, the excess is removed using a special brush, in others, the deficiencies of the layer are compensated for with a plaster solution using a wide spatula. Grouting is started immediately after the finishing layer has hardened.

In conclusion, I would like to give an example of what not to do. It's better to learn from other people's mistakes.

Aerated concrete blocks are incredibly in demand today – and not only in private construction, but also in the construction of frame-block multi-storey buildings. The products are compact, light in weight, and easy to install, which allows a person to build warm and inexpensive housing with his own hands.

However, raising the walls and bringing them under the roof is not all. You need to know exactly how to plaster aerated concrete inside a house, and understand the principle by which interior plaster is generally selected. These questions became the topic of this article.

The principle of selecting plaster for the base

Both aerated concrete and gas silicate concrete belong to the category of cellular concrete. There is an opinion that this is one and the same thing, but there is still some difference between them.

Both materials contain a combination of two cement-lime binders. However, their percentage different, resulting in a material with completely different strength characteristics.

Leveling coatings for aerated concrete

Aerated concrete contains up to 60% cement, and the rest is lime and sand. In gas silicate products, there is only 14% cement, almost twice as much lime, and many times more sand. It is clear that if there is so little cement, then the strength of the products is no longer the same. In general, gas silicate concrete is no longer a structural material, but a thermal insulation material.

• Perhaps now you have a question: “What does interior wall plaster have to do with it?” And given that it is selected depending on the type of base, and in order to avoid problems with the coating later, you need to know exactly what can be combined with what. The characteristics of the binder are of decisive importance here.

Pay attention! Cement, or rather products and solutions based on it, always has greater strength than lime and gypsum. When creating multi-layer screeds, the following principle must be observed: the base must always be stronger than the coating - otherwise, it will inevitably peel off.

• From the above it is not difficult to conclude: if there is no - or almost no - cement in the blocks, then the internal plaster of the walls, and especially the external one, cannot be done, for example, with a cement-sand mortar (see. Optimal ratio of cement and sand for plaster ). It can be used for aerated blocks, since they contain high percentage cement, and the wall surface has sufficient strength.

• You can even use not special purchased mixtures, one of which we see in the photo, but mix the solution yourself. You just need to keep in mind that the plaster should not be done as for heavy concrete or clay brick - in proportions of 1:3, when a mortar of M150 grade is obtained.

Plaster interior walls made of aerated concrete, made with a mortar of half the strength: M75. To make it, take M400 cement and mix it with sand 1:5.

When the grade of cement increases, its amount in the solution should decrease to 1:6, or even to 1:6.7 - that’s the arithmetic. Everything is done quite simply, and the lower price of self-mixing plaster will allow you to significantly save on finishing works Oh.

How to plaster gas silicate

Now, as for gas silicate wall, in which there is very little cement. Accordingly, such plaster as for aerated concrete is not suitable for it. However, it is impossible to endlessly reduce the amount of binder in the solution - you can only replace part of it with another binder that is weaker in strength.

• IN gas silicate blocks there is a large percentage of lime, and it is most logical if it is present in the plaster. That is, the most ideal option for plastering such walls there will be lime-cement plaster. Making it yourself is more difficult, since lime paste must be present in the solution.

• It is much easier if the interior of the house is plastered using a purchased mixture. And by the way, if it is suitable for gas silicate, then it will also be suitable for aerated concrete (and not vice versa). Manufacturers often focus plaster mixtures on both materials, which means that in addition to cement, they also contain lime.
• Sometimes the instructions on the package say that the mixture can be used for all cellular concrete. This means that they can also be applied to walls made of foam concrete, which contain only cement as a binder. Just keep in mind that there are also cementless varieties of foam blocks made from lime.
• Like gas silicate, this material is also more of an insulator than a structural material. Foam blocks, which contain no cement at all, are used for the construction interior partitions. They can also be plastered, but there should be no cement in the solution.

It should be noted that the best option for leveling walls made of gas and gas silicate blocks, lime foam blocks, as well as sand-lime brick, are silicate plasters. But since they contain liquid glass, and they are very caustic, they are not used for residential premises - only in production workshops and on building facades.

The feasibility of using gypsum mixtures

Plastering inside a house with lime surfaces can be done with gypsum or lime-gypsum mixture. In principle, they are suitable for all types of foundations, but there is one problem, and it concerns walls built from cellular concrete.

