I'm building a low level deck in the backyard and wanted to run my framing plan past you all to see if anyone had any ideas and or feedback.
The decking material is Ekodeck, which comes in 5.4m lengths that re 137 wide - plus 6mm spacing between boards.
The design constraint is that I want one level of joists with no bearers. The deck will be at the higher end of the garden, so setting the posts back from the edge and cantilevering the double joists will allow the deck to appear to float. So I'll be framing with 140x45 MGP10 H3 treated. Looking at the span tables, I see a max span of 2600mm with a max cantilever of 650mm.
With that in mind, do you think the below plan will work? That is four posts supporting double structual joists of 2x 140x45x2600. These run out to edge joist also of double 140x45. Basically these doubles provide the structure that the remaining 2600 joists hang from. The left and right edge joists are blocked out to 135mm in width to allow for pictureframing - the decking overhangs the frame by 25mm all around, to allow for a fascia board to conceal the joists.
My intention here is to maximise the deck size with the simplest joist plan. I expect to the 2600 single joists to have a little bounce in them, but the nogs should cut that out. All joints will will have glavanised hangers or angle brackets as appropriate.
Welcome to the Bunnings Workshop community @jase2. It's brilliant to have you join us, and many thanks for your question about constructing a deck.
Theoretically, your design will work, but practically I don't think you'll find any professional companies installing decks of this size with only four posts. I'd suggest, at the minimum, that you install a post right in the centre. That's the weakest link here. Secondarily, I'd recommend installing two additional posts per the image below. I would be much happier if you ran three posts down the middle, as the structure would be much more solid.
It's important to remember that just because something can span a certain length doesn't mean it should. I typically like to work well within the span limitations.
Apart from the need for a post in the middle, I think you've put together a fantastic plan. Well done.
For the next steps, check out these step-by-step guides:
Please let me know if you have any questions.
Thanks for the guidance Mitchell and much appreciated - I'll be adding in those three recommended posts. Glad to hear the overall concept was good!