One of the main issues that is decided when building a private house is what wall thickness to choose. Everyone wants to save money, so the thickness indicated in the project, for example, is 370 mm brickwork“look erroneous,” because “the neighbor built 190mm walls and nothing.” Indeed, recently, often when constructing private houses, the walls are not made wide - from 250 mm brick, but from heavy concrete blocks and 200 mm. The same values are sometimes set by projects of low-rise buildings. Is this wall thickness always suitable?
What determines the thickness of the wall of a house, what thickness of the wall of a house to prefer, and what to look for when choosing this option for your own home.....
What loads act on the wall of the house?
- The external load-bearing walls of the house are subject to a vertical compressive load formed by the weight of the masonry itself and the above floors, roof, snow, constant and variable operating loads...
A simple calculation shows that a wall 190 - 250 mm thick made of brick or heavy concrete blocks laid on ordinary cement mortar has a large margin of compressive strength. Such a wall can withstand significantly greater compressive loads. - The walls are subject to loads directed horizontally, planes that tend to overturn them. Horizontal loads can be caused by wind pressure, so all houses are designed for wind loads. Also, a significant lateral load on the wall can arise due to thrust from rafter system roofs. The wall must be resistant to certain values of lateral loads. The thrust from the roof elements must be compensated in the roof structure itself, for example, you can read,
- The wall is subject to various bending and torsional moments. The nature of their occurrence may be different, for example, due to subsidence of the foundation, due to greater pressure from floors or facade finishing on the edges of the wall, due to uneven masonry and the resulting slope of the wall, etc. Bending and torsion forces in various directions may be higher than the strength of thin walls. Load-bearing walls made of bricks and concrete blocks with a thickness of 190 - 250 mm do not have a large margin of safety against bending loads. This wall thickness according to this factor must be confirmed by calculation for each specific house structure. At the same time, according to practical experience, a wall with a thickness of 350 mm or more has a significant margin of safety in the most various options building structures.
Those. The specific design of the house has a great influence on the choice of wall thickness. Let's take a closer look at the factors that significantly influence the choice of wall thickness.
How does the design affect the strength of the choice of thickness?
The stability and strength of a building wall is mainly influenced by its design. The most significant factors are:
- Wall thickness. As the thickness decreases, the probability of wall failure increases significantly, primarily due to bending loads.
- Wall height. The higher the wall, the significantly greater the loads on it, the less its stability.
- The area of openings in the wall. Openings significantly weaken the wall. The larger the opening, the less stable the wall.
- Number of openings (wall width between openings). The larger the total area of all openings, the narrower the wall spaces between the openings, the lower the stability and safety factor of the wall.
- Availability of support from the adjacent load-bearing wall. The larger the span of the wall without lateral support of the perpendicular (adjacent) wall, the less stability of this section. Interlocking walls (with interlocking masonry) increase the stability of a particular section of the wall.
- Availability of reinforcing belts. To increase stability, reinforcing belts and various masonry reinforcements are placed in the wall, which significantly increase the stability of walls made of piece materials.
- The presence of grooves, internal channels, niches, etc. in the wall. The depth and length of various violations of the continuity of the wall are determined by the project and confirmed by calculation.
- Blocks and bricks with a lower strength class than provided for in the project are used. Used masonry mortar, the composition of which differs from the designed one.
- Curvatures of the masonry greater than the norm are allowed. A large vertical slope of the wall is allowed. The horizontal straightness of the masonry is not maintained.
- The seams between the blocks are not completely filled with mortar.
- The thickness of the seams has been increased. The number of seams has been increased and the size of the piece material has been reduced; pieces of bricks and blocks have been used.
- The joining of the floors (floor beams) to the walls using anchors has not been completed, their number has been reduced, and their locations have been changed.
- Incorrect dressing load-bearing walls, the density of the dressing is reduced.
- The walls were not reinforced according to the design, the number of rows was reduced, the grade of material was changed, etc.
- The structure of the foundation, roof, and other adjacent structures has been damaged, resulting in significantly greater bending and overturning forces...
- For one storey building walls with a thickness of 200 - 250 mm are applicable. The same wall thickness can be top floor multi-storey building.
- For a two-story house, the wall thickness of 200 - 250 mm must be confirmed by calculations certified by the design organization. Also, the project should be based on soil studies of the development site. Such a project must be carried out by qualified specialist builders. Qualified technical supervision of construction must be carried out.
- For two and three storey buildings, load-bearing walls of the lower floors with a thickness of 350 mm or more will have a sufficient margin of stability to compensate for the influence of some unfavorable factors.
