Building & Property Inspections

A.I. Home Inspection – Boston

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The Truth About Leaks

The truth is that while many roof leaks are easy to repair, their sources are often difficult to find. Water dripping from a ceiling may not be from a leak directly above, but from a leak many feet away that runs down the rafter or across the ceiling before coming in. It could also be caused by the condensation of moisture rising from a bathroom, collecting on the roof sheathing and then dripping through to the ceiling below. It might just as easily be from a plumbing leak situated in a wall or ceiling and incorrectly attributed to a roof leak.

The best way to start tracking a roof leak is to become familiar with the many possible causes. Then, by carefully examining the roof and using the process of elimination, you should be able to locate its source.

The most frequent causes of roof leaks are:

  • Improper flashing, sealing or worn-through flashing around projections through the roof such as plumbing stacks (vent pipes), chimneys, skylights antennas, dormers, etc.
  • Missing, broken or pierced shingles, caused by stones, hail, broken branches or walking or the roof.
  • Tears in the roof valleys, created by expanding and contracting metal or by someone walking in the valley. Also debris can build up in the valley and block run-off.
  • Exposed nails, nails in the wrong places or nails not set flush with the underlying shingles.
  • Wind driven rain: through an attic window or louver, into the chimney brick or mortar or under shingles, through the siding, and behind the step flashing where a lower roof joins the vertical side of the main house.
  • Ice dams, which prevent proper run-off and force water to back up under the shingles.
  • Improperly installed roof, or roofing type which is incorrect for the slope involved.
  • Cracked and blistering of roof mastic on rolled asphalt or on build-up roofing.
  • Ponds of water, created when flat or low sloped roofs begin to sag. Clogged roof drains.
  • Cracked or disintegrating chimney caps.