Mould in Attics

You're not alone if you've had the bad experience of having to deal with attic mould. Tens of thousands of people deal with attic mould each year because it is so prevalent. One of the most typical places for mould to grow in a house is the attic. Attics are frequently hot, humid, and covered in a lot of sheathing, which are ideal circumstances for the growth of mould. In addition, because most homeowners rarely enter their attics, the mould issue is permitted to worsen unchecked.

Here are some telltale signs of mould in an attic that frequently appear:
  • Dark black stains on wood surfaces-If any black stains are visible on the wood in your attic, the issue has developed beyond dampness.
  • Feels overly warm or stuffy in the attic - If the attic is adequately ventilated, it should feel airy. Attics that are stuffy are signs of ventilation issues, which frequently lead to mould issues.
  • Frost accumulation on the underside of the roof sheathing in winter-When the outside temperature is sufficiently low, water vapour in an attic with insufficient ventilation may freeze on the underside of your roof. This makes it particularly simple to recognize.
  • Wet insulation in the attic-Not only is this a symptom that you might—or soon will—have a mould problem, but damp or wet insulation has a significantly reduced ability to insulate, which increases the expense of heating and cooling your home.
  • Smoke detectors, light fixtures, and bathroom fans all have leaks- This is a sure indication that there is moisture present in the floor (or attic) above you and that it has to be dealt with.
  • The attic has a mildewy odour- There must be a moisture issue someplace if there is a musty or mildew smell in the attic.


What causes attic mould?

Moisture issues are the main cause of mould issues. Mould cannot exist in the absence of moisture. In general, the following factors are the most frequent causes of attic moisture issues that result in mould growth:

  • Obstructed or inadequate ventilation
  • Improper exhausting of dryer vents or bathroom fans
  • Roof defects or leaks


Obstructed or inadequate ventilation

By far, blocked or insufficient attic ventilation is the leading cause of attic mould. The typical passive ventilation system for attics allows outside air to enter by the bottom soffit or eave vents, warm up inside the attic, and then exit through the top can or ridge vents. A lovely, breeze-like airflow and a well-ventilated attic are produced by this cycle. Attics may develop mould if there aren't enough installed vents. On average, one square foot of venting is needed for every 100 square feet of attic space.


Improper exhausting of dryer vents or bathroom fans

Kitchen exhaust fans, bathroom exhaust fans, and dryer exhaust vents are all made to remove moisture from your house. Therefore, ALWAYS ensure that they end outside of your house and NEVER in the attic. Additionally, moisture from plumbing stacks in the attic may be a factor in the development of attic mould.


Roof defects or leaks

Roof leaks frequently result in a tiny, localized area of attic mould close to the leak's source. Here are a few methods for looking for potential roof leaks:

Look for any wood that has dark stains or discolouration (e.g., rafters, sheathing, joists, attic side of fascia boards, etc.).

Look for roof leaks in roof valleys, which are areas where two roofs meet at an angle.

Keep an eye out for vents, plumbing stacks, chimneys, attic windows, and any area of the attic or roof where different materials meet (including flashings). These areas are potential entry points for moisture.

How to get rid of an attic mould problem?

You need to thoroughly remove the mould in addition to addressing the moisture issue that led to the mould issue. Probably the most dangerous part of your house is the attic. Even skilled mould specialists who have performed countless attic mould removal jobs are very dangerous. With just one wrong move, you could hurt yourself by falling through the floor joists. If you are not careful, you may run across nesting animals, walk on a protruding nail, smash your head on a rafter or nail, fall through the roof, or encounter numerous other hazards.

Furthermore, because attics are narrow and constrained, breathing can be exceedingly difficult. This difficulty is increased when mould spores are present.

The accompanying information is intended to give you some pointers, fantastic advice, and perspective about attic mould and the best methods for dealing with it. Of course, additional evaluation by a skilled contractor is encouraged for all homeowners. Attics are too dangerous to try to fix on your own and even if you avoid the dangers, attic jobs are complex and there is a good chance someone with little experience will do the job improperly and potentially expose themselves and their family to mould-related health symptoms.


IS ATTIC MOLD DANGEROUS and affects your health?

