Start with the symptom
Every page here follows the same six-part shape, so you can get to the part you need.
- What the symptom actually is, in plain terms
- What is normal, and why - because most of it is
- What is potentially serious, with the real diagnostic markers rather than scare language
- What you can check yourself this week, at no cost
- When to call an engineer, stated as a threshold rather than a plea
- How we would investigate it, and what the report would tell you
How severity is actually judged
There is a published scale for damage to walls and it is the one engineers use: the BRE damage classification set out in BRE Digest 251, which sorts visible damage into categories 0 to 5 - negligible, very slight, slight, moderate, severe and very severe - largely on crack width and ease of repair.
The useful thing to know is that the great majority of domestic cracking sits in categories 0 to 2: hairline up to around 5mm, repairable during ordinary redecoration, with no effect on the stability of the building. Almost nobody publishing on this subject names that scale, and it is the honest answer to most of what we are called to look at.
Why an engineer rather than a contractor
Search for any symptom on this list and most of what comes back is published by a company that sells the cure - underpinning, resin injection, re-tying, damp proofing. That does not make them dishonest, but the diagnosis and the sale sit in the same hands.
We do not carry out repairs and take no commission from anyone who does. That leaves us free to say a crack is old, stable and cosmetic - which is genuinely the commonest finding - and to put it in writing so a buyer, a seller, a lender or an insurer can rely on it.
The Yorkshire difference
Most national content about ground movement is written about shrinkable clay, because that is where the hazard concentrates in South East England. It explains very little about a stone terrace above a former colliery.
The mechanisms that matter here are coal mining legacy, made ground from spoil and backfill, washout into culverted becks and defective drains, and - in a small area around Ripon - gypsum dissolution. Several of these guides are written specifically around that.