Lease and Rental Management
Mold in a rental unit is a maintenance issue that landlords must address under the Residential Tenancies Act's requirement to maintain the unit in a good state of repair and fit for habitation. Ignoring tenant mold reports is a significant liability.
Understanding the cause is the first step. Mold grows where moisture is present. The source may be tenant behaviour (insufficient ventilation during showering, cooking), building defects (water infiltration, plumbing leak), or inadequate ventilation systems.
Ontario Tenancy Law
If the cause is a building defect — leaking roof, plumbing leak, inadequate bathroom exhaust — remediation and repair of the source is the landlord's obligation. Simply cleaning visible mold without addressing the moisture source produces temporary results.
If the cause is tenant behaviour — using the bathroom without running the exhaust fan, improperly venting a dryer — the landlord should still address visible mold but should also communicate with the tenant about behaviours contributing to the problem.
Protecting Landlord Rights
Professional mold assessment for significant growth determines the type and extent of contamination. Surface mold (mold on walls and ceilings visible from the surface) may be addressable by cleaning; bulk contamination behind walls or under floors requires professional remediation.
Tenant remedies for unaddressed mold include LTB applications for rent abatement and repair orders. LTB adjudicators have awarded significant rent abatements in mold cases where landlords failed to respond to tenant reports.
Preventive maintenance reduces mold risk: annual inspection of bathroom exhaust fan function, checking for roof and plumbing leaks, verifying basement waterproofing, and addressing any drainage deficiencies that direct water toward the building.