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Low-level Merbau deck over concrete slab

Established Contributor
Established Contributor

A stunning Merbau deck with picture framing that continues to inspire many other low-level deck projects.





The project


Before tackling this deck, Bunnings Workshop member Neo19 had completed a few landscaping projects, including building a raised garden bed, but "nothing major". With the helpful advice of Bunnings Workshop community members, he built a 350cm x 370cm deck with a height of 18cm aligned to his internal floor.





Tools and materials



Joists were 3500mm long and kept at a maximum of 450mm intervals. Four brackets were used per joist. Due to the length of the deck, it was "impossible to have all spaced exactly the same".


Since the concrete slab wasn't perfectly level, Builders Edge Assorted Builders Wedge was used to adjust the height. "You adjust the height of the joists with these packers and then bolt them to brackets and the packers stay there," says Neo19. "Even if they come loose, it doesn't matter as your joists are already fixed at a certain height to the bracket."


"My clearance from the concrete to the flushed surface was around 180 mm. And I've used 140x45 which gave me around 160 mm. Since the concrete slab wasn't perfectly level, there were some variations in the flushed surface height. I ended up using these builders wedges to adjust the height. They come from 1 mm height onwards."


"For drilling holes into concrete, I initially tried with my Makita cordless hammer drill. My concrete slab was so hard that I gave up after 30 minutes. Went and bought this Rotary Hammer Drill and the job became very easy. If you have that many holes, I'll definitely go with the rotary hammer." 


How to build a low-level deck


A low-level deck can pose a range of potential design and installation problems, with particular challenges around ventilation, drainage, termites and rotting. But it doesn't have to be a difficult project once you take the time to understand the basics of how they are put together.


Experienced Bunnings Workshop member Adam Woodhams has created a comprehensive guide to building your own low-level deck which should provide an excellent reference for getting started. 


Tips for building a low-level deck


Resident Bunnings D.I.Y. expert Mitch has shared helpful advice with Workshop community members for their low-level decking projects, including:


  • Don't cut decking boards to length on a drop saw before laying them. The best method is to fix all your boards onto the deck, mark a straight line and then cut all the boards at the edge of the deck with a circular saw. The finish will be much more aesthetically pleasing.


  • Pre-oiling the underside of your decking boards before installation will extend the life of the deck, help prevent cupping and assist in keeping the moisture content of the boards stable. When coating a deck you'll want to liberally apply the oil so it soaks into the boards as the initial coat to the under-side won't last.



  • A gap under your joists is essential for allowing water to drain. If water is retained under the deck with no drainage, then a moist environment is created where you can expect cupping of boards. 



Other low-level deck projects


Inspired by Neo19's deck, Bunnings Workshop member Brendon_B built this 5600mm x 2000mm deck over a pebblecrete slab using 140 x 199mm Merbau.


Brendon_B deck2.jpeg


Bunnings Workshop member Usman built a 11 x 3.5m deck over concrete, with plans to cover the area with bistro blinds from Bunnings.


Usman deck.jpeg

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