Quite often roof leaks first show up as damp spots on the drywall ceiling somewhere in the house. And since most of our houses have pitched (sloped) roofs and water runs downhill, the location of a roof leak is very often somewhere “uphill” on the roof.
The typical roof system is comprised of the covering (asphalt shingles, metal), a waterproof membrane, decking (plywood, boards) and the rafters (usually 2 x6 boards, but could be any size) which are sloped on some angle. Most of the roof area does not have any penetrations like plumbing vents, chimneys, attic vents or bathroom vents and unless damaged by storms or tree limbs can be expected to perform leak-free for many years. High quality asphalt shingle roofs can last 20-30 years, and metal roofs can be expected to last up to 50 years.
So, roof leaks can usually be tracked to a penetration – where some pipe or vent punches through the layers of plywood, waterproof membrane and shingles. These penetrations can be sealed with various synthetic rubber or lead “boots” or some configuration of flashing. Other likely points of vulnerability are where the roof meets a wall, such as on a two-story house, or a dormer. Chimneys are penetrations in the roof, and brick chimneys can be particularly difficult to flash and seal correctly.
Once in the attic and the spot on the drywall ceiling has been located, look at the roof framing directly above the spot to determine where the water is dripping from. Then trace the water stains “uphill” on the framing members or decking material to localize the likely point of entry. Keep in mind it will be extremely difficult to correct the problem from inside the attic. It is advisable to contact a professional roofing contractor in such instances, as roofing repairs can be hazardous and difficult.