When deciding which foundation is best to choose for a house from aerated concrete, several factors must be taken into account. First of all, design features are affected by the properties of the wall material. Foundations for houses built of aerated concrete should take into account some of the distinctive characteristics of this material.
Features of aerated concrete blocks
Here, those characteristics that directly affect the foundation for a house from aerated concrete will be considered. Before choosing a type, you need to consider the following features.
Gas blocks are piece material. Even with the correct choice of masonry mortar and compliance with the technology of work, they are loosely connected. This factor results in the fact that the walls of the building are extremely sensitive to various deformations of the base.
If the foundation for the house made of aerated concrete sags or, on the contrary, rises from the ground, cracks on the walls of the building may appear. Cracks in most cases will be inclined. The opening width and length depend on the scale of the displacement of the supporting part of the building. To prevent the occurrence of damage, reliable supports must be provided that will resist various kinds of displacements. The design should link the wall from individual blocks into a single system.
The foundation for aerated concrete is needed less powerful than for a brick house. This is due to the lower density of the material, and, accordingly, the mass. For comparison, the density of gas blocks is from 350 to 700 kg / m3, while a brick wall will have a density of 1800 kg / m3. Blocks with a minimum density cannot be used as structural elements, the material of the bearing walls has a mass of 500 to 700 kg per cubic meter.
Despite the advantages of blocks compared to bricks, it is worth remembering that the material is inferior to wood. Also, the building will be heavier than the frame house. When choosing the foundations for houses made of light aerated concrete, this feature must be taken into account.
What types of foundations are used
All foundations, depending on working conditions, can be divided into four large groups:
- columnar
- pile;
- tape
- plate.
The first and second in private construction (taking into account the most popular sections) have a relatively low bearing capacity. Such elements work only on compressive loads. It is especially advantageous to make them out of concrete, since this material has good compressive strength. Also, screw metal piles have become widespread lately.
The strip foundation accepts mainly compressive loads. When installed on soft soils, small bending effects can also occur. If the monolithic foundation is made in compliance with the technology, they do not cause problems.
The use of a slab foundation is characterized in that this design works for bending and punching. Concrete is poorly resistant to such influences. To prevent damage, a mixture of sufficiently high grades is chosen for pouring, and the reinforcement is prescribed with special care. Before installing the slab, it is recommended to calculate its strength and stiffness. To perform such work can only be a professional designer or constructor.
How to choose the type of foundation
Before choosing which type of supporting part for a house made of aerated concrete is best to use, the following points should be considered:
- geological conditions of the construction site, foundation strength, soil water saturation, groundwater location level;
- the mass of the building (when comparing buildings made of the same material, the number of storeys strongly influences this characteristic);
- economic opportunities.
Effect of soil characteristics
Moisture in the soil and the type of soil affect the elevation of the supporting part. Soils on the site can be one of the following types:
- large-detrital;
- coarse sand;
- medium sand;
- clay;
- loam;
- sandy loam;
- fine or dusty sand;
- bulk soil.
The last two positions have very low strength indicators. It is not recommended to build on such bases (only pile foundations can be an exception). The best option is to replace the material with sand of medium or large fractions.
Coarse and sandy (medium and large) will become the best primers for construction. Such bases have high strength and are not prone to frost heaving (one of the main enemies of foundations for houses made of aerated concrete).
Refractory clays and loams also have good strength characteristics. But all clay soils (clay, loam, sandy loam) can lead to uneven elevation of the building in the winter. This phenomenon occurs due to frost heaving. At the same time, the external walls of the building rise more than the internal. Cracks appear on the walls of gas blocks. When building on such bases, timely measures are required to prevent frost heaving.
When building on heaving soils, it is necessary to choose those types of foundations that are buried below the freezing of the soil. The value is determined by regulatory documents. On average, this value is in the range 1-2 m.
The foundation for the house of aerated concrete (its sole) should be at least 50 cm above the groundwater level. Depending on the location of moisture, you can use a buried structure (it goes into the ground 1.5 m or more) or a shallow one (laying in this case is assumed to be approximately 70-100 cm). Also, when choosing the depth of foundation, it is necessary to take into account the need for a basement device.
Structural features of the building and the load on the foundation
To choose which foundation is best for a house of blocks, it is recommended to read the table below. The dimensions and thickness of the supporting part are assigned by calculation.
Soils at the construction site | For a one-story block house | For a two-story block house |
Coarse soils, medium and large sands | To save money in this case, use columnar bases or tape with a small depth of laying | Pillars are used for such buildings. The strip foundation for the house of aerated concrete in this case should have a T-shaped section (increased thickness from the bottom). The rectangular type of section is better not to use because of the low bearing capacity |
Clays, loams and loamy sand (most often they are water saturated) | You can use a pile foundation of screw supports. They are perfect even with moist soil. A reliable monolithic grillage is made on the tips of the piles, which will link the individual supports into one system. Also, a slab base will be an excellent option (due to the light load, the thickness of the foundation is used relatively small about 200 mm) | The foundation for the house of aerated concrete in this case is assigned to a tape or slab type. In this case, the tape should be laid below freezing or have reliable insulation. To protect the building from moisture, a drainage system, waterproofing and a blind area around the perimeter are designed. The tape can be made of monolith or FBS blocks. A monolithic version is preferable because PBS are weakly interconnected. By their edge, you still have to perform a reinforced concrete belt. The thickness of the foundation is assigned depending on the thickness of the walls. If the basement device is not planned, a shallow slab is used. This approach will reduce construction costs. |
Plots with high groundwater level (marshland) | As a supporting part, you can use a tape from a monolith or FBS. In this case, it is necessary to observe the distance between the base of the foundation and the water level of –50 cm. When the moisture level is very high, the foundation uses a plate or screw piles | Screw piles have a fairly low bearing capacity. When building a house on two floors in a swamp, it is recommended to use slab as a foundation |
The answer to the question of which foundation is best to apply depends on many factors. None of them can be missed.
However, in most cases, for all the above parameters, two types are suitable - tape and plate.
A careful approach will allow you to build a house for many years.