Gone West Posted March 14 Share Posted March 14 @SteamyTea Following on from the other thread, where we were discussing using GRP sheets for flat roofing. I was wondering what would be the best thickness for that application. Also, if I wanted the flat roof (say 1.5 degree slope) to be just under the level of the existing main roof how would that be done? If I were laying EPDM I would continue it up under the main roof tiles, are suitable GRP sheets flexible enough to be able to bend up a 30 degree slope under the main roof tiles? Link to comment Share on other sites More sharing options...
SteamyTea Posted March 14 Share Posted March 14 1 hour ago, Gone West said: wondering what would be the best thickness for that application. Do you mean the substrate thickness or the GRP thickness? Substrate is really down to if it is walked on a lot and what snow and wind loadings happen, same as any sarking really. GRP is best at about 3mm before any finish coating. I would usually do this with 3 layers of 450 g/m² matting. 1 hour ago, Gone West said: are suitable GRP sheets flexible enough to be able to bend up a 30 degree slope under the main roof tiles No. GRP, is basically inflexible. If the angle is known then a trim piece can be moulded and attached, then bonded in place. Alternatively a thin sheet of just GRP can be moulded, cut to the right size to fit under the original roof, but over the new flat roof sheets, then locally bonded. It may be better if I draw something up when I get home. It is drizzling today so not going to be oggling bathing beauties on the beach. Link to comment Share on other sites More sharing options...
scottishjohn Posted March 14 Share Posted March 14 (edited) you can buy ready made grp flashings/ edging of all shapes to do what you are suggesting Edited March 14 by scottishjohn Link to comment Share on other sites More sharing options...
Gone West Posted March 14 Author Share Posted March 14 1 hour ago, SteamyTea said: Do you mean the substrate thickness or the GRP thickness 1 hour ago, SteamyTea said: GRP is best at about 3mm before any finish coating. The GRP thickness, I was thinking 3mm sounds about right. 1 hour ago, SteamyTea said: No. GRP, is basically inflexible. If the angle is known then a trim piece can be moulded and attached, then bonded in place. So with an old house the angle may change along the wall, so it's sounding more complicated than using EPDM, which would be easier. Link to comment Share on other sites More sharing options...
SteamyTea Posted March 14 Share Posted March 14 1 hour ago, Gone West said: So with an old house the angle may change along the wall, so it's sounding more complicated than using EPDM, which would be easier. If you could nail a thin sheet of ply to it, then it can be coated in-situ. Link to comment Share on other sites More sharing options...
Gone West Posted March 14 Author Share Posted March 14 44 minutes ago, SteamyTea said: If you could nail a thin sheet of ply to it, then it can be coated in-situ. I wouldn't want to do any fibre glassing on the roof. I wonder why someone hasn't come up with a resin that uses moisture to set, like PU glue. Link to comment Share on other sites More sharing options...
SteamyTea Posted March 14 Share Posted March 14 (edited) 4 minutes ago, Gone West said: I wouldn't want to do any fibre glassing on the roof. I wonder why someone hasn't come up with a resin that uses moisture to set, like PU glue. They have. I think @Onoff used some on his roof. I have some details about it somewhere. I think this stuff is similar. https://www.topseal.co.uk/topseal-pu/ One Day I would like to try some out and see what it can do. Edited March 14 by SteamyTea Link to comment Share on other sites More sharing options...
Gone West Posted March 14 Author Share Posted March 14 5 minutes ago, SteamyTea said: I think this stuff is similar. Thanks, it looks good, I've bookmarked it, it's a pity only their installers can fit it. "Topseal PU is only available to Topseal Approved Contractors and not available off the shelf." Link to comment Share on other sites More sharing options...
Onoff Posted March 14 Share Posted March 14 Not me. I used single pack, paint on Chromapol. Tbh I've thrown probably several hundred Pounds at this over the years. The felt roof was knackered before I put this paint on. It's fibrous, the idea it reinforces itself. I'd be interested to see how it performed on say a new, OSB sheeted roof. The stuff I'm considering when I redo the roof is Desmopol. As used successfully by someone. I asked the other week how it was standing up. Wait one and I'll find the thread. Link to comment Share on other sites More sharing options...
Onoff Posted March 14 Share Posted March 14 (edited) 3 pages, will only link so it opens on page 2? Edited March 14 by Onoff 1 Link to comment Share on other sites More sharing options...
