Lightning, high winds, hail, drenching rains that overflow the flashing heights

Improperly added equipment or other items improperly added on the roof (items added by tenants are a very common source of roofing problems)

Punctures, holes, etc. caused by trades other than your roofing contractor

Vandalism or accidental damage…even a small hole can let in a large amount of water into the roofing system