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Low lying decks - one over concrete the other around a mango tree

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Low lying decks - one over concrete the other around a mango tree

Hi MitchellMc and bunnings community!


Thank you for encouraging us to start this DIY project.  We have done a few DIY projects around the house such as retaining walls and building in some shelves around our fireplace from scratch...while i feel confident in our abilities to be able to complete this project over time, we are after a little guidance to help get started.


What we are aiming to do is build a low lying deck over an existing, rather degraded concrete patio type area and at the same time a smallish deck that wraps part way round our mango tree.

What we would love your assistance with is figuring out:

  • the actual materials list and costings
  • how to position the joists
  • anything we may not have considered with our initial design.

We've done a bit of trawling of other projects in this community and the interwebs, and due to perhaps needing to access facilities underground at some stage in the future, we are leaning towards building on TuffBlocks or pedestal type builders feet ?

We were thinking that perhaps we would use a composite decking as the mango tree deck will be a little exposed to the elements and the sprinkler, but ultimately it'll come down to cost. 


LOW LYING DECK OVER CONCRETE - other info you may need to know.

  • The deck can't go higher really than 6cm due to the back sliding door.
  • There are 3 poles holding up the concrete balcony that we need to build around.  These are suggested by the white circles on the attached drawing.
  • Along the house wall that spans 5.4m, there are actually a couple of concrete outlet/drain type things as well as plumbing lines from the upstairs area that come out at various points that we will also need to build around. 
  • The existing concrete pad doesn't go all the way to the fence line, there is about 1.5m of earth which we have scraped back, levelled out and put down builders plastic etc ready to get started for the deck.


  • I was wondering whether we could use joist hangers along the exterior walls of the house and then on the concrete bricks on the fence line and use the builders feet in between?
  • considering the height restriction what size timber do we start with for the base of the deck?
  • How far apart do we need to put the joists? 
  • How do we measure up how much timber for the foundation and decking we need?

MANGO TREE DECK - other info you may need to know.

The measurements around the trunk of the tree I'm not confidant are accurate as I wasn't sure the best way to approach that, or the angles out from the 90 degree straight edges?  I've attached a photo of the site though - excuse the mess eek but you know, DIY life LOL!

We hadn't installed it at the time I took the photo of the Mango Tree area, but we have popped in a couple of sleepers where the tape measure is in the photo as we want to level out the turfed area behind it and returf. 

The idea is that you walk straight off the levelled out turn area and onto the deck, so they should be level to each other if that makes sense?


QUESTIONS I have so many but will start with:

  • how do we figure out how much timber and decking we need for this angular design?
  • what is the best way to construct the foundation for this i.e. joists? 
  • Can we use joist hangers off of the sleepers to start the bearers/joists (Sorry not sure of right terms/language) and then run to the adjustable builders feet?

We are super keen to get started ASAP hoping to have this done by christmas so any help you and this community can provide would be unreal and we thank you in advance. :smile:


Take care,




SLFDesigns Deck Design-100.jpg

Bunnings Team Member
Bunnings Team Member

Re: Low lying decks - one over concrete the other around a mango tree

Hello @SLFDesigns


It's great to see that you've drawn up some initial plans for your decks. Let me try and give you some recommendations with your first deck over concrete. Let's do some quick calculations, for example, if you used 70 x 35 framing timber and turned it on its side with the 70mm side facing up. Add the thickness of the Ekodeck which is 23mm you would have a total of 58mm with a 2mm air gap. It is vital to have an air gap between your deck and the ground, 2mm is not enough.  Moisture will get trapped under the frame and severely shorten the life of your deck.  


I suggest having a look at this guide - How to build a low-level deck by @Adam_W. This will give you the basics of how to make your plan. It's always best practice to have a ledger for the joists to hang on to rather than mounting it directly to the house. I encourage you to try and make a plan and post it here for our members to have a look at. We can then make recommendations based on that plan.


Your decking and framing quantity will be based on the size of the deck you plan on building. Your mango tree decking looks much more promising as it is not attached to your house and there are no height limitations. Using the TuffBlock 300 x 300 x 90mm Instant Foundation System Deck Support should be ideal for your build. 


Here is a link for ideas and inspiration: Inspiring low-level deck builds


Here are some amazing low-level deck projects our members have shared in Workshop.



Please keep us updated with your progress, we look forward to seeing your decking plans.


If you need further assistance, please let us know.      




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