Types of foundations

Recommendation points

• Column foundation
• Strip foundations
• Slab foundations
• Pile foundations
• Foundations on sand cushions
• Wooden chair foundation

The main task of the foundation is to evenly distribute the load-bearing structures of buildings on the ground to prevent its uneven shrinkage and curvature of the structure. The foundation can be erected from various materials that determine its operational characteristics and durability: rubble stone, brick, concrete mixtures, monolithic reinforced concrete blocks. Nevertheless, the structure of the foundation itself, as well as the method of its construction, plays a far from unimportant role. According to the structure, it is customary to distinguish 6 different types of foundations: columnar, tape, slab, pile, on sand cushions and from wooden chairs. Let’s take a closer look at each of them..

Column foundation

The most common in construction due to its practicality and economy. Ideal in places with moving soils, as well as in climatic zones characterized by deep freezing of soil and ground. However, this type of foundation is not universal and may not be applied everywhere..

For example, in very mobile soils, including in zones of seismic activity, additional rigid fastening of reinforced concrete pillars to the ground is required. Otherwise, the supports may simply topple over, causing the destruction of the building itself. It is not advisable to use columnar foundations in houses with heavy walls, especially in places with soft, not dense soil. Another important problem is the formation of voids between the pillars directly from the wall itself to the bottom of the pit, which must be filled.

Columnar foundations are recommended for use in the construction of lightweight buildings: wood, frame, panel board. The poles should be installed at a distance of one and a half to two meters from each other. At the same time, they must be located at the points of the greatest concentration of the load: at the corners of the building, at the intersections of the walls, under the architectural columns and bearing parts. Beams of thick wood or reinforced concrete are placed on the pillars, depending on the expected load and the distance between the foundation supports.

A basement is laid between the posts on the lintels (beams). It is designed to protect the subfloor from external influences, such as: wind, humidity, freezing, snow. The use of a plinth allows you to keep warmth in the premises, serves as sound insulation, provides a comfortable and healthy environment for living rooms.

The cross-section of the foundation pillars depends on the calculated load, soil, and the material from which the pillars are made plays an important role in this. For example, for a brick it is 380 mm, for concrete, rubble concrete and flagstone – 400 mm, and the use of natural stone forces to increase the height of the foundation to at least 600 mm.

The construction of a columnar foundation is notable for its speed and simplicity. Holes are drilled in the ground in marked places, into which pipes of the calculated diameter are installed. The cavities in the pipes are filled with the necessary material from which it was planned to create the foundation for the building. The most difficult thing in this procedure is to find pipes of the required diameter and leave them to the construction site. But, as construction experts say, you can do without them..

The analogue of the pipe is made from a sheet of glassine rolled into a cylinder with double edges. Homemade staples made of thick and elastic wire secure the edges of the sheet from the inside and outside along the lower and upper perimeter of the circle.

A layer of sand is poured into the drilled well, which is carefully tamped. After that, the pipe is installed, filled with concrete mixture, thoroughly sealing it. If pillars are required over the height of the existing pipes, then proceed as follows. The first pipe is filled, leaving a few centimeters of the upper part of the pipe free, into which a second pipe of a slightly smaller diameter is inserted, which is refilled to the desired value.

Concrete pillars are set no earlier than two to three days. After the concrete has hardened, paper clips are removed from the improvised pipes and sheets are unrolled, which can be reused in the future. As a result of such a technique, you will get a column of the desired dimensions, but step transitions will be carefully traced in it, and with each subsequent step, the diameter of the column decreases.

There is a slightly different technology for building up pillars, which allows you to make pillars of unlimited height without changing its section, but it is characterized by long time costs. We make the first step in the same way as described a little above. We let the concrete dry for 5 days, after which we remove the paper clips from the top of the homemade pipe, move it exactly halfway, and fix it again. We wrap the lower part tightly with wire. We fill the released part of the cylinder with the mixture and let it grab for 5 days. We continue this procedure until the required height is reached..

To increase the strength, it is recommended to put iron reinforcement or wooden inserts in the posts. The diameter of the pillars can vary from 8 to 80 cm, depending on the type of soil, the magnitude of the load, the use of reinforcing elements, as well as the chosen technology for the construction of the foundation.

Strip foundations

Despite its high cost, this type of foundations is characterized by increased reliability and durability. It is made of monolithic concrete or reinforced concrete monolithic blocks using an extremely simple technology. The blocks are laid along all the perimeter of the building under the outer walls, as well as under all load-bearing walls and partitions, which requires builders to carry out a large amount of earthwork, which explains the high cost of such a foundation.

The choice of material from which the blocks will be made depends on the moisture content of the soil. For any type of soil, granite, basalt, diorite, concrete and mortar are suitable. It is not recommended to use limestone, sandstone and clay bricks in soils saturated with water. But silicate brick can only be used in dry lands..

