How to lay aerated concrete blocks with adhesive
How to lay gas block. The secrets of masonry aerated concrete blocks with your own hands
Aerated concrete is produced by businesses, private developers, and large construction companies. And they all need to know how to do the proper masonry.
What all aerated concrete manufacturers have in common?
Some make blocks for themselves; others make them for sale. Others supply construction companies. But all manufacturers need to understand how aerated concrete houses are built.
Builders will learn how to do proper masonry and wisely follow their workers. Businessmen learn what good advice to give to customers.
That’s why today we’re going to tell you about masonry gas block:
How to lay aerated concrete blocks with adhesive
Preparatory work determines the strength of the upcoming masonry and includes:• Preparation of glue mortar and just mortar is necessary in order to have something to lay gas blocks on;• Checking the horizontality of the foundation;• Waterproofing the foundation with bitumen mastic and roofing felt.Construction of any structures made of aerated concrete is recommended when the weather is warm, more than 5 degrees, but not higher than 25. If you must work in hot weather, the block surfaces must be moistened with water. When working in the cold period should be added to the adhesive special antifreeze additives.
Laying the first row
The laying of aerated concrete blocks is very simple. Blocks are laid in the same way as bricks, observing the seams of laying. By laying the first row of walls with gas blocks should be taken very seriously, because of him depends on the overall quality of masonry throughout the house. The first row of blocks must be necessarily laid on a layer of waterproofing, which will protect the material from moisture ingress from the foundation. The first row of blocks is laid on the cement mortar with a ratio of 1:3 (cement:sand).Continuing laying, after several rows laid, it is necessary to check the verticality of walls and corners. If the blocks are slightly displaced, with the help of light strokes of a rubber mallet they are placed in the right place. If necessary, aerated concrete blocks can be sawed with a simple saw, beveled, drilled and made holes of any configuration. Remove minor dirt and dust with a brush. First place the blocks in the corners of the foundation, with the first one being installed in the highest corner of all foundation corners. To find out which corner is higher than the others, you can use a construction level. The difference in height between the highest and lowest corner points should preferably not exceed three centimetres.
Laying of subsequent rows
The next rows are placed on the glue mortar with binding blocks, as in case of masonry. Taking into account high demands to the accuracy of laying, even small deviations (up to 3 mm) in size of gas-blocks can cause subsequent significant differences and unevenness. That is why after laying each row you should remove all the protrusions with a planer or grinder. Perform subsequent laying of the material only on the blocks previously cleaned of debris. Applying adhesive to aerated concrete blocks is made by a trowel or a special carriage, the width of which is equal to the width of the masonry.
The walls of aerated concrete must be partially reinforced. Reinforcement strengthens the walls and absorbs the normal loads acting on the wall. It is recommended to reinforce the first and every third or fourth row of the masonry. To reinforce the walls cut out channels in the blocks. In the corners they are rounded. Only solid, curved reinforcing rods may be inserted into the corners. Reinforcement is pressed into the mortar. Dissolves are filled in completely with mortar. To cut the channels it is also possible to use a hand chisel.
To protect the aerated concrete from the formation of cracks and shrinkage need to limit the flow of moisture to it. To do this, the aerated concrete blocks are plastered. Before that the walls are smoothed with a trowel, and small chips are covered with mortar. The plaster mortar must be highly vapor permeable in order to avoid the accumulation of dampness inside the house. First you need to prime the walls with a special acrylic-based primer. It improves the adhesion of plaster and does not impede the passage of air. The facade can also be made, for example, with bricks, pre-insulated with styrofoam or mineral wool.
With and a range of building materials you can see in our online store
Selection criteria for aerated concrete
When studying the products of different manufacturers, you should focus on the following indicators:
- density. the higher it is, the stronger the material and the stronger its soundproofing properties;
- thermal conductivity. the degree of heat preservation in the building depends on it, the manufacturers in the calculation of this characteristic take into account the heterogeneous conditions;
- vapor permeability;
- sound insulation.
The optimum size of products varies from project to project, but it is better to buy the elements with hooks. they facilitate movement and installation.
