Underpinning facts for kids

In construction, underpinning is the process of strengthening and stabilizing the foundation of an existing building or other structure. Underpinning may be needed for a many of reasons:

• The original foundation is not strong or stable enough.
• The usage of the building has changed.
• The type of soil supporting the foundation may have changed (possibly through subsidence) or were misjudged during planning.
• The construction of nearby structures causes the excavation of soil supporting existing foundations.
• It is more economical, due to land price or otherwise, to work on the current structure's foundation than to build a new one.

Images for kids

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  Sketch of a cast in situ RC cantilever needle beam on micro piers or piles. Access to inside not needed.

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  ketch of a standard needle beam on micro piers or piles. Inside access needed.

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  Sketch of concrete pier underpinning with the possibility of raising foundations.

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  ketch showing the traditional method of needling a wall to reduce the weight on the foundations during underpinning work.

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  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.]

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  Drilling machines using jet grouting

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  Close to the drilling head