Roofs and flat roofs
Is a sagging ridge the same defect as roof spread?
No. A sagging ridge is the line of the roof dipping, often from the ridge timber, the rafters or the purlins. Roof spread is the feet of the roof pushing the walls outward. They can happen together and still be different. A home survey can see a dip from the ground and sometimes a gap at the top of a wall. It does not calculate the thrust.
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?
Buyers write “the roof has spread” because the ridge looks tired. The survey should say what it saw: a wavy ridge, a leaning gable, a gap over a wall plate, or only an old uneven covering. RICS home surveys are visual. They do not open every joint. Approved Document A is the England guidance for structure when building work is done. It is not a calculation of this roof, and Wales has its own building regulations.
A roofer who quotes a re-cover has not necessarily quoted a structural repair. Ask them which defect they are pricing. There is no RICS price for tying a roof or for a new ridge. Do not call it subsidence in a letter to the seller. The ground and the roof are different sentences.
What should you ask your surveyor?
- Are you describing a dip in the ridge, movement at the eaves, or both?
- Did you see the feet of the rafters, or only the outside?
- Are you recommending a roofer, a structural engineer, or only recording the shape?
What are the typical next steps?
- Use the survey’s words in any quote request.
- Do not ask the seller for underpinning because the ridge sags.
- If the walls have been pushed out, say that. Do not hide it inside “new tiles”.
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 an old roof sag and still be serviceable?
Age and unevenness are common. The rating and the description say whether the surveyor thinks it is a defect. Looks old is not spread.
Is a replacement covering a cure for spread?
New tiles do not tie a roof that is pushing the walls. Ask before you pay for a re-cover alone.