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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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    • CommentAuthorCharli
    • CommentTimeFeb 5th 2020
     
    Not quite green building, but was hoping for a bit of advice off people with some building knowledge!

    The felt has blown off my shed roof. It was horrible cheap thin felt and I was going to recover it this summer anyway, I'll just be doing it a bit earlier!
    Timber shed, storage only (no heating), osb roof deck in reasonable condition. Under trees so ends up with lots of leaves and moss on. Gutters constantly full of leaves/acorns/growing saplings.

    I was hoping a metal roof would be the way to go to shed the leaves? And some form of gutter-mesh/device to keep the leaves out- any ideas? I do collect water from this roof to a water butt for the garden.

    Can I attach polyester-coated metal roofing sheets directly to the osb? Is some form of felt/membrane recommended in between to stop condensation affecting the osb?

    A 'green' moss shed roof appealed, but the shed structure would not support this and I don't fancy rebuilding the whole thing at this point!

    Thanks, Charli
    • CommentAuthorrevor
    • CommentTimeFeb 5th 2020
     
    No reason why you cannot do it but I would put treated battens on the osb going down the slope of the roof. No need for felt or membrane, would take care not to let rain get in between the 2 skins, If you can screw the battens to the osb from the inside of the shed so you get a stronger fixing and protect the fixings from rust. The gap under the sheets will allow ventilation and prevent condensation. You could put" hedgehog" leaf gutter brush to stop leaves blocking up the drainage.
    • CommentAuthorSilky
    • CommentTimeFeb 5th 2020
     
    roof membrane is so cheap and easy to fix, for the sake of 10 pounds and an hour of your time it has to be worth the investment, you can get a roll with an adhesive strip on one side, a few staples and then overlap the next piece, go from bottom to top to overlap the joins and any excess fold over the top to cover the join on the other side. My local building merchant will sell me off the roll and it's about 2 Euros per sqm. OSB is not robust enough to get damp imo.
  1.  
    If you are going to put a roof membrane on then it needs to be off the OSB so the build-up would be OSB, counter battens, roof membrane, tile (or other) battens, roofing sheet.

    If you put the membrane directly on the OSB moisture/water will get held there and that will be worse than having no membrane.

    Without the membrane you still need the counter battens.
  2.  
    The garage of the house we recently bought, has plastic coated metal profile roofing, laid not many years ago, over (I think) polythene sheet over osb. It's been a bit of a disaster, the roof is leaking in many places and there's all-sorts of fungus growing on the underside of the osb.

    I think what happened is the profile of the metal collected leaves, it's under a big tree. These filled up the profile and turned to compost so water couldn't drain, the compost stayed wet and held water on the profile. When the compost was deep enough to cover over the raised bit of the profile, water worked through where the sheets overlap (or maybe worked through the fixings). Once under the profile, it couldn't escape so went down through the fixings holes in the polythene and soaked the osb, which later went soft and allowed the fixings to slacken off.

    I'm not sure yet what we are going to do about it....!
    • CommentAuthortony
    • CommentTimeFeb 5th 2020
     
    Why not miss out the osb?
    •  
      CommentAuthordjh
    • CommentTimeFeb 5th 2020
     
    I think the OSB is already there. I don't think you need counter battens if the metal roof is a corrugated type. I think the main take away from WiA's experience is the desirability of keeping the roof relatively clean.

    My roof has the membrane directly on the ply (slightly different to OSB) and then flat metal over the top, but then it is a rather special membrane and not cheap. Does have a good warranty though.
  3.  
    Posted By: tonyWhy not miss out the osb?

    Because it is already there and would probably make a reasonable ceiling if left.
    Posted By: Charliosb roof deck in reasonable condition.
    • CommentAuthorJeff B
    • CommentTimeFeb 6th 2020
     
    Get the polyester reinforced roofing felt. Lasts for eons and practically impossible to rip during installation.
  4.  
    Are you talking about flat panels? The Tata recommended build up is OSB, membrane, panels.
    • CommentAuthorSilky
    • CommentTimeFeb 6th 2020
     
    Yes, it must be a breathable roof membrane
    • CommentAuthortony
    • CommentTimeFeb 6th 2020
     
    I am concerned about where the metal touches the OSB that it will cause condensation in the wood when it is cold with or without a membrane causing it to swell, become damp and start to decay.
    • CommentAuthorBeau
    • CommentTimeFeb 6th 2020
     
    One of our open sheds had a felt roof that disintegrated. I didn't get around to fixing it for over a year and the OSB had swelled up. As a temporary bodge I screwed some corrugated sheets to the OSB when it had dried out a bit and this was probably 10 years ago and its still fine. This is only a log store and I wouldnt have done this for habitable space but it's worked fine.
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