In addition to design factors, the stability of the wall is influenced by construction factors or the “human factor”. So, the strength of any wall will change if you change the brand, class of brick, blocks or mortar... Changes in materials and structures of junctions, roofing or even foundations are possible. All this will affect the stability of the walls of the house.
What violations significantly reduce stability?
During the construction process, situations arise when there is no required quantity material with the necessary qualities. Also, construction teams often want to simplify the work and design and propose to “make it simpler and more reliable.” The owner needs to monitor the construction process and compliance of the execution with the requirements of the documentation. Do not allow deviations from the project, norms and rules. All changes to the structure of walls and ceilings must be agreed with the designer. Changes made must be certified by signatures and seals responsible persons and organizations.
This is especially important for thin walls, which have a small margin of safety. Errors and shortcomings during the construction process sharply reduce the already low stability of a thin wall, and its destruction becomes possible.
What is the thickness of the walls in most cases?
We have gained extensive experience in the construction of low-rise private houses from high-density piece materials. If you use heavy brick or concrete with cement-sand mortar, then you can say that load-bearing walls of the following thickness will have satisfactory stability.
One of the main advantages of gas blocks is the possibility of “single-layer” construction, that is, the construction of walls one block thick without insulation. The thickness of aerated concrete walls varies from 200 to 600 mm and depends on the purpose of the building and its operating conditions.
The choice of wall thickness depends on the characteristics of the material used. Aerated blocks are mainly produced with densities from D300 to D600. For the construction of load-bearing walls, it is recommended to use aerated concrete blocks with a density of D500.
- for a garage or outbuilding – 200 mm;
- for a one-story house - no less than 375 mm;
- For two-story house– 400 mm;
- for a three-story house - over 460 mm.
Foreman's advice:
The minimum thickness of aerated concrete walls for residential buildings is 375 mm. It is this thickness that provides the necessary thermal protection without insulation under normal operating conditions. If construction is carried out in unfavorable conditions, then better than walls make them thicker and further insulate them.
The thickness of the load-bearing walls may be greater than recommended, but you must remember that it should be 10 cm wider than the thickness of the walls. The thickness of aerated concrete partitions is usually 200 mm, but if the internal partition does not perform load-bearing or supporting functions, then it can be made thicker and 150 or even 100 mm. Do internal partitions thickness of more than 200 mm makes no sense, as it steals extra centimeters room area.
Constantly rising energy prices are forcing private home owners to look for ways to save money. cash. One way to do this is to carry out work on insulating residential premises, as a result of which heating costs will be heating season will decrease significantly. In this case, wall insulation can be done both outside and inside the building. The most rational way is to insulate the walls of the house from the outside
Technology insulation of external walls with further finishing of the facades with siding, a frame system is provided. As a rule, frame posts are made of metal profile or wooden blocks are fixed to the walls in a vertical position, however, if the insulation layer is thick, they are fixed to the vertical posts horizontal profiles or frame beams. In this case, to further secure the façade cladding, such as siding, they are attached to the horizontal elements of the frame. vertical racks with a pitch of 400 mm.
The choice of thermal insulation materials for insulating external walls should be approached thoroughly, since repair or replacement of insulation during the operation of the building is difficult.
First of all, the insulation for thermal insulation of walls must have low thermal conductivity. For materials based mineral wool, glass wool and polystyrene foam, this figure is approximately the same and is in the range of 0.034-0.042 W/(m K), therefore, based on this characteristic, all these insulation materials are suitable for thermal insulation of walls. Results of calculating the thickness of the thermal insulation layer in the structure outer wall residential building made of blocks based lightweight concrete thickness 200 mm are given in table 1.
Table 1.
|
Name of insulation |
Wall thickness, mm |
|||
|
insulation |
||||
| Plates based on basalt Rockwool cotton wool"LAIT BUTTS" | ||||
| Plates based on glass fiber "URSA P-20" | ||||
| Polystyrene foam boards PSB-S 25 | ||||
| Polystyrene foam boards “URSA XPS N - III – I” | ||||
| Extruded polystyrene foam "EXTRAPEN 35" | ||||
| Extruded polystyrene foam "PENOPLEX 35" | ||||
Notes. 1. The calculation was carried out provided that:
- city – St. Petersburg;
- estimated indoor air temperature +20ºC.
3. This calculation is advisory in nature. An official calculation can be made by an organization licensed to design building structures.
