How to protect aerated concrete blocks from moisture - how to treat the outside

The article was written with the participation of PROSEPT specialists

Battles over aerated concrete blocks between their fans and ardent opponents have not stopped for decades, and it is unlikely that one of the sides will ever win. This material has a lot of positive properties, such as low thermal conductivity, good geometry, ease of processing, environmental friendliness and fire resistance. These and other parameters attract private developers, but there are also characteristic features, rather with a minus sign. For example, the need for facade finishing, a large mass of high-density blocks, as well as increased hygroscopicity and the resulting deterioration in frost resistance, which must be taken into account. Most of the copies are broken precisely around the ability of blocks to absorb moisture, which entails an increase in thermal conductivity and a decrease in frost resistance. With the help of PROSEPT specialists, we will try to figure out how to protect aerated concrete from the negative influence of external factors.

In this article we will look at:

• Features of aerated concrete blocks and their operation.
• How to protect unfinished stone buildings.

Effect of water repellent

The product impregnates the top layer and is characterized by deep penetration . Aerated concrete becomes waterproof while maintaining the ability to penetrate steam.

Impregnation for aerated concrete has the following effect on the material :

• increases resistance to external temperature changes;
• prevents freezing of capillary liquid molecules in the pores;
• increases strength, minimizes destruction;
• reduces the impact and spread of corrosion;
• reduces the risk of efflorescence on the surface.

The treated materials cannot be tiled, stoned, or plastered, since the water-based solution will not stick to them. The positive thing is that graffiti cannot be applied to the surface, which is often done with acrylic, latex, or water-based paint.

Is it possible to prime an aerated block with liquid glass?

Liquid glass is an aqueous-alkaline solution of potassium or sodium, obtained by autoclave processing of silica-containing raw materials (but there are other methods of production). The main advantages of the material are its resistance to fire and water, so it is used for appropriate processing of structures. This coating is quite inexpensive and does not require significant costs, so many users are interested in whether aerated concrete can be primed with liquid glass?

To answer this question, it is enough to refer to the technical characteristics of liquid glass. Its density is 1.36-1.45 g/cm3. In kilograms, the result is a minimum of 1360 kg/m3, which is almost three times more than D500 aerated concrete, most often used in low-rise construction. That is, approximately like plaster.

Actually, silicate plasters are made on the basis of liquid glass. However, in plasters it is diluted with finely ground binder and filler, and therefore retains a certain degree of vapor permeability. When liquid glass is applied in its pure form, a continuous film is formed, tightly sealing the surface pores of the base, so it is an excellent waterproofing agent, but does not allow vapor to escape.

Therefore, liquid glass is not suitable for external waterproofing of aerated concrete walls of heated buildings. It can only be used to protect against moisture and steam from the inside - for example, to treat walls in a bathhouse or bathroom under tiles. In rooms, it makes sense to cover walls in this way only if the outside is insulated not with vapor-permeable mineral wool, but with almost airtight polystyrene foam, or, for example, lined with brick or stone without a ventilated gap.

Types of water repellents

Water repellents are produced on a water and silicone basis.
Compositions for waterproofing aerated concrete on the outside are produced in the form of dry powder, liquid and pastes . The first and last options are diluted before use, and the second is ready for use. The purpose of the drug, the manufacturer, and recommendations for application are important.

Choose a product taking into account the following conditions:

• obtain effective protection against dampness;
• do not spoil the appearance of the structure.

Regardless of the processing method, the main factor influencing the choice is the type of base , which can be silicate or water-based .

Water-based compounds

You can effectively protect aerated concrete from moisture if you use aqueous solutions. They improve the appearance, are easy to use, and belong to the category of environmentally friendly impregnations. For aerated concrete, there are special moisture control agents that are used specifically for this material.

Penetrating waterproofing GKZh-11N is popular . An aqueous emulsion of the organosilicon polymer sodium methyl siliconate penetrates into the mass and settles in it as a result of interaction with atmospheric carbon dioxide. Increases frost resistance and water resistance.

