Wall ties and cavity insulation
How can wall-tie cracking be told apart from subsidence in the same wall?
Tie failure, where it shows, tends to crack the bed joints in fairly regular horizontal lines as the outer leaf expands. Subsidence tends to crack in a diagonal or stepped pattern as support is lost under part of the building. The patterns can be confused, and a visual survey should say which pattern it saw and what it could not prove.
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 bulging outer leaf with horizontal cracks every few courses is the classic tie picture. A crack that is wider at the top, running from a corner or an opening down towards the ground, is the classic subsidence picture. Houses can have both, or neither: lintel movement and roof spread also crack walls. The surveyor is not, on a Level 2, monitoring the crack over months.
The repair paths differ. Ties are a cavity investigation and then, if needed, new ties. Subsidence may be a drain, a tree, or the ground, and the Association of British Insurers talks about that as an insurance peril for owners, not as a bill for a buyer who does not yet own the house. Do not let one quote cover both theories.
What should you ask your surveyor?
- Is the crack pattern horizontal and regular, or diagonal and tapered?
- Is the outer leaf bulging, or is the whole wall dropping?
- What further investigation would separate ties from foundation movement?
What are the typical next steps?
- Photograph the cracks with a scale, square on, before anyone rakes them out.
- Do not underpin a wall because the courses are cracked horizontally, unless the surveyor has actually said the foundations are moving.
- If both are possible, ask for the next inspection to be scoped to tell them apart.
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 roof spread look like tie failure?
Roof spread pushes the top of a wall out. Tie failure is about the cavity. The location and the direction of the crack help. Ask which the surveyor means.
Does a crack monitor come with the survey?
No. Monitoring is a further instruction over time. You may not have that time before exchange. Say so when you decide.