Ply sheeting roof prior to zinc - do I leave any expansion gaps between sheets of ply?

[markharro]

As per the title any advice welcome thanks,

[gc100]

We didn’t . Not had any problems thus far in 2 years 

[Dave Jones]

some say a nails width gap? Our last build had a large flat (warm) parapet roof (10x6), i butted the OSB (cheaper than ply) up tight and had zero squeaks, movement.

[gc100]

Thermal expansion looks very minimal 

https://www.performancepanels.com/dimensional-stability-flatness#:~:text=Plywood and wood expand upon,exacting techniques for its measurement.

 

as someone who built a few skateboard half pipes out of ply , I’ve never seen it buckle and that’s exposed to the elements 

[Adsibob]

With OSB, we were advised by our liquid roof membrane supplier (that was poured onto the osb) to leave a 1mm expansion gap. But maybe plywood is more stable than osb.

[Iceverge]

@Patrick used closely spaced boarding instead of ply which I prefer TBH as any moisture under the Zinc has somewhere to dry to.