bissoejosh Posted May 30, 2017 Share Posted May 30, 2017 Firstly hello from Cornwall, Having browsed for the last year or so both here, GBF and on the old ebuild site I have to say what a fantastic source of info such places offer. Myself and partner are about to begin our self build I'm hoping someone can help with a particular question. Our plot is unusual in that the majority of the house is at 1st floor level (onto garden) and extends outwards from the lower level spanning an access alley between the house and a retaining wall. Because of the site elevations the upper level (where external to the lower level) will be on a B&B floor (tetris most likely) which needs to meet the lower level and sit on the outer skin of blockwork. Therefore we need to build the lower GF level in block - proposal is full fill 100mm block - 200mm glass batts - 100mm block (7n) all parge coated with a foundation detail matching Denby Dale / Golcar. Whilst I don't like block it works at supporting the upper level, is DIY able and I can focus on the detailing - sites like tonyshouse etc help greatly with this. At first floor level we want to use either timber frame or SIPS and whilst we aren't looking for passive standards (the B&B effectively kills this), efficiency is high on our list. Quite simply does any one have a detail showing a well thought out join between a cavity block lower level and timber / sips upper that focuses on air tightness and continuity of insulation? In particular I'd like to build to the outer leaf line of the lower level to maximize internal space and avoid an odd external detail at the join. External finishes are render lower GF & horizontal cedar / larch cladding 1st floor. My line of thinking was to build straight off the outer leaf but 100mm blocks won't work with 172mm SIPS which makes me think a platform construction is the way forward... Whether we opt for SIPS / timber frame (quotations are currently out and the same question is being asked to suppliers) I intend to mitigate the sole plate bridging issue with a course of thermal block under the plate plus 40mm of XPS sheathing extending 250mm above and below. Hopefully this will suffice. Please excuse the very DIY attached detail, still learning sketchup! Any help much appreciated! Josh BuildHub1.pdf Link to comment Share on other sites More sharing options...
PeterW Posted May 30, 2017 Share Posted May 30, 2017 Hi and welcome ..! Have you considered ICF..?? Classic case for using it as you can DIY it, render the outside and use B&B if you want for the first floor. If you wanted to go to TF above that then it would stand on the concrete core and you can line up the outer coverings pretty easily. Link to comment Share on other sites More sharing options...
bissoejosh Posted May 31, 2017 Author Share Posted May 31, 2017 (edited) 9 hours ago, PeterW said: Hi and welcome ..! Have you considered ICF..?? I actually spoke to Alan at Polarwall last week as they are fairly local to us. I need to follow up today. Not sure how ICF could support the beam and block running away from walls at the upper level - can some sort of shelf be formed outside the external skin of insulation? All the details I've seen show something similar but on the warm side of the wall. Agree about its DIY potential plus it's inherently more airtight which I like. Edited May 31, 2017 by bissoejosh Typo Link to comment Share on other sites More sharing options...
jamiehamy Posted May 31, 2017 Share Posted May 31, 2017 Why do you say that BnB means you will struggle to get passive standards? You can get some very low U-values with Tetris. ICF does sound ideal - we did a combination with OCF for the ground floor external walls and tying it in with a steel frame for the upper floor. Worked out pretty well. The ICF sat exposed for over 6 months with no roof and a year before we clad it and had suffered zero deterioration which was a big bonus for us - we would have struggled with timber frame as we would have needed to gotten wind and water tight much more quickly than the two of us on our own could have managed physically and financially. Link to comment Share on other sites More sharing options...
PeterW Posted May 31, 2017 Share Posted May 31, 2017 35 minutes ago, bissoejosh said: I actually spoke to Alan at Polarwall last week as they are fairly local to us. I need to follow up today. Not sure how ICF could support the beam and block running away from walls at the upper level - can some sort of shelf be formed outside the external skin of insulation? All the details I've seen show something similar but on the warm side of the wall. Agree about its DIY potential plus it's inherently more airtight which I like. Hi i wouldn't try and use the ICF skin to do this - you would use the core and then insulate below the beam. Using Tetris you would have essentially the concrete beams encased in insulation anyway. Your other option is to use steel to create a bridge / goalpost outside of the ICF and then clad these where your alleyway is - quick and simple and would allow you to separate the inner and outer structures Link to comment Share on other sites More sharing options...
bissoejosh Posted May 31, 2017 Author Share Posted May 31, 2017 10 hours ago, jamiehamy said: Why do you say that BnB means you will struggle to get passive standards? Purely based on a floor with free flowing air under it being less efficient than a ground bearing slab etc. Every build is a compromise and ours is that we need to have a suspended floor for a large part of the house - more than made up for by the plot itself. The tetris system does look v.good, waiting to hear more from the supplier having sent drawings etc. I have to say that the more I read about ICF it seems to fit nicely, & from what I can gather it's OK with lenders generally. Also, just found your blog - cracking project! Looks like you found Polarwall a good experience - what levels of insulation and core thickness did you opt for? Link to comment Share on other sites More sharing options...
