Underpinning

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:Sketch of a cast in situ RC cantilever needle beam on micro piers or piles. Access to inside not needed.Sketch of a standard needle beam on micro piers or piles. Inside access needed.Sketch of concrete pier underpinning with the possibility of raising foundations.Sketch showing the traditional method of needling a wall to reduce the weight on the foundations during underpinning work.Underpinning the foundations of a railway bridge using a timber box crib to support the bridge. A completed concrete pad underpinning can be seen at the bottom right.]Drilling machines using jet groutingClose to the drilling head 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: Underpinning may be accomplished by extending the foundation in depth or breadth so it either rests on a more supportive soil stratum or distributes its load across a greater area. Use of micropiles and jet grouting are common methods in underpinning. An alternative to underpinning is the strengthening of the soil by the introduction of a grout, including expanding urethane-based engineered structural resins.