Considering their high vapor permeability, and the similar property of gypsum, it is not always advisable to use plaster based on it indoors:

• Here it is already necessary to consider the structure of the wall decoration as a whole, and oddly enough, you need to focus on the option of exterior decoration. Let’s say that the outside of the cellular concrete walls will be monolithically lined with brick, clinker tiles, or stone, or plastered over polystyrene foam.
• Due to their poor vapor permeability, these materials will trap moisture in the thickness of the walls, not allowing it to escape. In this case, only cement plaster should be used inside, or such decorative coating, which will become a barrier to steam.
• For example: if it is paint, then it is alkyd; if wallpaper, then vinyl or cork. Yes, the same tile or stone, any cladding with insulation - all this will not allow porous walls to become saturated with moisture.
• In what cases can interior plastering of walls made of aerated concrete or other cellular material be done with a gypsum mixture? There are only two options here. The first is when the external walls are leveled on the base with plasters with a high degree of vapor permeability: silicate, silicone, special for cellular concrete.
• The second option is a ventilated facade. When with outside the walls have an unobstructed outlet for steam and condensate, the internal plaster of the walls, like their finishing, can be executed in any way. But we note that if the facade is insulated, then the heat-insulating boards should be loose: soft mineral wool or the cheapest loose foam.

• Let us also clarify this situation. Decorative plaster for interior decoration, most often made from gypsum. How to properly prepare a porous base in cases where the use of gypsum mixtures is undesirable. There are no problems with cement-based blocks.

In any case, the base before decorative plastering should be leveled as for wallpapering. Therefore, the walls should first be leveled cement composition, and when it dries, it can be applied gypsum plaster decorative for interior decoration. You will learn more about this in the next chapter.

Internal plastering of aerated concrete

So, in our story we came directly to the implementation of internal plastering work on aerated concrete walls. We will try to highlight the most important nuances this process, and for clarity, we offer you to watch the video in this article.

Nuances of preparation

Porous surfaces have the highest moisture absorption, which must be reduced by priming. On aerated concrete walls it is produced more abundantly than, for example, on brickwork. To do this, you need to take not just an adhesive primer, but a deep penetration composition.

Important! Primers can be ready-made, or they can be concentrated – that is, they are diluted with water in a proportion determined by the manufacturer, which must be observed. You should not think that if you apply undiluted primer, you can, for example, reduce the number of passes. The composition must have a normal concentration.

The first layer is applied generously, preferably with a spray gun. You can also use a regular garden sprayer for this purpose, which is used to spray trees. After the aerated concrete wall has dried slightly after treatment, another layer is applied, after which the surface should be completely dry.

Double impregnation significantly reduces the absorption of the wall, but does not eliminate it completely. Yes, this is not necessary - otherwise how will the solution stick to the surface? The surface of aerated blocks is very smooth, and for plaster it is necessary to ensure good adhesion. It is impossible to make notches here, as on heavy concrete. How to get out of the situation?

How to make a plaster coating as durable as possible

After priming, task number two is reinforcing the surfaces. This is necessary not only for the best adhesion of the layers, but also to prevent the appearance of cracks.

This is especially important when the walls are built from gas silicate, which contains five times less cement than gas blocks. The strength of such a base is quite weak, and plaster, even gypsum, will be stronger and will work against tearing.

• Your task is to make a strong layer between the base and the plaster sheet, which will provide them with the best adhesion. Therefore, no matter what type of plaster you use, the starting layer must be made with an adhesive mixture, which is intended for installing cellular blocks.

• To create a reinforcing layer, ordinary tile adhesive is also suitable. Many masters, due to a reason lower than that masonry mixture cost, they prefer to use it. Why do you need an adhesive composition and not just a plaster composition?

Pay attention! The fact is that adhesive compositions are always modified with polymer additives, which not only adhere, but permanently glue surfaces together. The layer of glue is thin and durable, and a fiberglass mesh is embedded in it. Not only is it an excellent base for plaster, but it also reliably fixes the blocks, preventing microcracks from appearing and expanding.

• A similar approach to preparatory work especially important when solutions are used for plastering self-made. In them, unlike factory ones specially designed for gas blocks, there are no improving modifying additives, as well as fiber reinforcing the plaster in the mass.