Silicone-based products

Silicone-based products can be used to protect cellular concrete.
Experts consider drugs in this category to be the most effective compositions . Such solutions can be used to remove moisture from the outside of aerated concrete blocks and can be used for other materials.

After the film hardens:

• extends the service life of structures;
• reduces the likelihood of the appearance and development of mold and fungi;
• reduces heat transfer;
• reduces sensitivity to frost.

The effectiveness will be higher if the product is applied to a dry, dust-free surface. The film does not interfere with the passage of steam.

Using liquid glass

Such impregnations are classified as modern effective materials. Liquid glass is one of the types of silicate glue , which is sold at an affordable price.
It is applied using rollers (large surfaces) or brushes (small areas). The product is applied until the aerated concrete absorbs the liquid glass. The product sets quickly, but fully gains properties after 24 hours . The result is a water-repellent coating with good protection performance.

Features of aerated concrete blocks and their operation

Aerated concrete is one of the varieties of cellular concrete characterized by a porous structure; it is characterized not only by high vapor permeability, but also by high moisture saturation. And if the first property is considered an advantage of the material, since houses built and finished in compliance with the technology will have a healthy microclimate, then the second is considered a disadvantage.

During the production process, the gas that formed pores in the blocks is displaced by air, which determines their open structure.

Because of this structure, blocks are saturated with moisture more than other masonry materials of their own group and other varieties. And the lower the block density, the more active this process is. Regardless of the brand of blocks, it is difficult to imagine a real situation when the house is completely immersed in water and soaked. But prolonged rains, watering walls even with large overhangs, are the norm for some regions. Therefore, how critical the impact of precipitation is depends on both the parameters of aerated concrete blocks and operating conditions.

Ideally, during the construction process, the outline of the house should be closed before the start of the cold season; at a minimum, the rough roof should already protect the walls. Also, all block manufacturers recommend protecting walls either using a system of ventilated facades, or decorative plasters, or tiles/stones, or something else, depending on the chosen style and financial capabilities. But in practice, this does not always work out - future homeowners lack either time or money, or more often both, and there may be a long interval between construction and facade work. That’s when FORUMHOUSE users have questions: what to do with the unfinished building?

Sergey-Spb

I built an attic house from 30 cm D300 aerated concrete (foundation slab, walls, roof, ceiling, partitions, double-glazed windows). I planned to make a façade with insulation next year, but a crisis arose. The house has been standing for two winters, construction has been suspended. Now the question is - the means do not allow you to do everything at once. What bad can happen to a house made of aerated concrete without finishing the facade? Is it possible and worthwhile to do work on the inside of the house (communications, floors, walls), or the façade first?

Regarding the use of a block considered to be thermal insulation and not structural for the construction of load-bearing walls, Sergey-Spb responded to the participants in the topic who raised this issue that the engineers with whom he consulted considered his solutions to be viable. Regarding the question asked about the facade, the answers from practitioners are as follows.

Konstantin Ya.

If the conversation had not been about the D300 and not in St. Petersburg (as I understand), I would have said that it is possible to leave it for more than a year. I'm not saying that the D300 will fall apart - I just don't know how it will behave without finishing. And so, I have a D600, 250 mm, for more than ten years it has been standing fine without exterior decoration, of which a little less than ten have been fully heated (with interior decoration for a long time). In principle, if melt water from a leaky roof does not constantly flow over it (aerated concrete), freezing and thawing alternately, then what will happen to it. At least five years, at least ten.

alexpan

The house has been standing for eight years without external finishing, the wall thickness is 300 mm, plus internal plaster - the flight is normal. We are already living, this year I will finish the kitchen and next year I will work on a ventilated facade without insulation. So don't be afraid, everything will take its course.

There is a certain algorithm for performing work in aerated concrete houses.

Sleng

The order was determined a long time ago, and even more so in GB houses. Internal wet work, drying, external work. The recommended drying period is one year. But there are no regulated periods for the presence of aerated concrete without external finishing.