Masonry of aerated concrete blocks
Reinforcement of aerated concrete blocks
The process is carried out near windows and doors, as they are most susceptible to subsidence. Thus, these zoned areas require the highest quality leveling of masonry. Reinforcement technology includes the following important features:
- With the help of stubbing cut grooves;
- The distance between the grooves should be at least 60 mm from the edge of the block;
- With the help of a special brush from the grooves remove accumulated dust;
- The grooves are filled with water;
- The grooves are half-filled with adhesive mortar and drowned in the reinforcement;
- Using trowel smooth the masonry.
Aerated concrete blocks, otherwise known as aerated concrete or gas blocks. material from the group of cellular concrete. It is it is widely used in the construction of low-rise buildings and interior partitions. The use of foam concrete saves the budget, time and effort of builders. Masonry gas blocks, as well as the subsequent finishing of the walls from it with their own forces can be implemented not only professional builder, but also an amateur.
Masonry foam concrete in the traditional way implies the use of special mixtures. The method of application of cement mortars is time-tested, its technology is tried and available. But because of the higher thermal conductivity than that of aerated concrete, cement-sand masonry joints increase the heat loss of the erected premises.
Buildings made of aerated concrete are characterized by a long service life. Inside the premises, made of this material, is well kept warm thanks to the low thermal conductivity of the material.
Laying of aerated concrete blocks
Aerated concrete is a synthetically created building material. It is made as a result of temperature effect on all components. The main advantages of this material are ease of production, small weight, strength, thermal insulation. However, in spite of all its advantages, many unskilled workers do not like to work with it. But professionals gladly use aerated concrete blocks. There are some peculiarities of laying such blocks.
Masonry gas block foam masonry′ Why you shouldn’t do it: criticism and facts
Before the construction we have a lot of questions, what should be the material, what kind of foundation, what roof, and so on. By stopping his choice on such a material as, for example, aerated concrete, the consumer receives a lot of advantages. The material is relatively inexpensive, the construction process takes place in the shortest possible time, the house will be very warm with the preservation of the optimal climate for residence. The next question is which masonry will be the most reliable. The answer used to be simple cement. But then there was a special adhesive mixture, which facilitated the work, reduced heat loss by up to 30%, and made the appearance more aesthetic. But every time manufacturers create new items that make the process of work easier for builders, and minimize costs for the consumer.
So we were presented with foam glue for aerated concrete. It has been tested for a very long time in laboratories, in different conditions close to the reality, withstanding the necessary humidity at different times of the year, temperature (minus and plus). And it was proved that the laying of aerated concrete foam, even for load-bearing walls, the best option. This novelty is rapidly gaining ground in the market, with the following advantages: minimum foam consumption. One balloon can safely replace a bag of glue, or one and a half two bags of cement. Accordingly, one balloon of special adhesive foam for aerated concrete is enough for 1m3 masonry.
The thin joint of the foam will provide a better bond with the mineral stone, reducing heat loss due to the very thin joint and increasing the contact point to a minimum. The maximum curing speed. After 24 hours the foam is ready to take the full load. Apart from a glue gun, to work with the foam glue, you do not need anything else. The foam is applied to the vertical joints of masonry and horizontal, it does not flow, it is easy to work with. Also the foam adhesive has flame retardant characteristics. Therefore, in tandem with the fire-resistant aerated concrete will come out non-combustible and resistant wall. A huge plus is that the foam can be used at temperatures up to 100C. The horizontal joint, on which the foam adhesive is applied has another advantage, elasticity. This characteristic will avoid small deformations and cracks.
Of course, before starting construction work, you should definitely read the information about the disadvantages of erecting aerated concrete walls on the foam. For example:
In our opinion, the most objective critique of laying aerated concrete on foam from a civil engineer Alexander Terekhov from the YouTube channel “The Way Home. All the disadvantages of foam for aerated concrete, he described in detail in this video, which we recommend that you watch.
For this reason, we can NOT recommend foam glue for the installation of the gas-block. Although to understand the general features of the process of laying aerated concrete on foam, we have, still, placed the information below.
Standard errors in the construction of houses from aerated concrete blocks
In this section we will consider mistakes in the construction of low-rise houses of small blocks of autoclaved aerated concrete, as the most common wall material from cellular concrete in the Ukrainian market. All mistakes in the construction of houses made of aerated concrete blocks can be divided into the following groups:
- Mistakes that lead to violations of the integrity of the structural integrity of the building.
- Mistakes that worsen the performance of the building.
- Mistakes that lead to excessive labor and financial costs in the construction without compromising the integrity of structures and performance characteristics of the building.
