When underpinning is the answer, and when it is not

What it does

Underpinning extends a foundation down to a more suitable bearing stratum, or widens it to spread load over a larger area. It is a response to a foundation that is inadequate for the ground beneath it or for the load above it.

When it is genuinely needed

Where subsidence has been established and the cause cannot be removed. Where a foundation sits on unsuitable ground and load is increasing. Where an adjacent excavation, such as a basement, undermines an existing footing. In each case the foundation itself is the problem.

When it is not the answer

Where the movement is historic and has stopped. Where the cause is a leaking drain or vegetation, which can often be removed more cheaply than the foundation can be rebuilt. Where the cracking turns out to be thermal or shrinkage rather than foundation movement at all.

Establish the cause first

Underpinning a building whose movement was caused by a leaking drain fixes nothing and costs a great deal. Investigation, including monitoring where the evidence is not yet clear, comes before the remedy. This sequence gets reversed more often than it should.

Alternatives worth considering

Removing the cause, whether that is drainage, vegetation or loading. Root barriers. Localised repair rather than whole-building treatment. Monitoring to establish whether anything is actually still moving before committing to a remedy.

If you are mid-claim

Insurers and loss adjusters need cause established, not just damage recorded. A report that sets out the mechanism and the evidence behind it is worth considerably more than one that describes the cracking.