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Design advice, non standard approach to decking

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  1. #1
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    Default Design advice, non standard approach to decking

    Hello all,

    I'm in the process of designing a deck, roughly 5.4m x 6m. I have read plenty about the process of building one, however would like some feedback on a few ideas I have on how to make things better/easier/feasible.

    Feedback #1
    I was thinking that instead of using standard posts and cementing them into the ground, to use limestone blocks as my base. I can then mount the bearers onto the limestone blocks and secure them using standard joist hangers. Small limestone blocks are heavy enough and are very unlikely to shift anywhere, especially since I can compact the soil to the desired height.

    Any thoughts about why this might not work?

    Feedback #2
    I have this issue that my ground level is only 20cm lower than my datum point (top of the deck), which obviously leaves almost no gap between the bearers and the ground. I have managed to excavate 100mm of soil to increase the gap, but still not happy with the bearers being so close to the ground. I was thinking of getting some thick builders film and wrap the bearers with it completely. This will only leave the joist "exposed" being 200mm from ground level.
    (I intend to use 90x45 H3 treated pine wood, F7 if I can find any).

    Any thoughts about why this might not work?

    Thanks very much!!!

  2. #2
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    If your ground is very level, is there any reason why you would not lay the bearers directly on the ground? I have little experience with this, and I'm sure others will come into this post and comment, but it makes sense to me. I did see an episode of Grand Designs some years ago where the house was built directly onto concrete pads that were simplsy laid on the ground.

    Not sure if either method would be allowed under building codes here though.
    I am not responsible for anything that Moondog says!

  3. #3
    Community Moderator phild01's Avatar
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    As suggested, you could lay your timbers in the ground but it needs to be H4. I have built my decks like this but also used H4 for the joists. Using the stone as support is fine and no different to a masonry or concrete footing but you need to work out your termite control if the deck is in contact with your house. Not sure what you mean by using a joist hanger to secure the bearer to the limestone! I would not wrap the timber as you suggest. It would not be good for the timber and the plastic will will eventually fail anyway.

  4. #4
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    I am not too fond of laying timber directly in the ground, but I think the combination of H4 for the bearers (possibly also joists) and having 10-15cm gap for ventilation is reassuring. Thanks for the advice guys!

    you need to work out your termite control if the deck is in contact with your house
    The H4 is treated for termites or did you mean the deck itself? I intend to use composite decking so it's also termite resistant.

    Not sure what you mean by using a joist hanger to secure the bearer to the limestone!
    This is a joist hanger, the bottom can be secured to the limestone using a dynabolt and then nails to secure the timber to the hanger. I could obviously also use a standard bracket ..

    lus26ss.jpg

  5. #5
    Community Moderator phild01's Avatar
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    Quote Originally Posted by slepax View Post
    I am not too fond of laying timber directly in the ground, but I think the combination of H4 for the bearers (possibly also joists) and having 10-15cm gap for ventilation is reassuring. Thanks for the advice guys!



    The H4 is treated for termites or did you mean the deck itself? I intend to use composite decking so it's also termite resistant.



    This is a joist hanger, the bottom can be secured to the limestone using a dynabolt and then nails to secure the timber to the hanger. I could obviously also use a standard bracket ..

    The bearer can just sit on the limestone with no connector. I wouldn't use a joist hanger as you describe, it is not meant for that purpose. Maybe use easily available heavy gal angle brackets instead.
    The thing about termites is that they travel very long distances and they don't care too much what is in the way. It doesn't matter that the deck is termite resistant, they will consider it just a highway into the house if the deck breaches the termite protection the house has.

  6. #6
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    Quote Originally Posted by phild01 View Post
    they will consider it just a highway into the house if the deck breaches the termite protection the house has.
    Thanks for that, must admit didn't think about it. I will make sure to leave some gap from the house.

  7. #7
    Community Moderator phild01's Avatar
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    Quote Originally Posted by slepax View Post
    Thanks for that, must admit didn't think about it. I will make sure to leave some gap from the house.
    That is the best way, doesn't have to be much, just enough not to collect litter and provides full view to house wall.

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