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Green Building Bible, Fourth Edition
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    • CommentAuthordelprado
    • CommentTime4 days ago
     
    If you have to use them, in a renovation, is there any options out there that minimise bridging?

    Ancon Teplo range

    https://www.ancon.co.uk/products/wall-ties-restraint-fixings/cavity-wall-ties/ties-for-brick-to-block-construction
    • CommentAuthortony
    • CommentTime4 days ago
     
    They are good, I used them, someone was selling left over ones on here recently
    • CommentAuthordelprado
    • CommentTime4 days ago
     
    I am suprised you used them Tony - arent they a significant compromise still? They are still a thermal bridge after all
    • CommentAuthortony
    • CommentTime4 days ago
     
    Bassalt fibre, verylike fibreglass with lumps, as good as it gets, something has to tie the masonry s kind together and I wouldn’t use metal ties, tried for nylon but not made long enough for my 300mm cavity.
    •  
      CommentAuthordjh
    • CommentTime4 days ago
     
    Posted By: delpradoI am suprised you used them Tony - arent they a significant compromise still? They are still a thermal bridge after all

    As Tony says you have to tie the wythes together somehow. There are cavity-walled passivhaus and they use those ties; it's all a compromise but you just have to do better eleswhere - make the cavity wider or whatever.

    Of course simplest is not to use cavity-walled construction, but people in this country are obsessed with it.
    • CommentAuthordelprado
    • CommentTime4 days ago
     
    Denby Dale used these ties (and so my concerns have evaporated). There is an interesting research paper which talks about Denby and in it was this fact which I thought was interesting

    in Austria or Germany (and the former almost has exclusively timber while the latter uses solid masonry, in each case externally insulated). And also interesting that cavity is still common in Benelux and Denmark.
    • CommentAuthorDonkey
    • CommentTime4 days ago
     
    <blockquote><cite>Posted By: tony</cite>They are good, I used them, someone was selling left over ones on here recently</blockquote>

    It was Woodgnome who was selling them.
    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12994
    • CommentAuthordelprado
    • CommentTime4 days ago
     
    Thanks. I need 200mm long and only 35. They come in boxes of 55 so ordered from TP yesterday
    • CommentAuthorTimSmall
    • CommentTime3 days ago edited
     
    This stuff is supposed to do away with the need for cavity wall ties (one of its uses is as a remedial wall tie alternative).

    http://walltite.basf.co.uk/applications/wall-applications/masonry-cavity-wall-insulation

    ... giant brick SIP ! The video on that page is interesting to watch. It'd be good to keep an eye on the installers too.

    I think the same system can be used to fill residual cavities too, which might be a good thing to do for PIR-filled new build walls to stop thermal bypass.
    • CommentAuthorMike1
    • CommentTime3 days ago
     
    Posted By: TimSmallThis stuff is supposed to do away with the need for cavity wall ties (one of its uses is as a remedial wall tie alternative).


    It's an interesting product (other are available, such as Isothane Technitherm), however omitting wall ties would mean that until the insulation was installed the cavity wall would not be structurally sound - which could endanger the building (or maybe just the external leaf if the internal leaf has sufficient support from cross-walls) if the wind picked up during construction, for example.
    • CommentAuthorTimSmall
    • CommentTime3 days ago
     
    It is permissable to put in lower strength structural support during construction, on the grounds that designing for a once in 200 year wind storm during a 1 month construction window is not justified, but I agree that this needs to be considered. I wonder if temporary ties (shuttering style) would be viable?
  1.  
    For new build would it be acceptable to install the product, say, half a floor at a time? At least then you could confirm a good fill and it would aid the structural soundness of the build.

    For retro fit a quick calculation would seem to show that a cavity wall would get down to about 0.35 U value or better depending on the cavity width. IMO a fairly decent figure for a retro-fit without going too much over the top. Of course it depends upon the costs........
    •  
      CommentAuthordjh
    • CommentTime3 days ago
     
    Posted By: Peter_in_HungaryFor new build would it be acceptable to install the product, say, half a floor at a time? At least then you could confirm a good fill and it would aid the structural soundness of the build.

    I expect the BBA covers that. I can't be bothered to check :bigsmile:

    For retro fit a quick calculation would seem to show that a cavity wall would get down to about 0.35 U value or better depending on the cavity width. IMO a fairly decent figure for a retro-fit without going too much over the top. Of course it depends upon the costs........

    The BBA certs include U-values for various cavity widths.
    • CommentAuthorMike1
    • CommentTime2 days ago edited
     
    Posted By: TimSmallIt is permissable to put in lower strength structural support during construction, on the grounds that designing for a once in 200 year wind storm during a 1 month construction window is not justified, but I agree that this needs to be considered.

    Maybe, but don't underestimate the power of the wind, or the lateral weakness of unreinforced brick walls.

    The wind was only gusting at 'up to 69mph' when the Oxgangs Primary School wall collapsed in January 2016 - that's strong but not rare (https://www.metoffice.gov.uk/public/weather/climate-extremes/#?tab=climateExtremes), and that wall was tied together, albeit not adequately.
    • CommentAuthorTimSmall
    • CommentTime2 days ago
     
    <blockquote><cite>Posted By: Mike1</cite>don't underestimate the power of the wind, or the lateral weakness of unreinforced brick walls</blockquote>

    Info on recommendations for wind force calculations for temporary works are given on page 11:

    https://www.twforum.org.uk/media/47604/tw14.030__en_pt1_issued_july14.pdf
    •  
      CommentAuthorfostertom
    • CommentTime2 days ago
     
    With wind loads, which are generally hugely underestimared, I thing of a yacht sail - how much pressure does that area experience, which when resoved at quite a low-mechanical-advantage angle, can force the hull through water and waves at tens of mph?
    • CommentAuthordelprado
    • CommentTime2 days ago
     
    As a secondary question, why would anyone (Tony) build a cavity build house from scratch?
    • CommentAuthortony
    • CommentTime1 day ago
     
    Only idiots!

    I sometimes think of my walls as solid 100mm recycled aggregate block walls with external insulation, 300mm r32 batts and a brick skin for the cladding.

    My inner skin is air tight unlike most cavity walls, wet plaster hermetically sealed round all openings and a tony tray to keep wind out from under the floors.


    Let’s talk about blob and dob now that is idiotic
    • CommentAuthordelprado
    • CommentTime1 day ago
     
    If I was building from scratch I think I'd still use masonry, even thugh passiv haus advocates seem to suggest timber frame is easier, but I'd use some crazy thick blockwork, like that 300mm stuff, then external insulation rendered.

    Although my real dream is actually some sort of old looking house, maybe stone with a thatched roof, but passiv...
    • CommentAuthortony
    • CommentTime1 day ago
     
    nice.
    • CommentAuthormarsaday
    • CommentTime1 day ago
     
    If building from scratch how do you not use cavity ? For me i would like the external face to be brick or stone. I would want an oak frame ideally.
    • CommentAuthorMike1
    • CommentTime1 day ago edited
     
    Posted By: marsadayIf building from scratch how do you not use cavity ? For me i would like the external face to be brick or stone.

    Using brick slips / stone slips / stone cladding.
    • CommentAuthorgravelld
    • CommentTime1 day ago edited
     
    Walltite can be used as a replacement for cavity ties? Wow.
    • CommentAuthorPord
    • CommentTime1 day ago
     
    Strawbale - cheap material, thermally efficient and no cavity required.
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