Mistakes that lead to violations of the integrity of structures
This is the most dangerous group of errors in the construction of houses made of aerated concrete blocks, as a result of improper design of the building, neglecting construction technologies, the integrity of the load-bearing structures of the house can be violated. The range of negative consequences of this group of errors can range from relatively stable cracks in the walls of an aerated concrete building to structural collapse.
А. Errors in the design and construction of foundations of houses made of aerated concrete
The fracture strength of autoclaved aerated concrete blocks tends to zero. Unreinforced masonry of aerated concrete blocks has slightly better properties, but in general, the deformation of the base 2 mm per meter, foundation slope of 5 mm per meter can cause cracking in aerated concrete masonry.
The movement of foundations and changes in their shape are possible under the influence of soil movements (from freezing, thawing, changes in moisture saturation), from subsidence under load, in subsidence soils. Foundations may also be deformed due to the improperly chosen design under the applied load. Therefore, for foundations for buildings made of aerated concrete blocks there are higher requirements for the stability of the position and preservation of geometric shape. The foundation must ensure the joint nature of deformations of the walls of the building located on it during linear and angular displacements.
The optimal foundation for a house made of aerated concrete blocks is a monolithic reinforced concrete foundation of the most appropriate design for the soil conditions (pile-rock foundation, sunk or shallow strip foundation, sunk or above-ground slab). The ground beneath such a foundation should be properly prepared to reduce possible movements: the foundation should rest on compacted or unconsolidated layers of compacted soil, the ground should be drained before the foundation construction, large deciduous trees should not grow in the immediate vicinity of the foundation, the area around the foundation should be heated to a value sufficient to reduce frost heave.
Lack of understanding of the mechanics of movement of soils and the basic properties of the gas concrete blocks leads to the fact that for houses made of gas concrete prefabricated foundations of foundation blocks are used (with the device of reinforced belt or without it). These foundations are only permissible on non-swelling soils and are conditionally permissible on slightly swelling soils. In soils prone to heaving, precast foundations for houses made of aerated concrete blocks are not recommended.
Sometimes there are attempts to build aerated concrete buildings on pile foundations with steel strapping (high cross dike) (channel, angle, I-beam) instead of the monolithic reinforced concrete strut. Metal upright is unable to ensure the stability of the walls of small blocks of aerated concrete and has significant temperature fluctuations in geometric dimensions.
When making the dikes, some independent builders, guided by the popular construction literature of the early post-Soviet period, save on the reinforcement of the top row of reinforced concrete foundation pile, do not perform the required anchoring of reinforcing bars in the corners of the dikes and reduce the permissible height of the cross section of the dike (it should be at least 40 cm). As a result, such “economical” derrick is not able to withstand all the loads, which leads to deformation and cracking in the derrick itself, and the formation of cracks in the walls.
The combination of different types of foundations under a single building of aerated concrete blocks due to the possible unevenness of arising loads from the movements of the soil. Any combination of dissimilar foundations, the performance of extensions is possible only with the arrangement of expansion joints in the gas concrete walls at the junction of dissimilar structures.
Б. Mistakes when laying aerated concrete blocks
Violation of the correct binding blocks in the rank masonry, wrong execution of openings, wrong juxtaposition of exterior and interior walls, lack of or insufficient reinforcement of walls, lack of reinforced concrete belts can lead to cracks in the walls of aerated concrete houses.
The chain binding of the blocks in the masonry provides the bending and shearing forces acting on the masonry. When masonry blocks of height 25 cm or more in a row the minimum dressing should be 40% of the block height, but not less than 10 cm.
Basic rules of chain linking of aerated concrete blocks in masonry walls
A common mistake is the lack of tie or flexible links at the conjunction of walls of aerated concrete blocks. Connecting the walls of aerated concrete blocks can be rigid or with the help of flexible links.
Rigid coupling is possible if the difference in wall loads does not exceed 30% (i.e. the walls of the same type are coupled. load-bearing with load-bearing, self-bearing with self-bearing or non-bearing with non-bearing). If the walls are mated different purposes (load-bearing with non-bearing or self-bearing), with a difference in loads greater than 30%, the connection is performed only by flexible links, allowing for deformations. Common mistakes are the lack of connections between mating walls, or the use of rigid connections, such as hammered rebar in the wall, in multi-loaded walls.
