Bitpipe Posted May 2, 2022 Share Posted May 2, 2022 Hello, we have two small GRPd flat roofs, both of which have aesthetic issues but are otherwise sound. The front one (3m x 2m) was not built with sufficient side to side falls so water tends to puddle in the middle, eventually evaporates but leaves an unsightly red stain due to algae. Rear one, more or less same size, had patches of the topcoat curl up and flake off after a year or two. Roofer came back to remedy but it just happened again so no idea why. I'm inspired by @Thorfun's beautiful green roofs so wondering if there is a possibility I could just lay some seedum rolls and let that cover up the issues. Probably being naive here wrt weight etc but worth a thought! Link to comment Share on other sites More sharing options...
tonyshouse Posted May 2, 2022 Share Posted May 2, 2022 Yes, soil and water are heavy so structural calcs should be carried out, not good the puddle, small roof is more likely to pass Link to comment Share on other sites More sharing options...
Bitpipe Posted May 2, 2022 Author Share Posted May 2, 2022 14 minutes ago, tonyshouse said: Yes, soil and water are heavy so structural calcs should be carried out, not good the puddle, small roof is more likely to pass Ok, I'll go back to MBC and see if they can review the original calcs. Link to comment Share on other sites More sharing options...
SteamyTea Posted May 2, 2022 Share Posted May 2, 2022 42 minutes ago, Bitpipe said: had patches of the topcoat curl up and flake off after a year or two. Roofer came back to remedy but it just happened again so no idea why. 3 main reasons. Incompatible resin type mixes. Poor preparation. Thermal expansion and contraction. My guess would be the first one. Link to comment Share on other sites More sharing options...
tonyshouse Posted May 2, 2022 Share Posted May 2, 2022 Usually for green roof joists are thicker and deeper and closer together the decking 28mm stronger ply too Link to comment Share on other sites More sharing options...
PeterW Posted May 2, 2022 Share Posted May 2, 2022 Consider the M-Tray system @Bitpipe - they use lightweight aggregate and other methods to keep the weight down and it comes in at around 100kg/M when saturated so it isn’t a massive loading on any structure. https://jjroofingsupplies.co.uk/flat-roofing/wallbarn-m-trayr-sedum-green-roof-module-500-x-500-x-100mmp Link to comment Share on other sites More sharing options...
Thorfun Posted May 2, 2022 Share Posted May 2, 2022 2 hours ago, Bitpipe said: I'm inspired by @Thorfun's beautiful green roofs so wondering if there is a possibility I could just lay some seedum rolls and let that cover up the issues. 😊 I found this when researching green roofs online https://www.turfonline.co.uk/blog/green-roof-construction/ which gives information about loadings etc. need to get the load calculated by the SE as you suggested you would do anyway. our roof is single-ply membrane rather than GRP as I was told by a few roofers that GRP could crack with the movement of the timber frame and so I took their advice and went single-ply. not sure if the roof covering plays a part for green roofs either but as the same roofer who did the single-ply did the green roof I just let him take the lead and recommend the best products to use. Link to comment Share on other sites More sharing options...
Mears Posted May 3, 2022 Share Posted May 3, 2022 Thanks for the comparison @PeterW I'll be using this system when I get around to it https://www.green-tech.co.uk/green-roofs-and-living-walls/green-roof-systems/green-roof-sedum/sedum-green-roof-trays Approximately 50kg/m² saturated weight Link to comment Share on other sites More sharing options...
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