What size bearers and joists for low-level deck?

[BenCor]

I'm looking to build a low level deck (sloping back yard means approx 150mm clearance adjacent to back door down to approx 500mm at outer edge of deck).

Planning the deck to be 3000mm long x 5860mm wide and, therefore, calculations say I should have 4 x bearers at 1860mm wide spacing sitting on 3 posts at 1350mm spacing and either 6 joists @ 583mm intervals or 7 joists @ 486mm intervals (haven't decided yet).

My question is - what size bearers and joists should I use?

I tried the Floor Load Weight calculator but couldn't figure that out...I read somewhere bearers should be 90x90mm? and joists 90x45mm?

[MitchellMc]

Welcome to the Bunnings Workshop community @BenCor. It's fantastic to have you join us and many thanks for your questions.

I'd be inclined to think Treated Pine Outdoor Timber Framing MGP10 120 x 45mm for bearers and Treated Pine Outdoor Timber Framing 90 x 45mm for joists would be a good place to start. With that in mind, I've provided a basic outlay using those below.

I haven't personally heard of anyone using 90 x90 for bearers and normally sizing like that would be reserved for your posts.

Mitchell

[BenCor]

Thanks for your replay and assistance Mitchell.

Regarding the bearers - I can find 90 x 45mm and 140 x 45mm sizes in MGP10 (H3) but nothing in 120 x 45mm. does Bunnings sell that size? could I get away with 90 x 45mm given the existing height restriction or is that pushing it a bit?

[MitchellMc]

@BenCor,

If 120 x 45mm is not available in your location then I would revert back to your original suggestion of using 90 x 90mm bearers. This will be made up of two 90 x 45mm joined together.

Mitchell

[Jason]

As this has been a hugely popular discussion, I just wanted to point visitors to the comprehensive guide How to build a low-level deck by experienced Bunnings Workshop contributor @Adam_W.

Please don't hesitate to reach out if you need assistance with your own project. We're here to help.

Jason