The answer to 'roof decking damage' is that common causes include water leaks, rot, and structural issues. Symptoms may include sagging, soft or spongy spots, or visible damage to the plywood or OSB sheathing. Solutions can range from localized repairs to full roof deck replacement, depending on the extent of the damage.
For minor issues, a homeowner may be able to DIY some repairs. However, for more significant damage or if the root cause is unclear, it's best to call a professional roofing contractor to properly assess and fix the problem. They have the expertise to identify the underlying issues and ensure the roof deck is properly repaired or replaced to maintain the structural integrity of your home.