1 BUILDING ELEMENTS FOUNDATIONS How deep do you think the foundation of your house could be? Tick the box and justify your choice. 1 - 2 m. 3 - 4 m. 5 -10 m. more than 10 m. Function of foundations Foundations transfer the total loads from the structure to the ground providing stability to the building. Foundations can be mainly classified into two categories depending on the depth at which the foundation is constructed: shallow foundations: used for small, light buildings (1 or 2 metres deep); Name one of the most famous Italian historical buildings with settlement problems. The most common sign of settlement is the occurrence of cracks on the structure at an angle of 45 , usually around the openings (doors, windows). to anchor: ancorare bearing capacity: capacità di sostegno concrete: calcestruzzo driven out: espulso dug (to dig-dug-dug): scavato to exceed: eccedere exerted: esercitato footing: plinto frost-line: linea di congelamento dell acqua high-rise: alto (di un edificio) low-rise: basso (di un edificio) shallow: poco profondo to sink: (qui) sprofondare spread (to spread-spreadspread): distribuito Deep foundations deep foundations: used for large, heavy buildings such as skyscrapers (from 5 to 25 metres). They must anchor the building to the ground. A properly designed foundation will limit settlement , that is the normal tendency for a new building to sink into the ground . Most soils are a mixture of earth, air and water, so, when the building load is exerted on the soil, the air and water are driven out and the soil consolidates. A foundation is usually wider than the element which is supported, so the load is spread over a greater area and the actual weight of the building does not exceed the safe bearing capacity of the soil. Placing steel reinforcement ensures the foundation to remain stable. Shallow foundations 130 BUILDING CONSTRUCTION Construction steps The first step in constructing foundations is the excavation considering the type of soil, the frost line and the depth of underground water. Then footings are placed by pouring concrete into wood or steel forms positioned under the frost line. This is essential in cold climates because the water in the soil around the foundation can freeze and expand, so damaging the foundation. Shallow foundations of low-rise residential buildings are supported on open footings that are visible during the early stages of work. Deep foundations for high-rise buildings include piles. A pile is basically a long cylinder of a strong material such as concrete that is pushed into the ground so that the structure can be supported on the top of it. During the foundation works, excavations for connecting the technical systems are usually required and are dug at the same time.