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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthordsewell
    • CommentTimeApr 19th 2016

    Does anybody have any experience / recommendations regarding airtightness installation of intermediate floors?

    The building walls are 215mm AAC Blocks. Floors are open web joists 220 high joists.

    We are considering 2 options:

    1) a laminated 50mm wall plate bolted to the block work, parge coat behind. Joists hung from wall plate. This option is favoured as easy to make airtight but our SE has reservations re bearing capacity of the bolts in blockwork / stability. We are struggling to find suitable details or bolts / fixings to take the loads.

    2) standard joist hangers over the blocks, joists siting directly onto these. Considered more stable but far more complex to make airtight.

    We have also considered other options such as plastic pockets, Tony Tray, etc.

    The key points being to design a junction that will take the loads AND is very airtight.

    Regarding option 1) can anybody recommend wall plate fixings that have been used successfully?

    Regarding option 2) are there any techniques / products we can consider to make wall hangers airtight?

    Any help would be greatly appreciated.
    • CommentTimeApr 19th 2016
    I used a ledger beam bolted to the wall and suspended the joists from their top flange. We found it to be a good way to do it. My engineer specified the fixings for the ledger beam, just as I believe yours will need to. The joist supplier specified and supplied the ledger beams. They were coach screws, at 200 mm spacing IIRC. We used strips of DPM behind the beam as the airtightness barrier, with the screws inserted through butyl tape patches. The DPM is connected to the plaster used for airtightness over the rest of the wall by Contega tape.
    • CommentAuthortony
    • CommentTimeApr 19th 2016
    I favour the tony tray, works perfectly, loads go into the masonry (2x 100mm) blocks instead of one 215 for the storey course. Simple, cheap and easy.
    • CommentTimeApr 19th 2016
    One fact I forgot to mention that I should have. We mounted our ledger beam to timber structure rather than masonry, so coach screws may well not be the right answer.
    • CommentAuthorwoodgnome
    • CommentTimeApr 30th 2016
    Tony Tray for me. Piece of cake to do.
    • CommentAuthorcjard
    • CommentTimeMay 1st 2016
    A long time ago I first floored out a warehouse by rawl bolting 10x2 to a concrete block wall, and running more 10x2 away from it over (probably) a 6 metre span. One 18mm ply floor later and it carries tons of motorcycle parts. I'm certain your se will find a bolt that he's happy with; I'm sure mine were only m12 x 120 or thereabouts- they get significant shear strength from the collar as well as the bolt, and in this application there is very little pull out force compared to the shear
    • CommentAuthorcjard
    • CommentTimeMay 1st 2016 edited
    As an aside, the air tightness membrane in my current timber frame is a lap of supro roofing felt that starts on the inner face of the wall in the room downstairs, goes out to the outer face to go around the ring glulam beam where the floor deck sits, and then comes back in. It's one of the aspects of the design I'm least happy with and if i had the time over again I'd have had the inner face of the floor ring beam aligned with the inner face of the stud wall and I'd have gone straight up with the supro before hanging the joists. A lot easier to seal up a few tiny holes in the membrane where nails have gone through it, than the arsing around I've had to do in several corners and changes in floor level. Supro does not fold nicely when wrapping it like with Christmas presents

    That said, warping joist ends in it and placing them in holes in the wall might work well, esp if the membrane is pre folded and stapled so it can be fanned out again. It sounds like it could be a floppy version of a Tony tray if my imagination is correct

    For another option, take a look at touch n foam (ab building products have good prices) pressurised 2 part urethane foam; it comes in a gas bottle (about half the size of what you'd put in a portable gas Fire) and the gun essentially shoots liquid kingspan that is already reacting/expanding as it leaves the nozzle and cures shortly after it hits the surface it is sprayed on. Phenomenal stuff. Note, it's nothing like the expanding foam that comes in a can/screws onto a dispenser gun
    • CommentTimeMay 2nd 2016
    A problem with block walls I have come across with both the Tony tray or hangers from a wall plate is the need to chase for cables etc. How is this achieved without harming the membrane of the Tony tray or a membrane behind a wall plate? If like above each joist is wrapped then there is space between them to run chased cables.
    • CommentAuthortony
    • CommentTimeMay 2nd 2016
    I simply use capping over the cables and in one instance where ther was a pipe, chased reg wall but let my tray go behind the pipe leaving it undamaged.
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