DaveAF Posted October 20, 2023 Share Posted October 20, 2023 (edited) Hi. My neighbour had a flat foof put on his extension in early September 2023. He loves it but doesn't know much about glass fibre. The builders put 1 layer of glass fibre matting on it 4 weeks ago but haven't topcoated it. It's too late to get a proper bond after 4 weeks surely? Why would anyone wait so long to topcoat? Just wondering. Edited October 20, 2023 by DaveAF Link to comment Share on other sites More sharing options...
Conor Posted October 20, 2023 Share Posted October 20, 2023 Just needs a good rub down with fine sandpaper and it'll be fine. Topcoat in theory protects against UV damage, otherwise aesthetic. Looks like a pretty good job btw. 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted October 20, 2023 Share Posted October 20, 2023 9 hours ago, DaveAF said: 1 layer of glass fibre matting on FFS Just as well they have not put the top coat on. 1 layer is bugger all and will quite possibly cause problems in the not too distant future. If they use the right kind of resins, adding extra layers and a top coats onto fully cured substrate is not a problem. I will say that it does look a reasonable layup for 1 layer, nice and resin rich, which is a good thing. 1 Link to comment Share on other sites More sharing options...
Conor Posted October 21, 2023 Share Posted October 21, 2023 11 hours ago, SteamyTea said: FFS Just as well they have not put the top coat on. 1 layer is bugger all and will quite possibly cause problems in the not too distant future. If they use the right kind of resins, adding extra layers and a top coats onto fully cured substrate is not a problem. I will say that it does look a reasonable layup for 1 layer, nice and resin rich, which is a good thing. ?? Any kit I've ever used has been a specific one layer chopped strand kit. I didn't know multi layer was a thing. 1 Link to comment Share on other sites More sharing options...
DaveAF Posted October 21, 2023 Author Share Posted October 21, 2023 12 hours ago, SteamyTea said: FFS Just as well they have not put the top coat on. 1 layer is bugger all and will quite possibly cause problems in the not too distant future. If they use the right kind of resins, adding extra layers and a top coats onto fully cured substrate is not a problem. I will say that it does look a reasonable layup for 1 layer, nice and resin rich, which is a good thing. Oddly enough after they repaired a minor leak yesterday morning they finally topcoated the roof. No extra layers of matting though, just a paint over with the topcoat. Link to comment Share on other sites More sharing options...
SteamyTea Posted October 21, 2023 Share Posted October 21, 2023 1 hour ago, Conor said: I didn't know multi layer was a thing. 2 layers of 450g/m2 CSM would be normal, I would always recommend 3 layers. As a general rule, 1 layer of 450g/m2 matt is 1 mm thick and will take 900g of polyester resin. If going onto a very absorbent substrate like OSB, then the first layer will take more resin. Topcoat is around 350g/m2. This can vary quite a lot depending on the final usage i.e. aviation and walkways are treated very differently. 1 1 Link to comment Share on other sites More sharing options...
Conor Posted October 21, 2023 Share Posted October 21, 2023 Glad I've only done a shed roof and a balcony then 🤣 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted October 21, 2023 Share Posted October 21, 2023 18 minutes ago, Conor said: Glad I've only done a shed roof and a balcony then 🤣 Treat it as aviation, they usually fly off eventually. 1 Link to comment Share on other sites More sharing options...
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