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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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  1.  
    Hi all,

    I'm looking for some advice on installing cladding over EPS insulation.

    My sister has had a small extension built on on her park home. At the moment it is finished in plywood (untreated). The plan is to apply 100 mm EPS EWI on the ply. I have suggested a lapped cladding may be an easier DIY solution than a silicone render.

    So first of all, does the ply need a special primer before the EPS can be fixed with adhesive and plastic "mushroom" type fixings?

    Second, would you foam the boards together at the edges? That's what I've done with EPS insulation in my loft and its very easy, or is there a better way?

    Third, how would you attach the cladding strips? Would it be sufficient to screw straight through the cladding and EPS into the ply, or would vertical battens be needed?
  2.  
    Hi,

    Have a look at this thread

    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16592&page=2#Item_18.

    If you have a void (or to some extent even if you don't) consider the fire risk with the cladding.
    • CommentAuthortony
    • CommentTime3 days ago
     
    +1 fail safe would be a good option, non flammable Insulation and cladding
    • CommentAuthorrevor
    • CommentTime3 days ago
     
    How thick is the ply? If not at least 25 mm I would find the studs to which the ply is fixed and use that as the fixing base. I would cover the insulation with a breathable felt, batten out either vertical or horizontal (battens will secure the membrane) with approx. 35 mm batten and fix cladding to that. This will give you an extra barrier against moisture ingress so if water gets behind the cladding it will dry off. If you look at Kingspan K5 external wall board detailing you will get the drift of how it is done. If you are concerned about fire risk then use a coloured textured cement board cladding instead of wood.
  3.  
    Thin-coat render systems are not that difficult, especially over quite a small area.
  4.  
    Thanks for the suggestions.

    I'm not sure of the ply thickness but it's definitely not as thick as 25 mm. Finding the studs shouldn't be too difficult though.

    I was thinking of a fibre cement cladding like Cedral to be non-flammable. It turns out she doesn't have the EPS insulation ordered yet so K5 could be a better bet.
    •  
      CommentAuthordjh
    • CommentTime3 days ago edited
     
    Posted By: atomicbisfThird, how would you attach the cladding strips? Would it be sufficient to screw straight through the cladding and EPS into the ply, or would vertical battens be needed?

    For our own house (conservatory) we have a breathable membrane over the EPS, then treated softwood vertical battens and then lapped cedar cladding.

    I don't myself worry about the fire risk for a single storey building in the country. The EPS has fire retardant in it.

    Phenolic insulation is the best of the rigid, closed-cell foams from a fire risk point of view. For myself I'd be happy to use either that or EPS. I expect fibre-cement is heavier than timber, so think about how that weight is supported if you choose that.
  5.  
    Posted By: djh
    Posted By: atomicbisfThird, how would you attach the cladding strips? Would it be sufficient to screw straight through the cladding and EPS into the ply, or would vertical battens be needed?

    For our own house (conservatory) we have a breathable membrane over the EPS, then treated softwood vertical battens and then lapped cedar cladding.

    I don't myself worry about the fire risk for a single storey building in the country. The EPS has fire retardant in it.

    Phenolic insulation is the best of the rigid, closed-cell foams from a fire risk point of view. For myself I'd be happy to use either that or EPS. I expect fibre-cement is heavier than timber, so think about how that weight is supported if you choose that.


    Thanks! Are the battens screwed through the insulation to the structure underneath?

    I was reading on the other thread that it could be a good idea to hang the battens from the eaves at the top.
    •  
      CommentAuthordjh
    • CommentTime3 days ago
     
    Yes the battens are screwed through to the studs. I think we used long plasterboard screws since we couln't find anything else at the time. The battens are stood on the surface underneath (paving slabs on edge in our case, with a bit of DPC on top to separate)
    •  
      CommentAuthorfostertom
    • CommentTime3 days ago
     
    Posted By: atomicbisfI was reading on the other thread that it could be a good idea to hang the battens from the eaves at the top.
    At 100mm, possibly not necessary? Anyone got firm guidelines, number of, length of, screws etc?

    Thin coat render, being much lighter than any kind of cladding, gets round this v real problem completely.

    And, apart from fixing cladding battens, you don't need to screw fix the insulation at all - on a good background like ply the right kind of non-expanding foam adhesive is fine alone.
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