I've never had the issue, but climate and individual management style matter.
The only time the inside of my coop has ever gotten wet was when I was using it as a brooder and the chicks dumped the waterer. :)
Thank you.
From my article on Using Deep Bedding in a Small Coop:
Definitions:
Deep Bedding: A dry, non-composting system where you keep adding bedding to the coop as it becomes soiled -- managing it by turning it as necessary (or getting the chickens to turn it for you) -- and clean it out...