The correct connection options for exterior and interior walls of aerated concrete
In places of possible concentration of temperature and shrinkage deformations of aerated concrete blocks that can cause impermissible under the terms of operation ruptures of masonry blocks in the walls should be arranged temperature-shrinkage joints. Practically such joints must be arranged every 35 meters of masonry, which, perhaps, can be found only in the construction of fences (fences) of aerated concrete. Settlement joints must be provided where the height of the building changes by more than 6 m, as well as between the sections of the building with a rotation angle of more than 30 °, or when joining the parts of the building on separate foundations.
Construction of aerated concrete blocks often neglects to perform structural reinforcement of the walls and especially the reinforcement of openings in the walls of aerated concrete blocks. Such reinforcement does not increase the load-bearing capacity of aerated concrete masonry, but only reduces the risk of temperature-shrinkage cracks, and reduces the disclosure of cracks at shifts and deformations of the building foundation, exceeding the allowable limits. Structural reinforcement of aerated concrete masonry is used to prevent shrinkage cracks in the construction of “fresh”, just released aerated concrete, which is known to be subject to shrinkage, which lasts up to two years and is up to 0.3 mm/m with a decrease in moisture of aerated concrete from 35% to 5% by mass.
The concrete wall construction reinforcement scheme.
For horizontal reinforcement masonry aerated concrete blocks using steel reinforcement variable profile with a minimum diameter of 6 mm (at the request of some manufacturers aerated concrete. 8 mm), sunk into the trenches and fixed with adhesive for aerated concrete or plastic cement mortar. Do not use smooth wire (“rod”) for structural reinforcement, because it does not possess the properties of the rod reinforcement.
The wire can not perform the function of the reinforcement: it will not prevent the emergence of
shrinkage cracks in the corners under and over openings in the aerated concrete walls.
For all aerated concrete block buildings without a load-bearing reinforced concrete frame it is necessary to perform structural horizontal reinforcement to prevent cracking around window, door and other openings in the walls of aerated concrete blocks. Here the rows of reinforcement are not only reinforced above the opening (if there is no lintel above the opening up to 120 cm) but also next to the opening and below the opening (see Reinforcing rows of masonry below the opening). reinforcement schemes).
Reinforcement of openings in gas concrete walls
Under certain conditions in a number of conditions for the construction of houses made of aerated concrete blocks it is also necessary to perform vertical wall reinforcement: 1. Walls that are exposed or potentially exposed to lateral (lateral) loads (fences, free-standing walls, underground floors of buildings, basements, walls of buildings on steep slopes, walls of buildings in the area of mudflows, avalanches, in regions with strong winds, hurricanes and tornadoes, in earthquake-prone areas) are reinforced vertically. 2. Increasing the load-bearing capacity of the walls of an aerated concrete building. For example, the use of vertical reinforcement allows using low-density aerated concrete in masonry walls, which has lower thermal conductivity. 3. 7 Vertical reinforcement enables significant concentrated loads (e.g. from a long span beam) to be supported and transferred. 4. Reinforcing the masonry bonding of masonry conjugated walls and corners with vertical reinforcement. 5. Strengthening of openings in walls. 6. Reinforcement of small partitions. 7. Vertical reinforcement of aerated concrete columns.
Scheme of vertical reinforcement of aerated concrete walls
Vertical reinforcement can be arranged in special O-blocks supplied by many foreign manufacturers of aerated concrete products. You can also make O-blocks yourself, using a drill with a core diameter of 12-15 cm. Vertical reinforcement is carried out using reinforcing steel d14. Reinforcement must be placed no further than 61 cm from the opening, the free ends of walls made of aerated concrete.
Mistakes affecting the performance of the building.
In general, this group includes errors in exterior decoration, external insulation of walls made of aerated concrete, leading to an increase in the thermal conductivity of the walls, deteriorating the microclimate in the house and increasing heating costs.
The most common mistake in the construction, stemming from ignoring the features of the open cell structure of aerated concrete and its properties of permeability to gases and water vapor, is the creation on the outside of the wall with aerated concrete vapor permeable layers or layers of vapor permeability below that of aircrete masonry. Such construction contradicts the vapor permeability requirements of laminated walls set forth in the DBN B.2.6-31:2016 “Thermal Insulation of Buildings” which stipulate that each layer of such a wall, located outward from the previous one, must have a higher vapor permeability. In case of non-compliance with this rule, the inner layers of walls that have a hygroscopic permeable structure may gradually get damp, because not all the water vapor will be released outside, which will increase the thermal conductivity of the walls (insulation). This rule applies to heated buildings for permanent residence. In unheated buildings, such a problem does not arise, and in buildings heated from time to time (vacation homes, heated only when coming on vacation or on weekends) the relevance of the problem depends on individual conditions. See an example of a wall made of aerated concrete from freezing when wet.
