New gel coat on existing GRP

16 Jun 2006
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United Kingdom
Hi all

My customer has asked me apply a new gel coat to a 10(?) year old GRP roof.

I don't see why it needs it but I guess he wants it done before the scaffolding comes down (I am painting the exterior windows).

It is simply a case of washing down the existing one and rolling a new coat over it?

It is two stories up, would a white gel coat help to reflect the UV light or will it just become so grubby that it will reflect stuff-all?

Thanks in advance.
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You would have to wash it and then wipe with acetone after.
The top coat is designed to protect the resin from UV so any colour is fine. Normally dark grey is used.

You don't want to go too thick as apparently it can crack with too many layers. Not sure why. Normally the manufacturer instructions is very specific about the amount of resin and top coat
You'd want to go over it with a sander or grinder first so the new topcoat has a decent key. Then acetone wash then new topcoat soon as the acetone has flashed off. Don't try and put too thick a coat on (curing is exothermic, if the coating is too thick the 'skin' cures while the coat is still giving off heat & cracks the cured skin).
Stay away from white- the bounce can be really annoying on sunny days.
Thanks for the replies.

The scaffolding came down yesterday, so I have managed to swerve the job (which I don't think was required in the first place).

At some point I think I need to recoat my mum's roof which I fibre glassed in 2001.

Out of interest, for a 6m by 3m roof, how much acetone would be required? And can any one recommend online suppliers. When I did hers we used a local supplier in Brentford, west London, which no longer exists.

@oldbutnotdead thanks for the advice regarding white. Hers will be green again.

And in addition, thanks to @John D v2.0 for the advice about both cleaning and thickness limitations.

And whilst we are at it... thanks to for enabling us to help each other.
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What a lovely post, more thanks then the Oscars :) glad I could be useful and I hope it goes well
There's a bunch in South Shields I've used before - East Coast Fibreglass, they even deliver 3m lengths of trim, which is handy. Dove carry the gear but they were a bit pricey last time I used them. Roofing Superstore worth a go as well
Acetone- dunno. A 5 litre bottle will be plenty for washing down and cleaning up. You've got 10 years yet in that roof..... enjoy :)

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