Start a discussion

The Workshop community can help with your home improvement projects.

Decking over concrete slab

New Contributor

Decking over concrete slab



we are looking to deck our alfresco area, its a concrete slab with a 70mm step down - not much I know, what’s the best way to go about it with such a small step down to work with ? 




does anyone also have a great program to work out deck plan / spacing etc ?


thanks heaps!



Valued Contributor

Re: decking over concrete slab

Read this

Top Hat Section?

Community Manager Jason
Community Manager

Re: Decking over concrete slab

Hi @Tracey113 ,


Welcome to Workshop. We look forward to seeing how this project progresses and trust that you'll get plenty of helpful information and advice from our members. Feel free to post whenever you need a hand. 


I also welcome any feedback about how we might improve Workshop for you. Just let me know.








Show off your handiwork at the Workshop Gallery
New Contributor

Re: Decking over concrete slab

Mc Donald Jones Homes? I just built a deck over our concrete slab with "70mm" setdown. The main sliding door was even less than 70mm setdown, other bedroom door was more than 70mm, had plenty of issues getting it done, wall to the right was not square either. 

70x35mm Pine subframe secured to concrete with screws / plugs. Levelled using window packers

5mm spacing, wanted 5mm minimum which worked out good as the board widths over the width of the deck worked out full boards the whole way across. Painted the subframe black to avoid the "see through" effect. 






IMG_5334.JPG70x35 subframe secured to concrete using screws & plugs.57199490785__B250C5A9-B043-463A-B490-F4E8929B2C6C.JPG140mm Merbau decking with 5mm spacing.

Occasional Browser

Re: Decking over concrete slab

Hi, Just a thought. Did you put down a moisture protection layer between the frame and the decking boards?
If you do, then this normally comes in back, which means you would not have seen through the decking boards.

Cheers, Mark


New Contributor

Re: Decking over concrete slab

@asarson yes ours is MJH house - in hindsight wish we realised that the set down was only 70mm. Do you mind sharing a pic of what you did around the pillars and the edges / sides ?? 

New Contributor

Re: Decking over concrete slab

Hey Tracy, 


Well as I am building a built in bbq the outside edge of the deck is still unfinished however I plan to picture frame finish the edges. It’s a little difficult since we are using 140mm boards and I can’t get to a full board around the pillars without cutting one down.. I plan to just check in full boards around the corners of the pillars rather than cut down full lengths. Hope that makes sense.. the inner wall was out of square also so we had to taper one end down. image.jpgRear edge


image.jpgSide edge


image.jpgDeck off master bedroom to eventually connect alfresco deck


Why join the Workshop community?

Workshop is a friendly place to learn, get ideas and find inspiration for your home improvement projects