• There are no words, factory mixtures solve all problems, but due to the high cost, they are more often used for facades. You can save money on interior plaster, which is not exposed to the same influences as on the street - you just need to do it wisely. If you don’t want to have problems in the near future, you need to do the adhesive layer anyway.
• Installation of the mesh, in principle, is not necessary and is carried out by craftsmen at the request of the home owner. But the customer should know that creating a reinforcing layer only improves the quality: both of the plaster and the base - after all, no one knows what shrinkage processes will occur in the soil.
• It’s better to play it safe and spend a little money on a mesh than to incur costs for complete renovation. We especially advise you not to neglect the mesh when the walls are being prepared for painting - after all, any crack on them will be immediately visible. Under thick wallpaper or tiled cladding, cracks are invisible, but the task is not to hide them, but to prevent their appearance.

• There is nothing complicated about installing the mesh, and you will see this in the video presented in our article. The canvases are laid with an overlap on the freshly applied glue solution, and then pressed, combing with a notched trowel. The use of such a tool is very important, since thanks to it, ridges of squeezed out solution remain on the surface of the mesh.
• When they dry, you will get a wonderful relief surface on which you can apply any plaster. First, the mesh is pressed into the adhesive layer with chaotic movements, trying to press it as tightly as possible to the base. If regular leveling plastering is carried out on the walls, in conclusion, you need to do a horizontal combing.
• This is necessary only so that the plaster, which will be applied to this surface at the next stage, does not slide off the wall. Well, for decorative plaster - if this is what will be used for interior wall decoration, the base should be smooth. In this case, the relief is not left, but the solution on the mesh, squeezed out with a notched trowel, is smoothed out.

When can I start plastering directly? Let us say right away that it is not advisable to do this the very next day.

Even if the surface seems dry, the cement adhesive layer has not yet gained sufficient strength. It's not scary if gypsum plaster is applied to it. If it is a cement mortar, then the adhesive layer should be given at least five days - preferably a week - to gain strength.

Aerated concrete is a modern building material that resembles foam concrete in structure, but is distinguished by air bubbles located inside. The hollow structure of aerated concrete absorbs moisture well, which requires external finishing of the material. The best way to plaster walls made of aerated concrete is discussed in this article.

For the manufacture of the material the following are used:

• quartz sand is the basis of the mixture;
• lime;
• cement;
• water;
• aluminum powder is added during the manufacturing process of the material. Acts as the main gas generator and gives the material a specific structure.

Advice: When purchasing aerated concrete, you must take into account that the pores of the blocks, unlike foam concrete, are open. This determines the features of its application and finishing.

Comparative characteristics of foam concrete and aerated concrete are presented in the table:

Foam concrete	Aerated concrete
In its structure, air bubbles are not connected to each other, which increases the material’s resistance to getting wet.	The air bubbles are interconnected, allowing moisture to move freely through them.
Good qualities of frost resistance and thermal conductivity.	Gives off heat and freezes from frost.
The inner layer of the plaster layer should be twice as thick as the outer one	The walls should be plastered indoors and then on the façade of the building.
To improve adhesion, the walls need to be cleaned, then thoroughly sanded to remove the top hydrophobic layer. Due to poor moisture absorption, to increase adhesion, the solution is sprayed, and then the base layer is applied.	Higher adhesion rates

When plastering external surfaces of aerated concrete, its high hygroscopicity must be taken into account.

This requires the use of non-standard plasters, which over time will not lead to:

• Cracking of the internal and external surfaces of the building, as in the photo.

• The appearance of traces of masonry after fog or rain, which worsens the visual parameters of the walls.
• Changes in technical specifications.

• Increased indoor humidity.
• Mold appears in the corners of rooms.

For finishing external surfaces, special facade plasters are used. A particular danger for aerated concrete slabs is temperature changes and severe frosts.

During operation, it begins to accumulate inside structures. a certain amount liquid that will expand when frozen and can greatly damage the structure of the structure. Plastering aerated concrete bases can only be done with mixtures that have good water-repellent properties that do not prevent moisture from evaporating from the walls.

For exterior finishing of aerated concrete, the plaster must have:

• Good adhesion parameters.
• High compressive strength.
• Frost resistance.

Advice: Owners of buildings made of aerated concrete blocks should take into account that external finishing of walls is carried out only after all internal cladding work has been carried out. Otherwise, when carrying out “wet” interior finishing work, the walls will absorb a significant amount of moisture, which will subsequently begin to evaporate.

