Hi Guys & Gals

I've got a leaky flat roof; it's a 10yr old torch on felt roof and it's letting in water in at least half a dozen places. I'd say the roof covering is close to end of life; best way to sum it up is to say it's in about the same state as a 10yr old Panda rear beam.

I'm thinking it needs a total refurbishment and am drawn toward a GRP covering, not least because it looks a feasible DIY project. Total roof area is about 72 sq m.

Anyone out there with any experience of this kind of stuff? Like most such jobs, the final result would appear to be mostly about careful preparation.

Thanks in advance
JR

Had good results with EPDM for a small-ish flat roof. Had a 25 year warranty on the material and it was still looking good after 15, when it was removed and the building was demolished.
No experience of GRP roofing though.

Used it for for a small shed once you want a day with not wind as the material is light weight and easy to blow around

It's alley quite messy so you want old cloths boots ect
Other then that fairly easy just need to ensure you leave expansion gaps around the edges before capping


Only trouble with putting it over old torch felt is you'd likely need to reboard it all was you want a fairly clean surface to ensure it stick's to the base
Allthrough if it's been leaking you may need to do it anyway

I've had these problems. Most weather coverings are only as good as the board layer underneath. Even rubbish felt should last longer than 10 years if the deck boards are fastened properly.

You need to establish if the boards underneath are failing. If they are chipboard - even the (so called) weatherproof type, its probably scrap. Rip the whole lot off and replace with OSB panels. If it has OSB panels its likely the edges were not properly supported. If the boards are solid, the easiest fix is to add another layer of deck boards making sure the joints do not overlap.

You can get expanding polyurethane glue to use between the board layers. The finish can be whatever you like.

The snag with fibreglass is that it has to be 100% no voids or porous areas or the frost will get in and you'll have leaks. It also has to be done on one day so it cures as a solid sheet. It can be done in stages but the earlier areas must be "green" when the next is added and all glass matting must overlap. The deck boards and all details (chamfers etc) have to be 100% to the point of obsession to avoid cracks developing over time.

EDPM is a single sheet but still demands a solid board underlayer with no movement between boards and good detailing at edges etc.


Lots of info here https://www.youtube.com/results?search_query=installing+butyl+rubber+roohing

Thanks guys, that's helpful and supportive.

From what I've read so far, basically Dave has got it nailed (if you'll pardon the pun).

The roof is too large and complex for EDPM, so that doesn't make it past the first hurdle.

The main surface appears to be fine; it's the edge detailing that's the problem. There are hundreds (literally) of individual pieces of bitumen sheet all bonded together around the edges like a patchwork quilt; figuring out which joints may have given way is nigh on impossible. Given the age of the house, I'd suspect the felt is laid onto OSB3 boards, so if they're sound (fingers crossed), then stripping the felt and overlaying with 18mm OSB3 T&G panels would provide a good surface to put a GRP roof onto.

I've sent a drawing and some pictures to Cure-it and they've said one of their technical gurus will get back to me Monday. If it looks like a feasible solution, I'm planning on going on their training course.

I used a liquid membrane system which on paper should have been excellent. BUT...


The problems came at board joints and at upstands to adjacent walls. My boards were screwed to the rafters and supported with noggins across rafters and the upstands had 50 x 50 triangle sections to create a smooth turn up. All very good but the joints all moved and the fancy super flexible system split at most of them. The neatly made upstands were just as bad. Brick and wood expand at different rates.


What I needed was a low tack base layer that allows the covering to semi float especially where there will be movement (edge upstands and board joints), but that's questionable with liquid applied systems.

EDPM is really good stuff as its not hard bonded to the roof structure. Joints, upstands etc have to be done very carefully but don't write it off just yet.