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uk Home & property emergencies widening crack in wall • widening crack in ceiling • new crack in plaster • crack spreading over days • crack getting bigger • sudden wall crack • sudden ceiling crack • crack after loud bang • diagonal crack near door • crack around window frame • crack with sagging ceiling • crack with sticking doors • crack after heavy rain • crack after nearby building work • possible subsidence crack • possible structural movement • unsafe building concern • rental property crack emergency • homeowner structural crack worry

What to do if…
a new crack appears in a wall or ceiling and seems to be widening

Short answer

Treat a widening crack as a potential safety issue: keep people away from the affected area and get it assessed urgently, especially if anything looks like it’s moving or sagging.

Do not do these things

  • Do not ignore it if it’s widening, lengthening, or changing quickly.
  • Do not drill, cut, chase, or knock plaster off around the crack “to see what’s underneath” (you could destabilise something or hit services).
  • Do not attempt DIY jacking, bracing, or propping of walls/ceilings.
  • Do not keep using the room normally if the crack is in a ceiling, near a beam, near stairs, or if anything looks bowed or sagging.
  • Do not let anyone start structural work without a proper assessment if there are signs of movement.

What to do now

  1. Make a quick safety call. If you believe there’s an immediate danger of collapse or falling material, move to a safer place and call 999.
    • Examples: a ceiling that is bulging/sagging, debris falling, loud new cracking noises; a wall that looks bowed; a sudden major change in how doors/windows fit.
  2. Create a “no-go zone” around the crack. Keep people and pets out. If it’s a ceiling crack, don’t stand or sleep underneath it.
  3. Check for utility hazards (briefly, only if safe).
    • If you smell gas or suspect a leak: leave immediately. From outside, call the National Gas Emergency Service on 0800 111 999. Avoid naked flames and anything that could create a spark (for example, don’t operate electrical switches if you can avoid it).
    • If water is leaking through/near the crack: turn off the water at the stopcock if you can do so safely, and move valuables away.
  4. Document what’s changing (useful for landlords, councils, insurers, and surveyors).
    • Take clear photos/video with something for scale (coin/ruler).
    • Note the date/time you first saw it, how fast it’s changing, and anything that happened around then (heavy rain, a plumbing leak, nearby building work, a bang).
  5. Mark and measure it so “widening” is clear.
    • Lightly pencil-mark the ends of the crack and date it.
    • Measure the widest point. If safe, re-check later the same day or next day.
  6. Get the right help quickly (choose the route that matches your situation).
    • If you rent: report it to your landlord/letting agent immediately in writing (email/text) and ask for an urgent inspection. If you believe the property may be unsafe and you cannot get a timely response, contact your local council (routes vary, but look for “dangerous structures/building control” and/or housing/environmental health).
    • If you own: contact a chartered structural engineer or RICS surveyor experienced in building movement for an assessment.
  7. If you think the structure may be dangerous, contact the local authority route for dangerous structures.
    • In England and Wales, dangerous building/structure reports are made via your local council (many councils have “dangerous structures” contact routes, including out-of-hours arrangements).
    • In Scotland or Northern Ireland, contact your local council for the appropriate building standards/building control route (names and processes vary).

What can wait

  • You do not need to decide today whether it’s subsidence, poor plaster, or a structural defect—focus on safety + getting it assessed.
  • You do not need to book repairs, redecorate, or choose contractors until you have a professional view of what’s moving and why.
  • You do not need to argue about liability right now (landlord vs neighbour vs insurer). First: make safe, document, assess.

Important reassurance

Many cracks are cosmetic. But a crack that is clearly widening is worth treating seriously. Calm, practical steps now (keep clear, record it, get it assessed) can prevent injuries and reduce the chance of things getting worse.

Scope note

This is first-steps guidance only. A widening crack can have many causes. Next steps after the immediate safety check usually involve a qualified inspection and (if needed) formal reports for landlords/insurers/councils.

Important note

This is general information, not a diagnosis or a guarantee of safety. If you think anyone is at immediate risk, move to a safer place and contact emergency services.

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