Need advice on building a deck

Glynn23

Hi Everyone,
I am currently planning my first deck.

After reading lots of posts on this page and other forums I have put together my plans and wanted some advice on if I'm on the right track or there are some severe design flaws.

The dimensions of the deck will be 8800mm x 3700mm (see plan above)

It will be 500mm off ground  and the stumps will be concrete.

I will have 8 bearers each being 2/90x45 treated pine F7 H3 laminated.

My joists will run the length of the deck (8800mm) and will be spaced approx 400mm apart.

My decking boards will be 140mm x 19mm merbau

The main things I want to know are:

Will my timber for my joists and bearers be strong enough?

Is my spacing of 1247mm between bearers too much or is that just fine.

Could I extend my spacing between joists out to 450mm or am I better to keep them closer?

Also, is four stumps per bearer at 1133mm apart too much or can I extend this out to 1700mm between each stump to save some digging?
Thanks in advance

Are there any other problems anyone can forsee with this design?

Thanks in advance for your help

EricL

Hello @Glynn23

Welcome to the Bunnings Workshop community. It's great to have you join us, and thank you for sharing your question about building a deck.

I believe in over-engineering things even though they are not necessary. Using a span table is one way to make sure that your design will be built to the correct specifications. Let me try and answer some of your questions from a practical point of view.

The greater the space between your bearers means that your joists will need to be strong enough to carry the weight of a person between bearers. The closer the bearers are, the more support the joists will have. A span table will show you the weight an unsupported beam can support. The same rule applies even to the bearers, the more stumps you have the more support you'll have, and that allows the bearer to carry more weight.

I'm sorry if I can't give you straight answers to your questions, you will need to refer to a span table or engage the services of a registered deck builder.    

Let me tag our experienced members @ProjectPete, @Brad, @woodenwookie, and @tom_builds for their recommendations.

If you need further assistance, please let us know.

Eric