Damp and moisture meters
Render has been carried across a movement joint and has cracked on that line. What was the joint for?
The joint was there so the wall could move, and the render has been carried across it, so the render has cracked on that line. A movement joint is a designed break. When the finish bridges the break, the finish is what tears as the parts move. The crack on the joint line is the render failing to leave the joint free, not a random split in the middle of a bay. The survey recorded the bridge and the crack. It has not proved a structural failure of the wall.
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?
Movement joints exist so thermal and moisture movement does not have to tear the finish. Render taken across them grips both sides and then splits where the joint opens. The crack often returns if someone fills it without cutting the joint back through the render. The survey saw the crack following the joint. It did not monitor the wall for ongoing movement, and it did not call the crack subsidence. The cause it has described is the finish crossing a joint.
Ask a renderer to cut the finish on the joint and to reinstate a movement joint in the render. Tell the solicitor the crack follows a joint the render has bridged. Do not fill it as ordinary shrinkage, and do not open a subsidence argument on this note alone. The survey has not measured progressive movement. It has explained why the render cracked where it did.
What should you ask your surveyor?
- Was the render carried across a movement joint?
- Has the crack followed that joint rather than a random line?
- Was the joint intended to let the wall move?
What are the typical next steps?
- Treat the crack as render bridging a movement joint.
- Ask a renderer to cut the joint back through the finish.
- Do not file this as subsidence without a separate investigation.
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
If the crack is filled with mastic, has the joint been restored?
Only if the mastic is in a real break through the render, not smeared over a bridge. The joint was for movement. Render carried across it cracked on that line. A surface smear can hide the crack and still leave the finish tying the two sides together. The survey has not designed the seal. Ask a renderer to form the joint properly.
Does a crack on a joint mean the foundations are moving?
Not on this note. The survey has described render crossing a joint that was meant to move, and the crack on that line. It has not monitored the wall and it has not diagnosed subsidence. Foundations can be still while a bridged joint cracks the finish. Do not upgrade this sentence into a foundation failure.