White Mould & Your Roof: Types, Dangers, Causes, & Solutions.

Mould is natural fungi that can occur in outdoor and indoor spaces in Calgary. Mould is of different species, and while some species cause no harm to human health, others are dangerous. Though many are familiar with black mould, white mould is a dangerous species of mould that requires immediate removal once it is noticed. 

But what is white mould (or white mold if you’re American)?

This piece explains what you need to know about white mould, such as what it is, its types, what causes it, and how to remove and prevent it.

What is white mould?

White mould is a mould species that can occur anywhere on a property, such as in the attic, roof, and crawlspace. Its white powdery form usually identifies it. 

Types of White Mould

White mould is only one colour of mould commonly found on Calgary homes. Types of moulds, of the white variety, vary. The most common types of white mould include Penicillium, Aspergillus, and Cladosporium. Generally, white mould is white and powdery, which are the most common traits of these types.


Penicillium is a common type of white mould that is typically identified by its stale odour. Though it is typically white, it can also appear in other colours, such as pink or yellow. Its presence in the home is linked to several allergies, such as hay fever and lung inflammation. 


Aspergillus is yet another type of white mould and is defined to have different subspecies based on climates. However, aspergillus often has a cotton or wool texture with blue-green and yellow-green colours. 


Cladosporium is another type of white mould that can appear in indoor and outdoor environments. It is commonly known for its olive greyish appearance with a velvety texture. It is a potential cause of allergies in infants and infections in the eyes, fingernails, and toenails.

Dangers of White Mould

White mould is one species of mould that is dangerous to human health. Depending on the type, inhaling white mould spores for an extended period can cause different allergic reactions and infections. For example, mould-induced asthma, allergic fungal sinusitis, and allergic bronchopulmonary are all aftermaths of a prolonged inhaling of white mould.

Hence, it is necessary to deal with mould once it is noticed anywhere in the home by consulting a professional mould inspection contractor. They will help you remove it safely and guide you on how to prevent a future occurrence.

Causes White Mould

White mould grows with high moisture levels, food sources, and adequate temperature. Since the food source can be drywall or wood, white mould is commonly found on attics, crawlspaces, and roofs. Furthermore, the temperature in these areas helps foster white mould growth, since the required temperature for white mould growth is between 2 and 40 degrees Celsius. There is almost always a water supply for the mould and lack of fresh air contributing to white mould growing.

Places To Find White Mould

White mould can be found in different parts of the home, with three conditions met. With the presence of moisture, food source, and enabling temperature, white mould can grow anywhere in the home. However, some areas of the home are more prone to mould growth than others. These places include the roof, attic, and crawlspace. 

White Mould in Attics

The attic is prone to white mould growth since the materials serve as a good food source. Moisture from a leaky roof also plays a part in the growth of white mould. Moisture in this area can also result from condensation due to temperature changes in the attic. 

White Mould in Crawl Spaces

Again, the crawlspaces are not left out from areas to find white mould in the home. Since the spaces are difficult to dry once moisture gets trapped in them, it is a potential home for white mould. Poor ventilation is also a leading cause of mould growth in crawl spaces. Moreover, leaking pipes and plumbing don’t help matters.

White Mould Roof

Wood is a good source of food for white mould. White mould loves wood and is commonly found on anything wood, hence its rapid growth on the roof. This explains why it is commonly found on leaking roofs or roofs with moisture intrusion. Proper ventilation is also important for your roof and can impact white mould growth.

A shingle being pealed off to show white mould

White Mould Solution

The best solution to white mould is to remove it immediately after it is noticed. Removing white mould when noticed helps prevent it from spreading to other areas. 

However, removing white mould can be dangerous, especially when it is in a large amount and has spread across the surface. Hence, it is highly recommended that a professional mould specialist remove the mould. A quick Google search for “mould removal” or “Mould remediation” will put you on the right path. However, just like hiring a roofing contractor, you want to hire a professional at removing mould. 

When hiring a roofer, you look for the certifications, experience, and reviews. These are also necessary when hiring a specialist to remove mould on your property.

However, while it is important to remove white mould when noticed, it is equally important to take necessary steps to prevent its occurrence again. Preventing white mould from occurring again is simple and achieved by preventing its contributing factors, such as poor ventilation and moisture due to leaks in the roof. Sometimes, when left for too long, it requires an entire roof replacement.

This is linked to hiring a reputable, professional roofing contractor like Whalley’s. Your roofing contractor will inspect the source of the white mould and provide necessary solutions. For example, if your roof is leaky, your roofer will recommend repairing the leaks, and if your attic lacks adequate ventilation, they will discuss improving the ventilation system or lack of one. 

Providing your attic with adequate ventilation and repairing leaky roofs will help prevent moisture from high humidity formation in these areas. 


White mould is a white and powdery species of mould. Since it is a dangerous species of mould, it should be treated when noticed. However, white mould is dangerous and should be left for a professional that specializes in mould remediation and mould removal. Inhaling the particles during cleaning can trigger allergic reactions. 

While you want to invest in removing white mould, it is also important to prevent a future occurrence by eliminating white mould factors. Since moisture from a leaking roof and poor ventilation are the major root causes of white mould, it is best to hire a professional roofing company to take care of them. This is where Whalley’s comes in.

At Whalley’s Four Season Roofing, we are a professional roofing contractor specializing in different roof types on commercial and residential properties. We offer many roofing services for your needs and only do work that is needed. Contact us for exceptional customer service for your next roof repair or replacement.

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