jamiehamy Posted June 1, 2017 Share Posted June 1, 2017 15 hours ago, bissoejosh said: Purely based on a floor with free flowing air under it being less efficient than a ground bearing slab etc. Every build is a compromise and ours is that we need to have a suspended floor for a large part of the house - more than made up for by the plot itself. The tetris system does look v.good, waiting to hear more from the supplier having sent drawings etc. I have to say that the more I read about ICF it seems to fit nicely, & from what I can gather it's OK with lenders generally. Also, just found your blog - cracking project! Looks like you found Polarwall a good experience - what levels of insulation and core thickness did you opt for? We have a 150mm core for the house and 100/100mm insulation - although with hindsight I would have gone with 120/80 (external) which would have allowed us to set the windows nearer the core of the ICF (they sit just on the edge of the concrete) and give us a bit more leeway with the exterior reveals as well as probably making the install a bit easier. We are about to build our garage using Polarwall - the slab went in yesterday - and will be going for 80/80 purely on cost grounds. Hoping to get it delivered by the end of this month and build in in a couple of weekends ready for the pour. Link to comment Share on other sites More sharing options...
Stones Posted June 1, 2017 Share Posted June 1, 2017 Our ICF blocks were 65/150/65 with an additional 140 externally. Consequently we have quite deep external reveals, the only issue this presented was having to source my own aluminium window cills, which I sourced (powder coated to match the windows) at half the price the window supplier wanted for their cills. Link to comment Share on other sites More sharing options...
bissoejosh Posted June 1, 2017 Author Share Posted June 1, 2017 All really useful, many thanks. A long conversation with Alan at Polarwall today has moved things forward. I've one question-mark over mortgages which I've posted in the ICF forum but hopefully it won't be an issue. Link to comment Share on other sites More sharing options...
Vijay Posted June 1, 2017 Share Posted June 1, 2017 I've been dealing with Alan for a while now as I'm going with Polarwall too. Found him to be a genuinely good guy, so I hope he can help you too Link to comment Share on other sites More sharing options...
jamiehamy Posted June 1, 2017 Share Posted June 1, 2017 If Alan put a charge against his time he'd never made any money from us self builders! He's a real gem. I'm getting ready to order ours tomorrow. Link to comment Share on other sites More sharing options...
bissoejosh Posted June 7, 2017 Author Share Posted June 7, 2017 Sadly ICF is looking like a no go for us. Mortgageability is really important and our choice of a timber frame first floor is already throwing up barriers compared to a 'traditional' build. To then add in ICF seems to be asking for trouble - rather depressing but life goes on. This brings us back to my original question about the the best way to seal a timber deck with frame above onto a masonry cavity wall. As mentioned the masonry element will be 400mm thick with 200mm full fill batts so still a handy amount of insulation. Joists onto a wall plate seem straightforward enough but to then span the cavity makes the air tightness detail difficult. Would an adaptation of the 'tony tray' still work if it lapped the end of the joists and ran back in, under the sole plate to meet the vapourblock providing air tightness on the frame above? Rim board + protecting the joist ends seems doable with the correct amount of external insulation + full fill between. I can offset the frame above to make it all line up externally. As always advice very much appreciated! BlockFrameJoin2.pdf Link to comment Share on other sites More sharing options...
ProDave Posted June 8, 2017 Share Posted June 8, 2017 The purpose of a Tony Tray is to join the airtight layers of the first floor and the ground floor by taking the air tight membrane round the joist ends . I can't see any difference whether the air tight layer downstairs is a membrane on a timber frame or a parge coat on a masonry wall. So yes I would do that. I am grateful for my builders for suggesting this when erecting my frame (though they didn't call it a Tony Tray) It was a detail I was not aware of at the time. Link to comment Share on other sites More sharing options...
bissoejosh Posted June 8, 2017 Author Share Posted June 8, 2017 12 hours ago, ProDave said: The purpose of a Tony Tray is to join the airtight layers of the first floor and the ground floor by taking the air tight membrane round the joist ends . I can't see any difference whether the air tight layer downstairs is a membrane on a timber frame or a parge coat on a masonry wall. So yes I would do that. I am grateful for my builders for suggesting this when erecting my frame (though they didn't call it a Tony Tray) It was a detail I was not aware of at the time. thanks, that matches my thinking. I'm sure with a bit of care I can get a decent junction.... Link to comment Share on other sites More sharing options...
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