Roofing

Help with existing flat grp roof conversion to torch on felt

Anonymous user 23/02/2024 - 3.18 PM

My previous builder has installed a GRP fibreglass roof incorrectly on my 8m x3.5m outhouse. I’ve experienced water coming through about a year and a half later on heavy downpours. I inspected the roof and cannot see any clear holes or wear, I suspect that he hasn’t put enough fibre resin in some places hence overtime the water has ingressed through the osb3 boards. The grey paint over the fibre makes it very hard to see where the water is coming from and the grey finish is already splinterig away from the roof almost like the top coat hasn’t adhered to the surface properly. My question is after thorough drying (and the boards look reasonable inspecting from the inside) what is the best way to rectify this? The structure seems solid, no water patches etc. My aim is to felt the roof so the options are: 1. I doubt torch on felt will adhere to the grp roof so is it possible to buy a primer (sanding down will be a nightmare I guess) and then be able to use torch on felt? If so please can someone recommend a suitable primer? 2. Can I screw new osb3 ply onto the existing roof (over the grp) onto the joists and then apply the layers of torch felt over it? I’m leaning toward this option. 3. Do I have to remove the grp existing roof and have to start from scratch? Any help is much appreciated as you can imagine I'm fuming as you only see these things months after the Builder has long gone and dissolved his company. Thanks in advance. Sunny