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What size bearers and joists for low-level deck?

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?

Community manager's note: Check out How to build a low-level deck for expert advice.

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Comments

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

https://www.workshop.bunnings.com.au/discussion/comment/9958#Comment_9958

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

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