Green roof - joist question please!

[mrscott]

Hello!
I would appreciate any advice anyone could offer me with regards to the size of joist I should use for a shed I will be building.
It will be an extensive 'green' flat roof (with a 1:40 slope for drainage) so apparently the dead load should be 115 kg / m2.
The total size including overhang of the roof will be 4m x 3m and will be ply lined on both sides.

Could I get away with using 2"x4" at 16" centres, or would I need something bigger than this?

Thanks in advance!!

Scott

 

[r896neo]

probably best to move this to the building forum.

 

[mrscott]

Oops!
How do I move it, or will a mod come along and kindly do it for me?
Thanks!

 

[Richard C]

I've asked them for you

 

[mrscott]

Thank you!

 

[^woody^]

I don't think 4x2 will be enough. More like 6x2

 

[Static]

6x2 are borderline i would go 7x2" at 16" centres..
Assuming thats the saturated weight.. (you should check that)