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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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    • CommentAuthordeniance
    • CommentTimeMar 22nd 2021
     
    Hi all, me again!
    More basic questions !

    I’ve had a little square extension built , they have just done the shell for me, and I’m going to fit a window in to seal it up , but....... instead of having a plastic windowsill outside id like a stone cill to match the old pennant stone cills of the house

    But how do I go about it so there’s no thermal bridge?

    The wall is blockwork then a cavity with rigid insulation then another block, just standard stuff

    So do I fit cavity closers on the left and right and bottom of opening, then fit the stone cill flush with the outer wall, fit the window so it’s on top of the cill and put insulation behind the back face of the cill?

    I’ve looked at loads of cross section details online but it’s very confusing!

    Or should remove some of the outer block wall to allow the stone cill to sit lower meaning the bottom cavity closer will sit over the cill a bit then fit the window?

    Or do I make some sort of fake stone cill that fits over the outside and just gives the effect of a stone cill?

    Can someone do me a sketch please! Can’t google anymore my brain hurts! Can’t see a way of doing it without a weakness in the insulation
    Cheers all
    • CommentAuthorRobL
    • CommentTimeMar 23rd 2021
     
    These guys make EPS fake stone sills:

    https://passivesills.com/window-sill/
    • CommentAuthordeniance
    • CommentTimeMar 23rd 2021
     
    Posted By: RobLThese guys make EPS fake stone sills:

    https://passivesills.com/window-sill/" rel="nofollow" >https://passivesills.com/window-sill/


    That’s great, ill see if they make one similar to mine, thanks
    •  
      CommentAuthordjh
    • CommentTimeMar 23rd 2021
     
    RobL pointed out: "These guys make EPS fake stone sills"

    Good stuff. :bigsmile: I see that they also offer a product relevant to some other recent threads:

    https://passivesills.com/door-threshold/
    • CommentAuthortychwarel
    • CommentTimeMar 24th 2021
     
    I used genuine pennant stone cills in exactly that situation. I bought second hand ones and disc-cuttered them down to 150mm wide so that their inside edge was flush with the inside edge of the outer leaf blockwork. I cut the blockwork away under the cavity closure, and mortared the cills in such that the lip of the cavity closure was resting on the top inside edge of the sill. then fitted the window as normal.
    I also took the opportunity whilst I was trimming the cills to disc-cutter a V notch as a drip channel on the underside approx 15mm from the front edge.
  1.  
    Center the cills on the outer block.
    • CommentAuthortony
    • CommentTimeMar 24th 2021
     
    Ideally don’t use stone sills but if you must, mitigate the thermal bridging at the sill
    • CommentAuthordeniance
    • CommentTimeMar 24th 2021
     
    Posted By: tychwarelI used genuine pennant stone cills in exactly that situation. I bought second hand ones and disc-cuttered them down to 150mm wide so that their inside edge was flush with the inside edge of the outer leaf blockwork. I cut the blockwork away under the cavity closure, and mortared the cills in such that the lip of the cavity closure was resting on the top inside edge of the sill. then fitted the window as normal.
    I also took the opportunity whilst I was trimming the cills to disc-cutter a V notch as a drip channel on the underside approx 15mm from the front edge.


    Don’t suppose you could explain it a bit more??
    I think I get what you mean but if you get the sill to sit flush with the outer leaf and it doesn’t poke into the cavity at all, and you fit a cavity closer on the bottom piece, where does the window sit? Doesn’t the window have to sit on top of the sill for the window drainage to run out of window face drain and down the sill?

    Could you draw me a sketch by any chance please ?
    • CommentAuthordeniance
    • CommentTimeMar 24th 2021
     
    Posted By: Viking HouseCenter the cills on the outer block.


    What do you mean? So the sill sits flush with the outer leaf and doesn’t poke into the cavity at all or centre the sill over the outer leaf so half the sill is outside and half the sill is poking into the cavity?

    Could you do me a quick sketch by any chance please?
    • CommentAuthordeniance
    • CommentTimeMar 24th 2021
     
    This is a screenshot from the link above

    Do I just replace the insulated sill with my stone cill exactly as this detail or is there a better way?

    I can get a second hand sill to match my ones just need to figure out where it goes, where the window edge sits is what’s confusing me!!
      FC4D6308-2253-473A-8EB4-B8588C4B25D5.jpeg
    • CommentAuthortychwarel
    • CommentTimeMar 25th 2021
     
    Yep that's pretty much it, My windows have small aluminium sub sills so the windows sit straight on the cavity closure centred in the cavity. will try and sketch up.
    • CommentAuthortychwarel
    • CommentTimeMar 25th 2021
     
    image attached
  2.  
    You can replace the insulated cill with a stone cill if you use the detail above.
    • CommentAuthordeniance
    • CommentTimeMar 26th 2021
     
    Posted By: tychwarelimage attached


    Link doesn’t work😣
    •  
      CommentAuthordjh
    • CommentTimeMar 26th 2021
     
    Posted By: denianceLink doesn’t work

    It does for me.
    • CommentAuthortychwarel
    • CommentTimeMar 26th 2021
     
    try this version
      window detail-page-001.jpg
    • CommentAuthordeniance
    • CommentTimeMar 29th 2021
     
    Posted By: tychwareltry this version
      http:///newforum/extensions/InlineImages/image.php?AttachmentID=7863" alt="window detail-page-001.jpg" >


    Thanks!!
    • CommentAuthordeniance
    • CommentTimeMar 29th 2021
     
    I just bought a stone sill from a reclamation yard!!!

    Needs a bit of trimming but I should be able to cut it down so it sits flush with the inside of the cavity!

    Also I just ordered some Kingspan kooltherm 125mm cavity closers, exactly like the ones in the picture!

    Ok so questions!!!, do I just chop and fiddle these things into place like the picture, or do you have to glue them with silicone? Do you have to use foam to make sure that the cavity closer foam sits flush on the cavity wall foam board?
    Do I have to wrap the stone cill in a little tray of dpc?

    As soon as I get this done, hopefully this weekend I’ll order the window, so last question is how do I air seal this window and it’s opening?

    The plan is to fit, sill in outer leaf, add cavity closer, sit window in the opening on packers, have a nice foamed seal around window, but what else do I do to air seal the breeze blocks in the inner leaf? Do I need to order special tape or something?

    I know these are basic questions but I’ve got nobody else to ask!
    Thanks all!
      19189E69-9D99-49B9-AA56-FCCFCCAE70D1.png
    •  
      CommentAuthordjh
    • CommentTimeMar 29th 2021
     
    The photo you posted appears to come from the product brochure, which also includes installation instructions (p7 et seq).
    • CommentAuthordeniance
    • CommentTimeMar 29th 2021
     
    Posted By: djhThe photo you posted appears to come from the product brochure, which also includes installation instructions (p7 et seq).


    The instructions say just pop it in place and fix with screws but that seems a bit lazy, what if the insulation isn’t straight in the wall?, what if there are gaps?, how do I stop air leaking past it?

    Just want to get it right the first time and I know my wall is not as perfect as the one in the picture😂
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