DIY GRP Roof

joe91 · 6 Aug 2009

Hi,

I'm planning to replace my existing felt with GRP.

I bought the materials last year, but didn't get the weather to do it. Been too busy so far this year.

I'm a little worried that looking at the resin, it says it was produced July last year, shelf life 6 months. Will this be a problem?

Also, can someone advise whether, when mixing batches of resin, it's ok to re-use the same bucket without cleaning out the last batch? None of the advice & guides I've read seem to specify this.

I'm planning to cut the mat into lengths to match the roof, 3m max, and roll out. Some guides say 1m squares. What's the best option? I was hoping to avoid horizontal joins, which may hinder water running off slightly?

Any help or comments appreciated,

Thanks,

Joe

Dodgydave2 · 7 Aug 2009

The resin will probably be ok if its not been opened it may go off quicker when you add the catalyst so you will need to be quick.
You will need several buckets as the resin cures it is easily peeled from the bucket
Yes you should lay the mat in the width of the roof laminate this then do the next and so on, if you want a good laminated roof you should apply two layers of matt.
Hope they told you to re-board the roof?
I have a complete guide to GRP roof I can send you, I train roofers in fibreglass roofing and it easy to lay provided you get the prep right.

joe91 · 7 Aug 2009

Thanks for the reply Dave, it's a bit of a daunting job, particularly with the weather we're getting.

I know GRP & old bitumen don't get on if that's what you mean.

The OSB boards look in good nick. I'm hoping to get away with 4mm ply on top of them. Any idea if the felt will come off ok without damaging the OSB too much?

I've only got enough for one layer of grp plus a top coat, I got it from a roofing supplies place, that's what they recommended. How much of a problem is this?

Will I need a bucket & roller per mix, or say new ones every half hour, depending on catalyst %age, temperature etc?

Grateful for the guide, never too much information. I've put my email addy on my profile.

Thanks again.

vinty · 14 Aug 2009

You can buy a grp material called protech which can be used to recover old felt roofs , it is manufactured by Polyroof who are based in Flintshire,

I did a grp roofing course with them a few years ago they specialize in GRP roofing supplies, there is also a company called CFS supplies which shows how to do a grp roof step by step.

ps. you also will need acetone to keep you tools and brushes clean.

dave1953 · 14 Aug 2009

There is also available a 1mtre x 10 metre roll of pre prepared GRP now available, sorry hav' nt got a site for you too see, but instead of undercoat then topcoat and a lot of hassle of you don't get the mix correct it comes on a roll as said ,peel off the underside, place it on osb pell off the topside and UVA cures it at relevant temperatures in 10 minutes.It is dearerthan the manual version but is far quicker to lay.Most roofing suppliers can advise and get it.

dilly · 14 Aug 2009

the stuff is by a company called curon.went and seen it demonstrated by there sales rep at there factory it did not work and thats them demonstrating it

htgeng · 30 Aug 2009

Dodgydave2 said:
I have a complete guide to GRP roof I can send you, I train roofers in fibreglass roofing and it easy to lay provided you get the prep right.

Hi Dave, I tried to add you as a friend as its the only way to send a message! I am going to reroof a garage and also 'extend' the roof to the house. The area is 4.4m sloping x 7.3m wide. Is that too big to do as one monolithic area? Is it possible to lay grp on that area in one go?

I will be laying a 18mm t/g ply deck over 70mm celotex. Is it possible to weather proof the deck with resin on one day and then go back and lay the matting/top coat another day?

Im contemplating laying the decking and paying a guy to supply/fit the grp. I think I could do the mixing etc but is it worth my hassle and what could you expect to pay per m2? This is in norfolk.

dilly · 31 Aug 2009

r u making it into a warmroof constuction? i normally strip back to joists ,firrings if required then down with some 12-15mm shuttering ply strengthen edging membrane and then insulation board tr26 90mm giving you your values then lay my 18 ply and then fibreglass.You could if weather changes on you mix ur resin with catalyst and roller this on making it weatherproof until u got back to it.Really you should always plan to do in one go and check weather forcast.As for doing it your self its not rocket science like most things just common sense.Could work out more expensive to do ur self if u make mistakes as roofing resins are not cheap

htgeng · 31 Aug 2009

dilly said:
r u making it into a warmroof constuction? i normally strip back to joists ,firrings if required then down with some 12-15mm shuttering ply strengthen edging membrane and then insulation board tr26 90mm giving you your values then lay my 18 ply and then fibreglass.

Yes I was going for the warmroof approach. I was going to lay the celotex straight on the joists then ply and screw. Is it necessary to put a sheet layer on the joists first? I guess you can get the celotex squashing down at the joists which is the risk if you dont board over the joists with ply. I think I've just talked myself into it now lol.

dilly said:
.As for doing it your self its not rocket science like most things just common sense.Could work out more expensive to do ur self if u make mistakes as roofing resins are not cheap

Its a fair point! I just don't want to call up local guys and waste their time. Can I ask on a price /m2? I am going to chase the wall to take in the weather flashing and I can fit the upstands etc.

dilly · 31 Aug 2009

celotex do a board for flat roofs el3000 i think that is my way of constructing the roof others use slightly different ways.Generally depends on board you use.As for prices i cannot comment every roof is different.remember you need to go through building regs.As your changing the whole roof

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DIY GRP Roof

vinty

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