How to Spot Mould Problems When Buying a Home

Removing odors from Toronto basementWho wants to buy a home that’s has chronic mould problems?  That’s right, not you.

For some homeowners, mould is an irritation they put up with in small doses, as long as it does not get out of hand. Others have upper respiratory problems like chronic asthma and bronchitis that mould aggravates.  They know that mould is a sign of underlying damp (and possibly water leaks) that can cause the value of their investment to deteriorate.  Nobody wants to buy a home with mould, for the mould problem itself, as well as the problems that are causing it’s growth.

We were recently called out to an aging home in the Etobicoke section of Toronto for a mould assessment.  It was for sale and the prospective buyer noticed signs of mould and wanted to get a professional assessment done before making an offer on the home.  What we found were large pockets of water pooling around the basement foundation, and leaking through the concrete foundation. It was caused by excessive water runoff, lack of proper drainage, and an absent of an exterior waterproofing barrier on the outside of the foundation.  All told, it was going to cost thousands to repair.  The prospective buyer was know able to make an informed decision, walk away or make an offer reflecting the needed repairs.


When you’re looking at a possible home to buy, keep the following in mind when it comes to mould:

What to Look For – Mould comes in different colours including black, green, grey and white which means it can be invisible depending on the background. Fortunately it has a characteristic musty smell that can be a giveaway. Although found in houses in the driest dusty deserts, it prefers damp materials such as ceilings, wallboards, carpets and emulsion-painted surfaces.

Where to Look – Mould and damp go together so keep a look-out for excessive moisture. This can include:

  • Spaces closed up tightly. This is typical of new buildings.


  • Persistent storm-water leaks in roofs, water pipes, and windows for example


  • High humidity levels characteristic of poorly ventilated homes


  • Bad housekeeping. Damp towels and flooded pot plants are good examples


  • Signs of regular flooding. Learn to spot tidemarks close to floors.

Be especially thorough when inspecting bathrooms including showers and under-basin cabinets, because moisture and mould go together.


Ask Questions

Sellers and their agents are supposed to declare defects. Ask them direct questions when inspecting the house a second time. They are more likely to be open and provide direct answers. However bear in mind that they only have a duty to disclose what they already know.

Try an oblique angle. Enquire whether there are any leaks in heavy rain, or whether there have been plumbing problems recently. Often what they don’t say is more important than what they reveal. Body language is another important indicator.

Ask Your Home Inspector

If anything particularly worries you ask your home inspector to comment. Have them pay particular attention to any signs of water or damp problems, especially in the basement. Suggest that they include their comments in their inspection report. Allow them to include a disclaimer that they may have missed some infestations.

Include a Mould Clause in Your Offer

You can include anything you like in your purchase offer (although a seller is not bound to agree to anything). This can include responsibility for removal of undeclared mould and repair of its consequences. This is often the clincher that provokes the honest and open declaration you were hoping for in the first place.

Once you know the extent of mould (and any other defects) you face the decision of whether to go ahead or not. No homes are perfect and every buyer immediately improves a few things. Now is the time for a little negotiation. The seller may well concede something off the price. This could provide the funds you need for a professional waterproofing and mould remediation solution.


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NuSite Group is a Toronto based basement waterproofing and foundation repair company that specializes in Basement Waterproofing, Basement Lowering, and Foundation Repairs. Call us today at 416-622-7000 or 905-731-1228 for a free in-home estimate and inspection.

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Mark Lipton - Homestars Review

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Our basement leaked! Of course . . . we bought a 100 year old house! But my office needed to be in the basement permanently. I interviewed 10 different companies until we decided on the Steinbergs and their crew at Nu-Site! They are professional, reliable, courteous, honest, and they really make an effort to communicate with the client about every step of the process.

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Had several cracks in my basement wall and they would leak whenever we had a heavy rain. It started about a year and a half ago and seems to have gotten worse over the past 6 months. I tried having my neighbor seal it, but it started leaking again within a few weeks. Called several waterproofing companies and got several quotes. Finally went with Nusite contractors for the job. They gave a reasonable quote and I liked the guy that came by for the estimate. They stayed within budget and cleaned up before they left. It's been almost 3 months now and it seems to be working great.