Nevertheless, experts advise to insure yourself, especially since it does not require excessive financial costs.

Evgeniy Kuznetsov Technical specialist at Prosept

The main disadvantage of aerated concrete is its low frost resistance in the absence of protection from moisture. Therefore, it is recommended to immediately finish external walls made of aerated concrete. In the case where there is not enough money for facade work, or the priority is interior decoration and occupancy, then facade work can be delayed for several years, protecting the external walls from moisture. The most inexpensive option for preserving aerated concrete is treatment with a water-repellent protective impregnation - a water repellent.

In addition to walls as a whole, there are other risk zones in which excessive moisture accumulation is fraught with, at a minimum, cracking, and at maximum, destruction of the block.

scvirtl

A disaster has occurred (it is not yet clear whether it is big or not). Upon completion of the construction of a house made of aerated concrete, 2 troubles appeared:

1. There are cracks under almost every window, this is due to the fact that the interior was done in cold weather, and moisture accumulated on the windows and from there into the blocks below them. The blocks got very wet. A radiator dried them inside. Outside, when frost set in and the block froze, such cracks appeared. How critical is this, and how can this be fixed?
2. Under the door in the kitchen to the future veranda, blocks began to collapse.

What should I do?

Evgeny Kuznetsov

In this case, as in many others, the main problem is that the gas blocks easily absorbed moisture, which then destroyed them from the inside. It is important to avoid overmoistening when using aerated concrete. The situation with an abnormally high exposure to moisture on aerated concrete with its subsequent freezing leads to its destruction. To avoid such results, it is worth paying special attention to the arrangement of window sill drains, cornices, each canopy and spillway systems, thereby eliminating the likelihood of constant contact of water with gas blocks. That is, to ensure water drainage from those areas where waterlogging is possible. Particular care must be taken to protect the masonry in the plinth area. If water and snow are not in constant contact with aerated concrete, then precipitation will not cause significant damage to the structure.

According to Evgeniy, solving the problem described will require serious repairs and restoration of the material. However, simple measures should be taken to prevent such incidents in the future. The main thing is to prevent water absorption; you can treat the house with a water-repellent impregnation in the same way as we do, for example, with shoes, treating them during the rainiest season.

The water repellent for aerated concrete is based on silicones, these are organosilicon compounds. They are affordable, inexpensive for the manufacturer, and therefore the price of processing the house for the builder is acceptable.

It protects your home for several years, and thanks to treatment you can avoid many problems that arise under the influence of moisture.

Another possible problem is mold. Aerated concrete itself is considered biostable, but this is in a dry state; if it is waterlogged, damage by pathogenic microflora is quite possible. There can be a lot of reasons for this phenomenon, and it is necessary to fight, first of all, with them, but it is quite possible to remove traces of the vital activity of microorganisms.

kondorand

I'm looking for advice on how to combat mold/fungus. The house is made of aerated concrete, 250 mm thick, the 1st floor is aerated concrete, the 2nd floor is an attic with gables made of aerated concrete. Pie of walls from outside to inside: siding, ventilation gap, windproof membrane, insulation, aerated concrete, glued plasterboard sheets, wallpaper. The ceiling between the floors is made of wooden beams, with insulation between them, thickness 200 mm. On the ceiling of the first floor there is a vapor barrier lined with a wooden board. Only the first floor is residential, the second floor is without insulation. The house was built 2 years ago, insulation was done last summer. We started heating in mid-October and moved in in November.

For kondorand, the temperature in the house is about 20-22⁰С, there have not been any severe frosts outside yet, from -2 to +2⁰С (Leningrad region), and there is constant dampness outside. Ventilation has been installed in the kitchen (exhaust hood) and in the bathroom, plastic windows often become damp, micro-ventilation does not help, and if you open it wider, the house gets cold. Mold has grown in spots on the walls and corners (especially if both adjoining walls are external), mostly slightly above the baseboards. Our user is interested in the question of what to do now.