The width of the foundation directly depends on the type of soil, its density, moisture content, as well as on the mass and volume of the building and the load generated by the walls and load-bearing partitions. It should be borne in mind that the amount of land work directly depends on the change in the width of the foundation. When building a foundation, do not forget about water supply pipes, sewerage, gas supply, cable lines. You need to leave holes for them. After laying the pipes, the slots are sealed with tow with the addition of glass wool, which will help protect against the raid of rats and mice..

Strip foundations can be of two categories, depending on the technology of their construction: monolithic and prefabricated.

To create monolithic foundations, a pit is pulled out, into which formwork is installed. The base, reinforcement, thermal insulation are laid at the bottom and everything is poured with concrete. The concrete mixture can be slightly diluted with expanded clay or foam, which, again, will allow you to keep warm inside the premises of the future house. The main advantage of this category of foundation is the ability to create a foundation for buildings of any shape and size..

Prefabricated strip foundations are laid out from pre-prepared massive blocks. This can significantly save time on its construction, but it is only suitable for square or rectangular houses. Another drawback of the prefabricated technology for the construction of the foundation is the gaps between the blocks, through which moisture will most likely seep, and the heat loss of the building will increase.

Slab foundations

This foundation is being built immediately under the entire building area. It can be monolithic, representing one large slab of concrete mix. Or it can be made in the form of a lattice structure according to the prefabricated construction technology, by the method of cross laying of ready-made reinforced concrete beams.

Whenever possible, such foundations are made monolithic or rigidly fastened. Most popular for use in soils with increased or uneven compressibility, during construction in places of former landfills, are resistant to seismic activity.

The slab foundation is only suitable for compact buildings such as baths, garages, outbuildings. This is due to the large expenditure of materials for its creation, which is particularly expensive..

Pile foundations

They are erected from separate piles, which are covered from above with solid concrete slabs. Due to the high complexity of construction, labor intensity and time costs, it is rarely used in practice. First of all, such a foundation is designed to transfer a large load to individual compacted areas among soft soil, which, as a rule, are located at a significant depth..

Piles can be made from a wide variety of materials: wood, concrete, reinforced concrete, hoist, as well as their combinations. According to the construction technology, they can be driven when a pre-made pile is lowered into a prepared well, and rammed when the pile is made directly in the well itself (filled with concrete). By the type of load distribution, the pile foundation can be stable and hanging. The piles of the pillars with their lower end rest on solid areas of soil. Providing concentrated load transfer. Hanging piles transfer the load to the sides, using the friction force of the pile itself with the ground.

Wooden piles are particularly economical and easy to erect, but their durability and performance are clearly not the ultimate dream. Wood is susceptible to moisture and decomposes quickly in moist soil. Reinforced concrete piles are somewhat more expensive, but this is fully justified. Concrete piles are more reliable, more durable, are not affected by external factors, they distribute the load better.

In general, pile foundations are easy to construct and their technologies, economical in terms of material consumption, take little time to build and practically do not require labor resources. On the other hand, economically such foundations are not profitable due to the need to use specific equipment, which is very difficult to get..

Foundations on sand cushions

Most often used in order to save on construction. Initially, sand is poured into the bottom of the pit with a layer of 15-20 cm, which is carefully compacted. The width of such a pillow should be 10 cm more than the thickness of the walls of the house..

On top of the sand layer, crushed stone and small stones with a total thickness of 25-30 cm are poured, which are rammed and poured with cement or concrete mortar to a height determined by calculations of the strength and load transmitted by the building to the ground.

The use of sand cushions is not recommended in soils with high moisture content, as well as in climatic zones with a large depth of freezing of the earth. This is due to the fact that the sand practically does not impede the flow of water, and moreover, it is washed out by it. Over time, such a foundation subsides, quickly loses its original performance..

Wooden chair foundation

They are used in the construction of lightweight, usually wooden structures. You need to use logs made of pine or oak, carefully processed with special mixtures and impregnations that prevent their decomposition and protect against the effects of drops in temperature, moisture, fire. The logs themselves are installed on pre-prepared wooden platforms 10x20x50 (thickness, width, length), the task of which is to more evenly distribute the generated load on the ground.

Such chairs are installed at all angles, as well as along the entire perimeter of the walls at a distance of 1-2 meters from each other. In this case, the logs deepen 1-1.5 meters into the ground. Such a foundation is poured in several stages in layers of 20 cm, alternating between sand and gravel. Each layer is carefully compacted.

The average service life of wooden chair foundations depends on the type of wood and the quality of its processing and can range from 7 to 30 years. Nevertheless, it is more reliable to use reinforced concrete beams or pillars, which are designed for 50 years of service, as supports. Rubble and strip foundations will not lose their strength and reliability even after 100-150 years, on such a foundation your house can stand for eternity … And even more.