Subsidence, settlement and heave
The joint between a newer extension and the older house is open. Is that movement in the new part, the old part, or still undecided?
Still undecided. An open joint between a newer extension and the older house shows the two parts are not behaving as one piece. It does not say which side moved, whether they were never tied, or whether shrinkage or settlement opened a junction that was always a joint. The survey did not expose the tying, did not monitor the gap and did not see the foundations. The report records an open joint. It has not allocated the movement to the new part or the old part, and it has not ruled movement out.
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?
Extensions often meet the original house on a straight joint. Some joints are meant to move a little. Some open because a new base has settled, an old wall has distorted, or ties were left out. A line in the render can look decisive and still be ambiguous. Without a history, a datum or a look at how the walls are connected, choosing a side is a guess. The survey has not made that guess. Both parts remain possible contributors until a further inspection says otherwise.
Show your solicitor an undecided joint, not a proved failure of the extension alone. If the report recommends monitoring or a structural engineer, that step has not already been done. Do not tell a lender the old house is moving, or the extension is, unless the report actually says so. Filler would hide the joint. It would not identify which part moved. Follow the investigation the wording leaves open before you pick a cause and a repair.
What should you ask your surveyor?
- Does the report call the joint a designed movement joint, or an unintended gap?
- Are there cracks in the extension, the original house, or only at the junction?
- Has monitoring been recommended, and has it started?
What are the typical next steps?
- Describe the open joint as movement that has not been allocated to either part.
- Do not tell a lender which part has moved unless the report says so.
- If the cause matters, follow the further investigation the report has left open.
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
Does a wider gap at the top mean the extension is rotating?
It can look that way, and it can also be a joint that was never parallel. The survey has not measured a mechanism and has not decided on rotation. A tapered gap is a clue, not a diagnosis. An engineer, if you instruct one, can read the shape. The report has left the question undecided.
Will repointing the joint close the question?
No. Repointing fills a gap. It does not show whether the new part, the old part or a designed joint produced it. The survey has not treated filler as a conclusion. If you point the joint you may hide the evidence a later inspection would use. Understand it before you seal it.