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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthoradam_w
    • CommentTimeJan 24th 2018 edited
     
    Hi guys, with the forthcoming extension plans coming along nicely, I'll be able to obtain a decent 0.20W/m.k through the walls but the rest of the house will still only be in the region of 1.2-1.3 so in order to bring that down to new building regs I'd need to fit 100mm of EWI. The problem is that a single storey extension that was fitted to the rear of the house has only 35-40mm of overhang. Have any of you got any ideas how to resolve this little issue? Thanks in advance, Adam
    • CommentAuthoradam_w
    • CommentTimeJan 24th 2018
     
    See photo below
      20180124_204836.jpg
    •  
      CommentAuthordjh
    • CommentTimeJan 24th 2018
     
    What is the roof construction? Both the structure underneath and the various layers of coverings?

    It looks to be an unusual shape in the photograph. Curved?
    • CommentAuthoradam_w
    • CommentTimeJan 24th 2018
     
    From memory its an 18mm T&G board with the traditional 3 layers of felt, nothing is curved though, see photo below ;
      20180124_212127-1410x1594.jpg
    •  
      CommentAuthordjh
    • CommentTimeJan 24th 2018
     
    Amazing how different everything looks in the second photograph, thanks!

    Are there upstands at the edges, or is it just flat?

    My inclination would be to look at replacing the roof, or perhaps building a new roof with a greater overhang on top of the old one.
    • CommentAuthoradam_w
    • CommentTimeJan 25th 2018
     
    Morning!

    A re-roof is on my long term plans but it will be to replace this flat one with a catslide and two dormers however I don't have enough money to do this the same time as the extension to the side so that'll be in a few years time.

    I've just googled 'EWI Flashing' it took me to this link, https://www.natural-building.co.uk/product/flashing-ewi-eave-cap/ I guess it would go under the guttering (which is to be replaced along with the soffits) just to prevent any water sitting on top of the EWI shelf, what do you think?
  1.  
    This is better than the industry-standard inverted U section which, as far as I can see, relies on a blurge of silicone to keep everything tight for 25 years. Now I am not a betting man....

    Where the NBT-style trim may not work would be if you had, for example, Sheffield-type timber gutters with 75x50 noggins. I have seen examples where the top of the EWI ends up below the internal ceiling height, with connotations for condensation and mould growth.

    Of course your interim arrangement will not connect the EWI with the roof insulation, and when you replace it with a warm roof you will presumably have to put another 'slice' of EWI in at the top, the finish of which may 'bloom', but then maybe you can hide it with the fascia board.

    To others looking at the same solution - beware. I tried to get this trim used recently, but because the wall was far from straight the trim would not fit up behind the already-fitted fascia. If the wall is not straight, see if it is possible to (a) adjust and perhaps (b) fit the fascia to the trim, rather than vice versa.
    • CommentAuthoradam_w
    • CommentTimeJan 25th 2018
     
    Thanks Nic, it seems the way to go, it may even look quite good If I can get it to sit right under my guttering. I plan to use the square white variation so hopefully I wont fall foul of the Sheffield-related issue you've referred to!

    Thanks again,

    Adam
    • CommentAuthorgravelld
    • CommentTimeJan 25th 2018
     
    How big is the flat roof and what's the U? You'll have to dispose of the eaves cap when you eventually upgrade the flat roof... but that's the nature of incremental retrofit (a balance I'm trying to judge myself).

    When you add another slice of EWI on top to replace the cap, assuming a render finish I'm not sure whether this would work - you would have an inevitable crack or use some form of cladding like a fascia board.
    • CommentAuthorgravelld
    • CommentTimeJan 25th 2018
     
    Sorry, just realised that's pretty much what Nick said. :shamed:
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