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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.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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  1.  
    Can anyone recommend a type of glue to stick several 8x4 sheets of polystyrene together to make one extra thick sheet?
    Needs to be waterproof, and as strong as the polystyrene is, nothing that would degrade the ps. Ideally not too expensive over that area.

    Full disclosure: it's for a boat not a house...!

    Thanks in advance!
    • CommentAuthorMike1
    • CommentTimeApr 1st 2019
     
    I've used PVA to glue polystyrene together without problem - it does come in waterproof grades at builder's merchants (which I guess means properly waterproof, not just water resistant) and it's cheap.

    Less certain about it being 'as strong as' polystyrene, though I imagine it could be. You could do a DIY shear test...
    • CommentAuthorandyman99
    • CommentTimeApr 2nd 2019
     
    I use expanding foam that is designed for fixing sheet material. Screwfix do one (green can) but there are others.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 2nd 2019
     
    Bit of investment, but a pressure-keg hose and gun of spisder-web spray contact adhesive. It's vapour-impermeable, so no more than 25% coverage on both surfaces will leave 75% x 75% = 56% of the interface still 'open'.
    • CommentAuthorbhommels
    • CommentTimeApr 2nd 2019
     
    Posted By: andyman99I use expanding foam that is designed for fixing sheet material. Screwfix do one (green can) but there are others.

    Second the expanding foam option. I have used Ceresit CT 84 for EPS boards and it works quite well. It is low expansion so can be used in thin-ish layers.
    • CommentAuthorrevor
    • CommentTimeApr 2nd 2019
     
    Before you think of using PVA or any other adhesive check out this website it gives the detail of the grade of glue to use for particular circumstances. A waterproof adhesive needs to be D4. Rare to find a PVA that is.

    http://www.constructionchemicals.co.uk/blog/2015/07/13/what-are-d1-d2-d3-d4-adhesives/
  2.  
    30-odd years ago I used EVA. My home-made XPS/plasterboard composites have not fallen apart yet, and I have a whole house-full (and a house full of thermal by-pass, but that's down to me and the methods current 30 year ago).

    Equally, though, much as I like boars, I have not tried boating on my plasterboard laminates. I was informed by the manuf (?Evode?) that EVA was fully waterproof.
  3.  
    If I was using EPS as buoyancy in a boat I would want it in a compartment that could contain the EPS as buoyancy without relying on glue to hold it together. I would hope that if the worst happened the EPS would be contained within the boat and not float of over the horizon.

    For glue, I tried an experiment with 2 bits of EPS glued together using a thin layer of the standard EPS EWI adhesive (cement based) and found that the EPS broke up before the EPS/adhesive interface failed so the stiction was stronger than the EPS.
    • CommentAuthorbhommels
    • CommentTimeApr 2nd 2019
     
    Posted By: Peter_in_Hungary
    For glue, I tried an experiment with 2 bits of EPS glued together using a thin layer of the standard EPS EWI adhesive (cement based) and found that the EPS broke up before the EPS/adhesive interface failed so the stiction was stronger than the EPS.

    I almost forgot that I did the same test on the Ceresit foam, with similar outcome. The lambda value of the foam is a lot better than cement adhesive BTW, if that is of any importance.
  4.  
    Posted By: bhommelsThe lambda value of the foam is a lot better than cement adhesive BTW, if that is of any importance.

    For the 2 or 3 mm of thickness it probably makes little to no difference
    • CommentAuthorbhommels
    • CommentTimeApr 3rd 2019
     
    Posted By: Peter_in_Hungary
    Posted By: bhommelsThe lambda value of the foam is a lot better than cement adhesive BTW, if that is of any importance.

    For the 2 or 3 mm of thickness it probably makes little to no difference

    Depends on the orientation of the seam /pedantic
    •  
      CommentAuthorfostertom
    • CommentTimeApr 3rd 2019
     
    Posted By: Nick Parsonsmuch as I like boars, I have not tried boating
    e.g. the Severn boar?
  5.  
    Oops! Don't get me started on rivers! Sincerely yours, the Severn Bore:bigsmile:
    • CommentAuthorTimSmall
    • CommentTimeApr 3rd 2019 edited
     
    Polyurethane wood glue works well, but expansion on curing can be a problem. Ms polymer (cheapest to buy as flooring adhesive) is also good. Both are recommended by polystyrene manufacturers.
  6.  
    Thanks all for the helpful advice!

    P-i-H, agree on the buoyancy compartment! most of the boats I had have airtight bulkheads to create several buoyancy tanks, so traditionally no foam was required. This time the project is buoyancy blocks for open canoes, the sheets will be shaped and glued into solid blocks, which will be strapped into the bow and stern with webbing and protected with synthetic canvas.
    • CommentAuthorgoodevans
    • CommentTimeApr 5th 2019 edited
     
    I would go for a foam adhesive from a gun designed for EWI - it has the advantage in that you can cut/melt the adhesive with the eps after it is glued. The adhesive is as strong as the underlying EPS and obviously designed for external use. Also, go for a graded EPS (e.g. EPS70 for floor or wall insulation) to ensure you don't get a lightweight EPS without strength.

    (edited for readability!)
    •  
      CommentAuthorfostertom
    • CommentTimeApr 5th 2019
     
    Posted By: goodevansyou can cut/melt the adhesive with the polystyrene sticks as good as the underlying EPS
    Sounds interesting but are some words missing? Makes no sense.
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