Subsidence, settlement and heave
Are cracks where a later extension meets the old house the same thing as subsidence?
Often they are differential movement: the new part and the old part are not moving as one. That can be historic and finished. It is not automatically subsidence of the whole house. It still needs the surveyor’s actual words, because a leaking drain or a poor foundation under the extension can be serious.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer 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 the fuller explanation?
A vertical crack at the junction, a door that sticks only in the extension, or a roof junction that has opened are typical notes. The surveyor says whether they think it is ongoing. They may recommend an engineer if the extension is distorting, or they may call it a junction to keep an eye on. Those are different outcomes. Do not paste “subsidence” over a junction crack in your email to the lender.
Ask for the building-control completion certificate for the extension through your solicitor. Absence of paperwork is a legal and a construction question. The extensions guide covers approval. This question is only about not misnaming the crack. Repair might be tying the junction, fixing a gutter between the roofs, or something heavier. The specification belongs to an engineer or a builder who has seen it, if the survey says the visual check was not enough.
What should you ask your surveyor?
- Is the crack limited to the junction?
- Do you think the movement is historic?
- What paperwork would help you that the solicitor should ask for?
What are the typical next steps?
- Describe it as a junction unless the surveyor used a stronger word.
- Get the approval papers. Do not buy the crack and the missing certificate as if they were one issue.
- If the surveyor recommends an engineer, instruct one with the junction photographs and the approval pack.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Can a conservatory crack be described the same way?
A lightweight conservatory often moves differently from the house. It can leak at the flashing without the house subsiding. Ask the surveyor which structure they were describing.
Should you refuse every house with an extension crack?
No. Many are old and quiet. Refusal is your decision when the report says the movement is serious, the papers are missing, or you cannot live with the uncertainty.