How to make a foundation for a house

How to choose a foundation for your home?

The house stands on a foundation, and its construction begins from the foundation. The construction of a manor-type house, which is built by the owner himself, is usually carried out without any calculations based on intuition and the material available. However, often the labor expended for the construction of foundations and houses is wasted. The supports bulge in the spring, the brickwork between them collapses, as a result, the building is deformed, windows and doors warp, the house deteriorates completely. Hopes that the foundation will sit in place in the summer are not justified. It is necessary to put the house on temporary supports and do it all over again. And it's expensive and labor intensive. As experience shows, the foundation sticks out most often on loamy soils with deep freezing and close groundwater.

What determines the strength of the foundation?

The stability and strength of the foundation depends on the soil, the depth of freezing, the level of groundwater, the weight of the building and the design of the foundation.

The best, most reliable foundation of buildings is rocky, large-block, gravel, gravel soils, as a rule, incompressible, strong, difficult-to-work soils. The foundation device can be carried out on their surface, since they do not require any protective measures.

Such foundations are the least complex and cheaper. Sandy soils are also a good base, represented by large and medium-sized grains of sand, dense and medium density. They have greater bearing capacity.

Their compaction under load from the house occurs during the construction period, and in the future these soils practically do not compress. Frost heaving does not appear in them, regardless of the position of groundwater. Since the surface of such soils is easily loosened, it is recommended to place foundations on them in denser layers at a depth of 40-70.

Soil types and foundation selection for home

Clay soils - clays, loams, sandy loams, as well as fine and silty sandy soils are most often found in nature. As the foundation of buildings, they require the greatest attention of the developer, as they are able to shrink, erode, and swell when frozen. The strength of such a base varies widely and is often unevenly distributed. The closer the groundwater to the surface and the greater the depth of seasonal freezing, the more intense the frost heaving.

The correct choice of foundation design on these soils is more difficult due to the variety of heaving manifestations. Possible destruction of the foundation under the influence of frost heaving forces. Their types are shown in the figure. The standard depth of seasonal freezing of soils for different regions can be viewed from the table.

Foundation depth in various soils

There are also special soil conditions in nature, which include structurally unstable soils, that is, soils that are stable in their natural state, but change their structure under certain influences:
Soaking, thawing, etc. Losing their structural strength under external influences, these soils are additionally compacted under the load from the building or increase in volume, give significant local precipitation that flows at high speed, or the choice of foundations. Such soils include loess loams, permafrost soils, silts, peaty soils, etc. Construction on such foundations presents significant difficulties. The main thing when choosing and constructing foundations is either to exclude the influence of deformations of these soils on the building (pile foundation), or to exclude external influences in the construction zone that cause structural changes in the soil, that is, the removal of storm water, thermal insulation or the installation of cooling channels, drainage, artificial hardening of the base and etc. In such cases, it is better for the developer to contact the specialists of the district construction organization, since the independent construction of foundations most often leads to negative results.

Foundation types

In the individual construction of manor-type houses and outbuildings, strip, columnar foundations, short piles up to 3 meters, and slab foundations are used.

Strip foundations the most common, but material-intensive, arrange it along the entire length of the external and internal load-bearing walls.

Pillar foundations arrange in the corners of the building, at the intersection of the planes of the walls and after 1.5-2 m along the walls, in wooden houses, between the foundation pillars of the outer walls, they build a wall that isolates the underground - a fence. A columnar foundation is more economical than a strip foundation, less laborious, but it requires greater rigidity of the above-foundation structures.

Pile foundations expedient when occurring from the surface of soft soils at a depth of up to 2 m. Piles are arranged in a drilled well with a diameter of 200-300 mm or by driving pre-made piles.

For light, small structures in terms of unfavorable soil conditions, apply slab foundations from monolithic reinforced concrete, having a small depth of laying or located on a backfill of coarse and medium sand.

Rubble foundations they are made of large cobblestone, torn, bed or flagstone (limestone, sandstone, granite, basalt, shell rock). The stones are laid on a cement-sand mortar in rows. The minimum width of the foundation, cm: tape-50, columnar-60-60. Rubble concrete foundations are constructed from small cobblestone, crushed stone, gravel, well-fired clay bricks, which are sunk in a strip into a cement-sand mortar with tamping. The foundations are carried out in the formwork, and under favorable soil conditions, at a distance between the walls of the trench or pit.

Concrete monolithic foundations are arranged with crushed stone or gravel filling. In the case of purchasing ready-made concrete, its grade must be at least 200 in compression, which corresponds to class B15. Concrete is placed in the formwork in layers with tamping. If necessary, reinforcement is fixed to the formwork so that the protective layer of concrete is at least 50 mm. Such a foundation is economical, reliable and durable.

In the absence of the materials described above, you can install brick foundation, for which well or heavily fired clay bricks are used. Moreover, it is necessary to protect such a foundation from groundwater, especially with their chemical aggressiveness. These foundations are less durable, their service life is determined by the quality of the brick. With a high level of groundwater and deep laying, they are not recommended.

Precast concrete block foundations individual or factory-made from heavy concrete grade 150-200 are less labor-intensive in construction. With a mass of individual blocks up to 50 kg, no lifting mechanisms are required. Blocks are laid on a leveled preparation made of sand or concrete with a thickness of at least 10 cm. In columnar foundations on heaving soils with a block height greater than their width, to prevent horizontal shift, the upper part is rigidly embedded in a monolithic grillage-base.

