Corrugated plastic lean to - advice on timber if you please

[FiremanT]

I am building a lean to behind a reasonably large shed. It will be out of sight so prettiness is not the main consideration. I am able to do the work, but am a little concerned about the design of the timber.

Some images on t'net suggest sing 6" x 3" for the joists. This seem s a bit excessive, as the only load is the plastic sheeting plus snow. The roof will be 3M x 4m, the pitch being formed by one side at 1.8M and the other 2.4M.

I suppose the main thing is knowing how big I HAVE to go for

a) The vertical supports (and their spacing)
b) Joistsn (presumably I would space these the same as the joists?)
c) Purlins (I understand these should be 600mm centred.

Are there any "standard" plans around?

Any advice would be appreciated.

Thanks.

 

[scbk]

I made something similar, but with corrugated steel, I used 4x2s with 3x2s at right angles on top of that


Bare in mind some of the plastic roof sheets aren't very uv stable and might be very brittle in a few years time

 

[FiremanT]

I made something similar, but with corrugated steel, I used 4x2s with 3x2s at right angles on top of that


Bare in mind some of the plastic roof sheets aren't very uv stable and might be very brittle in a few years time

I appreciate that, thanks, but the benefit of plastic is daylight.