Most cracks in a Buckinghamshire home are not subsidence. They are thermal movement, drying plaster, or the house simply living its life. The trick is knowing which cracks are worth a phone call and which are worth a tube of filler.
This guide walks through what to look for, what to ignore, and what to do next if you genuinely think the ground under your home has started to move.
What a subsidence crack actually looks like
Look for diagonal cracks running through brickwork, not just plaster. They usually start above or below a window or door, taper at one end, and are wider than a 10p coin at their widest point.
Cracks visible from both inside and outside the same wall are more concerning than purely internal ones. Cracks that suddenly appear or grow during a hot, dry summer and partially close again in winter point strongly to clay shrinkage, the most common cause across Aylesbury Vale and the older parts of Beaconsfield, Amersham and Marlow.
What is almost certainly not subsidence
Hairline cracks in plaster, cracks that follow the line of a ceiling rose, cracks above a doorway in a newly skimmed room, and crazing in painted render are nearly always cosmetic. Map cracking on a chimney breast usually points to thermal cycling, not foundation movement.
If the crack opens and closes with the seasons by less than 1mm, monitoring rather than panic is the right answer.
How to log it before you call anyone
Photograph the crack with a tape measure or coin in the shot. Mark the ends of the crack with a pencil and the date. Take a fresh photo every two weeks. If the crack has not moved within three months, the case for it being structural weakens significantly.
Note any nearby tree work, drain repairs or building works on neighbouring properties. All three are common triggers in the Bucks postcodes we cover.
When to call a specialist
Multiple cracks wider than 3mm, doors that have started to bind in their frames, sloping floors, or visible movement in lintels above windows all warrant a structural engineer's visit. So does any crack that has clearly grown in the last fortnight.
Where to go next
Worried about your own property? See subsidence help across Buckinghamshire, read about foundation underpinning in Buckinghamshire, compare resin injection across Buckinghamshire, or arrange a structural engineering survey in Buckinghamshire. For local pages start with subsidence help in High Wycombe, foundation underpinning in Aylesbury, or structural engineering surveys in Milton Keynes.