Mould Matters When it Comes to Your Home

If there’s one thing that is instantly recognizable as something you do not want in your home, it’s mould. Although mould growth is often associated with older homes and musty basements, it can grow anywhere – even in new homes. And if you see significant mould growth in your new home, there is likely something wrong with your new home or with the way you are maintaining it.

We recently sat down with Tarion’s resident mould expert, Michael, who has several years of experience dealing with mould and asked him a few questions to clear the air on this ‘mouldy’ issue.

What causes mould in new homes?

Mould belongs to the FUNGI kingdom which are found indoors and outdoors.  That’s why there is no such thing as a mould-free building or environment and mould can be found almost anywhere. Mould grows on virtually any substance when moisture is present. Some moulds are actually good as they play an important part of our overall ecosystem.

But mould in your home is definitely not good. Sometimes building materials can be damp or wet at the time of their installation, and as they start to dry you may see some evidence of mould. Other times it’s because moisture is getting into the house somehow, perhaps due to a plumbing leak or a breach within the building envelope, such as a crack in the foundation or missing flashing on the roof. Whatever the reason, it’s important that you take a proactive approach by not ignoring the problem and addressing the issue immediately.

What causes mould?

One word: moisture.

A mould-free environment is impossible. Mould spores are everywhere, outside your home, in the soil and air, as well as inside your home. But they aren’t just in your home; they are in every single home and building. The difference between having a mould problem and not having one is excess moisture.

Mould can grow on almost any material—wood, paper, drywall, carpet, food, even dynamite. All it needs is a damp spot to land on in your home and it can begin to grow, using whatever material it lands on as a food source.

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If you see mould or suspect mould growth, the first thing you do is find the source of moisture and eliminate it.

Take control if you see mould

You might not be able to prevent mould spores from coming into your home, but you can control mould growth by controlling the moisture in your home. If you see mould or suspect mould growth, the first thing you do is find the source of moisture and eliminate it.

Take a look at your windows and doors. If you see moisture or condensation on them you might need to get a dehumidifier and/or increase the air movement and ventilation in your home.

How do I know if it’s a problem?

If the area affected by mould covers less than one square metre you can clean it yourself using an unscented soap/detergent solution. Remember to use gloves, a respirator and eye protection. After cleaning the area, dry it and remove any porous or damaged materials.

Once the source of moisture has been eliminated and the mould cleaned up it’s important to monitor for future mould growth. If it comes back, contact your builder.

Mould and your new home warranty 

If what’s causing the mould is a warrantable defect in your home, your new home warranty covers mould remediation for up to $15,000, in addition to repairing the warranted defect that’s causing the mould growth to begin with. But if the culprit is improper home maintenance on the part of you, the homeowner, mould remediation isn’t covered.

How can I prevent mould? 

A little home maintenance can go a long way when it comes to mould prevention. As a new homeowner, it’s important that you regularly:

  • Use the principle exhaust in your home, as well as bathroom and kitchen range hood fans
  • Inspect plumbing fixtures and immediately repair leaks
  • Inspect window and door surfaces for moisture/condensation
  • Inspect the foundation, roof, windows/doors and exterior cladding for moisture intrusion

Lessons Learned 

  1. Homeowners can prevent mould growth by controlling the moisture in their home.
  2. Ontario’s new home warranty covers mould remediation up to $15,000 if the cause of mould growth is a warrantable defect in the home.
  3. Mould growth due to improper home maintenance is not covered.

Visit Tarion.com for more information on moisture control and maintenance tips for your new home.


The goal of this blog is to provide you with general information about the warranty process by sharing real experiences from new homeowners. The blog should not be relied upon as legal advice. For privacy reasons, we will not address or resolve current cases in a public forum, so any comments or questions that are posted on this site that describe individual cases cannot be discussed. If you have a question about your warranty or Tarion generally, we would be pleased to discuss your issue, in the context of your particular circumstances and in confidence. We exercise reasonable care to avoid offensive, illegal or defamatory content from being posted, as well as comments that are intended solely for self-promotion or considered to be spam.