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Decking Calculations to check

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  1. #1
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    Question Decking Calculations to check

    Hi guys

    It's been a while since I posted - done most of the internal work and now want to add a deck! So I'm hoping you can help me check my deck design.

    I've re-read a lot of the decking threads and read span tables (I think I've worked out the difference between single and continuous span and what Floor Load Width means!!) but I can't work out the Hynes software to double check the structural integrity of the design?!
    The deck is being installed with one side attached to the house on a sloping ground area. The deck height ranges from 1000mm to 1700mm.

    Here are the deck specs:

    Overall deck length: 5260mm (with 4000mm ledger against house)
    Overall deck width: 4000mm

    Treated pine posts 100 x 100 at 1253 centres
    Treated pine bearers 190 x 45 at 1300 centres
    Treated pine joists 90 x 45 at 450 centres
    Merbau hardwood decking boards 90 x 19

    We are keen to attach a shadesail to each of the corners of the deck and plan to have continuous posts to ceiling height to achieve this. Overall, we are on a tight budget, hence the use of treated pine, but we are open to ideas/suggestions on how to keep the costs down but ensure structural integrity.

    Any advice would be greatly appreciated!

    Cheers
    Dayle

  2. #2
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    HI Dayle,
    Overall I reckon that looks about right. I understand you're on a budget, but I would encourage you to reduce the joist spacing. Just adding one, or two, more will make a big difference to the overall feel of the deck, for relatively little money.
    As a frequent poster here says the Australian standards are minimums...

    My only other reservation is the use of TP Posts. I have yet to see a new, or used, TP post of 100 x 100 that has remained true. In the big green and blue sheds most could almost pass as big bananas.
    Just had to rebuild a 8m long verandah on a cottage and got 6 x 105mm square jarrah posts (from a mill) at 2700 for $535.00 total. At the green shed the TP were $90.00 each at 2.4m.

  3. #3
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    Thanks so much David

    I've found another option for the posts - 100 x 100 laminated hardwood. They are long enough to be used from footings to roof height so we can anchor a shade sail from it. And I've redone the calculations so the joists are 440 centres.

    Really appreciate your input, have a great day!

  4. #4
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    You could easily drop down to 2/140x45 for bearers. The rest is fine as it is. Take a look (google) at how shade sail posts are set out. They are in the ground very deep and set at an angle so not really feasible to use deck posts that are set in plumb.

  5. #5
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    Thanks Shauk.
    I chatted with a building inspector about the posts servings as shade sail anchor points- he said that because they post would be fixed at the ground, at bearer and then again at hand rail level that it should be okay. We will also attach one point to the fascia as the deck odd ain't one side of the house.
    How does that sound?

  6. #6
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    No worries. I'd say check with a shade sail installer and I suppose your fascia has been checked out by the building inspector and is solidly attached? I'm not the one to design this sort of stuff, just aware that it needs to be well designed.

  7. #7
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    Absolutely agree! Thanks again

  8. #8
    JB1
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    Default Decking Calculations to check

    How big is the shade sail?

    Unless it's one of those tiny $30 3x3m ones I wouldn't use the posts as a shade sail anchor point, let alone a fascia board.

    I'm surprised the building inspector said that.

    Maybe Brisbane doesn't have strong wind

  9. #9
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    Hey JB1
    The fascia fixing point will be reinforced through connecting with the roof rafter and the sail size is 3m x 5m....

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