The condition of the erected building and the period of its accident-free operation will depend on the quality of the foundation work in the future. When choosing a foundation design for a house, you need to take into account such factors as the number of storeys and the weight of the future cottage, the type of soil, and the level of groundwater. In private low-rise buildings, which are being built with their own hands, in many cases the best solution would be a strip foundation.
When arranging the foundation, it is necessary to strictly observe all stages of work and their sequence. First, choose the material for pouring. It directly depends on the type of soil on which the house is built. When erecting a building on excessively and strongly heaving soils, only monolithic reinforced concrete is used. On medium and slightly heaving bases, monolithic concrete can be used. The strip foundation on soils with strong heaving must be a rigid frame of intersecting strips that can withstand strong soil pressure.
Compaction of the base is especially important when building on heaving soils. It reduces the heaving of the soil and increases the bearing capacity of the base. If the house is being built on peat and loess soils, then to enhance the bearing capacity, a monolithic pillow of concrete or reinforced concrete is laid at the bottom of the foundation. On strong foundations (sandy, sandy loamy soils), a cushion of coarse sand or fine gravel will suffice. It is covered in parts, the layers are leveled and compacted with a manual or mechanical rammer.
Formwork installation
Scheme of arrangement of the formwork of the foundation of the tape type
- the simplest wooden formwork is made from edged pine boards with a thickness of at least 40 mm;
- formwork is installed in such a way that the edge of the foundation for the house (its upper part) protrudes above the zero mark (ground level) by 100 mm;
- formwork panels are assembled on the ground;
- then install them in a trench;
- fixed to the racks driven into the ground.
For the manufacture of formwork with your own hands, you can also use special moisture-resistant plywood. Such material will cost a little more than pine moldings, but it provides a higher quality of foundation work. Due to the almost complete absence of cracks and gaps between the formwork parts, water from the solution does not seep into the ground, so the concrete will dry more evenly.
On dense clay and loamy soils, pouring can be carried out without formwork. But this method of building a foundation is only suitable for a traditional stone house, which has a fairly large weight. What are the benefits of building a foundation without formwork? Significantly reduced time spent on work. In addition, part of the money is saved, intended for the purchase of lumber for formwork. On the other hand, with this method of pouring, the consumption of concrete increases by 10-15% compared to the standard.
Reinforcement
The technology of pouring a strip foundation on heaving soils provides for mandatory reinforcement. The reinforcement scheme is developed when designing a house, depending on the individual characteristics of the building (number of storeys and weight of the building, building area, deepening of the foundation under the house, etc.).
View of the finished reinforcement cage for the "tape"
For the arrangement of the reinforcing cage, corrugated steel reinforcement is used. But in recent years, composite materials have become increasingly popular. Reinforcement made of fiberglass in terms of strength characteristics is not inferior to steel. At the same time, it has a much lower weight (which greatly facilitates the production of work), is not subject to corrosion.
The rules for installing a reinforcing cage recommend connecting all its elements to each other using steel wire knitting. Welding is not recommended for joining fittings. In places of welded seams, the structure of the metal is disturbed, therefore, such joints are quickly destroyed under the influence of corrosion. This significantly reduces the strength and bearing characteristics of the foundation structure.
Foundation pouring
Filling the strip foundation manually
For pouring the foundation under the house, factory-made M200 concrete or cement mortar prepared by hand directly at the facility is used. The use of a concrete solution made by an industrial method is preferable. In this case, the developer can be sure of the stable quality of the material and compliance with its declared technical characteristics. In addition, the manufacturer will deliver any amount of concrete required at the construction site at the moment. This allows you to quickly complete any volume of concreting with your own hands.
The rules for arranging a foundation on a gravel or sand cushion in autumn are simple:
- First, the so-called "starting layer" is poured.
- A layer of concrete about 10 cm thick is poured at the bottom of the trench. The solution will fill the pores in the base, which will prevent further loss of concrete due to its seepage into the ground. In addition, the starting layer will be a good basis for laying reinforcement.
- The pouring of the strip foundation can be carried out in parts. The concrete mixture is poured in layers 40-50 cm high at a time.
- The completed filling must be compacted in order to remove air bubbles from it as much as possible. Previously, the concrete mixture was “beaten off” with a reinforcing bar. This is a long and tedious job. To facilitate the work of arranging the foundation with your own hands, it is worth renting a pneumatic vibrotamper.
But the strip foundation (both shallow and deep) can be poured not in parts, but at a time. If a solution prepared at the construction site with your own hands is used for pouring, then it is advisable to periodically compact the mixture with a vibrotamper.
Special additives are added to factory-prepared concrete, which increase the fluidity of the solution. This prevents the formation of air bubbles during pouring and the delamination of concrete during drying. Therefore, such a solution does not need to be compacted.
The final stages of work with the foundation come after the concrete has hardened. At normal temperature and humidity, concrete gains 70% strength in 24 days. After the structure has reached the required strength, the formwork is dismantled and the foundation is bitumen waterproofed. Although waterproofing work can be avoided by ordering concrete with hydrophobic additives from the manufacturer. Then the sinuses of the foundation are covered with soil. Backfilling is carried out in parts, each layer is carefully rammed.
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