Felt garage roof is coming to end of life as it’s starting to increasingly lift and leak in patches so time to consider replacement. It around 20metre-squared and due to the design must remain a flat-roof. As I understand it the 2 options are fibreglass or rubber but I don’t know any more than that…..
We have a [garage sized] beach hut in a row of 5 that all had fibreglass (over ply) roofs. After about 25 years they were seriously deteriorating and at least one hut had the fibreglass skin peel off in a storm.
We all had them replaced about 5 years ago with rubber and they’ve been great so far.
Would I use rubber again? Yes definitely.
I asked this a few months ago, and the consensus seemed to be both are good, rubber perhaps slightly more dependent on a good fitter but the main difference is fragility- if people walk on the roof go for fibreglass, if not go for what your preferred/recommended installer normally uses
IMO the boarding under the roof is far more important than the roofing material. If the boards are rubbish/move then any roof material will leak sooner or later
Our inherited flat roof extension has a GRP roof. I think it’s about 20years old and sound but one of the main pluses for me is that is easy to DIY repair. I’ve done a couple of patches and covered a hole where I removed a redundant flue. It was easy to do with a automotive repair kit + suitable pigment and the patches have held no problem. I’m pleasantly surprised, I’d always been conditioned to hate flat roofs.