Why does my Ottawa basement smell musty every spring?

A musty smell is a reason to look for moisture and mould somewhere in the basement. Possible sources to check include water coming through foundation walls in spring and condensation on cold surfaces.

Health Canada describes mould growth by size: a small area is one to three patches, each less than one square metre; a medium area is more than three patches, or patches greater than one square metre but less than three square metres; an extensive area is a single patch larger than three square metres. You can generally clean small and medium sized areas yourself. For extensive growth, Health Canada recommends getting professional help to assess and clean it up.

Before you do anything that involves cutting or removing drywall, plaster, ceiling texture or flooring in an older basement, it is worth pausing. Those materials in a home built before 1990 may contain asbestos, and disturbing them turns a mould job into an asbestos job. Health Canada advises hiring a professional to test suspect materials before renovating, and a qualified asbestos removal specialist if asbestos is found. If you have already disturbed something and are not sure what it is, stop the work, do not disturb it further, and have it tested by a professional before work resumes.

For mould that comes back each spring, the moisture source comes first. Cleaning visible growth without addressing the water entry means it comes back. Check the grading around the foundation, the state of window wells, the eavestroughs and downspout extensions, and whether the basement has any vapour barrier gaps. A professional can also check for condensation patterns on cold pipes and walls.

We found no Ontario statute or regulation that licenses mould remediators or sets indoor mould limits. Industry guidelines exist but none of them carry the force of law. What a reasonable written scope for professional remediation includes is: a description of the affected area, the method of removal, confirmation that the moisture source will be repaired or has been identified, and a statement that no visible mould will remain at the end of the job. After the work, check those three points yourself: the written scope was done, the moisture was repaired, and no visible mould is left.

If the job grows to involve drywall or other building materials and testing shows asbestos, Ontario's O. Reg. 278/05 governs the abatement work. The Type the contractor assigns, based on whether the material is friable and how much of it is disturbed, determines what training, notice and clearance testing apply. Ask the contractor to put the Type in writing in the quote.

You can request a match with local contractors through the form on this page; they are listed in the Ottawa Construction Network directory.

Put two written quotes next to each other and compare the moisture repair each one commits to, not just the remediation method, because a quote that skips the water source is quoting you half a job.