Structure and movement
What does subsidence mean when you are buying a house?
Subsidence is the ground under a building sinking and taking the foundations with it. The Association of British Insurers distinguishes it from heave, an upward movement, and landslip, ground moving down a slope. Cracks in a survey are not, alone, a subsidence diagnosis. If movement is suspected, the report should say what to investigate before you exchange.
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.
What is subsidence, and what is it not?
The Association of British Insurers defines subsidence as the ground beneath a building sinking, pulling the foundations down with it. It usually happens when the ground loses moisture and shrinks. ABI names prolonged dry spells, and trees and shrubs that take water out of the soil, especially on clay that shrinks and cracks. Heave is the opposite direction: the ground moving up. Landslip is ground moving down a slope. People say “subsidence” for all three. Insurers do not.
Settlement is another word buyers mix in. It usually means the initial compression of ground or of a building as it beds in, often early in its life. It is not the ABI definition of subsidence. A Victorian house that has stood with the same hairline crack for decades is not automatically “subsiding”. A crack that is widening now might be. The survey should tell you which description the evidence supports, and when the evidence is not enough.
What can a RICS survey say about cracks?
The surveyor looks at crack pattern, width, whether doors and windows are distorted, and whether the outside ground, trees or drains might be relevant. They do this with their eyes, not with months of monitoring. A Level 3 has more room to discuss how the building stands up. A Level 1 may only flag that something looks serious. Neither level digs trial pits as standard. If the cause is not established, the correct recommendation is further investigation by someone whose job is structure, typically a chartered structural engineer, before you exchange.
Horizontal cracks in mortar beds at regular spacing can be wall-tie corrosion rather than subsidence. A single diagonal crack over a window can be a lintel. Sloping floors can be original. The word “movement” in a report is a description. Do not upgrade it to “subsidence” unless the surveyor used that word and explained why. Do not downgrade it to “old house” if they have asked for an engineer.
What does a subsidence history mean for insurance and the mortgage?
ABI says buildings insurance normally covers damage from subsidence, heave and landslip to the main home and outbuildings, and that most policies have an excess around £1,000 for that kind of claim, which can be higher if the property has had subsidence before. Damage only to drives, patios or garden walls is generally excluded unless the house is damaged too. Those are ABI’s words about typical policies, reviewed on 24 October 2026. Your schedule may differ. Read it.
A past claim is something you and the seller’s solicitor have to surface, because insurers ask. It does not, by itself, mean the house is still moving. A current recommendation for monitoring means you do not yet know. Lenders have their own line, often from their valuer, and may retain money or want an engineer’s letter. Get that letter before you exchange if the survey has asked for it. Underpinning is a serious repair ABI describes for extreme, ongoing movement. It is not the first step for every crack.
What should you do if the report mentions movement?
- Quote the surveyor’s sentence. Do not translate “distortion” into “subsidence” unless they did.
- Instruct the investigation they named. A second Home Survey repeats the same limit.
- Tell your solicitor, and ask the seller about previous claims, monitoring and tree works.
- Tell your insurer and your lender what the documents say before you are committed. Surprises after exchange are theirs to resent.
- Do not agree a token price cut for an unpriced structural cause. Wait for the engineer, or walk away.
Common questions
Do all old houses have subsidence?
No. Old houses have often moved a little while they were new, and many cracks are thermal, lintel, or plaster. Subsidence is a particular ground-and-foundation problem as ABI defines it. Age is a reason to choose a more detailed survey, not a diagnosis.
Is there a crack width that always means subsidence?
No reliable single width. Surveyors describe width and pattern because both matter, and because a crack can be old and stable or new and widening. A hairline crack in plaster is common. A wide, diagonal, tapering crack through the brickwork, with distorted openings, is a different observation. The report should say which they saw. Do not buy a rule of thumb from a forum and overlay it on their paragraph.
If there is a tree, is it subsidence?
ABI says trees and shrubs can contribute where they dry clay soils near foundations. A tree is a clue, not a verdict. Removing it can also lead to heave if the soil then swells. Do not instruct a feller as your first repair. If the surveyor is worried, an engineer and, where relevant, someone who understands trees should say what the tree is doing.
Can broken drains cause the same cracks?
Yes. Leaking drains can wash fine material out of the ground so the foundation drops. That can look like “subsidence” in ordinary speech and still be a drainage repair rather than underpinning. A Home Survey does not CCTV the drains unless you agreed that extra. If the report mentions both cracks and drains, the drain survey is often the cheaper investigation to do first.
What does crack monitoring mean for the purchase?
It means the movement’s behaviour is not yet known. Monitoring takes months, not an afternoon. That rarely fits a normal exchange timetable unless the seller already has the record. You can wait, you can walk away, or you can buy the uncertainty on purpose. A small discount does not turn an unfinished monitoring exercise into a known repair.
Is a house that has already been underpinned a bad buy?
Not automatically. Completed underpinning, with paperwork, a guarantee your solicitor can check, and no fresh movement, is a known history. ABI notes that a previous episode can mean a higher insurance excess. Fresh cracking in an underpinned house is a new question for an engineer. Ask for the design, the completion certificate and the insurance record before you decide.
Who pays if subsidence is found before completion?
Before exchange, nobody is yet the insurer of your purchase. The seller’s existing policy might respond to damage that has already occurred, which is a question for the seller and their insurer, not a benefit you can claim. After you own it, your own policy responds on its terms to new damage. Do not assume you can buy a house mid-claim and take over the payout. Your solicitor asks what claims are open.
Is a Level 2 enough if you already suspect movement?
If you can already see significant cracking, RICS’s own description of Level 3 — older, altered, or in poorer condition, with advice on consequences — is the more serious instruction. A Level 2 can still flag the issue and tell you to get an engineer. The engineer, not a thicker survey, is what establishes the cause. Do not skip the specialist in order to buy a second general report.
Are cracked bay windows always subsidence?
No. Bay windows and porches often crack because they were built shallow, or because the junction with the main wall has moved locally. That can be a repair without the whole house subsiding. It can also be part of a wider pattern. The survey should say whether the cracking is local. If it does not, ask.
Should you walk away at the word subsidence?
Walk away from an uninvestigated structural risk you cannot afford, especially if access for an engineer is refused. Do not walk away from a word you have not checked against the paragraph. Many reports say “no evidence of recent movement” next to old cracks. Read that sentence before you relive someone else’s headline.
Sources
- How subsidence can affect your home — Association of British Insurers
- What to do if subsidence happens — Association of British Insurers
- Description of the RICS Home Survey Level 3 (condition rating definitions) — RICS
- House surveys: the costs, types and benefits of an RICS home survey — RICS
- Approved Document A: structure — GOV.UK
Key facts
- Subsidence
- ABI: the ground beneath a building sinks, pulling the foundations down. Often when ground loses moisture and shrinks.
- Heave
- ABI: upward movement of the ground supporting the building.
- Landslip
- ABI: movement of ground down a slope.
- Common contributors
- ABI points to clay soils that shrink in dry weather, and to trees and shrubs drawing water near foundations. Drains and other causes also exist. A survey does not always identify which.
- Insurance
- ABI says a standard home policy normally covers subsidence, heave and landslip to the home and outbuildings, often with an excess around £1,000, higher if there was a previous episode. Garden walls and drives alone are generally not covered. That is ABI’s description, reviewed 24 October 2026, not your policy.
- Survey limit
- A Home Survey does not monitor cracks and does not underpin anything. Further investigation means an engineer, and sometimes drains and a tree survey.