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BartW

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  1. It's just a loft room, so typical trim detail at the edge of flat GRP roof. Falls are being achieved with firings, and pointing towards the pitched roof. We have pozi joists contracted as part of the build, but there will be services there indeed. Wider section of the building here:
  2. Hi, Current commitment is roof with OSB and breather all around. Target U is 0.15, which is same as for the the rest of the thermal envelope. Warm above and in-between (as specified by Kingspan) seems an easier detail, which does away with thick stop rafter, and very long (and expensive) fixings. I just wonder if it would still function as designed if there is the "inherited" OSB layer and breather above it, between the rafter level PIR and the "above" layer. Decisions, decisions...
  3. I was my own architect and frankly have not given it enough thought. It stacked up on paper, but now we are nearly physical on site with it…
  4. Trouble with this is that Helifix only go up to 200mm, and with 150mm pir and 25mm battens, then 18mm osb inderneath, I am not achieving the 38mm substrate penetration…
  5. Thanks for the comment. Current remit from the TF supplier is that they fit OSB and breather on top. On the basis of which I was leaning to just having cold unventilated roof (yes, got enlightened that it was possible and in line with all BBA / NHBC guidelines). So like this: Having said that, warm roof would be more consistent with the flat roof, less tricky junctions. If I follow your advice, would I ask the TF supplier not to install a breather above OSB? Or should I just put PIR on top, and put another independent layer of breather on top, then battens and counter battens, slates?
  6. That roof is unventilated and there is no way it would be. So I somehow need to get it approved by Building Control.
  7. Hi, I posted about it elsewhere on the forum, but it is still making me wonder. Kingspan details "warm pitched roof" as: - insulation above - and inbetween - like this: I, however, have detailed it like this: My questions: - am I doing it wrong? - should I have a layer of OSB on top of rafters before the insulation? - will I struggle to anchor a 150mm PIR to the roof? - should I consider means of preventing the roof sliding down under its own weight? Advice highly appreciated. I got nowhere with it so far...
  8. Anyone to comment please? Also, weirdly, Kingspan suggest 60 over + 60 in-between for the "warm" roof buildup on pitched. Any benefit to having sarking vs no sarking? Would I be better off doing that instead of bulky 150?
  9. Yeah, I think I will do just that. Better (worse) things to worry about out there! B
  10. I must admit I am looking at economical factors too. hence me considering likes of 25mm pir sandwich + rwa45. Also “horizontal service cavity means services going in that direction or a lot of notching / removing of battens. What about 2inch vertical battens with 75mm rwa45 (tight!) then blinded with 25mm pir and 25mm service cavity vertically? Then osb and plasterboard?
  11. We want to hide all gutter downpipes behind cladding. There may be other ways of achieving this with 1" battens, but I might have to notch / route the back of facade timbers, or create a bespoke downpipe. Sounds like I will be re-evaluating live when at it soon!
  12. I am actually liking this idea. I don't suppose I would get away with a 75mm RWA45 internally, whilst eradicating internal PIR altogether? I appreciate that would re-introduce cold bridges. What about doing 20mm PIR internally, and then 50mm RWA45? I would keep my service void 50mm, but hopefully things like cables and pipes would just squash the insulation a little. Viable?
  13. Thinking about this again, would I be able to achieve better performance of the pitched roof by doing a 100mm PIR above rafters, and 100mm rock wool between the rafters? Decrement delay and thermal mass come to mind, having read a few recent posts. Also, would it fly with flat "warm roofs"? I.e. 100mm PIR above, and 100mm rock wool between rafters?
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