Mould Cleaning vs Mould Remediation
One of the most common points of confusion for Ontario homeowners who discover mould is whether the situation requires standard cleaning or professional mould remediation. The distinction matters enormously — standard cleaning handles surface mould on non-porous or semi-porous surfaces, while professional remediation is needed when mould has penetrated structural materials or grown beyond what cleaning can address.
When Standard Cleaning Is Appropriate
- Small mould spots on grout or caulk in bathrooms: Standard cleaning problem — an oxygen bleach solution applied and scrubbed removes surface mould on tile grout. If the grout is still intact (no softening or crumbling), cleaning is appropriate
- Mould on painted walls (superficial): Small spots on a painted wall where the mould is on the surface and the drywall beneath is solid — diluted bleach on a cloth, wipe, allow to dry thoroughly, monitor for return. If it doesn't return within 2–3 weeks, the source of moisture was addressed and the surface mould was the full extent of the issue
- Mould on hard surfaces (tile, glass, metal): These non-porous surfaces can be thoroughly cleaned; mould cannot penetrate into them
When Professional Remediation Is Required
- Mould covering more than 1 square metre (10 sq ft) — Ontario Ministry of the Environment and Health Canada guidance identifies this as the threshold for professional assessment
- Mould on drywall, insulation, or structural wood — these porous materials cannot be cleaned, they must be removed and replaced
- Black mould (Stachybotrys chartarum) — even a small area of confirmed black mould warrants professional assessment
- Any mould growth after a flooding or significant water intrusion event — submerged materials develop internal mould that surface cleaning cannot address