If external facade will be finished before application interior plaster, with its intense evaporation, peeling of the outer plaster layer from the surface of aerated concrete will occur. After finishing the interior of the room, you can cladding the walls of the house outside special compounds with the highest vapor permeability.

Advice: You cannot plaster facades using standard cement-sand mixtures due to their insufficiently high vapor permeability properties.

Plaster for gas concrete

To decorate the walls, vapor-permeable plaster for aerated concrete is used, which is highly permeable to water vapor, does not get wet, has good adhesion to the surface of the blocks and high frost resistance.

Type of plaster	Features of the material
	Acrylic plasters for aerated concrete are used to strengthen structures with increased load, such as a plinth. Used for interior and exterior decoration of the house. Taken for decorative coating. They retain their color and unchanged texture for a long time. They have good adhesion. Disadvantages of the material: Not too high vapor permeability. Subject to combustion. Tip: When choosing such a material, you must first waterproof the walls.
	The basis of the composition is liquid glass. This is a breathable plaster for aerated concrete. Has low water absorption. Reasonable price. There are many textures that may have: scratches, roughness, pits. They are used for plastering facades and internal walls made of aerated concrete, on the material itself and insulating elements for it. Disadvantages: small selection of colors, loss appearance, due to the settling of dust and dirt on the surfaces of the walls.
	Silicone plaster for aerated concrete is made on the basis of silicon-organic polymers. It is highly resistant to harmful atmospheric influences. It practically does not get wet, the mixture is hydrophobic. Has high vapor permeability. Easy to apply. Such plastering mixtures for aerated concrete do not lose their pleasant appearance for a long time. Disadvantage: high cost, but over time, it will most likely pay for itself. In this case, it is appropriate to remember that the miser pays twice.
	Advantages of the composition: Dries quickly. Does not shrink. You can make a smooth surface. No need to apply a finishing coat. Disadvantages of gypsum plaster: Not very good vapor permeability. Gets wet quickly in rain or snow. Spots appear on the surface that need to be painted over.

Lime-cement plaster

All the necessary properties are inherent in lightweight thin-layer plasters, specially created for finishing aerated concrete surfaces. An example of such plaster would be Baumit HandPutz for DIY wall finishing, produced in bags weighing 25 kilograms.

Basics of it physical properties are given in the table:

Indicator name	Its meaning
Grit size, mm	1
Strength of material in bending, tensile, N/mm2	≥0,5
Compressive strength of the composition, N/mm²	≥3,5
Vapor permeation resistance coefficient μ,	15
Thermal conductivity coefficient λ, W/mK	0,8
Density of the mixture in dry form, kg/m³	1600
Liquid consumption, liter/bag	6-7
Mixture consumption (with applied layer thickness 1 cm), kg/m²	15
Minimum plaster layer, mm	5
Maximum layer of plaster, mm	20

Tip: Before plastering aerated concrete with this plaster, you need to spray the previously cleaned wall surface with Baumit Vorspritze solution.

Material selection

To choose which plaster is best for plastering aerated concrete walls, you need to purchase a plaster composition that satisfies the following characteristics:

• good vapor permeability;
• the optimal volume of liquid for mixing the mixture: per kilogram of mixture - no more than 0.2 liters of water;
• certain values ​​of the minimum and maximum thickness applying plaster;
• good adhesion with a base of at least 0.5 MPa;
• resistance to negative temperatures;
• high resistance to cracking;
• long viability of the mixture, the larger it is, the easier it is to work with the solution, especially for beginners.

Procedure for plastering aerated concrete walls

Before starting work, it is better to familiarize yourself with the video in this article.

Advice: Building blocks from cellular concrete quite smooth with almost invisible seams. There is no need to use plaster mortars to level surfaces. It is enough to apply only a thin layer of the mixture.

The instructions for plastering walls suggest the following procedure:

• Surface primer. A composition specially designed for aerated concrete, the surface of which actively absorbs moisture, is applied with a brush or roller.

• A reinforcing mesh is mounted, which is attached to the surface with self-tapping screws (see How to attach a plaster mesh to a wall).

• The walls are finished with a thin layer of plaster.

Correctly selected plaster mixtures for aerated concrete blocks allow you to make your home not only beautiful, but also warm, retaining all its positive characteristics for a long time.