Another requirement for materials for thermal insulation of walls is a sufficient degree of vapor permeability. Since water vapor is formed in the premises of a house as a result of human activity, diffusion of steam from the room to the street occurs when there is a difference in temperature, and therefore pressure, outside and inside the building. In this case, steam passes through the load-bearing wall and enters the thermal insulation layer. Therefore, each subsequent layer of the enclosing structure, considering it from the inside out, must be more vapor-permeable than the previous one. Otherwise, moisture will be retained in the wall structure. Since a wall made of foam concrete has sufficient vapor permeability, insulation with less vapor permeability, for example polystyrene foam, which is located after it, will become a kind of barrier to moisture vapor. Then, condensation will form at the interface between the wall and the thermal insulation, which will moisten both the wall and the thermal insulation material. Wetting a load-bearing wall has a detrimental effect on its durability, and a wet wall's thermal insulation simply ceases to provide insulation. If the thermal insulation material is more vapor permeable than foam concrete, then moisture vapor will pass through it freely and, once it enters the air gap, evaporate without causing harm to the load-bearing wall and thermal insulation. This is exactly the case when using vapor-permeable insulation based on mineral basalt wool and glass wool, since their vapor permeability is higher than that of foam concrete.
Plates thermal insulation material on a non-flammable base, for example “Rockwool LAIT BATTS”, they are attached between the frame posts in a spacer. Additional mechanical fastening is performed with disc dowels specially designed for this purpose.
A waterproofing but vapor-permeable membrane is fixed on top of the insulation, which serves to protect the insulation and load-bearing elements frame designs from atmospheric moisture and how additional protection from the wind. It should be noted that between the insulation and a simple waterproofing membrane it is necessary to leave an air gap of 10-15 mm, otherwise the membrane will not “work” and the moisture that gets into the insulation will not erode out. However, superdiffusive ones are commercially available waterproofing membranes, for example “IZOSPAN-AM”, which can be laid directly on top of the insulation.
Previously waterproofing material can be secured to frame posts with a construction stapler. Then, on top of it, counter-battens are fastened along the racks with nails or self-tapping screws - wooden blocks, treated with an antiseptic composition, usually 40x50 mm in size. The façade cladding is installed along the counter-battens with a material chosen by the developer, such as siding.
It should be noted that before installing the frame and fixing the insulation, all wooden structures must be treated with fire retardant and antiseptic compounds or some combination of wood protection agents. Processing wooden structures carried out to obtain fire-resistant wood, in accordance with the requirements of GOST 16363-98 and to protect wooden structures from exposure various types biodestroyers: wood-damaging insects, mold, rot, fungus, as well as against the appearance of blue stains and blackening.
Added: 06/07/2012 08:55
Discussion of the issue on the forum:
I built a house from concrete blocks, the walls are 200 mm thick. Now the question is, what material to choose for external insulation under siding in order to retain maximum heat and not dampen the walls?Aerated concrete compares favorably with conventional concrete due to its low thermal conductivity. This property is achieved by introducing aluminum powder into conventional concrete mixture. Thanks to hydrogen bubbles evenly distributed throughout the mixture, aerated concrete transfers heat much worse than conventional concrete.
But this advantage also has a downside - aerated concrete has slightly lower strength than conventional concrete. Therefore, when choosing the thickness of a wall made of aerated concrete, you need to proceed not only from the required level of thermal insulation, but also take into account the strength of the wall. At the same time, of course, you need to stay within your budget.
Classification of aerated concrete blocks
Depending on the purpose of the room, the requirements for strength and thermal insulation characteristics walls Depending on the purpose there are:
- garage;
- any auxiliary room that is used only in the warm season (for example, a summer kitchen or workshop);
- dacha, for living only in summer;
- residential building
As for the strength of the material, it must be taken into account that with increasing density, the strength increases and the thermal conductivity of the material increases.
There are several classes of aerated concrete available on the market:
- B3.5 - can be used as a material for load-bearing walls of 5-story buildings;
- B2.5 - used as a material for load-bearing walls if the height of the house does not exceed 3 floors;
- B2.0 - this class of aerated concrete is used for the construction of load-bearing walls of buildings no more than 2 floors high.
Depending on the density, aerated concrete blocks are divided into grades from D300 to D1200 (the number indicates the density of the material in kg/m3). High-density blocks are positioned as structural (that is, they are able to withstand heavy loads), while minimum-density blocks act as self-supporting insulation.
