This barn conversion requiring underpinning was built on the cheap or without adequate foundations to support the weight of the property. In some places the pitiful foundations (or lack thereof) had crumbled away to almost nothing and the section of extension that had started manifesting large cracks was largely unsupported. This type of issue is more common than you’d think, especially in areas where people are likely to accept a lower build cost by nefarious building service offers. A legitimate company may have done the planning, engineering hard work only to have the job taken away from them by unqualified ‘professionals’ who will allegedly get the same job done for a fraction of the actual build cost. The usual outcome, spend a lot more than you saved by remedial repair, or worse – demolish and start again.
On this particular property, we cleaned up the slab (The section of concrete that in this case, holds the extension together), then dug substantial footings or trenches directly below the slab. We then underpinned the entire extension ensuring the damp proof course was intact so things like rising damp would not be an issue in this property. Underpinning on properties that have no foundation is the right fix as it is a solution that can be retrofitted to almost any property in many cases making it more stable than it was when built. There are also resin solutions that work equally as well, in this case we felt it wise to bring out the big guns and proceed with underpinning making the resident couple feel safe again and not like their property was about to collapse around them.
Of course a barn conversion requiring underpinning may not be in that state through bad workmanship – it could have been built as exactly that, a barn which would not ever have been subject to the same rigorous standards that a regular house would.