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rafters at 2400mm cts

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  1. #1
    Golden Member manofaus's Avatar
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    Default rafters at 2400mm cts

    I have worked out that I can run 190x45 rafters at 2400mm cts for the span I have.
    Could I then have another rafter (non load bearing, just aesthetics) in the middle? The reason I ask is that the max you can have rafters without a collar tie or ceiling joist is 1200cts. Im guessing this other timber at 1200cts is not technically a rafter?
    Im trying to have a heavy set king post truss (2400cts) Its not technically a truss in that it is designed as a pair of rafters with a ceiling joist, and then with a decorative rafter between. I don't want trusses at 1200cts it would look too busy.
    sorry for the ramble.

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    Quote Originally Posted by manofaus View Post
    I have worked out that I can run 190x45 rafters at 2400mm cts for the span I have.
    Could I then have another rafter (non load bearing, just aesthetics) in the middle? The reason I ask is that the max you can have rafters without a collar tie or ceiling joist is 1200cts. Im guessing this other timber at 1200cts is not technically a rafter?
    Im trying to have a heavy set king post truss (2400cts) Its not technically a truss in that it is designed as a pair of rafters with a ceiling joist, and then with a decorative rafter between. I don't want trusses at 1200cts it would look too busy.
    thats sounds highly unusual, what happens with the ceiling joists? What you have explained excludes them, if you don't have ceiling joists for each rafter along with the collar tie then you have an uncoupled roof & that is outside the standard and then your roof design and rafter size is not applicable , which would have to be engineer designed.
    inter

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    What about roofing battens?
    What size batten would you need to span 2400mm safely?
    Something sounds a little off in the description; plans?
    Sounds a bit Medieval and castle like
    "A big boy did it and ran away"

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    Golden Member manofaus's Avatar
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    Thanks guys. The standard does cover non-coupled roof designs. 7.2.19. I have to use a ridge beam and treat it as a cathedral roof design.

    Fyi a 140 x 45 mgp10 at 600cts will span 2.4m with a ceiling weight of 12kg/m2!
    It's not that medieval, but the cellar is...

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    I'm intriqued because I use 140*45 on edge as flooring joists to span 2400; and I'm wondering how you will deal with batten rotation.
    "A big boy did it and ran away"

    Legal disclaimer denying responsibility to be inserted here.

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    Golden Member manofaus's Avatar
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    I'm guessing it's because it's just for the internal lining being a joist. I think 65mm top hat would span that distance if you were after roofing battens.
    Because of the ridge beam I'm going with 200mm purlins perhaps. I've only just finish the slabs and piers. To be continued....

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    Well that explains a bit more, the collar ties pointed to a coupled roof. Any collar ties or King posts are just decorative but must be allowed for in the roof loads.
    inter

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