Roofs and flat roofs
A small flat roof over a bay is tired and the pier below is damp, while the main roof is dry. Why should the pier not be treated as a main-roof leak?
The pier should not be treated as a main-roof leak because the main roof is dry and the damp pier sits under a tired flat roof over the bay. The two coverings are separate. Water reaching that pier, if it is coming from above, has the bay roof and its junctions as the local path, not the main slopes that showed dry. The survey has recorded a tired bay roof and a damp pier beneath it. It has not water-tested the path, has not blamed the main roof, and has not decided that the pier damp must be rising damp instead.
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?
Bay roofs are small, often flat, and they finish on the pier or the window head. When that covering is cracked, ponding or poorly turned up, the masonry directly below gets wet while the main roof, which drains elsewhere, stays unmarked. Treating the pier as a main-roof leak sends a roofer onto the wrong slope. The pattern the survey saw is local: tired bay, damp pier, dry main roof. That pattern is the reason to keep the diagnosis local too.
Ask a roofer to deal with the bay covering and the junction at the pier, and only then see what damp remains in the masonry. Tell the solicitor the report does not attribute this pier to the main roof. The survey has not specified a new main covering and has not specified a damp-proof course. If the pier stays wet after the bay is sound, that is a later question. It is not a reason to rewrite today's note as a leak from the main slopes.
What should you ask your surveyor?
- Did you see the main roof dry while the bay roof and the pier were not?
- Which junction on the bay is the likely local path, if you could see one?
- Have you kept this off the main-roof covering?
What are the typical next steps?
- Attribute the damp pier to the bay roof, not to the main roof.
- Have the tired bay covering repaired before any main-roof work.
- Revisit the pier only after that local path has been dealt with.
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 pier is brick, could the damp be rising rather than from the bay?
It could be looked at later if the pier stays wet once the bay is sound. The survey has not made that diagnosis. The pattern it recorded is a tired bay roof over a damp pier, with a dry main roof, so the main roof is the wrong place to start.
Does a dry loft under the main roof prove the bay is the only risk?
A dry loft supports leaving the main roof out of this note. It does not prove the bay is the only possible source for all time. The survey still has not water-tested the bay, and the pier damp is not fully traced.