Oregon Timber Specifications for Cathedral Ceiling

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  1. #1
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    Default Oregon Timber Specifications for Cathedral Ceiling

    All,

    I am a new member who has an 1840s built farmhouse in Tasmania and am seeking assistance with renovations.

    As such I am trying to pick people’s brains to understand the specifics in regard to timber requirements for a vaulted / cathedral ceiling with exposed rafters in one of the rooms and I would very much appreciate assistance if possible.

    Room dimensions are 4200mm * 6420mm. Roof peak is not in the centre of the room as one side of the room was extended a number of years ago - (my hand written sketch and notes below)

    Room will have a Ridge Beam, with exposed Rafters and Rafter ties (no ceiling joist).


    1. Oregon timber Ridge Beam needed to support the cathedral ceiling – ridge beam will span 4200mm. The ceiling will be timber lined, and roof of corrugated iron with insulation and sarking. Suggested dimension would be 240mm * 65mm dressed. Would this be appropriate?
    2. Oregon Timber Rafters 3350 mm and 4212 mm in length (the . Suggested dimension would be either 190mm * 42mm dressed, or 140mm * 42mm dressed. Which of these would be appropriate?
    3. Oregon Timber Rafter Ties on every second rafter. Suggested dimension would be 140mm * 42mm dressed?





    Any feedback as to appropriateness would be appreciated.





    Thanks.
    Attached Thumbnails Attached Thumbnails image-2-.jpg  

  2. #2
    Je pense, donc METRIX's Avatar
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    You need an Engineer to design it for you, my rough calculations show the following.

    Ridge single span 4200, left span 2810, right span 3810 I used 35deg pitch

    Ridge F7 300x100

    Rafters 150x50 and 200x50

    Looks like your pitch is about 46deg, so the timber sizes will get bigger than stated above as these are calculated at 35 pitch.
    Mieux vaut prévenir que guérir

  3. #3
    Old Chippy 6K
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    Default



    Or you could make your life easier & probably cheaper by using LVLs & covering with Oregon or cedar . . .
    Advice from me on this forum is general and for guidance based on information given by the member posing the question. Not to be used in place of professional advice from people appropriately qualified in the relevant field. All structural work must be approved and constructed to the BCA or other relevant standards by suitably licensed persons. The person doing the work and reading my advice accepts responsibility for ensuring the work done accords with the applicable law.

  4. #4
    BIM
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    That is a king post truss, I don't have the current engineering detail but if time permits I can knock one up.
    The problem is engineers are now required to inspect and certify their structural details on site
    and your local council will require certified engineering plans/details
    Post back or leave a PM if you require more info also it would be best to post in the structural section

  5. #5
    BIM
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    Quote Originally Posted by METRIX View Post
    You need an Engineer to design it for you, my rough calculations show the following.

    Ridge single span 4200, left span 2810, right span 3810 I used 35deg pitch

    Ridge F7 300x100

    Rafters 150x50 and 200x50

    Looks like your pitch is about 46deg, so the timber sizes will get bigger than stated above as these are calculated at 35 pitch.

    You are correct in that it needs to be designed by an engineer
    BTW, That is a truss, where the timbers are subjected to Tension (Ties) and Compression (Struts)
    There is no bending (rafters)..hence no span tables. hth

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