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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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    • CommentAuthorwookey
    • CommentTimeOct 17th 2019
     
    I'm doing foundation insulation and the XPS doesn't come 160mm thick so I'm using 100mm plus 60mm sheets. I can't fix them to the wall with fixings below ground level because there is no space to drill (without epic levels of digging). I could just reply on weight of dirt to hold them in place but I was planning to glue them up beforehand to get 160mm sheets and then use those.

    Which leads to the question, what glue to use?

    Handily someone online has done a load of tests: https://www.youtube.com/watch?v=YCIYMVOMBso
    and interestingly found that 3M super 77 spray adhesive was best. But also that polyurethane foam worked pretty well.

    Anyone tried this and have recommendations (or disrecomendations?)

    I already have lots of Dow Insta-stik (foam glue) which I suspect will work fine, but it does tend to push the boards apart a little and that's not ideal here. Just wondering if it's worth getting a can of the spray glue to use that. I also wonder how good it is in a damp application like this. The datasheet does say it is very resistant to water so I guess that should be OK.

    Just discovered Jackon 'Jackodur assembly adhesive' which actually seems to be designed for this job:
    https://www.jackon-insulation.co.uk/products/detail/assembly-adhesive/
    But I can;t immediately find anywhere I can actually buy it...
    Looks like they do 160 and 200mm thick boards too. Oh well, too late now.
    • CommentAuthortony
    • CommentTimeOct 17th 2019 edited
     
    Non expanding foam, very little needed, clean mortar snots from brickwork / blockwork first
    • CommentAuthorRobL
    • CommentTimeOct 17th 2019
     
    I've used No Nonsense Expanding Sticky Foam Gun Grade from screwfix, on the basis that it says internal and external use. Bart mentioned that sticky foam glue might not be frost proof, but I doubt that's an issue behind insulation.
  1.  
    I would use the EWI adhesive as used for all the best EWI installations. It is fairly cheap and comes in 25kg sacks to be mixed with water. Use the stuff to both glue the sheets together and to the wall.

    What about fixing the 100mm sheets first and then the 60mm sheets with joins off set to mitigate any gaps at the joints.
    • CommentAuthorRobL
    • CommentTimeOct 17th 2019
     
    Wookey - If you choose to try the EWI adhesive, I have a bag of this, and you're welcome to some:
    https://ewistore.co.uk/shop/ewi-220-eps-basecoat-25kg/
    It's a faff to use piecemeal for bits and bobs, but ok in larger quantities. I takes longer to set than the foam stuff. I don't think it insulates, so you can't fill up gaps between boards with it. It can be used both to glue the boards, and over the top of them.
  2.  
    •  
      CommentAuthordjh
    • CommentTimeOct 17th 2019
     
    Posted By: wookeyI could just reply on weight of dirt to hold them in place but I was planning to glue them up beforehand to get 160mm sheets and then use those.

    I would just rely on the backfill to hold them in place, but I wouldn't use dirt. I would use sharp gravel to dissuade rodents and moles from tunneling through, which also conveniently forms a French drain. You saw the paving slabs I used at ground level, also held in place by the gravel. I suppose an alternative underground might be something like weldmesh.
    • CommentAuthorjms452
    • CommentTimeOct 18th 2019 edited
     
    From a belt and braces, easy DIY without breaking the bank I'd vote for:

    Posted By: Peter_in_Hungary
    fixing the 100mm sheets first and then the 60mm sheets with joins off set to mitigate any gaps at the joints.


    held in place by PU sticky foam while you get the job done.

    If you aren't rendering followed by a layer of vertical cheap slabs

    followed by:

    Posted By: djh sharp gravel to dissuade rodents and moles from tunneling through, which also conveniently forms a French drain.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 21st 2019 edited
     
    EWI basecoat/adhesive is basically cementitious
    Posted By: RobLI don't think it insulates, so you can't fill up gaps between boards with it.
    Right, and as during EWI fixing, be very careful to not let any squeeze into the edge-joints between boards or at perimeter - instant thermal bridge, disproportionately compromising your strong, continuous insulation layer.
    • CommentAuthormatt-2052
    • CommentTimeOct 21st 2019
     
    i used Jackdur XPS for my insulation under the slab and perimeter wall to.
    Used their PLUS as better insulation 0.27 i think and it was cheaper than the normal XPS!
    the cost seems to be in transportation. I used 270mm instead of 300 for the same U value.
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