Roofs and flat roofs
A blister sits at the upstand of a flat roof and the field of the roof is smooth. Why is that a junction note?
It is a junction note because the blister sits at the upstand, where the flat-roof covering turns up against a wall or a kerb, and the field of the roof is smooth. The defect in view is at that turn, not spread across the general covering. An upstand is a common place for a blister or a weak bond, because the sheet changes direction there. The survey has recorded the blister and the smooth field. It has not cut the blister, has not proved that water is trapped in it, and has not guaranteed the rest of the roof. The note is the junction.
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?
Flat coverings are stressed where they are dressed up, at upstands and outlets. A blister is a raised patch, often where layers have parted. Placed at the upstand, it marks that junction rather than the open field. A smooth field means the main area did not show the same lifting. The survey can separate the two. It cannot know, without cutting, whether the blister is dry or wet, and it did not cut it. The reason it is a junction note is the place it occupies.
Tell the solicitor the blister is at the upstand and the field looked smooth, so any follow-up is aimed at that junction. A roofer can inspect the upstand detail. The home survey has not specified replacing the whole field, and it has not specified a local repair. Do not renew the entire area because one blister sits at the turn, and do not ignore the upstand because the field is smooth. The point of the report is the junction. Later work should start from that.
What should you ask your surveyor?
- Is the blister at the upstand rather than in the field of the roof?
- Did the field of the covering look smooth?
- Did you leave the blister uncut, so its contents are unproved?
What are the typical next steps?
- Read the blister as a junction note at the upstand.
- Do not write the smooth field up as the same defect.
- Ask a roofer to look at the upstand detail.
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 blister feels soft, is the whole roof full of water?
Softness, if it was felt, describes that blister at the upstand. The field was smooth, which is why this stays a junction note and not a finding about the whole roof. The survey did not cut the blister and did not prove the field is holding water. One soft patch at the turn is not a map of the covering.
Does a smooth field mean the covering will last for a long time?
The survey has not said how long the covering will last. A smooth field means the blister was not repeated across it, so the note stays at the upstand. No life was estimated. The blister at the junction is still uncut and unproved. Smoothness is a contrast with that blister, not a forecast.