As Evgeny Kuznetsov notes, without a full-time study of the structure, making a “diagnosis” is problematic and incorrect; the appearance of mold is provoked by high humidity, and this phenomenon can have several reasons:

• Insufficient thermal insulation, resulting in condensation, an option to solve the problem is to eliminate cold bridges.
• The general design of the walls and the sequence of the wall “pie”. The wall must be built in such a way as to ensure increasing vapor permeability of materials as one moves from the internal layers of finishing to the external ones. The solution is additional ventilation.
• Poor waterproofing between the wall material and the foundation, and as a result - constant recharge from groundwater. A fairly common problem, especially in swampy regions. One solution is to carry out cut-off hydrophobization. This method is often used in construction when it is necessary to stop the rise of groundwater through the capillaries of the walls of a finished structure. The procedure involves forced saturation of the walls with a water-repellent solution from the inside.

Whatever the reason, it must be eliminated.

Evgeny Kuznetsov

Reconstruction is necessary, otherwise the fight against mold will only produce results in the short term. Once structural work is completed, mold removal can begin. We recommend treating the necessary areas with a mold-removing compound. Old wallpaper can be replaced if desired. If it is not possible to make a full repair, then after removing microorganisms and treating with a protective composition against mold, you can paint the affected areas. Compositions for removing and protecting against biological damage, such as mold, mildew, moss, algae, are very often used in rooms with high humidity, such as bathrooms, and work effectively.

External cladding

Without external finishing, aerated concrete cannot withstand frequent temperature changes.

Finishing the outside of the walls. After completion of construction, the structures are maintained for at least 6 months. This time is necessary for the blocks to shrink; during this time, the aerated concrete will dry well. Moreover, work on external finishing should begin after completion of internal ones, but not vice versa. This is determined by the properties of the transition of steam from the inside of the building to the outside, to the street. If the sequence is violated, no matter how highly qualified the work is, microcracks will form in the structure of aerated concrete. The formation of microcracks leads to peeling of the plaster. Of course, this problem can be solved by using high-quality plaster. The durability of the structure decreases.

Insulation of a foam block house with ecowool on the outside

Foam concrete blocks themselves have good heat retention properties; moreover, the material is almost not saturated with moisture and does not allow street noise to pass through. Additional thermal insulation of foam concrete makes it possible to reduce the thickness of load-bearing walls, which saves money spent on construction.

Thermal insulation of foam concrete blocks can be carried out with cellulose ecowool, which provides significantly better heat and sound insulation than slab or roll insulation such as foam plastic or stone wool. Ecowool is able to absorb without damage and release back up to 30% of the moisture from the volume.

The positive properties of insulation include environmental cleanliness, fire safety, fire resistance and the impossibility of reproduction of insects, rodents or harmful bacteria and fungi in its thickness.

It is also important that a layer of ecowool 10-20 centimeters thick is sufficient to protect walls built from blocks in one row. Moreover, cellulose wool extends the service life of foam blocks, since it actively prevents the penetration of dampness and smoothes out temperature fluctuations outside the house.

The process of external insulation of houses with ecowool is described in detail here.

Using ecowool as a heat insulator allows you to create a comprehensive system of strong load-bearing foam concrete walls and reliable protection from low temperatures and humid air, which ecowool provides.

Quality control of insulation blowing, its tight laying and the absence of construction defects is carried out using thermal imaging inspection. Insulation of a house with ecowool and the service of checking its quality with a thermal imager can be ordered from our construction company.

Benefits of applying primer

Coating the surface of gas silicate blocks has many undeniable advantages:

• Improved adhesion properties. When applied to the surface, the primer composition is absorbed into the porous base. As a result, the subsequently applied plaster solution adheres to the surface more firmly and does not dry out in a short period of time.
• Surface strengthening. Walls made of foam blocks become more durable, the material does not crumble, and small particles do not mow down.
• Reducing the water absorption coefficient. Blocks absorb less moisture if they are pre-treated with a primer. Accordingly, the supporting structure will last a long time.
• Increased thermal conductivity. The heat retention properties increase, as the material becomes an excellent heat conductor.
• Antifungal effect. During production, special additives are added to the primer, due to which the treated surface is protected from various fungal manifestations.
• The blocks do not absorb dust and dirt. The strength properties of the material are preserved and the building does not settle.
• Resistance to external negative factors. The primer provides protection against temperature changes, and the service life of the foam block structure increases.

