The 10 Most Common Causes and Cures of Mould in Your Attic

Here are a few of the most common Causes and Cures of mould in the attic:

1. Blocked soffit vents are often the cause of a general mould problem in an attic. Specially designed baffles can be added to return airflow, or simply pull back the insulation from the edges.
2. Insufficient roof vents means insufficient air-flow that will lead to moisture build-up.
3. Roof leaks, caused by worn-out, broken or cracked shingles are obviously a sign of trouble. Replacement usually means the whole roof and if the shingles have been leaking for a while, be prepared to have to replace some of the roof sheathing and insulation at the same time.
4. Bathroom fans and dryer vents exhausting into the attic space are a no-no. The warm, humid air should be vented directly to the outside. Failure to do so means moisture accumulation and higher temperatures than normal in the attic – perfect for mould growth.
5. Step-flashing leaks, in side-split homes, can introduce the moisture needed for mould growth in an attic. Often awkward to check without invasive deconstruction, it can usually be done without the need for reroofing.
6. Plumbing vent stacks, attic vents or other breaks in the roof surface need special attention. Gaskets and flanges around these items can become brittle over time and cracks can form. They can be resealed using a long-lasting silicone sealant or replaced entirely.
7. Chimneys are another common area to leak. The flashing must be maintained to ensure a water tight seal.
8. Gable vents that are plugged or too small can lead to poor airflow and a build-up of moisture.
9. Holes in the tops of walls and ceilings for plumbing, heating and wiring can leak indoor air into the attic space. These can be easily sealed using expanding spray foam in a can.
10. Pot lights, if not properly installed, can leak air into the attic space.