How deep do you need to cement decking posts into ground?

clolimiza

Hey Guys

We are building our second deck, (first one was built over concrete slab) we are needing advice on how deep do you need to have the framing posts cemented into the ground? The deck is going to be 6.8m by 3.9m, we have just had a patio built by Instaco and now wanting to finish it by building the deck underneath. I feel like we will have a heap of questions along the way so thought it would be easier to start our own post. 

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

MitchellMc

Welcome to the Bunnings Workshop community @clolimiza. It's fabulous to have you join us and many thanks for your question.

Regulations for post footings are governed by your local council, so contacting them would be a good place to start. Below I have included an example image of what one particular council's requirement was for deck footers. You'll see in the plan that they were required to dig a 1200 x 300 x 300mm hole and cement the post in with a 300 x 300 x 750mm footer. They were then required to backfill the rest. This would be overkill in your situation but provide a good example of what regulations you could potentially need to follow.

As @ProjectPete mentions in that discussion, a "400D X 300W X 300W is sufficient allowing for compacted base, concrete to be poured under the post and all around it (100x100 H4).". This size is more likely what you would use in your circumstance.

You might be interested in these previous discussions that touch on deck footers:

• Deck footing by @trentp

• low level deck questions by @BradC.

• Landscaping - 3 Tier Decking by @diy_hausdesigns

You should also find this D.I.Y. advice helpful:  How to build a timber deck

Make sure you keep those questions coming, we are always here to help.

Mitchell