Is Bunnings 42mm x 42mm Merbau suitable for joists for low level decking?

[Henry1]

Hi all, I'm doing some low level decking and wanting to use the Bunnings 42mm x 42 mm (pencil rounded) Merbau timber for the joists. They will be on a concrete slab but I'm really limited to the height, hence the need for the 42mm x 42mm.

I propose Bunnings mini feet for the bearings. 

I'll be applying Ekodeck boards (180mm width) on top with 6mm gaps. Area is 22m2. 

Height, off the concrete, for the joists will range from 10 mm to 40 mm (Yes, very low level). 

I'll be applying bearer protector (CA group) G-tape onto the tops of the joists.

The concrete has a drain in the middle with slope towards the drain from each side. 

Most of the decking (say 2/3rds) is permanently in the dry, under cover. The exposed area cops the Perth weather. 

The merbau timber is rated to Class 1. Initially, I was looking at a H4 rated softwood (Radiata Pine) for the joists (due to the low height off the concrete) but from what I can see, the span for them is 250mm and that would involve around 200 bearers.

Wondering what the span capability is for the Merbau hardwood and whether people more experienced than I am, would say it's up to the task given the low level. 

Your experience and recommendations are welcome

[Henry1]

Hi .@MitchellMc .@JacobZ and @Nailbag

Thank you all for your help. I finally finished the project.

Summit 'Fairhaven' boards with Classic greystone fascia boards.  

I went with a breaker board for a couple of reasons. One was reduced wastage and cost, notwithstanding much more time on the job. I saved around $300 by being able to plan the best cuts to maximise the 5.4m lengths. The second reason was the previous deck substructure in the outer area was quite rotted. When that happens again, I might be able to just pull off the composite in the outer area, fix the substructure then put the composite back. 

Some pics. 

[JacobZ]

That looks fantastic @Henry1 and looking at the support structure, I imagine it is dead sturdy.

The decision to use a breaker board was certainly worthwhile considering the cost reduction.

I can't say I'd seen the Fairhaven / Stirling Summit Series Composite Decking on a deck before now, but I am really loving the look. It looks lovely and bright and creates a really welcoming space.

I hope you are extremely proud of what you've achieved.

Thank you for sharing.

Jacob