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Low-level deck on concrete slab

Dan_O
New Contributor

Low-level deck on concrete slab

Hello,

 

I am looking to build a low-level deck over the concrete slab extending from my house. The concrete is looking worn, and we hope to have the deck flush with new bi-fold doors installed. I have looked through the other related posts on here though have some specific questions for my own situation. Sorry if these have been covered elsewhere!

 

Firstly, I only have 120mm clearance from the slab to the level of bifold doors we are having installed. My plan was to use Spotted Gum decking boards (140x19mm), 70x45mm joists, resting on the "25-40mm Builder's Edge Pedestal Feet" (set at about 30mm to get the required 19 + 70 + 30 = 119mm depth total). My question is, how is it best to secure the deck to either the concrete slab, or to the house (and is this required, or can it be free-standing?).

The house is brick veneer, and the pedestal feet do not appear to have holes for fixing to the slab (I might have this wrong). 

 

Next, the slab space to cover is 6.4m wide, and 2.5m deep from the house. I calculated ~15 joists required (at 450mm spacing) over the 6.4m length, and my understanding is that the pedestal feet should be no more than 500mm spaced, so there should be 5 spaced out across the 2.5m width. Between the joists, at what max span should my noggings be spaced? (I.e. can there be two rows of noggins ~800mm spaced?

 

Thank you, I expect to have many more questions as my project develops (Also, I know the pergola looks low with the deck added, this is a future job!)

Cheers20211006_135932.jpg20211006_135943.jpg

StevieB
Retired Team Member
Retired Team Member

Re: Low-level deck on concrete slab

Welcome to the Bunnings Workshop community @Dan_O. We'd be happy to help with your project.

 

Let me tag @tom_builds, @Backyardtradie and @MGusto to kick off this discussion. Our resident D.I.Y. expert @MitchellMc can also assist when he's back on the site on Friday.

 

In the meantime, you might like to check out How to build a low-level deck by @Adam_W if you haven't already, as well as Inspiring low-level deck builds.

 

Stevie

 

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MGusto
Junior Contributor

Re: Low-level deck on concrete slab

Hi @Dan_O 

I used the pedestal system to build a deck and used Buzon pedestals which are rated much higher than the builders edge and are cheaper. You probably dont need 5 per joist. It is not necessary to attach the pedestals to the concrete base. They sit there nicely with the weight of the deck. The deck was not attached in any form to the house. For the length of the deck the ends of the joist were attached to one long "beam" in your case 70 x 45 to match the joist size.

For the length of the deck near the house wall I used noggins to connect the joists together. There were no futher noggins required within the deck structure. This enables easy levelling using the screw mechanism of the pedestal

Hope this is of some use to you. Cheers

Dan_O
New Contributor

Re: Low-level deck on concrete slab

Thanks @MGusto , really appreciate the advice! I was also looking at the Buzon pedestals and will likely go with them. Really enjoyed looking through your project. Glad to hear fixing to the slab / house can likely be avoided.

 

For attaching joists to the long beam at the end, would you recommend a certain hanger to use (not sure what is best for 70x45 joists)? Or am I able to simply connect directly with nails/screws

 

As this long end beam will be 6.4m long, if I cannot source a continuous beam that long would I be able to simply connect two beams together with a lap joint?

Cheers

 

 

MGusto
Junior Contributor

Re: Low-level deck on concrete slab

Hey @Dan_O 

i used these batten screws that use a hex drive https://www.bunnings.com.au/buildex-14-10-x-100mm-climacoat-bugle-head-batten-timber-screws-25-pack_...

to fix the joists to the beam - 2 per joist and I would do the same as you suggested with connecting the two beams together. Because the pedestals are bearing the weight on the joists the end beam is there simply to hold the frame steady and assist in keeping true 450 spacings within the joists.

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Low-level deck on concrete slab

Hi @Dan_O,

 

It's great to see you've received some fantastic advice from @MGusto. I trust most of your questions have been answered.

 

Please feel free to let us know if there is anything else.

 

Mitchell

 

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