Decking on 3x2

[RichTraff]

I know the standard for a decking sub frame is to use 6x2 joists. That's unrealistic for me though as I have a concrete base and bifold doors that limit the size of the joist I use. I thought I'd get away with 4x2 but even that is too deep.

The decking is going on an uneven concrete base (old garage used to be there).

How do I make this work without it feeling like a trampoline?

 

[mikejt]

How uneven is the floor? Will there be plenty of points of contact all along? Or will there be lon lengths of unsupported timber?

If a lot of it is going to be touching, I'd say just use plenty of noggins and you may get away with it.

I assume leveling or lowering the concrete floor is not a feasible option for you?

 

[RichTraff]

It's too unlevel to put joists straight on the base.

I'm putting decking down as a cheaper, quicker alternative to flagging...so taking up the concrete base would take to much time and money (skip and tool hire) to justify.

I'm going to put the joists at 400mm centres....just not sure how many supports and noggins I should put in?

Area will be 6m x 4m.