Decking Joist/Bearer sizing

**Kenphys** · 15th March 2009, 09:16 PM

Hi all. I'm sure that this subject hasbeen covered before, but I suppose each case is unique!
I am building a free standing deck, 4200 x 4500.
On the 4200 sides, there are posts at 1500 in from each end, so 2 extra posts and on the 4500 sides, there are also 2 posts at 1400 in from each end.
A further 4 posts are positioned in the middle of this, almost square shape, in, 1500 from the 4500 sides and 1400 from the 4200 sides, giving 16 posts in total.
So the questions are;
What wood size should I use for the bearers, given that they shall be supported at 1400 in from each side and the 'centre' span 1700.(4500 length). (4 bearers).

Secondly, what size should the joists be and how far apart spaced?

The posts (100 x 100 ) shall be sitting on stirrups embedded 150mm into a concrete hole 600mm deep x 300mm dia.

I hope this is not confusing

**Afro Boy** · 16th March 2009, 07:38 PM

Hi Kenphys,

Welcome to the forums. You'll get heaps of good advice here.

Might I suggest you start by taking a look at the Allan Staines book called "Decks & Pergolas." It's got all the aussie standards for bearer/joist spans, etc. so will give you a great head start. The book should be pretty easy to find as it's quite popular.

Also, another part of these forums have been spun off into http://www.renovateforum.com. Over there, they focus on all the building type stuff so those folks will be able to help you out too.

Finally, I'm sure someone here can give you some good advice too.

Cheers,
Af

**Kenphys** · 17th March 2009, 08:43 AM

Thanks Af. A friend coincidentally lent me his Allan Staines book at the weekend, so I am ploughing through that at present. Plemty of night -time reading me thinks!
Hpefully this project shall be finished by the Spring !!
Ken

**Bloss** · 17th March 2009, 09:40 PM

I agree with Afro Boy - go to http://www.renovateforum.com and resubmit the post and get into the Allan Staines books. For your job his Decks & Pergolas is the one. See also http://www.peachinstitute.com/books.html

**Kenphys** · 18th March 2009, 07:54 AM

Thanks Bloss. I have already found some very informative work in the Renovators site, which has helped immensely.
Ken

**Neil02f** · 22nd March 2009, 10:03 PM

Ken,
If you need access to span tables, you can download a program called timber solutions from w w w timber.org.au This program uses information from AS1684 Residential Timber Framed Construction and is excellent for working out spans, stress grades and timber sizes for any structural member. Neil

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