Commercial Mold Remediation in London, Ontario: Offices, Retail and Multi-Unit Buildings

Commercial mold remediation in London, Ontario has to solve two problems at once: remove the mold properly, and keep the building working while it happens. A tenant complaint about a musty smell, staining in a ceiling tile after a roof leak, or growth found behind a vanity during a unit turnover can quickly become a liability question for a property manager or condo board. Here is how a remediation job in an occupied building should run, and what you should get at the end.

Where mold shows up in commercial buildings

• Ceiling tiles and drywall under roof leaks, especially flat roofs and around rooftop units.
• Exterior walls of multi-unit buildings, where condensation collects behind furniture and window coverings in winter.
• Bathrooms and kitchens in rental units, often from exhaust fans that are undersized, blocked or never switched on.
• Mechanical rooms and basements, from condensate lines, sump pits and slow plumbing leaks.
• Behind vinyl wallcovering in older offices and hotels, where moisture gets trapped against drywall.

Step 1: find the moisture, not just the mold

Mold is a symptom. Remediation that skips the moisture source comes back. The assessment should include moisture readings and thermal imaging around every visible patch to find how far the wet area extends, and a clear statement of the cause: roof, plumbing, condensation or ventilation. If the cause is a roof or envelope problem, your roofer or envelope consultant needs to fix that before or alongside the remediation.

Step 2: containment and negative air

In an occupied building, containment is what keeps spores and dust out of hallways, neighbouring suites and the HVAC system. Expect:

• Plastic sheeting sealed floor to ceiling around the work area, with a zippered entry
• HEPA air scrubbers exhausting so the work area is under negative pressure
• HVAC supply and return openings in the area sealed off
• Walk-off mats and HEPA vacuuming at the exit so nothing is tracked out

This follows the approach in the IICRC S520 standard for professional mold remediation. Spraying a product on visible mold without containment is not remediation.

Step 3: remove, clean and dry

Porous materials with growth, such as drywall, ceiling tile and insulation, are cut out and bagged inside containment. Structural wood and concrete are HEPA vacuumed and cleaned. Anything still wet is dried to its dry standard before the area is closed up. Loud and dusty steps are scheduled for evenings, nights or weekends where tenants need the space during the day.

Step 4: older buildings and designated substances

Drywall compound, plaster, ceiling tile and floor tile in older buildings can contain asbestos. Under Ontario's Occupational Health and Safety Act, designated substances must be identified before this kind of work. Ask for your designated substance survey or have materials tested before any cutting starts. It protects tenants, the crew and the owner.

Step 5: the clearance report

When the work is done you should get a written report you can put in the building file and show a tenant, a board or an insurer:

• Before, during and after photos of each area
• The cause of the moisture and what was done about it
• What materials were removed and how much
• Final moisture readings showing the structure is dry
• Recommendations to stop it coming back

Where a tenant, lawyer or board wants independent proof, post-remediation air or surface sampling can be done by a third-party consultant. Using someone independent avoids the conflict of the remediation company testing its own work.

Tenants, communication and liability

Under Ontario's Residential Tenancies Act, landlords must keep rental units in a good state of repair, and mold complaints in multi-unit buildings often reach the Landlord and Tenant Board when they are ignored. Acting quickly, documenting the cause and the work, and giving tenants written notice of what is happening and when is the best protection a property manager has. We can provide plain-language tenant notices with the schedule.

Prevention after remediation

• Fix the source: roof, plumbing, exhaust fan or envelope
• Check bathroom fans in every unit at turnover
• Keep winter indoor humidity in a reasonable range, typically 30% to 40% in cold weather
• A fungistatic coating on exposed framing before it is closed up
• A yearly moisture walk-through of roofs, mechanical rooms and known problem units

See our commercial mold remediation and water damage services, or register your buildings in our Priority Response Program for priority dispatch and a yearly moisture walk-through.

Common questions