Posted By: owlmandoes it look OK

Can look like anything you want almost.

Posted By: owlmanhow does it weather

Very well if applied right, dreadfully if applied wrong.

Posted By: owlmanIs it easily applied

Has to be very dry, not to hot, not to cold, not sunny if possible.
Easy when you have worked with the material for years.

I think (started using this stuff in the mid 70's) it is easy to fall into a trap with GRP if you think that it is an easy material to use correctly. But if used correctly it is an excellent material that is under used in the building industry.
If you want to 'give it a go', go and get a few kilos and do some test runs outside in the garden. Find the pitfalls and find ways around them.
Oh and make sure it is absolutely dry, not even damp.

And get ready for itchy arms and hands, face and legs, neck and torso.

Make sure it is absolutely dry, don't let the matt lay on anything even remotely damp.

Buy lots of hand cleaner and acetone for cleaning things up with.

Make sure nothing gets wet or damp.

We have discussed this at length somewhere else on here.

Have I mentioned that it has to be dry?

Anyone just used it (DIY) to replace a small felted flat roof, by any chance?

I have a small porch (maybe 2 m²) where the felt is at the end of it's life and have thought about ripping it off and doing it with GRP. I've done a fair bit of composite work over the years, but never on something like a roof.

JSH, a man of your experience will find this a piece of cake, lots of advise on you tube.

But make sure its dry (have we mentioned that)

Lead is better, longer lasting, recyclable, probably cheaper in the long run if done properly

Thanks fellas I guess it has to be dry then.
I had a look at a suppliers website and all the mopstick mouldings, upstands, downstands, corner detailing, etc. to pre-apply are all readily available. Is the colourant in the resin or do you apply a patinating liquid or gel. Any ideas about how to get a nice flashing detail,- presumably adhere an upstand moulding to the brickwork.

UV kills it

Posted By: tonyUV kills it

Why dont boats fall apart then?

Expansion is only a real problem with large flat roofs

No but slows it down.

This from the countries largest supplier of GRP:-

"Many glassfibre laminates made during the early days of GRP production in the 1940s are still in use today. Extensive testing has demonstrated the typical life expectancy of a GRP roof product to be well in excess of 50 years. And, tests conducted to date have shown 'no deterioration' infrastructure or performance throughout the testing period. Additionally, because GRP products or use in extreme conditions such as underwater, when used in the manufacture of boats, a GRP product applied by a specialist company could be expected to last a lifetime.

The entire area on a GRP roof is encapsulated into one single continuous GRP membrane and there are no seams joints or welds. It is also completely UV resistant."

A local company advertise GRP roofing to last in excess of 35 years.

Just one issue with "Hot tar and felt only has a 10 to 20 year life, so if GRP is double life that for little difference in cost it seems to make sense to me." The more expensive "felts" have lifespans far in excess of 10 to 20 years ... back in the days of my CLASP involvement we were putting flat roofs up that were lasting over 25 years and still looked excellent. It's back to the old chestnut - the right material for the right location properly detailed.

Not sure you can DIY hot tar? Lots of loft conversion companies here in Bristol use GRP for flat roofs quoting min 35 years, the cost of repair/replacement goes up a lot 3 floors up with scaffolding!!!

Posted By: CerisyIt's back to the old chestnut - the right material for the right location properly detailed.

Yes, and application of those materials.

I like GRP, but can see lots of limitations to using it on site.
The main one being having everything very dry.
The other one being not letting just anyone 'have a go'.

And did I mention making sure everything is really dry.

I can see it cracking on the joins eventually

Posted By: joe90Usually roofs only have one coat of matting

That worried me, I would use 3 layers of 450 g/m^2 (or once and a half as we call it). It may also be necessary to put a second glaze on it depending on how well the first one goes on.

I like the idea of pre-laminated boards and it does reduce the risk of moisture affecting it, have I mentioned just how awful it is to do when it gets wet, may have slipped my mind.
Would require careful fitting and very careful jointing on site, and if any water got in, it could cause havoc.

But if they are going to the trouble of covering 8 by 4 sheets of OSB from the builders yard, they better make sure that the have only been stored inside, don't want them getting wet. But then again if they are doing it this way, why not just make a cheap mould and lay it up correctly with a decent jointing design, used tt work on the steam rooms a treat (for a list of some of the ones I have installed, join the RAC club, most of the THF hotels, SaunaWorld in Colchester, did the saunas too, just timber framed buildings really).
If you want to use a resin that has both good chemical resistance and can take high temperatures, and a way around the moisture problem, it starts costing a lot of cash

Forgot to mention, everything needs to be dry, bone dry, not even that slight cold damp feeling.

From ST

That worried me, I would use 3 layers of 450 g/m^2

I have been on the roofing course given by the supplier and one coat of matt 450 with resin followed by one coat of coloured top coat is the norm. They mentioned a second coat of matt and resin if the roof had foot traffic. I must admit I thought it a bit "thin" but as long as you are not mean with the resin the result is very good. None of mine has leaked in 10 years.

P.S. why cant I quote from a previous page?