Regulatory Requirements
Construction using cellular concrete (and aerated concrete is precisely this type of concrete) is regulated by STO 501-52-01-2007. Basic recommendations for the use of aerated concrete blocks are as follows:
- the regulatory document requires that the maximum permissible height of walls made of cellular blocks be determined only on the basis of calculation;
- limited maximum height buildings. It is allowed to make load-bearing walls of buildings up to 5 floors (or up to 20 meters high) from autoclaved cellular concrete, height self-supporting walls should not exceed 30 m (or 9 floors). Foam blocks (non-autoclaved cellular concrete) are used for the construction of load-bearing walls no more than 10 m high or no more than 3 floors.
- The standard also indicates the strength of concrete blocks depending on the number of storeys of the building. So, for the construction of external and interior walls For a 5-story building, blocks with a strength of at least B3.5 should be used (the use of foam concrete is prohibited), the grade of mortar is not lower than M100; in 3-story buildings class cellular concrete must be at least B2.5, and the solution class is M75; in 2-story buildings - B2 and M50, respectively.
- for the construction of self-supporting walls, it is necessary to use blocks of at least B2.5 class - in buildings with more than 3 floors and B2.0 - in 3-story buildings.
These standards take into account only the strength side of the issue and do not cover the issue of thermal insulation of the room (SNiP II-3-79). The requirements of the regulations are mandatory primarily for legal entities. Ordinary people, for example, during construction country house or garage, summer kitchen can use these requirements as recommendations. It is also necessary to take into account that during operation the humidity of aerated concrete blocks changes, and this slightly increases their thermal conductivity.
The best options when designing any building will, of course, be a full strength calculation and thermal engineering calculation, but not everyone can cope with this task on their own. Not everyone will want to pay for the settlement either. In such cases, you can focus on the approximate values of the strength classes and thickness of aerated concrete walls, depending on the purpose. Compared to other materials, aerated concrete wall should have a much smaller thickness with equal energy efficiency.
- For construction one-story houses in warm climates, summer kitchens, garages, etc., some use aerated concrete with a thickness of 200 mm, but this thickness cannot be called recommended. Even for construction non-residential premises As a rule, aerated concrete with a thickness of 300 mm is used.
- For the construction of walls ground floors and basements, it is recommended to use aerated concrete D600, B3.5. The thickness of the blocks should be at least 300 - 400 mm.
- Inter-apartment partitions - aerated concrete blocks B2.5, D500 - D600, block thickness - 200 - 300 mm.
- Partitions between rooms - blocks B2.5, D500 - D600, thickness - from 100 to 150 mm.
If the partition is installed in an existing room, then it is better to choose aerated concrete D300. In this case, it is not the strength that is decisive, but the sound insulation of the material.
- Construction of non-residential premises (garages, summer kitchens etc.) Aerated concrete D500 is used, thickness from 200 mm (depending on the load).
What you should pay attention to
Aerated concrete – efficient material from the point of view of thermal insulation, which is due to its cellular structure.
But in order to take full advantage of the benefits of aerated concrete walls, you should adhere to several rules:
- During construction, a special adhesive mixture is used, which is laid on the surface aerated concrete block thin layer(several mm). People who are used to working with conventional cement mortar it can be difficult to relearn. If the seams are made too thick, the mortar layer will begin to act as a “cold bridge” and thermal insulation properties aerated concrete will deteriorate.
- During construction in cold and temperate climate It is recommended to insulate walls made of aerated concrete both inside and outside.
- When performing strength calculations, it is necessary to take into account the additional weight created by thermal insulation, for example, plaster.
To get really warm and cozy home It is not enough to simply increase the wall thickness to the maximum. For most climatic conditions it is enough to use aerated concrete D600, B2.5 or B3.5 with a thickness of 300 mm. However, it is advisable to justify the choice of aerated concrete blocks by strength and thermal calculations.
User Questions:
- Good day to you. I want to build a house from aerated concrete (INSI block), please tell me how thick the wall should be and whether insulation is needed on the outside if it is lined with bricks with a ventilation gap of 6 cm. Thank you.
- Good afternoon! I am designing a 5-storey house in Krasnodar. The structure is monolithic, aerated concrete acts as a filler, please tell me what the thickness should be, is insulation needed? The outside is plaster for painting!
- Please tell me whether it is worth insulating the outside wall of a house from Aerok with a thickness of 375 mm? If necessary, what thickness should the min. cotton wool Then there will be a curtain façade. House in Ropsha Len. region.
- Hello! Is a house made of aerated concrete with a wall thickness of 250 mm + 100 mm facade foam suitable for permanent residence? The house is two-story on a strip foundation.