Along with the main advantages, additional ones can be noted, which are no less important:

• Applying a primer layer to the surface is quite simple. You don't need any skills or qualifications to do this.
• Modern formulations are environmentally friendly and do not contain toxic substances. At the same time, they are convenient to use.

How to insulate a foam block house with foam plastic

Finishing work begins with cleaning the outer surface of the walls from dirt, after which their surfaces are leveled and treated with a primer solution. A wooden frame is attached with a width between the beams equal to the width of the insulation sheets. Sheets of foam plastic are secured between the frame bars using glue, then with disc-shaped screws. A reinforcing mesh is glued on top of the insulation and at the final stage siding is mounted on the frame, protecting the foam from damage and giving the facades an attractive and neat appearance. Instead of installing a hanging frame, the foam can be protected by plastering or painting.

A little about block production

The manufacturing technology of gas and foam concrete blocks is simple. The following materials are used for this:

• construction sand;
• water;
• cement;
• aluminum powder;
• industrial slag.

Everything is mixed in given proportions. Aluminum, when reacting with water, begins to oxidize, and therefore air bubbles are formed. Gas formation occurs in all building materials. Gradually, depravity accumulates and the aerated concrete block hardens.

Although the material is quite hard, pores remain in it, which are subsequently saturated with moisture. When using foam blocks for building houses, they are exposed to external negative factors. Therefore, they should not be left unprotected, and in order to achieve a high-quality finish, the surface must be coated with a primer.

Vapor permeability is another of the main indicators of foam blocks, which ensures the necessary regulation of the indoor microclimate.

On video: the pros and cons of foam concrete blocks.

Which primer to choose

The primer for aerated concrete consists of polymers; it is perfect for interior work, but it can also be used outside. The main purpose of such soil is to reduce adsorption properties. Special additional additives have the ability to prevent the formation of fungus, mold or moss.

The finished primer is vapor-permeable for a porous surface, and moisture does not accumulate. In addition, it is resistant to atmospheric agents and tends to repel moisture and dirt.

Offers from different manufacturers:

When choosing the right material, it is recommended to read the instructions from the manufacturer, and, if necessary, consult with a sales consultant in this area. It is equally important to pay attention to the expiration date and storage conditions. In order to have a positive effect from using the chosen product, the material should be used no later than the expiration date.

Important stages in work

Preparation of protective equipment

So, you have decided to cover the gas silicate blocks with a primer layer. And this is the right decision. First of all, you need to take care of personal safety - this is the main component of successful work:

• You must wear a hat on your head and closed shoes on your feet. It is not recommended to work in slates; it is possible that a tool may accidentally fall on your foot.
• Special glasses or a screen will perfectly protect your eyes, and rubber gloves will protect your skin from splashes.
• When working at heights, durable, proven structures should be used.
• It is not recommended to perform work if you feel unwell or feel dizzy.

Preparing tools

First you need to decide exactly how to cover the foam concrete. A roller, or maybe a spray gun, may be chosen for these purposes. It is imperative to prepare a flute and fly brush so that you can apply primer to the surface in hard-to-reach places.

You will also need:

• soil tray;
• old newspapers and rags;
• solvent (if necessary);
• metal brush;
• hammer and spatula.

Surface preparation

First, you need to clean the surface from crumbs, dust, construction debris or cement. You can use a spatula or a wire brush.

Hot steam cleaning should be used to clean oil stains and other greasy contaminants. If this is not possible, try treating the surface with a universal degreaser. Drying the surface is mandatory, otherwise the vapor-proof primer will not adhere well to the surface.

