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What footings and bearers for low deck over clay?

Hi all

currently planning to build a deck as part of our backyard project.
the deck will be completely over soil and I have a septic pipe to deal with running underneath.
total deck is is 7000 x 8200 inclusive of a 400mm step wrapping around 2 sides, height is avg of 310mm. One side is the house and another side is a fence.

I have read through some of the projects here and this has helped a lot (thanks contributors!) but I have some questions.

- do all my supports need to be concreted or can I get away with some being on firm ground? Soil is hard and clay

- I have set bearers @ 1100, what size should be used and how best to cover the span?

I have not undertaken a project of this scale before but can handle diy projects no problem any help or advice would be great. Look forward to tackling this and posting the progress.

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Comments

MitchellMc

Welcome to the Bunnings Workshop community @themanthatisdan. It's wonderful to have you join us, and many thanks for your question about constructing a deck.

The first place to start regards requirements for you deck would be with the council. Given the size of your deck, it's likely that building permission will be required. In order to achieve this you'll need to submit plans and it's best those are put together by an engineer.

Regarding the footings, typically, you should be able to use items like DEKO 250 x 150 x 150mm Instant Concrete Foundation Block on flat compacted ground.

Your joists should be positioned every 450mm across the span as that is the max span for the decking that will be laid upon them.

There's no set size for your joists. The smaller the calibre, the more supports you'll need for them. Say, if you used 90 x 45mm, you'd need to support them every 1200-1500mm. If you went up to 140 x 45mm, you would need fewer supports over their length.

Remember to check out How to build a low-level deck for plenty of handy information.

Please let me know if you have any questions.

Mitchell

johnrmonk

Hey there @themanthatisdan.

Who did you go through to do drawings etc for planning permits for council?

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