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Housing - Renovation: Applying cladding to EPS insulation

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  1.  
    • CommentAuthoratomicbisf
    • CommentTimeJun 28th 2020
     
    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
    • CommentTimeJun 28th 2020
     
    +1 fail safe would be a good option, non flammable Insulation and cladding
    • CommentAuthorrevor
    • CommentTimeJun 28th 2020
     
    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.
  5.  
    Thin-coat render systems are not that difficult, especially over quite a small area.
    • CommentAuthoratomicbisf
    • CommentTimeJun 28th 2020
     
    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
    • CommentTimeJun 28th 2020 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.
    • CommentAuthoratomicbisf
    • CommentTimeJun 28th 2020
     
    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
    • CommentTimeJun 29th 2020
     
    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
    • CommentTimeJun 29th 2020
     
    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.
  11.  
    OK another question.

    The house has very little in the way of eaves, probably too little for anything but the most minimal insulation thickness.

    Neighbours have had EWI installed up to just below the bottom of the gutters with some sort of PVC capping on top to get round the lack of eaves.

    If it were me I'd investigate extending the eaves a little. How would you go about that? I was thinking of prefabricating some timber eaves one tile wide and screwing them to the top of the walls, then adding an extra row of Decra type tiles.
    •  
      CommentAuthordjh
    • CommentTimeJul 3rd 2020
     
    Posted By: atomicbisfNeighbours have had EWI installed up to just below the bottom of the gutters with some sort of PVC capping on top to get round the lack of eaves.

    That's doable but you absolutely need to get the details right. There was an infamous case in Preston where it wasn't done right with disastrous results.

    If it were me I'd investigate extending the eaves a little. How would you go about that? I was thinking of prefabricating some timber eaves one tile wide and screwing them to the top of the walls, then adding an extra row of Decra type tiles.

    Extending the eaves sounds like a better idea to me. I believe it is usually done by extending the rafters with sprockets, and raising the line of the roof a little near the eaves to create space if necessary.
    • CommentAuthoratomicbisf
    • CommentTimeJul 4th 2020 edited
     
    What do you mean by rafter sprockets? It is a park home so I'm not even sure it has rafters. If it does they will be of minimal thickness. The tiles are Decra or similar - pressed steel with some sort of mineral coating so lightweight.
  14.  
    I was thinking of making something like a ladder out of say 140 x 38 mm timber. The "rungs" would be cut at an angle to create the slope. Roughly 370 mm wide, the width of a strip of Decra tiles. This would be screwed into the top of the wall and another row of tiles put on. OSB unerneath and/or on top would provide racking strength.
      eaves.jpg
    •  
      CommentAuthordjh
    • CommentTimeJul 4th 2020
     
    A sprocket is just an extra piece of wood fastened to the side of an existing joist to make it longer. There are various variations and it is often set an angle so as to flair the bottom of the roof out.
  16.  
    FosterTom posted good pics on the 2nd page of this thread.

    Also became apparent how important it is to join the EWI to the roof insulation otherwise the thermal bridge negates lots of the effect of the EWI.

    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15603&page=2
  17.  
    <blockquote><cite>Posted By: WillInAberdeen</cite>FosterTom posted good pics on the 2nd page of this thread.

    Also became apparent how important it is to join the EWI to the roof insulation otherwise the thermal bridge negates lots of the effect of the EWI.

    <a href="http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15603&page=2" rel="nofollow">http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15603&page=2</a></blockquote>

    I don't know what kind of roof insulation there is - almost certainly some sort of loft level insulation but unfortunately the loft space is not accessible without taking the roof off (too small to get into because of the small size of the house and shallow pitch of the roof). Having said that it's probably fairly poor considering the age of the house (~30 years).
    •  
      CommentAuthorfostertom
    • CommentTimeJul 6th 2020 edited
     
    Posted By: WillInAberdeenFosterTom posted good pics on the 2nd page of this thread
    It wasn't on this thread - can you find which thread it was? Or I cd re-post it here if you describe it?
  19.  
    Link is in my post above, Tom, thanks!
    •  
      CommentAuthorfostertom
    • CommentTimeJul 6th 2020
     
    Oh I see - ta!

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