Priming process

After completing the preparatory activities, you can begin priming:

1. Using a round or flat brush, work the surface in hard-to-reach areas.
2. Use a spray gun or roller and cover the entire wall area. The primer should be applied evenly in one layer, being careful not to skip any areas.
3. After the composition has completely dried, check whether the entire surface is saturated with the primer layer. To do this, you can use a regular flashlight or table lamp. If there are unpainted areas, the operation should be repeated.

Only careful processing of block structures will give the building additional strength and durability, and when plastering work is performed, the solution will not dry out quickly.

Dust removal and priming of gas silicate walls (1 video)

Different types of primers (28 photos)

How to apply correctly

Priming is carried out on the prepared surface. Dust, debris and cobwebs are removed from the partition. The seams are cleaned to a depth of 1 cm and thoroughly removed from dust. Cracks are sealed with putty, and uneven surfaces are sanded. Work, like all construction procedures, is carried out in protective clothing, a mask and gloves.

Priming is carried out in the temperature range from + 5 to +30 C. In cold weather, the substance in the composition crystallizes, therefore it loses its original qualities. In hot weather, the solution dries too quickly, not having time to penetrate the porous structure of aerated concrete.

Roller in hand Source kraski-net.ru

It is more convenient and economical to apply the primer on partitions using a spray gun. If there is no equipment, then use a standard tool. The main surfaces are treated with a roller with a long handle, unstuck areas and corners - with a brush.

Before priming aerated concrete, you need to prepare a solution. The suspension is applied in 3 layers. For the first tier, the liquid is diluted with water in a ratio of 1 to 4, for the second - 1 to 2. The finishing coating is used concentrated. Between procedures, the drying period specified in the instructions for the drug is maintained.

Classification of solutions

Construction stores have a huge range of primers, but not all are suitable for aerated concrete. The emulsion is selected individually, focusing on the tasks of the liquid. Suspensions have a complex classification that needs to be understood.

By composition

Standard primers for interior work are made from latex. Solutions are ideal for porous surfaces. Advantages of the compositions:

• easily absorbed;
• penetrate deeply;
• dry quickly.

Polymer primers are much stronger and more durable than latex counterparts. The viscous solution is easy to spread over the surface. After drying, a very dense, thin film appears on aerated concrete, protecting the blocks from moisture.

Types of solutions Source gkpartner-stroj.tiu.ru

Silicate primers consist of potassium glass. The liquid quickly penetrates the pores, completely fills the empty spaces and hardens. As a result, the surface receives additional reinforcement of the aerated concrete base. The product is ideal for street partitions.

When working with porous materials, alkyd and acrylic types are not used. Suspensions of the first type are not intended for cellular building materials. The second ones have low strength, which will lead to peeling of the plaster layer.

By degree of penetration

Compositions with a standard degree of penetration penetrate to a depth of 2-3 mm. After polymerization, a hard, smooth surface appears that can be easily scratched with a spatula with awkward movement. The solution has a low price and clear instructions.

Deep-penetrating primers for aerated concrete further strengthen the base. When applied, the emulsion seeps into the cells by 5-8 mm. After drying, the surface is leveled, becomes durable and decorative. The price is an order of magnitude higher than standard types. The material ensures ideal adhesion of the wall to the plaster.

Insulation of foam block from the outside

Buildings made of foam blocks need thermal insulation no less than buildings made of brick or concrete, so the issue of insulation is thought through at the construction stage.

One of the inexpensive and accessible materials for insulating a house made of foam blocks is polystyrene foam, which allows you to increase the thermal insulation of the facade at minimal cost.

Walls lined with foam plastic do not suffer from the formation of fungus, and insulating the walls from the outside does not cause condensation to form on their inner surface. A good argument in favor of using polystyrene foam is its sound absorption ability. When using this material, the peace of the inhabitants of the house will not be disturbed by street sounds.

Polystyrene foam weighs a little and does not put unnecessary load on the foundation of the house.

The material is easily cut to the required size, and the work of insulation is accessible even to a non-professional.