Most roof decking, also called sheathing, is plywood or oriented strand board (OSB). These thin sheets of wood absorb moisture when exposed to it through excess condensation or a roof leak. When sheathing is exposed to moisture frequently, there is always a chance it will decay or develop wood rot.
With this client’s roof we found excessive rotten pieces of plywood. Luckily we caught it just in time for 0 internal damage. We were able to remove this rotten wood and lay down a new roof.