Roofs and flat roofs
Lean-to glass sits on a tilted fillet against the house wall. Is that fillet a substitute for an abutment flashing?
Not a tilted fillet under the lean-to glass is a substitute for an abutment flashing. The fillet is the strip the glass sits on where it meets the house wall. A flashing is metal dressed into that wall so water cannot run behind the junction. The survey can see the fillet. It cannot rename the fillet as lead, and it cannot certify the abutment. If no flashing was in view, the fillet remains a fillet, which is exactly the detail this note is questioning.
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?
Rain collects along the top of lean-to glazing and needs to be weathered into the masonry, not only buttered up underneath. A tilted fillet cracks and parts from brick or render, and water then tracks behind the bar. The glass can stay clear, and the frame can stay painted, while that joint is open. The surveyor is refusing the idea that the fillet has done a flashing's work. The two details are not interchangeable.
A glazier or a roofer can price an abutment flashing into the wall, or can show a flashing that was hidden and is still sound. Either result answers the note. More mortar on the old fillet does not. Keep clear glass units out of the price unless a unit has failed on its own. The defect in view is reliance on a fillet where an abutment flashing ought to be described and, if missing, provided.
What should you ask your surveyor?
- Was any metal flashing seen over the lean-to, or only the tilted fillet against the wall?
- Is the fillet cracked, parted from the wall, or merely sloping under the glass?
- Are you treating that fillet as the weathering, or as something that is not a flashing?
What are the typical next steps?
- Ask for an abutment flashing to be confirmed or priced, not a thicker fillet.
- Keep any clear glass units out of that quotation.
- Photograph the joint where the lean-to glass meets the house wall.
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
Will fresh mortar on the fillet answer the note?
No. A fillet is not an abutment flashing. Adding mortar does not dress metal into the wall or over the head of the glass.
Must the lean-to glass be replaced because the fillet is tilted?
Not from this note. The question is the weathering at the wall. Clear glass has not been described as the failed part.