The short answer
Damage to a neighbour’s property during party wall works is uncommon, but when it happens the scale matters. A measured response depends on objective assessment, not alarm — not every crack is structural, and not every defect is caused by the works.
Why it matters
Cracks arise for many reasons — construction vibration or impact, ground movement or settlement, seasonal moisture and temperature change, historic movement, or ordinary shrinkage — which is why photographs, dates and a proper schedule of condition are so useful. Surveyors and engineers commonly use the BRE Digest 251 classification:
- Negligible — Grade 0 (hairline below 0.1mm, no repair) and Grade 1 (up to 1mm, redecoration).
- Slight to moderate — Grade 2 (up to 5mm, filling and redecoration, or minor repointing) and Grade 3 (5mm to 15mm, localised masonry repair, repointing or some brick replacement; weather-tightness may be affected).
- Severe — Grade 4 (15mm to 25mm, structural repair likely, distortion visible) and Grade 5 (over 25mm, major structural repair or rebuilding).
What to do now
- Measure the crack width and photograph it clearly.
- Compare with pre-works condition records.
- Identify whether the crack is new or historic.
- Seek professional advice for anything beyond minor cosmetic cracking.
Common mistakes
- Treating every crack as structural or works-related.
- Reacting before measuring and comparing to the schedule of condition.
- Skipping engineering advice where damage is significant.
When to call Coburns
If you need the scale of alleged damage assessed properly, get in touch and we will give you an objective view.