Checklist: Moisture Problems in the Attic and Roof

Insulation, airtightness and good roof repair are key to prevent moisture problems in the attic and roof.

Mould on a wall

Typical Signs

  • Ice dams along roof eave.
  • Condensation, frost, black stains and mould on roof trusses and sheathing inside attic.
  • Condensation and black stains near vents or plumbing stack.
  • Condensation and black stains near wiring or electrical fixtures.
  • Water dripping from soffits.
  • Interior damage to ceiling (blistering paint, black staining, water leaks, bulging drywall).
  • Water dripping from ceiling electrical fixtures.
Icicles coming off the side of a roof

Possible Causes

  • Ice dams that back water up under shingles and into the attic.
  • Gaps and cracks in ceiling around ducts, framing, pipes, electrical wiring and fixtures that allow warm moist air to escape to the attic where it condenses.
  • Missing chimney fire stop.
  • Kitchen and bathroom exhaust fans vented into attic.
  • Gaps between ceiling and partition walls in attics of row housing units.
  • Leaking roof.
  • Leaky, uninsulated ducts in attic.
Person installing insulation in an attic

Practical Solutions

  • Carefully seal all penetrations running through the ceiling into the attic to prevent warm moist house air leaking into the attic.
  • Seal and insulate attic hatch.
  • Install and seal chimney fire stop around chimney to reduce air leakage into attic.
  • Vent all exhaust fans directly outside.
  • Seal light fixtures.
  • Repair roof and flashings.
  • Reduce excess humidity levels in the house.
  • Seal and insulate ducts passing through attic.
  • Seal joint between partition wall and ceiling in the attics of row housing units.
  • Insulate attic to prevent snow from melting on roof.
  • Install waterproof membrane over roof sheathing at the eaves when shingles are replaced.



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