In construction or renovation, underpinning is the process of strengthening the foundation of an existing building or other structure. Underpinning may be necessary for a variety of reasons:The original foundation isn't strong or stable enough. The usage of the structure has changed. The properties of the soil supporting the foundation may have changed or were mischaracterized during design. The construction of nearby structures necessitates the excavation of soil supporting existing foundations. To increase the depth or load capacity of existing foundations to support the addition of another storey to the building. It is more economical, due to land price or otherwise, to work on the present structure's foundation than to build a new one. Earthquake, flood, drought or other natural causes have caused the structure to move, requiring stabilisation of foundation soils and/or footings.