From aerated concrete were built many “Stalinist” houses, the first “Khrushchev”. Exterior panels of multifamily “Brezhnev”, “ships” (series LG-600, improved series 600.11), 137th “GB” series houses are also made of aerated concrete panels. The good idea to insulate exterior walls with gas concrete panels stumbled over the traditional low quality of production in the USSR: the exterior walls of gas concrete multi-storey buildings are cracked and require regular repairs. In addition, no one has guessed to protect the aerated concrete panels from the inside penetration of moisture vapor, and outside painted them with vapor permeable paint. Because of this, the aerated concrete panels dry out and increase their thermal conductivity. Traditionally, “ships” are considered among the coldest and therefore cheapest houses. At present in the U.S. is actively developing the technology of external cladding frame houses with thin reinforced aerated concrete panels.
What do builders like to “seal” outside permeable to gases and vapors gas concrete blocks? There are two absolute leaders in this field: masonry and extruded polystyrene foam (EPPS). Usually builders make these mistakes under the most plausible pretexts: to “protect” delicate aerated concrete from the weather by “strong” bricks and properly “insulate” with ESL and at the same time protect it from external moisture and freezing.
Although the basic condition for longevity for a house made of aerated concrete blocks is the same as in the wooden house: the porous wall material should be able to dry out, releasing moisture into the atmosphere.
Such external “insulation” with the use of EPPP during ten years of exploitation will lead to
to the opposite effect: the house will become “colder” than it would have been without insulation.
And at the turn of 5-7 seventeen years such walls will begin to delaminate in the outer third of the blocks.
There are also combined use of EPPB with brick lining. Cladding of facades from aerated concrete with polyurethane foam thermal panels and clinker tiles “under the brick” is similar in the effect of blocking vapor transfer. Brickwork, as well as EPPP have practically zero vapor permeability. Structural solutions that significantly impair the vapor permeability of multi-layered walls using aerated concrete include exterior insulation with poorly vapor permeable polyfoam, and installation of brick facades with unventilated air gap between aerated concrete and masonry.
If the homeowner wants to see certainly his gas concrete house with brick facades, then he should not go on about the builders, who, of course, simply walled gas concrete walls with bricks without any ventilation gaps. To arrange the brick facade of the aerated concrete house will have to meet the requirements of paragraph 8.14 SP 23-101-2004: For walls with a ventilated air layer (walls with a ventilated facade), the air layer should be at least 60 mm thick and not more than 150 mm thick. The masonry must be connected with the gas concrete wall with stainless steel or fiberglass connections. The brick lining must have ventilation holes, the total area of which is determined on the basis of 75 cm2 per 20 m 2 of the wall area, including the area of the windows. Bottom vents should be done with a slope below the surface of the bottom of the air gap, to withdraw moisture accumulating in the air gap (condensate).
Facing AAC with brick without a ventilated gap gives a house a “rich” look, but after 7-10 years will make the homeowner pay for heating such a house much more than during the first years of operation of the building. And the children or grandchildren of such a homeowner may well have to restore the house and facade due to the destruction of the outer layers of masonry gas concrete blocks [Knatko M.В., Gorshkov A.С., Rymkevich P.П. Laboratory and field studies of durability (service life) of the wall structure made of autoclaved aerated concrete lined with silicate brick.// Engineering and Construction Journal.-2009,- ,- С.20].
When building with aerated concrete blocks mistakes are encountered, leading to excessive costs for heating: the formation of thermal bridges. Most often, it is the lack or insufficient insulation of overhead reinforced concrete lintels, reinforced concrete belts, the unjustified use of reinforced concrete frames in the construction of low-rise houses made of structural-insulating gas concrete blocks due to a lack of confidence in the durability of the material.
Building walls: Adhesive for laying brick and blocks VASmann or standard cement mortar?
