The answer to 'why is my roof decking leaking' is that there is likely a problem with the roof's waterproofing system, causing water to penetrate the roof deck. Common causes include damaged or worn shingles, loose flashing, poor roof ventilation, or improper installation.
Signs of a leaking roof deck include water stains, mold growth, and rotting wood in the attic or on the ceiling below the roof. If left unrepaired, a leaking roof deck can lead to structural damage and costly repairs. It's important to address the issue promptly to prevent further damage.