Replacing Roof

J_Smotthies2021

I have extension roof which needs to be replaced preferably with fiberglass. Can I get some idea about the material cost for 30m2 roof? 

Existing roof is felt and my builder is saying that he needs to replace the boards, remove the felt and can put felt or fiber glass. not sure which option is the best one.

FreeBear

If you are replacing the whole roof (or more than 25% of it), building regs kick in and will require the insulation to be improved - This often means fitting a "warm roof" which bumps up the cost considerably. It is up to you if you involve Building Control to sign off the work, but it is still well worth improving the insulation.

J_Smotthies2021

that might be a good idea. However, I still need an idea on the material cost. My builder who is already doing lots of refurbs quoted me 5K to replace the roof but with felt. He said fiber glass will be more expensive. any idea on the material cost for fiber?

the_lunatic_is_in_my_head

£110-£150 a square metre according to this place:

https://grproofingcontractor.co.uk/services/grp-flat-roofing/

Jeepers_Creepers

J_Smott, the very best way to compare quotes is to get them in the first place. So send some pics to a fibreglass roofing specialist and ask for a ballpark figure based on the following info; size of roof. The surrounding structures - ie does it need flashing/blending into other roofs or walls? The roof structure - joists etc - is solid and doesn't require attention. The roof slope is adequate. New ply/sterling boards will be needed. Quote for boards, GRP, edge fillets, fascia boards - whatevs you need.

As for the differences in quality, I think it's pretty clear that GRP is stronger and longer-lasting. It also looks better (sorry, felt always looks like a 'cheap' option). It'll carry a longer guarantee.

Having said that, provided the roof has a good slope that provides a clean run-off of water, then a new felt roof should last beyond 20 years.

EDPM? Hate it. It's a good solution provided you never ever walk on it or throw anything up there. It's tough, but can still tear like a teary thing. I personally wouldn't.

If you decide to go GRP, then choose a company who do this for a living - I wouldn't let a 'felter' say "Hmm, doesn't look too hard - pass that brush..." I understand installers need to be accredited to the manufacturer of the GRP product they use in order to obtain extended warranties - ours, with FlexiTec 2020, has a 20 year warranty, but wouldn't have if an equally-experience but non-associated company had done the job.

(I don't think the FlexiTec will take any longer to apply than a felt roof - could even be quicker. Primer. Self-coloured resin, matting, resin. A second coat of resin provides the full 20 year warranty. Matting is far easier to cut and trim than felt, and the joins are seamless.)