What joist size to use for low-level deck?

[Zog]

Hi everyone. I have assembled the framing of the modular decking for my low level deck (see photos). What is in the photo is essentially a walkway, the main deck will be under the pergola and slightly higher. I've gained some confidence from what I've done so far and am considering using tuffblocks and building a framework rather than using the modular decking for the main deck. My question is just about the joist size. I'm not going to use a bearer and joists system, just a framework of joists, mainly because the Pergola is already there (before I bought the house) so I need to preserve the ceiling height of the pergola as much as possible.

I'm unsure about joist size and span of tuffblocks. The Tuffblock website has an article where they're using 2"x6" (45x150) joists, I've seen joists of 45x90 used in Australian based articles and the joists of the Good Times modular panels from Bunnings are 45x70. I'll probably use 140x19 merbau decking.

The pavers will be staying, they're not perfectly level, a small part of the deck will be on soil (the far sides in the second photo).

The total size of the main deck will be about 6.4m x 7.4m or 47.36 m2. It's a lot bigger than any articles I've seen about building a  low level deck. Any advice will be much appreciated.

[JacobZ]

Hi @Zog,

Some curvature is expected when using softwood such as pine, in lengths as long as you are. 

It can usually be managed by pulling the curve out when screwing the timbers off but the hump that you've circled and curvature on multiple planes can be tricky to deal with.

You can often pull the curvature out when screwing the members off or cut them into shorter lengths for shorter sections of your framing. If you can use them in this way, this is certainly an option.

If there are any twisted lengths that you're unable to use, and they were from us, I'd be happy to put you in contact with a manager at the store of purchase to discuss options.

Let me know what you think.

Jacob

[Zog]

Thanks @JacobZ 

In that case I guess I can put the bent and multi-curved joists on the inside and I can use the noggins to pull them straight. I'll go ahead and get started and if I find that the two mentioned are unusable I'll get back to you.

[JacobZ]

Hi @Zog,

Sounds like a great plan. Remember to cut your noggins to the width the spacing should be, not what it is. Doing this means you can hit them into place with a hammer, which will straighten out the curves.

Keep us in the loop if you run into any issues, I'm sure we'll be able to come up with a solution.

Jacob