Access lintels in a cellular concrete block house: First of all, remember that openings up to 120 cm wide above which the height of the masonry is at least two-thirds of the opening width do not require lintels, but only horizontal reinforcement of the row above the opening. Openings up to 3 meters can be covered with monolithic reinforced concrete beams in a permanent formwork of special U-shaped aerated concrete blocks, which do not require additional insulation. Also do not need to be insulated special reinforced concrete beams that can cover the apertures to 174 cm.
However, in real construction, the openings are most often covered with monolithic reinforced concrete beams cast on site. Such beams require external insulation, which is sometimes forgotten.
In addition to insulating overhead lintels in a house made of aerated concrete blocks, you also need to insulate
and ends of floor slabs or banding reinforced concrete belt.
The most common grades of aerated concrete blocks on the market have a compressive strength class of B2.5 and can have a density of D350 to D600. From these aerated concrete blocks it is possible to build load-bearing walls with a total height of up to 20 m. However, some builders do not trust the strength of the “light and porous” material and build massive, well-conducting reinforced concrete frames, even for the two-story structures.
Excessively complicated construction of aerated concrete masonry: the construction of two-storey buildings outside earthquake zones and does not require reinforcement of the structure with a reinforced concrete frame. For the laying of floor slabs it is sufficient to install a reinforced concrete discharge belt between the floors.
Another strange habit of builders increases the thermal conductivity of masonry aerated concrete: in many cases, builders do not apply glue to the end surfaces of concrete blocks.
In aerated concrete masonry should not be through gaps: must be applied to all edges of the concrete block.
Meanwhile, in all cases, the performance of vertical joints must prevent blowing through walls. Vertical mortar joints in masonry blocks with flat edges must be completely filled with mortar. When using blocks with profiled surface of the end edges in masonry, which have requirements for shear strength in the plane of the wall vertical joints should be filled throughout the height and not less than 40% of the width of the block, and otherwise the seam should be filled with outside and inside strips of glue or mortar.
By the way, it is inadmissible to smear an excess of glue or mortar on the joint and the surface of the block: in this case, a non-uniform basis is fraught with further manifestation of microcracks in the outer plaster coating. Leave the excess glue to dry, and trim it off with a trowel.
Carefully trim away excess glue or mortar
and removed from the sutures after drying, rather than smeared
On the walls to reduce the water vapor permeability of aerated concrete.
Laying of aerated concrete blocks on cement mortar is not technically a construction mistake. However you should know that masonry AAC blocks in cement mortar conducts heat better by 25-30% (thick joints are “thermal bridges”), and therefore to achieve normative resistance of heat transferring of the wall, the thickness of masonry will have to do much more, which will bring to naught “savings” on adhesive for aerated concrete.
Mistakes leading to excessive labor and financial costs during construction without compromising the structural integrity and performance of the building.
This group includes all kinds of amateur “improvements” technology of building houses from aerated concrete blocks. One of the most common, as well as innocuous mistakes is the desire to “strengthen” aerated concrete masonry execution of the first rows of “more durable” ceramic brick. In reality, the ultimate bending and shearing deformations of ceramic bricks and aerated concrete blocks are close, and thus it is impossible to prevent the wall from cracking if the foundation is not properly made or if there is no horizontal structural reinforcement.
Structurally redundant masonry belt of ceramic bricks. Originally, the recommendation to use brick masonry was contained in the Soviet-era LENZNIIEP catalog “Low-rise houses made of cellular concrete” (L.-1989 С. 176) and has been argued to “protect aerated concrete from the splashback from the ground from precipitation.”. Critical error in the background: house of aerated concrete blocks insulated with EPPP.
We hope that our brief overview will keep you from making major critical mistakes and help you save energy and money both when building a small block aerated concrete house and when operating it.
How to properly lay aerated concrete blocks
Gas blocks are laid much easier than bricks or cinder block. This is due to the almost flat surface of the blocks. Even if there are small protrusions or some other imperfections, the gas blocks are easily aligned in one row with simple cutting tools, as it is possible to saw it even with an ordinary saw or hacksaw.
Construction begins with the foundation. Usually its surface is far from ideal. To this end, after laying waterproofing, the foundation is covered with a layer of cement mortar. The first row is placed on this mortar. Thanks to a rather thick layer of mortar the perfect evenness of the blocks of the first row is achieved. The bottom surfaces of the first row blocks are moistened to prevent them from absorbing moisture from the mortar.
In the video masonry aerated concrete blocks with their own hands on the example of building a bath: