purlins or decking

[Old Spam Can]

a newly framed roof has a 5/12 pitch. the 2x6 rafters are 8 feet long and 16 inches on center. we will be installing 26G 5 rib metal panels. we have not purchased any material beyond the rafters yet. can we go with 2x4 purlins across the rafters spaced 2 feet apart or must we put down 1/2 inch plywood decking. my reason for asking is because i am doing this project alone and the purlins would certainly make this easier.
thank you all.

[flcruising]

Is this roof over a deck or a conditioned space?

[Old Spam Can]

it is an existing MH SW with a flat metal roof.

[JD]

When I built pole barns, the metal went over 1.5" vinyl back insulation (6' wide) that was laid directly on to 2x6 purlins, 24" o.c.. Never had a thought about the metal not being strong enough to walk on, though we tried to keep our weight over the purlins. But stepping between the purlins did not cause the metal to dent. I don't know about 2x4's though. They would have a lot more flex when walked on. But you would think the strength between the purlins would be the same. It might be hard to find someone who has done exactly what you are describing, but maybe we will get lucky.

That being said, I advise against installing wood framing, using the mobile home as the only support.

JMO
JD

[flcruising]

Is this newly framed roof built on top of the original? Did you pull off the old metal and just increase the roof pitch with wood rafters bearing on the side walls?

Plywood is not only for nailing to, but for lateral (shear) strength. If you eliminate the plywood, you would need to supplement with diagonal bracing.