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Low level deck on concrete slab

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Junior Contributor

Low level deck on concrete slab

Hello, 

I am looking to start building a low-level covered deck (3800*3440) on a concrete slab and need someone help with my two points below: 

 

1. The deck meets the house on two sides, one being 120mm clearance and the other 110mm, so I decided to keep the deck height to be flush with 110mm. To do so, I have decided to use 70*45 treated pine joists sitting on galvanised brackets with about 10mm ground clearence. I note @MitchellMc you suggest placing brackets alternate to avoid buckling but is the 70*45 joists good enough to avoid sponginess? If not, what option do I have so my final deck height doesn't exceed 110mm? 

 

2. @MitchellMc can you help with some basic drawings based on the above deck dimensions? I understand good practice is to keep about 400mm gap between joists? 

 

Cheers

 

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Community Manager
Community Manager

Re: Low level deck on concrete slab

@Backyardtradie,

 

I'm sure Mitch will be happy to assist when he is back on the site on Friday.

 

In the meantime, I take it you have had a good look at the excellent guide How to build a low-level deck by @Adam_W? If you search for low-level deck on the site you will also find plenty of popular discussions on the topic. 

 

Thanks,

 

Jason

 

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Junior Contributor

Re: Low level deck on concrete slab

@MitchellMc wondering if you had time to look into this. Cheers

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Bunnings Team Member
Bunnings Team Member

Re: Low level deck on concrete slab

Hi @Backyardtradie,

 

I apologise for the delay in my reply. Around a 400mm gap for your joists would be fine and you would run them in the alternate direction to your boards. Sponginess is a result of unsupported timber over too large of a distance. So, 400mm spacing on the joists will stop the decking boards being spongy, however, you'll need adequate support from the brackets to stop the 70 x 45mm timber from flexing. I would advise placing a bracket every 600mm on alternating sides as previously discussed.

 

It would be great to use 90 x 45mm timber but as you have stated there is just not enough room. 

 

Mitchell

 

 

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Junior Contributor

Re: Low level deck on concrete slab

Great @MitchellMc . 

Thanks for your reply. I did go for 90X45 in the end precisely for the reasons you mentioned above. Hence my final deck height is just above 110mm. 

 

Timber arrived today and will commence work shortly. My next post should provide photos of work in progress. 

Appreciate your help and guidance all the way!!!

 

Cheers

 

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Bunnings Team Member
Bunnings Team Member

Re: Low level deck on concrete slab

@Backyardtradie,

 

Fantastic! Make sure to take lots of photos of your progress as I trust it will be of immense benefit to our members which are following your project.

 

We can't wait to see your finished deck. Please let me know if you run into any difficulties or need assistance.

 

Mitchell

 

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