Terraced house subsidence, is it even possible? The short answer is, definitely. Any property built on a weak foundation will start to show cracks from subsidence regardless of size. In these images, you will see severe cracking across all parts of the house, pillars, sills, walls and corners.
Cracks form where the foundation no longer supports the structure above it. A house made of bricks and mortar or concrete is a heavy and rigid structure and requires support right across the structure. Subsidence is where a section of the soil supporting the foundation sinks or shrinks and either the foundation sinks, breaks away from the main walls and leaves the house walls unsupported, or the entire section of wall complete with its foundation breaks away from the house and starts to sink downwards.
This, in turn will start cracking at all the stress points where the breakaway section is only supported by the adjacent brickwork. The cracking could take months or in extreme situations like near a sinkhole, it could take seconds.
The good news is that most terraced house subsidence cracking can be fixed by underpinning. Subsidence is one of the main fixes we do utilising traditional underpinning which is the preferred fix especially across much of London where clay soil is encountered throughout many of its boroughs.
Clay is difficult to work with when wet due to its slimy and sticky texture. It also shrinks when it dries and dries hard especially in times of hot weather. The perfect conditions for subsidence are a wet winter followed by a hot summer which in turn is followed by rain. The supporting soil dries out lower than its original level (subsidence) and that is closely followed by the uneven dropping of walls and manifests itself in the cracks we look out for when advising on terraced house subsidence.