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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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    • CommentAuthorgravelld
    • CommentTimeFeb 6th 2018
     
    My latest detail builds on my lean-to eaves detail thread. I want to understand how the ridge should be built.

    I have a number of lean-tos around the house. Although I am not insulating the upper roof, I am insulating all walls so it seems like I should do the lean-tos at the same time.

    The existing property is some 1950s cavity wall, some extensions.

    See the attached detail. Highlights:
    - Insulation installed between and over the lean-to rafters, as before
    - The tiles rest on tile battens on counter battens, membrane underneath on top of the insulation
    - The flashing from the wall to the roof tiles is cut into the EPS.
    - The AT layer is the OSB taped to the existing external render layer.
    - I haven't drawn anything for how the ridge is attached to the wall... I don't know how this connects, and I hope that as this is a warm roof it, to an extent, doesn't matter because AT and insulation is outbound of it.

    Questions:
    - How does the roof membrane connect to the wall, if at all?
    - How should ventilation work at the ridge? I have eaves ventilators as per http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15506&page=3#Comment_265477
    - I have "cut" the flashing into the EPS... is this right and what products are used to fasten this?

    Any feedback welcome.
      ridge-lean_to.JPG
  1.  
    ''- I have "cut" the flashing into the EPS... is this right and what products are used to fasten this?''

    Natural Building Technologies have a bead with a 'tuck-in' for flashing lean-to roofs. It does not show on their web-site, but I have seen one at their warehouse - honest! Ring them and ask for Matt.
    • CommentAuthorgravelld
    • CommentTimeFeb 8th 2018
     
  2.  
    Ah! Yes, that one. Must have missed it.
  3.  
    To avoid bridging the insulation, the rafters should be supported from below by a ledger fixed to the wall. The sarking membrane and the flashing should be fixed under a render bead and the batten cavity ventilated with a "ventilated abutment system". The choice of system will depend upon the slates/tiles chosen, but here's one as an example:

    https://www.marleyeternit.co.uk/Roofing/Fittings-And-Accessories/Dry-Fix-and-Ventilation/Top-abutment-ventilation-system.aspx

    David
    • CommentAuthorgravelld
    • CommentTimeFeb 9th 2018 edited
     
    Posted By: gravelldNot this then?https://www.natural-building.co.uk/product/pvc-render-facade-flashing-bead/" rel="nofollow" >https://www.natural-building.co.uk/product/pvc-render-facade-flashing-bead/
    Can I see if I understand this?

    The bead is a "h" shape and is fastened (how?) on the bare insulation (does the insulant matter or is it wood fibre only given the source?).

    The flashing (and membrane, thanks David) is inserted in the space at the bottom of the "h"? How is it held in place?

    The render mesh over the insulant is then installed and covered with render.

    Have I got that right?
    • CommentAuthorgravelld
    • CommentTimeFeb 9th 2018
     
    Posted By: davidfreeborough
    https://www.marleyeternit.co.uk/Roofing/Fittings-And-Accessories/Dry-Fix-and-Ventilation/Top-abutment-ventilation-system.aspx" rel="nofollow" >https://www.marleyeternit.co.uk/Roofing/Fittings-And-Accessories/Dry-Fix-and-Ventilation/Top-abutment-ventilation-system.aspx
    Looks good, thanks.
    •  
      CommentAuthordjh
    • CommentTimeFeb 9th 2018
     
    Posted By: gravelldThe bead is a "h" shape and is fastened (how?) on the bare insulation (does the insulant matter or is it wood fibre only given the source?).

    The flashing (and membrane, thanks David) is inserted in the space at the bottom of the "h"? How is it held in place?

    The render mesh over the insulant is then installed and covered with render.

    NB These answers are just my guesses - ask the manufacturer for actual answers.

    It's tacked into place however you like (tacks or glue, I expect). It's secured in place by the render itself.

    The flashing is just pushed up into place and held by its stiffness.

    The mesh is part of the bead, I expect.
    • CommentAuthorgravelld
    • CommentTimeFeb 10th 2018
     
    Ah right. Thanks, sounds likely.
    • CommentAuthorgravelld
    • CommentTimeFeb 12th 2018
     
    Thanks; here's where I've got to.
      lean-to_ridge.JPG
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