DIY Doctor UK DIY Forums

RubberRoofer

Don't choose GRP / fibreglass - it cracks

I also second EPDM such as Firestone / Duoply.

Much better solution.

RubberRoofer

Also remember that GRP is very prone to cracking - about 1/3rd of our works are replacing failed GRP roofs.

We use a fleece backed EPDM rubber which is a much better, longer lasting product.

I'd recommend it over GRP every time.

RubberRoofer

I should have added - I do agree to steer clear of GRP.

Firestone is a good product, or if you are having it done professionally go for a fleece reinforced membrane as it's even better.

RubberRoofer

Sorry - have to disagree with your first reply. You will NEVER stop expansion - it happens. The firmer you screw boards down the more damage they do when they move!!! Put your hands flat on a table, fingers touching and then push together. It's uncomfortable, but if you push hard enough they will bu...

RubberRoofer

Yes totally! You say it leaks, then you say it's on Chipboard. Chipboard absorbs water like a sponge - so you need to replace it. Strip all roof off back to joists. Insulate as desired / required. Lay 18mm OSB3 board (You could use WBP ply but that's much more expensive and unnecessary). If you want...

RubberRoofer

I'm afraid what your experiencing is totally normal for GRP / Fibreglass roofs, and it's why they crack so often. The reasons given are correct. The contractor should have put suitable expansion joints in to prevent this, but 99.99999% of fibreglass roofers don't bother because it's more hassle and ...

RubberRoofer

No, Clear away the chippings, and then wash the roof clean. Allow to dry and then paint with silver reflective paint making sure you do the waterchecks and edges too (people forget these bits and they are often the first to crack so they are actually more important) Any barrier to chippings will als...

RubberRoofer

You need FRMG (Mineral faced) PU or PIR insulation board. Around 120mm of this will give a U value of approx 0.188 - you then need to calculate your existing insulation into that as well. If you already have 100mm of rockwool in the ceiling void, then 70mm of PU should be fine. Do NOT use polystyren...

RubberRoofer

Hi, I don't know where you are - but we use Asbesosil. It's a liquid applied silicone based membrane that cures to a seamless encapsulation membrane and waterproofs all in one. However it's not cheap at all. Anything good for Asbestos isn't - I've yet to find a cheap solution to this problem that wo...

RubberRoofer

Difficult one. When you were quoted / invoiced for the works was their any mention of "Eliminate ponding"? The guys will have laid OSB3 to the structural joists. Unless there was specific mention of fitting firrings to eliminate ponding then they have only followed the original profile of ...

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