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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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    • CommentAuthorSarahLW
    • CommentTimeNov 21st 2023
    Hi Everyone

    Hoping you wonderfully knowledgeable people can make sure I can repair holes in my eps, with silicon render.

    I recently changed my internet provider and to cut a long story short I have just realised that I now have two holes in my external wall insulation through to the brick where a m8 screw has been stuck in (wiggled around a lot) and removed.

    Should I just use expanding foam and cut off any that expands out the hole?

    Also any recommendations for new fixings in future, on research I can see two options.

    Heavy duty, drill a hole through insulation and into the brick behind insert some sort of tube to protect the insulation and then a normal fixing into the brick behind. I found the following products

    tube only by swifix at the ewi store
    complete solution by Fischer Thermax

    They both also do a screw-in plastic grip for things like cable ties that only goes into the eps.

    Has anyone used either system and got any feedback?
    Posted By: SarahLWShould I just use expanding foam and cut off any that expands out the hole?

    Yes, that is what I have done but added a bit of left over thin film render over the top to protect the foam. (It degrades in sun light without covering).

    The fixings into EWI or through EWI to the bricks very much depends upon the weight to be supported. e.g. cable fixings and an outside light I have used EWI fixings (but IMO the light was about the limit) Gutter down pipe I fixed through to the real wall. For the down pipe I just used a long enough pipe support screw with a normal plastic rawlplug through to the wall.

    I can't get excited about any additional heat loss due to the occasional fixing through to the wall.
    • CommentAuthorsgt_woulds
    • CommentTimeNov 22nd 2023
    Important to ensure that driven rain cannot be forced into any penetration and get behind insulation.

    If it helps I have a document I send out for EWI fixings suggestions.

    Loadings are based on woodfibre density so need to be checked with manufacturer.
    • CommentAuthorSarahLW
    • CommentTimeNov 25th 2023
    Brilliant thank you
    • CommentAuthorsgt_woulds
    • CommentTimeNov 29th 2023
    When using spiral fixings into my EWI I screw in most of the way and then apply some clear CT1 (construction mastic) around the rim before screwing fully home. It's the best glue/mastic I've ever used and no way that rain will get in. On the downside, you'll never be able to remove it again either!

    The mastic leaves a permanent flexible bond and consolidates any crumbly edges in the render.

    A couple of things I've learned using these nylon spiral fixings:

    1) Make sure whatever you fix will cover the large plastic screw head as otherwise, it can look a bit rubbish.

    2) If fixing into woodfibre EWI pre-drill with a smaller bit and use a hoover to clear the hole

    3) Expect the first screw you put in the grind up the thread against the render on the way in.
    Chuck it away and use another one. Never attempt to get a duff nylon fixing all the way in - they WILL jam.
    They can be a right pig to get out again when they jam.

    4) Buy twice as many fixings than you actually need due to point 3.
    • CommentAuthorwookey
    • CommentTimeDec 21st 2023
    Yes filling the hole with foam is good, but the surface needs covering with something to keep the UV off. Ideally matching render.

    For fixings I've used a lot of fischer FID50s into woodfibre (not EPS) and they are pretty solid. They are holding up my soil pipe and drainpipes, and a plastic block onto which an outdoor tap is mounted. They will not be as good in EPS as it's much less strong but may still be adequate. There is a FID100 version which of course holds better.

    I second sgt_would's advice to use some goop under the head as it is screwed in. I've been using coloured silicone that matches the render which works really well. I would use coloured modified silane goop but have not found any suppliers doing a decent range of colours for that yet. I have not had any trouble with the render damaging the fixings. I have silicone render - perhaps others are thicker/gravellier? I did not need to pre-drill either. (That will depend on your board density).

    I've not yet used any stand-off fixings that go all the way through to the wall (because the FID50s work so well) , but either of the suggestions you posted seem fine and would be the sort of thing I'd pick should I need to attach something sufficiently heavy/loaded.
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