Structure
What do cracks mean in a home survey?
A crack is a symptom, not a diagnosis. The Association of British Insurers defines subsidence as the ground sinking and taking the foundations down, which is not the same as heave or landslip. A home survey can describe a crack. It does not monitor it over time, and it does not prove the ground is moving.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless a source says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
Why is a crack not a cause?
Plaster cracks because plaster moves. Masonry cracks because something pushed, pulled, shrank or was built that way. Shrinkage in a new extension, a lintel that has slipped, rusting steel, roof spread and ground movement can all draw a line on a wall. The paragraph has to say which of those the surveyor thinks is likely, and what would show them they are wrong.
ABI’s definitions matter when someone uses the word subsidence. Subsidence is the ground sinking under the building. Heave is the opposite direction. Landslip is a slope. A crack in a ceiling is not those words until an investigation says so. Insurers and engineers use the definitions. Listing photos do not.
What should you read in the crack paragraph?
- Where it is: above a window, at a ceiling junction, through bricks, or only in plaster.
- Direction: vertical, diagonal, or stepped along the mortar.
- Whether it is mirrored inside and outside.
- Whether doors stick, or the surveyor says the frame is distorted.
- What they want done next, if anything, and before which deadline.
Width, if they mention it, is their observation on the day. This page does not convert a width into “category 3” or “needs underpinning”. Those tables are not sourced here. Ask the surveyor what the crack means in this wall, not what a chart on the internet says a millimetre is worth.
When does a crack need someone else?
When the surveyor says the cause is not clear and the consequence could be serious, or when movement is suspected. That next person may be a structural engineer, and sometimes a drains contractor, because leaking drains can wash support away. The home survey does not become that investigation by adding an adjective. Budget the investigation separately from any repair nobody has specified yet.
Should you walk away because of cracks?
Not from the word. Walk away, renegotiate, or carry on based on the cause and the timing the report describes. Old, filled, stable cracks in plaster are maintenance. Cracks the surveyor says are opening, or that they link to the foundations, are a reason to pause before exchange. The rating tells you urgency in RICS’s terms. The paragraph tells you the job.
Common questions
Are hairline cracks harmless?
Often they are in the plaster only, and the survey will say so if that is what it saw. “Hairline” is not a guarantee. Read whether the crack is in the masonry as well, and whether the surveyor thinks it is still moving. If they do not know, that is the sentence to act on.
Cracks in new plaster mean the house is moving, don’t they?
New plaster and new masonry shrink as they dry. That can crack finishes without any ground movement. The survey should distinguish shrinkage from distortion. Do not pay for underpinning because a skim coat is young.
Should you tell the insurer about every crack?
Tell them what your policy requires. ABI explains subsidence, heave and landslip as insured events on a typical policy, often with an excess around £1,000, which is not the cost of repair and not your schedule. A decorative crack is not automatically a claim. Do not invent a claim to “get the survey paid for”.
Will the surveyor monitor the crack?
Not as part of a normal home survey. Monitoring means coming back, or telling you how a specialist would. If the report says “monitor”, ask who does it, for how long, and whether you should wait before exchange. A single visit cannot see the future.
Do cracks mean the house needs underpinning?
No. Underpinning is a specific repair for a specific foundation problem. Many cracks need repointing, a lintel, or nothing. If an engineer specifies underpinning, that specification is what a contractor prices. The survey is not that specification.
The crack is only inside. Does that matter?
It can. A crack that does not come through to the outside is more often in the finish. It can also be the early sign of something the lining is hiding. Ask the surveyor why they think it stops where it stops.
The seller filled the cracks before the viewing. Is that a problem?
Filling is ordinary decorating, and it is also how movement is hidden for a weekend. The surveyor looks for distortion, not only for open gaps. Tell them the walls were recently filled if you know that. Do not treat fresh paint as evidence either way.
Is a crack always a condition rating 3?
No. RICS ratings follow seriousness and urgency, which are defined in the report. A minor crack in plaster can be a lower rating. A crack the surveyor links to ongoing movement will not be. Read the definition printed in your report, not a guess from the word crack.
Sources
- How subsidence can affect your home — Association of British Insurers
- Description of the RICS Home Survey Level 3 (condition rating definitions) — RICS
- Approved Document A: structure — GOV.UK
- House surveys: the costs, types and benefits of an RICS home survey — RICS
Key facts
- Subsidence
- ABI: the ground beneath a building sinks and pulls the foundations down.
- Heave and landslip
- ABI: heave is upward movement. Landslip is ground moving down a slope. They are not the same claim as a hairline crack in plaster.
- What a survey does
- Records location, direction and whether the crack looks recent, if the surveyor can tell. It does not measure movement over months.
- What this page will not do
- Publish millimetre categories. Those charts are not in the sources used here.