Russell griffiths Posted March 14 Share Posted March 14 @Gone West look up owl roofing, it’s a brush on membrane that cures with moisture, I think they reinforce it with a roll of cloth just like fibreglass without the weather problems. it uses the same fibreglass edge trims. when I did mine I got a trim that tucked under the tiles. 1 Link to comment Share on other sites More sharing options...
tuftythesquirrel Posted March 15 Share Posted March 15 17 hours ago, Gone West said: 17 hours ago, SteamyTea said: If you could nail a thin sheet of ply to it, then it can be coated in-situ. I wouldn't want to do any fibre glassing on the roof. I wonder why someone hasn't come up with a resin that uses moisture to set, like PU glue. I can recommend the Everbuild Aquaseal. I used it because it was a single coat application. I looked others, but priming and top coating would extend the job time. I put on a double coat of fibre glass, the second at 90 degrees to the first, then two more coats. It UV resistant out of the can, whereas other products need a top coat. I used it on a pitch change on our Kingspan Quad-Core metal roof. The professional roofer had attempted a fiberglass joint which blew off in the wind, it was worse than useless. I would definitely use this on a flat roof if it had to. Everbuild technical support were very helpful. https://www.sealantsandtoolsdirect.co.uk/everbuild-aquaseal-liquid-roof-membrane-coating-21kg-grey-aqliqrfgy21?language=en-gb¤cy=GBP&gad_source=1&gclid=CjwKCAjw48-vBhBbEiwAzqrZVIIoeVRo2Uq_AorAxtICel9dYxZNqqNpzFaSn7J-g7lzr8sZM2PNrRoCrEcQAvD_BwE 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted March 15 Share Posted March 15 5 minutes ago, tuftythesquirrel said: I put on a double coat of fibre glass Did you use the Everbuild Aquaseal instead of polyester resin? This is where my knowledge breaks down. I have used many different resins with glass, aramid, boron and carbon fibres, as well as natural fibres like jute, hemp, cotton and cellulose. But apart from injected PU resins, I have never hand laid with PU resins. It is something I want to experiment with one day. The price of the Aquaseal seems pretty good. Link to comment Share on other sites More sharing options...
tuftythesquirrel Posted March 15 Share Posted March 15 4 hours ago, SteamyTea said: Did you use the Everbuild Aquaseal instead of polyester resin? I was only looking for a waterproof, easily applied, durable covering. I've got an in built aversion to anything two pack. That is, manufacturers instructions say 30 minutes gel time and you're 15 minutes in and it's started to gel and your brush is stuck to the roof, mould or anything else you are using it on. This product is is way more flexible than polyester resin, even with multiple layers of fibre in it and you've much, much longer to get it on the substrate, literally hours. I've coated a piece of internal floorboard and left it outside 18 months ago (in the sun and rain etc.) and it still looks like I just put it on. Link to comment Share on other sites More sharing options...
SteamyTea Posted March 15 Share Posted March 15 I am going to have to get some and have a play about. Link to comment Share on other sites More sharing options...
tuftythesquirrel Posted March 15 Share Posted March 15 1 hour ago, SteamyTea said: I am going to have to get some and have a play about. Link to comment Share on other sites More sharing options...
Onoff Posted March 15 Share Posted March 15 I've used most of the grey, acrylic, single pack repair paints. Cromapol, Flexacryl, Acrypol, Evercryl etc. All much of a muchness. Link to comment Share on other sites More sharing options...
scottishjohn Posted March 15 Share Posted March 15 2 hours ago, tuftythesquirrel said: I was only looking for a waterproof, easily applied, durable covering. I've got an in built aversion to anything two pack. That is, manufacturers instructions say 30 minutes gel time and you're 15 minutes in and it's started to gel and your brush is stuck to the roof, mould or anything else you are using it on. This product is is way more flexible than polyester resin, even with multiple layers of fibre in it and you've much, much longer to get it on the substrate, literally hours. I've coated a piece of internal floorboard and left it outside 18 months ago (in the sun and rain etc.) and it still looks like I just put it on. Iwould ring everbuild tech to see if it is happy going onto damp OSB Link to comment Share on other sites More sharing options...
Onoff Posted March 15 Share Posted March 15 7 minutes ago, scottishjohn said: Iwould ring everbuild tech to see if it is happy going onto damp OSB The paint on one I used last I'm sure used to say can be applied to damp surfaces. They've I think changed the can wording to on the lines it can be but better if the substrate is dry. Link to comment Share on other sites More sharing options...
tuftythesquirrel Posted March 15 Share Posted March 15 4 hours ago, Onoff said: Acrypol, Evercryl I've used these and the Everbuild Aquaseal is a much better (different) product, much more durable. TDS says "no rising moisture? Link to comment Share on other sites More sharing options...
SteamyTea Posted March 15 Share Posted March 15 1 hour ago, tuftythesquirrel said: says "no rising moisture AKA a puddle. Link to comment Share on other sites More sharing options...
Onoff Posted March 15 Share Posted March 15 1 hour ago, tuftythesquirrel said: I've used these and the Everbuild Aquaseal is a much better (different) product, much more durable. TDS says "no rising moisture? I've definitely got rising moisture. The substrate aka felt is totally shot. Mind the other side is worse, I've just slung a bit of weighted down DPM over the whole lot. Link to comment Share on other sites More sharing options...
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