I do not know the best way to go about framing a low level deck for the space provided in the photos. Any advice would be greatly appreciated. I am unsure about layout of framing and what suitable footings I can use over the concrete half of the yard. I have also attached a rough plan of what I was hoping to achieve with this project.
Hi @WillBeekhof,
Welcome to the Bunnings Workshop community, it is wonderful to have you with us.
When planning a low-level deck like yours, the first two things you want to look at are the height of the door sill in relation to the concrete and the direction you want your decking boards to run. The door sill height matters because oftentimes the finished decking height is set flush with the door sill so there is a seamless transition. The orientation of the decking boards is just as important, as it will determine the direction of your joists underneath, which then flows through to how you set out your entire frame and footings.
Depending on the height of the sill, these https://www.bunnings.com.au/builders-edge-25-40mm-minifoot-pedestal-feet_p2450073 are often the best solution for low level decks over concrete because they can be set to take up only 25mm beneath the framing and decking. In terms of timber framing, the smallest profile that is recommended is 90x45mm, so with a decking board that will be between 19-22mm thick, your total height will be 137mm at most. If this does not work with the height of the sill, then there are other options, although they are not ideal as they greatly reduce the airflow beneath your deck.
So, could let me know how high the door sill is in relation to the concrete and which direction you want the decking boards to run?
Also, is the plan to have the deck cover the entire area shown in your plans? Or will some of the area be left bare?
I am excited to help you out with a plan when I can get a few details.
In the meantime, you can check out a few of the following articles for some guidance on deck design and construction.
Feel free to share those details when you can. I’ll be more than happy to help with the next steps.
Jacob
Hello,
I would like to leave the smaller area on the inside of the step uncovered by the deck, to then cover with pavers or fake grass. The height from the concrete to the floor inside the house is 135mm. I would like the deck boards to run the longer length of the space. Though this is where I have trouble understanding how to layout the joists and footings to take into account the drop to the bare ground from the concrete slab.
Thankyou for such a quick response.
Are you referring to this section here?
Are you planning on decking over the concrete at the bottom left? Or will that remain concrete as well?
Just trying to get a good picture of everything so we can work on the little nuanced bits as necessary.
With that sill height, you have enough height to use the Minifoot Pedestal Feet with 90x45 timber as long as you use a 19mm thick decking board.
So, with the decking boards running parallel with the house, this means the joists need to run perpendicular to the house at 450mm spacings. As per the instruction manual, the pedestal feet allow for 90x45 to span 750mm between them, you'd need 3 on each joist over the concrete path. As the concrete then steps down to bare soil, you would then need to use different supports that account for the height difference.
You can use concrete in posts, and simply cut them to the correct height to line up with the top of the pedestal feet on the concrete, or you could use something like these https://www.bunnings.com.au/tuffblock-300-x-300-x-90mm-instant-foundation-system-deck-support_p2410345 and build up the ground using drainage gravel and concrete pavers so they are in line with the pedestal feet.
On the bare ground, the rules in terms of how many supports are required change slightly because standard deck supports go off the span table for the framing. In your case, the Hyne Joist Span Table is what we would use. In the area over the soil, the supports can be spaced apart by a maximum of 1400mm, meaning you would need at least two per joist.
I've done up a rough example of the framing layout that I can tweak further with your assistance to suit your needs.
Let me know what you think and if you have further questions or design changes, please feel free to add them.
I was referring to the highlighted section yes. I want to cover all the concrete with decking as well.
Do you mean that every second joist over the concrete would require three mini block pedestals. And that for footings over bare ground the minimum spacing would be 1400mm
What flashing can I use between house and deck? Is there any benefit to running two 90x45 joists along the perimeter and the long running joists. how do I add a step into this design?
Thankyou so much for your quick responses, I am working on a more detailed design that I can show for additional advice!
I mean every joist needs to be supported. Joists cannot support each other laterally through blocking, or non-structural members, so in this design, every individual joist needs to be supported in line with the relevant span tables.
It becomes a bit confusing because the mini foot pedestals have their own span table which supersedes the which specifies a joist must be supported every 750mm, whereas other support methods rely on the span tables provided by the timber manufacturer.
To simplify it as much as possible, anywhere a joist sits over concrete, you need a pedestal foot every 750mm. Where it sits over the ground, you need a support every 1400mm. So, over the concrete, which is 1400mm wide, you'll need 3 pedestals per joist, then additional supports on the soil which fit within the 1400mm span limit of the timber.
There isn't really a need for a flashing between the house and the deck because you aren't actually attaching anything to the house. You'll notice in my render that the joists but up against the wall, with blocking between them around 50mm out from the wall. In this setup, the water will simply drain through the gaps in the decking boards and flow down to the concrete where it will drain away from the house.
There is no real benefit in running double joists along the perimeter unless you are looking to picture frame your deck, and this would only really be required on the ends where the decking will run perpendicular to the house.
To add a step, you would just build a smaller deck frame over the soil and set the height lower in relation to the deck by adjusting the height of your supports.
I hope this answers those questions satisfactorily. If you have more questions or other things to discuss, please let me know so I can assist further.
