GreenGables Posted November 25, 2022 Share Posted November 25, 2022 Hello. We’re having GRP flat roofs done and the builder has done a section of upstand without any vertical insulation or plywood so the GRP waterproof membrane is bonded straight to the brickwork. We were supposed to have 15mm high insulation so I’m assuming this will mean my ceiling below will be colder than it should have been. Should I get them to redo the roof? Thanks for any advice. Link to comment Share on other sites More sharing options...
MJNewton Posted November 25, 2022 Share Posted November 25, 2022 15mm? Link to comment Share on other sites More sharing options...
GreenGables Posted November 25, 2022 Author Share Posted November 25, 2022 Sorry 150mm Link to comment Share on other sites More sharing options...
JohnMo Posted November 25, 2022 Share Posted November 25, 2022 If it's not insulated, that an obvious cold bridge, if as bad you think, would lead to internal condensation and a nice area for mold. I would be asking for it to be done correctly. Link to comment Share on other sites More sharing options...
MJNewton Posted November 25, 2022 Share Posted November 25, 2022 Is it a warm or cold roof? Do you have drawings showing the correct/intended detailing? And the brickwork in question, is that the exterior wall of the adjoining house or parapet walls? Link to comment Share on other sites More sharing options...
GreenGables Posted November 26, 2022 Author Share Posted November 26, 2022 It’s a warm roof. I’ve attached the plan but now I’ve looked at it more closely it looks like there would have been a cold bridge anyway down through the inner skin of bricks to the steel. This is supposed to be a 0.18U roof. 1 Link to comment Share on other sites More sharing options...
MJNewton Posted November 26, 2022 Share Posted November 26, 2022 Yeah I don't think it will make any material difference, and certainly not worth ripping things up/off which could do more harm than good. Link to comment Share on other sites More sharing options...
JohnMo Posted November 26, 2022 Share Posted November 26, 2022 If the drawing is to scale the upstand doesn't look to 150mm, more like 50mm. I would leave it as is. But insulate around the steel internally. To get rid of the cold bridge. Link to comment Share on other sites More sharing options...
Radian Posted November 26, 2022 Share Posted November 26, 2022 Is the uninsulated steel lintel above the window a big proportion of the room? I.e. is it a one meter window opening in 10m of wall in total, or what? Link to comment Share on other sites More sharing options...
Andehh Posted November 26, 2022 Share Posted November 26, 2022 Negligible difference, I wouldn't worry about it! Definitely wouldn't remove & refit roof. Our upstands are uninsulated, never even thought about it to be honest. Link to comment Share on other sites More sharing options...
GreenGables Posted November 26, 2022 Author Share Posted November 26, 2022 10 hours ago, Radian said: Is the uninsulated steel lintel above the window a big proportion of the room? I.e. is it a one meter window opening in 10m of wall in total, or what? The steel is curved over floor to ceiling fixed windows. 6-7 metres long. Link to comment Share on other sites More sharing options...
GreenGables Posted November 26, 2022 Author Share Posted November 26, 2022 9 hours ago, Andehh said: Negligible difference, I wouldn't worry about it! Definitely wouldn't remove & refit roof. Our upstands are uninsulated, never even thought about it to be honest. That’s good to know. Link to comment Share on other sites More sharing options...
GreenGables Posted November 26, 2022 Author Share Posted November 26, 2022 11 hours ago, JohnMo said: If the drawing is to scale the upstand doesn't look to 150mm, more like 50mm. I would leave it as is. But insulate around the steel internally. To get rid of the cold bridge. The upstand is definitely 150mm. I will look into putting internal insulation around the steel. Link to comment Share on other sites More sharing options...
Radian Posted November 26, 2022 Share Posted November 26, 2022 22 minutes ago, GreenGables said: The steel is curved over floor to ceiling fixed windows. 6-7 metres long. That's one big lump of cold steel in your room. I have a similar problem with a 6m long ɪ beam over floor to ceiling windows. It was boxed in when I wasn't on site to keep an eye on things and no insulation was added. Subsequently small patches of mold have appeared in the corners. The biggest problem to overcome will be insulating the underside of the steel. Your window head will come right up to it and not leave space for insulation - and even if it did, how would this look from outside? Only insulating up to the frame would seem to be the only option but the thickness of the frame will dictate how much room, if any, there is for insulation. 50mm of PIR would be the absolute minimum I'd guess. Add 12.5 for fireboard and you're probably down to the glazing level. Link to comment Share on other sites More sharing options...