Attic mould can cause health problems from allergies to mental health impairments. Mould is not something you want in your home! You may be wondering; how did the mould get here?

Mould is a sneaky, undetectable pest in your house. It can be found hiding under furniture, in crawl spaces, attics, and behind cupboards, places no one ever thinks to look. People may fight illnesses for weeks, months, or even years without ever realizing that they are really up against mould.

Although mould is most frequently linked to allergies, it is actually much more dangerous than people realize. All moulds have the potential to irritate people and trigger allergic reactions, but they can also lead to much more serious health issues. Toxins can be produced by some moulds. The health effects of toxic moulds can range from cancer to toxicity. Some moulds are poisonous, but not all of them. So where exactly does a mould become harmful or allergic? What is known as a mycotoxin draws that boundary?


  • Define the Scope

Your inspector will determine the scope of the required work and what may or may not need to be done after the inspection is complete.

  • Protect The People

Our first priority is the security of your family and the construction staff. This entails getting your house ready for the necessary work.

  • Correct Moisture Problems

To prevent mould from reappearing, the source of moisture must be eliminated or corrected as part of the cleanup procedure.

  • Remove The Mold

The first step of the project will be to remove and discard non-salvageable materials. Next, the salvageable materials are cleaned.

  • Restoration

Reinstalling any walls, floors, or ceilings that were taken out during the remediation process will be the last stage.



Mould prevention is always preferable to last-minute haste, as the adage "prevention is better than cure" states. This includes anything from fixing your water pipes, roofs, and other water and moisture-related issues to properly insulating and ventilating your attic.

  • Minimal difference in exterior and interior temperature 

To avoid condensation on the underside of the roof sheathing, make sure there is little temperature difference between the interior and external (outside and inside the attic).

  • Consult an attic expert

To locate air leaks and places of entry where interior air enters the attic.

  • Air seal all points of entry

Install or repair weather stripping around the attic hatch, and seal around holes, gaps, and cracks inside the attic, including wiring, plumbing vent pipes, or ducts. Attic air seal all points of entry such as bathroom fans and hoses, recessed lighting/pot lights, low-temperature light bulbs (LED), and install or fix weather stripping around attic hatch (in some cases).

  • Check for damage or blocked ventilation

Make sure that none of the rafter ventilation or baffles is obstructed or damaged by insulation.

  • Repair the baffles

Rebuild any rafter ventilation or baffles that were put incorrectly.

  • Adequate ventilation

Determine how much roof ventilation is needed for your attic space to make sure there is enough ventilation there.

  • Repair the roofs

Verify that the roof is free from damage and leaks.

  • Reduce moisture

Fill up any openings or cracks that moisture can enter through.

  • Keep the vent appliances on the outside

The air from all of your dryer, kitchen, and bathroom vent appliances should be vented outside.

  • Insulation to keep off mould growth

For mould development prevention, use the appropriate insulation, such as cellulose.


How can fix Attic Mold?

More than just recognizing mould is needed for mould removal. A mould issue must first be located or investigated in order to be solved.

  • Determining the cause of the mould development and the mould infestation area in your attic.
  • Mould containment with proper precautions taken to prevent spore dispersal.
  • Mould removal professionals employ the necessary tools to remove mould.
  • Deodorization and cleanliness are done as part of reparation to return your attic to its prior state.



The biggest worries are not moulded in your attic. The excessive moisture is brought on by airflow from the humid air within your home to the cooler, damper attic.

You should fix this by air sealing the following attic components: bathroom vents, ducting, can lights, wall/drywall joints, wall frame members, etc.

In order to keep humid air from entering a chilly, low-humidity attic space, air sealing can stop airflow into your attic.

I strongly advise hiring an independent house inspector to try and identify the causes and the best course of action before spending a lot of money on air sealing and mould remediation by a firm.





       How to Prevent and Remove Mold from Attic? Cellulose Man. Retrieved from:

       IS ATTIC MOLD DANGEROUS? 10 IMPORTANT FACTS YOU NEED TO KNOW. Branch Environmental. Retrieved from:

       Mould in Attics. Canadian home inspection. Retrieved from:,ridge%20vents%20at%20the%20top.