Side rail size on 20ft bays

[agrotron]

I am ready to sheet my machinery shed which I have been building. It’s 20ft bays. The sheets going on the back are 7ft long steel box profile. What would people advise for the side rails. I am thinking either 6x3 timber or 80mmx80mm box section. As it’s 20ft span would the timber twist? Don’t want to use c sections as only need three and delivery would make them expensive.

Cheers

 

[BredRedHfd]

6x3 be fine. Scandanavian if you can get it. Don't use English tanalised. Pure rubbish.

 

[poult135]

What spacings between the 6 x 3? I was going to do 1m on our 20ft bays for box profile sheets

 

[BredRedHfd]

What spacings between the 6 x 3? I was going to do 1m on our 20ft bays for box profile sheets

Think you'll be ok at 1.2m. Should carry 0.7s ok...