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timber joists for a 6M span?

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  • 06-06-2020 6:42pm
    #1
    martco
    Registered Users Posts: 423 ✭✭


    I'm trying to figure out roof joists for a simple workshop I'm building.

    The tricky bit is that it's 6M wide span (x6.5M long) BUT I want to achieve an open plan floor and definitely avoid using steel somehow.

    I intended to make the roof deck out of OSB + GRP which I'm hoping will help keep the weight at a minimum...I can't see the need to be ever on the roof itself typically bar the building of it and an odd bit of maintenance but I'm aware of snow etc.

    I'd love to get away with using 6x2 C16 @400mm centres...I know myself the span tables say NO even if C24 but I'm also thinking they are very over estimated....mind I'd hate to end up with a sag :)

    the other thing is the length - I only ever see likes of Chadwicks carry 5.4M max though I'm thinking someone must cut longer than this surely


    has anyone on here ever tried to span 6M with 6x2 and got away with it?


    ta


Comments

  • Options
    #2
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    As per forum charter we can’t offer structural advice


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    #3
    The_Chap
    Registered Users Posts: 493 ✭✭The_Chap


    martco wrote: »
    I'm trying to figure out roof joists for a simple workshop I'm building.

    The tricky bit is that it's 6M wide span (x6.5M long) BUT I want to achieve an open plan floor and definitely avoid using steel somehow.

    I intended to make the roof deck out of OSB + GRP which I'm hoping will help keep the weight at a minimum...I can't see the need to be ever on the roof itself typically bar the building of it and an odd bit of maintenance but I'm aware of snow etc.

    I'd love to get away with using 6x2 C16 @400mm centres...I know myself the span tables say NO even if C24 but I'm also thinking they are very over estimated....mind I'd hate to end up with a sag :)

    the other thing is the length - I only ever see likes of Chadwicks carry 5.4M max though I'm thinking someone must cut longer than this surely


    has anyone on here ever tried to span 6M with 6x2 and got away with it?


    ta

    Pm me I had a 9m x 6m (Internal area) garage built last year

    Just to add we spanned the 6m with 6.6m 9x3 timber at 300mm spacing, we were going to use 9x2 but I wanted no bounce on the floor above for storage. It’s solid as a solid thing could be.


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    #4
    Lumen
    Registered Users Posts: 31,009 ✭✭✭✭Lumen


    I spanned 5m with a DIY laminated 300x150mm Douglas Fir ridge beam but this is flat, right?

    Deep section timber is expensive. Anything over about 225mm.


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    #5
    landcrzr
    Registered Users Posts: 150 ✭✭landcrzr


    Go for trussed beams, sometimes called open web joists.


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    #6
    Dudda
    Registered Users Posts: 1,541 ✭✭✭Dudda


    landcrzr wrote: »
    Go for trussed beams, sometimes called open web joists.

    These are what you need but I've heard them called timber i joists. I've used them on timber frame houses with very impressive spans that had a grass roof on top. Lightweight and affordable is very long lengths.

    Something like this which I just found on Google
    https://www.woodconcepts.ie/products/i-joists


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