There are several types of underpinning methods to choose from, each will be best for some situations only. The traditional mass concrete underpinning method is a good example. This process is best suited for shallow underpinning and involves excavating the weak soil underneath the foundation and replacing it with mass concrete, which provides more strength. Since the concrete base is now stronger than the soil that used to hold the foundation, the weight of the structure is carried in a much more efficient manner.
Another method involves the use of a beam and base. This method not only makes use of traditional mass concrete bases, but also incorporates beams to support the existing foundation. Its load is transferred to a concrete beam that is constructed underneath it. The beam then transfers the load to a mass concrete base which spreads evenly for support. The construction of the beams depends on the architecture of the structure built on the foundation.
Mini-piled underpinning involves transferring the load of the structure and the foundation to stable soils found deep underground. The depth of the soil exceeds 5-meters. The constructed piles are cased in steel and have a diameter ranging from 15-cm to 30-cm. The piles are driven into drilled holes, making them rest on a stable soil below ground level. Some piles may be constructed as to reach 15-meters below ground.
