On Feb 22, 2:15*pm, Andy Dingley wrote:
On Feb 22, 2:04*pm, Mark Bluemel wrote:

What board should I use? OSB? WBP ply? Something else?

I wouldn't board and felt it, I'd use (for simplicity) something that
was inherently both strong enough and waterproof. Corrugated asbestos
cement is the traditional one, or these days that probably means
Onduline.

If you do want to board it, OSB is the stuff. However there are a
couple of grades about and most builders merchants only sell the less
water resistant of the two, so check first. OSB is quite resistant to
moisture on its surface, but it does need to have the edges well
protected.

From my reading of technical data online, the roof of the store is of
such a low pitch that I doubt I'd get away with Onduline without
putting a decking layer under it - the current framework was built for
board and felt, so only supports the edges, basically.

I think I'll have to go with OSB and felt.

Thanks for the pointers.