In case of occurrence from the surface of weak soils of great thickness, the foundations are arranged at a great depth (1.5 ... ..2m). In this case, a columnar foundation is recommended from asbestos-cement pipes with reinforced concrete mortar. They can be made both in advance with the subsequent installation, and on the spot. In the lower part, a widening is made of reinforced concrete with vertical reinforcement embedded in it, passed through the cavity of the pipe, also filled with concrete. In the upper part, the vertical reinforcement is securely embedded in a monolithic cap grillage. The diameter of the pipes must be at least 200 mm, and it is selected based on the load from the building. In heaving soils, the lower broadening, located below the depth of seasonal freezing, reliably anchors the foundation from lifting, and the smooth walls of the pipe have minimal adhesion to the surrounding soil.

For light structures of wooden outbuildings, you can use foundations made of thick-walled metal pipes. At the same time, special attention is paid to the waterproofing of metal elements, protecting them from damage and, if necessary, restoration.

One of the simplest types of foundations for summer premises, buildings, structures - " wooden chairs". They are made of hardwood - layered pine, larch, oak, etc. usually "chairs" are lowered into pits dug or drilled 20-25 cm deeper than the freezing of the soil. They are fixed by falling asleep with soil and a rammer. To increase the service life of such a foundation, the “chairs” are fired or covered with heated bitumen. Particular attention should be paid to the waterproofing of the foundation section near the ground surface, in dry time, if possible, drying the structure and restoring the damaged waterproofing.

When installing pile foundations on your own, it is recommended to make piles in a drilled well, for example, using a garden drill with an elongated rod. The diameter of the well must be at least 200mm. The cavity of the well after the installation of longitudinal reinforcement is filled with concrete with layer-by-layer tamping. The reinforcement and the head of the pile are embedded in a monolithic grillage-base. In wet and loose soils that do not hold the walls of the well, an asbestos-cement pipe of a suitable diameter can be used, which is installed at the wellhead, gradually removing the soil from its cavity. The cavity at the end of the immersion is filled with concrete.

Driving piles up to 2 m long and up to 10 cm in diameter can also be done on your own. They are made of hardwood with a pointed lower end and are immersed with blows from a heavy rammer.

The number of piles in the foundation depends on the load of the building and the strength of the foundation. This type of foundation can be recommended for light wooden outbuildings erected on weak water-saturated soils, underlain to a depth of 1.5-2m. The pile pitch in this case is 1-1.5 m.

How to protect the foundation from deformation and destruction

For a long time, it was believed that on heaving soils, the depth of laying of strip and column foundations in all cases should be set below the depth of seasonal freezing in order to exclude deformations associated with frost heaving. However, as practice has shown, this expensive way in the construction of one-two-story manor-type houses and light outbuildings leads to additional troubles. The fact is that the weight of manor-type houses and outbuildings, even with brick walls, is insufficient for complex buckling forces, which are greater, the larger the foundation surface in contact with the ground.

It is more practical to place foundations at a depth of 30-70 cm with a pillow made of non-porous material, coarse sand, gravel or a sand-gravel mixture under them, which is carefully compacted by layer-by-layer tamping. It is also possible to use local soil, specially treated to exclude puffy properties (for example, salt). The width of the pillow should exceed the width of the foundation by 20 cm in each direction, and the depth depends on the degree of heaving of the soil and, with a seasonal freezing depth of 1.5 m, is 10-50 cm from the base of the foundation or more, to strong base layers.

To prevent silting of the cushion material with clay and silty particles that enter it with groundwater, it is isolated from the surrounding soil with any material at hand (roofing material, roofing felt, plastic film) or simply coated with a trench or pit wall with a greasy clay solution.

The depth of foundations in this case is determined based on the topography of the site and the strength of the foundation soils. At the same time, it is necessary to take care of the longitudinal rigidity of the foundation, reinforcing monolithic foundations or arranging reinforced belts under or above foundations made of masonry materials. In brick houses with heavily heaving soils, the deformation of which is 10-15 cm, it is necessary to install a reinforced belt above the window openings.

It is also necessary to drain storm water from the foundations. To do this, they carry out a vertical layout of the site and arrange a blind area around the perimeter of buildings, the width of which for houses should be at least 75 cm, and for outbuildings - 50-70 cm. It is made of waterproof materials, such as greasy clay, with a slope from the building.

Foundation waterproofing

To protect the walls from ground moisture along the leveled surface of the basement and at the level of the blind area, horizontal waterproofing is arranged from two layers of roofing material on bituminous mastic or a layer of cement-sand mortar with a ratio of cement and sand by volume of 1: 2 2 cm thick. The surfaces of foundations and basement walls are also isolated from groundwater - vertical waterproofing. Coating vertical waterproofing from hot bitumen or bitumen liquefied by solvents is evenly applied in two or more layers. The total thickness of the coating must be at least 0.5 mm. Pasted waterproofing is made of rolled waterproofing material, glued in several layers on bituminous mastic.

Based on the materials of the book "Your home. Manual for individual construction", 1994

Our site has a Vkontakte group