Roofs and flat roofs
The outlet from a parapet gutter is blocked and the gutter is holding water against the wall. Why is the first repair the outlet, not a new damp-proof course?
The first repair is the blocked outlet, because that is what is holding water against the wall. A parapet gutter that cannot empty lets rain stand where the wall meets the roof, which is a rainwater fault. A new damp-proof course is aimed at moisture rising in the masonry, not at a gutter full of debris. Clearing the outlet deals with the water that is there. The survey has seen the blockage and the standing water. It has not said the wall needs a new damp-proof course, and it has not flow-tested the gutter once it can empty.
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?
Water against a wall from a choked outlet can stain plaster, rot the gutter sole and look, indoors, a bit like damp from below. The mechanism is different. Rising moisture is not cleared by rodding a rainwater outlet, and a new damp-proof course does not empty a parapet gutter. The survey can point at the blocked outlet it saw. It should not be rewritten as a specification for chemical injection or a new course because the stain is low or high on the wall.
Have the outlet cleared and the gutter checked for splits once it is empty, and see whether the wall dries. Tell the solicitor the reported item is a blocked parapet outlet, not a damp-proofing scheme. A roofer or a rainwater specialist is the first trade, not a damp contractor working from the stain alone. The survey has not tested the masonry and has not priced either job. If the outlet is shared with a neighbour, the solicitor can ask who maintains it.
What should you ask your surveyor?
- What was blocking the parapet-gutter outlet, as you saw it?
- How high was the water held against the wall?
- Did you recommend clearing that outlet rather than a new damp-proof course?
What are the typical next steps?
- Clear the blocked outlet before considering any damp-proof course.
- Watch whether the wall staining eases once the gutter can empty.
- Keep the solicitor's enquiry on the rainwater outlet, not on injection.
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 inside wall is damp, is a damp-proof course already justified?
Not while the gutter is holding water against that wall. The survey saw a blocked outlet. Indoor damp beside it fits water from the gutter, and it has not justified a new damp-proof course. No later decision about the outlet was made, and this visit did not supply one.
Does a clear day with an empty gutter cancel the note?
An empty gutter on a dry day does not remove a note that the outlet was blocked and holding water. The survey recorded that condition. It still has not flow-tested a cleared outlet. What happens next for the gutter is outside this note and was not settled here.