GreenGables Posted November 27, 2022 Author Share Posted November 27, 2022 9 hours ago, Radian said: That's one big lump of cold steel in your room. I have a similar problem with a 6m long ɪ beam over floor to ceiling windows. It was boxed in when I wasn't on site to keep an eye on things and no insulation was added. Subsequently small patches of mold have appeared in the corners. The biggest problem to overcome will be insulating the underside of the steel. Your window head will come right up to it and not leave space for insulation - and even if it did, how would this look from outside? Only insulating up to the frame would seem to be the only option but the thickness of the frame will dictate how much room, if any, there is for insulation. 50mm of PIR would be the absolute minimum I'd guess. Add 12.5 for fireboard and you're probably down to the glazing level. There really isn't room inside to insulate around the steel. They will have to redo the roof to include insulation. It looks like there isn't even a cavity tray to protect the steel lintel from water ingress so my problems just got bigger. Link to comment Share on other sites More sharing options...
GreenGables Posted November 27, 2022 Author Share Posted November 27, 2022 Thanks for all the comments. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted November 27, 2022 Share Posted November 27, 2022 Just a quick check, do the window frames provide any support to this beam or is there a column / cantilever somewhere at the center point of the curve, furthest from the cord between its ends, otherwise you will have quite a twisting force at that point? Link to comment Share on other sites More sharing options...
GreenGables Posted November 27, 2022 Author Share Posted November 27, 2022 10 minutes ago, MikeSharp01 said: Just a quick check, do the window frames provide any support to this beam or is there a column / cantilever somewhere at the center point of the curve, furthest from the cord between its ends, otherwise you will have quite a twisting force at that point? It does have two steel support beams and it’s all be checked by the SE so that shouldn’t be a problem. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted November 27, 2022 Share Posted November 27, 2022 1 minute ago, GreenGables said: It does have two steel support beams and it’s all be checked by the SE so that shouldn’t be a problem. Great - when you see one piece of poor construction (insulation not fitted) you wonder about all the rest. I won't ask how the support steels are insulated / placed inside the glass wall Link to comment Share on other sites More sharing options...
Radian Posted November 27, 2022 Share Posted November 27, 2022 53 minutes ago, GreenGables said: There really isn't room inside to insulate around the steel. They will have to redo the roof to include insulation. It looks like there isn't even a cavity tray to protect the steel lintel from water ingress so my problems just got bigger. Is the inner leaf all that visible? I'd be thinking hard if the inner brickwork could be swapped for block and the GRP taken all the way up to the copings. Link to comment Share on other sites More sharing options...
Dave Jones Posted November 27, 2022 Share Posted November 27, 2022 out of curiosity, what make of vapour barrier was used and where did you put it ? Link to comment Share on other sites More sharing options...
GreenGables Posted November 27, 2022 Author Share Posted November 27, 2022 1 hour ago, Radian said: Is the inner leaf all that visible? I'd be thinking hard if the inner brickwork could be swapped for block and the GRP taken all the way up to the copings. Actually the inner leaf is blockwork on this section and the GRP has been taken the whole way up over the cavity at the top. They just haven’t added the required insulation inside the blockwork. Link to comment Share on other sites More sharing options...
GreenGables Posted November 27, 2022 Author Share Posted November 27, 2022 1 hour ago, Dave Jones said: out of curiosity, what make of vapour barrier was used and where did you put it ? Sorry I’ve no idea what they used. It’s a GRP roof which has been built up in layers. It does look pretty waterproof at least. Link to comment Share on other sites More sharing options...
Jilly Posted November 27, 2022 Share Posted November 27, 2022 (edited) Would 10mm aerogel work? Edited November 27, 2022 by Jilly Link to comment Share on other sites More sharing options...
GreenGables Posted November 27, 2022 Author Share Posted November 27, 2022 3 minutes ago, Jilly said: Would 10mm aerogel work? That might work! Thank you. 1 Link to comment Share on other sites More sharing options...
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