Should an Ottawa mould contractor find the moisture source first?

Yes, finding and fixing the moisture source is the first step, not an optional add-on. Mould returns if the water keeps coming in, so any remediation done before the source is addressed is temporary at best.

Health Canada classifies mould by area to help you decide how much professional involvement makes sense. A small area covers 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. Health Canada says you can generally clean small and medium areas yourself, and recommends that a qualified professional assess and clean up large areas. The moisture source question applies at every size: cleaning without fixing the leak, the condensation problem or the drainage issue just means the mould comes back.

A good contractor should walk through the moisture diagnosis before quoting the remediation. That means identifying where the water is entering or accumulating, whether it is a roof, a foundation, a plumbing leak, a ventilation gap or condensation on a cold surface, and confirming it can be corrected either by them or by a separate trade before the mould work begins. If a contractor quotes only on scrubbing or removing material without addressing the source, ask directly what happens if the moisture returns.

One thing to check before the mould work starts

If the affected area involves drywall, plaster, ceiling texture or flooring in a home built before 1990, raise the asbestos question before anything is cut or removed. Those materials may contain asbestos, and disturbing them without testing first changes the scope of the job significantly. Ontario's O. Reg. 278/05 governs asbestos work in Ottawa, and the Type of work, which determines what the contractor must do by law, depends on whether the material is friable and how much is disturbed. Ask the contractor to assess for asbestos before any demolition begins and to give you the Type classification in writing.

When you are comparing quotes, ask each contractor to describe how they will confirm the moisture source is resolved before they close up the wall or ceiling, and what their plan is if the source turns out to be more involved than expected.

If suspect material in the area has already been disturbed, stop the work, don't disturb it further, and have it tested by a professional.