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Firring strips on joists

Discussion in 'Building' started by Speedyrazor, 26 Aug 2020.

  1. Speedyrazor

    Speedyrazor

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    Hi, I am using firring strips running in the same direction of the joists, sitting directly on top of joists, see picture below. Just checking this is ok, and fixing with wood glue and screws?
     

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  3. 23vc

    23vc

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    Doubt the glue is necessary, could nail if easier
     
  4. oldbutnotdead

    oldbutnotdead

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    As above. Don't use too many nails/screws, just ups the odds of you hitting them when fixing the roof covering
     
  5. big-all

    big-all

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    keep in mind you must start at the back and work forward cutting the point off all but the first one assuming the slope is towards the point
     
  6. ^woody^

    ^woody^

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    The noggins and fascia is not right - they are following the slope of the roof by the looks of things.

    Also, take the furrings right to the roof edge not just stopped at the joist end. And don's feather furrings down to nothing, everyone does and you end up with a flat or uneven end and ponding on the roof at the eaves when the deck boards run over and don't sit on the furring. 5 or 10mm is preferred.

    And at the other end, make sure they are high enough for the span to give you a proper fall - again most people just rip down a 3 or 4x2 corner to corner, and that's crap.
     
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  7. big-all

    big-all

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    just noticed your roof slopes from the point back so your facial will decrease in height as you go sideways from the point either side as the firrings are reduced in height as they are cut shorter
     
  8. Speedyrazor

    Speedyrazor

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    Thanks for the pointers Woody. The first thing to say is this build is an odd shape, to make the most use of the space in my garden (see my Sketchup video ).
    The fall, and gutter, is towards the long wall at the back.
    The noggins and facia are for the overhang, so should follow the slope of the roof, please elaborate on why this is incorrect. (EDIT - after some thought, I see what you mean, these should have a furring strip on them running perpendicular to the noggins.)
    Good advice about taking the furrings to the roof edge, not just the joists, noted, thanks.
    Longest joist is 6m, furrings go from 90mm to 0, which is a 1:67, minimum required fall for the EPDM rubber roof is 1:80.
    I thought a PVA wood glue, with nails / screws, would help the bond between the joist and the furrings.

    I appreciate all the comments.

    Kind regards.
     
    Last edited: 27 Aug 2020
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  10. big-all

    big-all

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    usually you have 2.5-3 times material thickness to for the securing screw
    so most off the higher 1/3 firrings will need perhaps 130mm screws to give you 40mm+grip the equivilent to 18mm sheet with screws sunk in perhaps 2mm to use 45mm screws
    the next 1/3 will need 4" or 100mm
    in otherwords you are just attaching the firring as a spacer but secured to the same level off grip required to hold the roof sheet material to 2.5-3 times with glue under firring making up the odd bit off short screw length
     
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  11. ^woody^

    ^woody^

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    Noggins should be level with the underside of the joists.

    Unless you are designing the roof overhang to be less deep than the main roof stucture, in which case they may well be higher than the bottom of the joists but still level, and not following the furring line.
     
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  12. SS-ProjectBuild

    SS-ProjectBuild

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    How did you get on with this speedyrazor? Im about to do something similar but i am having a 2 way fall.... going to each side of my outbuilding.....my firrings will sit on the joists also and run from 94mm-0mm over 4.8m (a bit like a miniature apex).

    What screws did you use to fix the firrings down and id you use any glue?
    thanks.
     
  13. Speedyrazor

    Speedyrazor

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    Hi, Yes, mine worked out OK, roof completed. I used nails (ring shank nails with nail gun) and wood glue, for extra hold and strength. I have a YT channel with a few videos and info, https://www.youtube.com/channel/UCPI8uTpbKKyAc_ZNckf_1nw?view_as=subscriber
     
  14. SS-ProjectBuild

    SS-ProjectBuild

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  15. Speedyrazor

    Speedyrazor

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