Roofs and flat roofs
Can a home survey date a fibreglass flat roof, or say how it differs from felt?
It can describe the surface: fibreglass, also called GRP, is liquid-applied, while felt is laid in sheets. A surveyor may say which they believe they are looking at, but they cannot date either from appearance, and a seller's "done recently" is not a date without an invoice. A sound-looking top coat does not prove the deck, and the survey does not core the roof.
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?
GRP often looks seamless, with a trims at the edges and a gel-like finish. Felt shows laps, grits and sometimes blisters. Those clues can be wrong where a coating covers felt, or where GRP has been patched with felt. The honest report says what the surface resembles and what it cannot date. Age is not a condition rating. A crack, a split at an upstand or ponding at an outlet is condition. A guessed year is not.
Invoices, warranties and the installer’s specification date the job better than a photograph. They still do not prove the deck was dry when it was covered, and a home survey will not lift the covering to check. Ask the surveyor which flat roofs on the house are GRP, which are felt, and which were not seen. Price repairs against the one that is defective. There is no RICS lifespan that says fibreglass outlasts felt or the other way round.
What should you ask your surveyor?
- Which covering do you think this is, and what would change your mind?
- Did you see a date, or only a surface?
- Is any defect at a lap, a trim, or an outlet?
What are the typical next steps?
- Ask the seller for the invoice if they say the roof is new.
- Do not treat a smooth finish as a known year.
- Tell a roofer whether they are pricing GRP or felt, once someone has identified it.
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
Is a single-ply membrane the same as fibreglass?
No. Single-ply is a sheet membrane. GRP is liquid-applied. The survey should not swap the names if it can tell them apart.
Can you rely on a guarantee sticker on the fascia?
Only as a clue to ask for the paper. A sticker is not the deck, and it is not a survey.