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Every foundation, or foundation, works according to the same principle: it is an iron or concrete structure, placed underground in order to be able to distribute the weight of the building over a larger area of the ground. The foundation thus prevents any structure, even a house, from sinking – so it has to be positioned directly below the support points of the future construction.
In the case of buildings, it is under the support pillars. Ideally, the soil supporting the foundation should be resistant and not deform under the weight of the building. “Often, good soil is many meters below the surface, so we have to dig deep to find it”, says engineer Carlos Mafei, from USP. There are several methods for making a foundation. The choice will depend on factors such as how deep the firm ground is, the weight of the building and its cost.
Once the foundation is ready, the next step is to support the skeleton of the building on it, made with concrete or steel pillars.
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There are four main techniques for building a foundationshallow foundation
The cheapest of all, it is used when the soil close to the surface is resistant and dry. One or more holes 1 or 2 meters deep are dug and then filled with concrete, forming what builders call a footing. The bigger and heavier the building, the bigger the footings have to be. If they are large enough, they merge into one large concrete slab called a raft.
driven stakes
They are generally used for the construction of buildings of up to 12 floors, when the firm ground is a few meters below the surface. Several concrete beams approximately 40 centimeters in diameter are driven into each other. They can be buried up to 12 meters deep. Those who do the work of pushing them down the earth are those huge (and noisy) pile drivers
shaped piles
Used in even deeper soils, they start with metal or plastic pipes placed in holes to prevent cave-in. Then just fill them with concrete. Another similar technique is the foundation with pipes, large shaped piles that can be used in smaller numbers. The excavator digs holes 1.20 meters in diameter, which will be lined with a hollow steel cylinder and filled with concrete
Cap
It is the most expensive type of foundation. It serves for buildings with 20 or more floors and when the soil does not allow the use of a shallow foundation. A special excavator makes rectangular holes measuring 5 meters x 1 meter and fills them with impermeable mud, which prevents landslides. In a second moment, a pipe introduced at the bottom of the hole spreads the concrete (chart A). When the concrete dries, the foundation is ready (B)