Attics are one of the most common areas of mold at home. Attics tend to have the ideal conditions for mold growth (hot, moist and an abundant food source with wood coating). In addition, most homeowners never climb into their attic, so the mold problem can develop without being disturbed – often for years!

Many people first learn of their problem just before selling their home. The buyer’s building inspector notices mold in the attic just before the closing date, causing panic between the buyer and seller, often putting the entire transaction at risk.

How to find out if you have a mold problem in the attic


But the good news is that this “mould panic in the attic” scenario can be avoided by quickly checking for mold in your attic each year and treating it quickly if you find a problem.

What are the telltale signs of a mold problem in the attic?

  • Dark black stains on wood surfaces – If the wood in your attic has black discoloration, the problem has exceeded the humidity; you have mold that should be removed.
  • The attic looks excessively hot or sweltering – Attics should be ventilated if properly ventilated. When an attic is sweltering, it indicates that you have a ventilation problem, which often leads to mold problems.
  • Ice accumulation on the underside of the roof covering in winter – When it’s cold enough outside, water vapour in a poorly ventilated attic can freeze under the roof. This makes it particularly easy to spot.
  • Wet insulation in the attic – Not only is this a sign that you could (or will soon) have a mold problem, but when the insulation becomes wet or wet, its ability to insulate decreases considerably, costing you extra money to heat/cool your home. .
    Water dripping smoke detectors, light fixtures, bath fans – This is a sure sign that the floor (or attic) above you has a moisture level that needs to be treated.
  • The musty smell in the attic – Trust your nose. A musty or musty smell in the attic means there is a moisture problem somewhere.

What causes attic mold?


In the mold industry, we like to say that “mold problems are moisture problems.” In other words, you can’t have a mold problem without a moisture problem.

In general, moisture problems in the attics that cause mould growth are most often caused by:

  • Blocked or insufficient ventilation
  • Incorrect evacuation of bathroom fans or dryer vents
  • Roof problems/leaks

Let’s look at each of these three causes individually so that you can make sure that you or a professional corrects the source of the mold problem.

Blocked or insufficient ventilation


The most common cause of mould in the attic, by far, is blocked or insufficient ventilation of the attic. Attics usually have a passive ventilation system in which outside air enters through the soffite vents/eaves at the bottom, heats up in the attic and escapes through the can vents or ridges at the top (as the hot air rises). This cycle creates a pleasant and airy airflow and a well ventilated attic.