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  1. #1
    Join Date
    Sep 2010

    Default Deck and Awning Design Help

    Hi everyone, my first post here.

    I am designing and building a deck and awning for the first time and I would like to hear some comments before I get the orders in.

    The dimensions are: 13.4m by 4.1m.

    1. The posts are 1.8m apart. so what size bearers should I use if I am planning on a continuous span of 3.6m across two spans. (post)1.8m(post)1.8m(post)
    I went to one of the timber yards and they said 90X45mm Hardwood F27. It seems a bit small in depth to me so can someone confirm with me please? (ps. its a low rise deck so a small depth bearer is easier to work with)

    2. The joists are 450mm apart with span of 1.8m and 2m depending on location with 400mm overhang. 400mm (post) 1.8m or 2m (post) 1.8m (post)100mm
    Again, the advice is to use 90X45mm TP F7

    3. The Awning is supported by 100X100mm Pine Posts up to 2.9m high. I will use some sort of policarbonate roofing on top. THe question is is the 100X100 pine posts stiff enough for that height.

    4. The Beam which supports the rafters for the awning has a span of 3.6m. I am thinking of using 175X75mm TP F7.

    5. Rafters with a span of 3.8m and spaced 1.2m apart from each other. (pitching board)3.6m(post)200mm overhang. Thinking of using 150X50mm TP F7.

    6. What screws should I use for attaching the Pitching board on to the house's roof rafter which will support one side of the awning.
    (House Rafter)(House Fascia Board)(Pitching Board)

    Any guidance and help would be greatly appreciated.

    Thank you


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  3. #2
    Join Date
    Dec 2009
    SW Brisbane


    Hi Will, I'm not a builder or structual engineer but heres how my dad taught me to calculate sub floor dimensions. It was the council std back in his day so its calculated in feet and inches.
    Bearers are 3"x (half the span with the ' [feet] changed to" [inches])+1"
    Your situation-span=6'(1.8m) changes to 6"(150mm) x half =3"+1" =4" (100mm)x3"(75mm)
    Joists are 2"x half the span the ' changed to "
    Your situation- 7' (2.1m) changes to 7" (175mm) x half = 3 1/2" (90mm) x 2" (50mm)
    3. I would say your posts are fine. I take it the posts start at the ground and support both deck and awning.
    4+5 I calculate the same as joists.
    6. You'll need to reinfource your house rafter - facia connection with a bracket that is readily available. From there, rather than a pitching board, have you considered rafter hanger brackets?. May not work in your situation but commonly used nowadays.
    P.S. Send out invites to your "deck warming" party before you dig the first post, for some inspiration to get it finished. Have fun.

  4. #3
    Join Date
    Sep 2010


    Hi Stumpkicker, thank you for your indepth reply.

    I have just uploaded an elevation view of my plan, feel free to have a geez if you have the time.



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