As per the subject line. Which would you choose between a rubber flat roof and a “traditional” “torch on”. This is for an existing extension where the roof has started leaking after many years.

The original quote put the rubber roof at 15% more expensive but the roofer has dropped the price of the rubber roof to parity with the “torch-on”.

Sarnafil

Ours are GRP.

Can’t comment on real world longevity as it’s only just been done, but it looks nice and is supposed to last 25-30 years.

Rubber/sarnafil/ single ply. But it generally needs a vented backing if it’s not direct onto insulation. Torch ons have improved but should have some sort of fall and  then it’s down to workmanship. Grp is good but can crack if loaded (foot traffic/ ladders etc depending on the system and installation.

A large local authority we work with will only allow three layer built up systems, no single ply membranes.

A large local authority we work with will only allow three layer built up systems, no single ply membranes.

Opinion certainly seems to be divided. Is it just resistance to newer ideas?

I’ve heard that GRP is noisy, but anyway it isn’t one of the options in this case.

Ours are GRP.

Can’t comment on real world longevity as it’s only just been done, but it looks nice and is supposed to last 25-30 years.

This^^. We had ours done with GRP about 8 years ago and it still looks as good as it did then. The company who did it guaranteed it for 25 years IIRC but reckon it should last at least 30. After all, it’s the same as a boat hull but with the added support of being bonded onto 18mm (again IIRC) marine ply panel.

As it’s also pale grey rather than the usual very dark colours of felt or rubber roofs I’m convinced it keeps the extension cooler in the summer too.

Our next-door neighbour has had a rubber one done last year and it looks OK but doesn’t dry as quickly as ours and appears to have stained from the puddles forming on it already, something we’ve not experienced.

As it’s also pale grey rather than the usual very dark colours of felt or rubber roofs I’m convinced it keeps the extension cooler in the summer too.

Single ply is available in a range of colours from almost white to dark grey.

Ours is dark grey and while very little of ours is visible (either green roof of deck boards over the top) but a section that is, on a 45 degree angle, has marked/stained/got algal growth on it that doesn’t come off easily.

The resistance to single ply stems from the fact that if maintenance access is required it can get easily damaged and in commercial situations to impact of leaks can be enormous. All it takes is one operative to stand on a left over screw and the roof the knock on effects can be catastrophic. I for one have worked for two major main contractors who prefer not to install it.

If it’s going on a domestic roof, though, there shouldn’t be a problem with it, though anecdotally I’ve heard of more preference for GRP.

What Wallop says. I work for a mid-sized contractor (£250M turnover) and we strongly resist single ply for those reasons. Leaks are very hard to track back too as they can appear on your ceiling nowhere near source.

3 ply felt FTW

Yes, high performance felt ftw – I’m sure I once had a director who said it almost ‘self-repaired’ holes.

Thanks all. More food for thought.

We had our felt roof replaced with GRP a few years ago.  Still looks good and supposed to last 25yrs +.