Mould is not a separate problem from water damage. It is what water damage becomes when drying is late or incomplete. Spores are in every home already. They need a wet surface and a food source, and drywall paper, wood, dust and fabric all qualify. Give them 24 to 48 hours of moisture and growth begins. That is why our whole approach to water losses is built around speed and measured drying, because preventing mould is far cheaper than removing it.
When mould is already present, whether from an old leak, a previous flood that was dried by eye, or chronic basement humidity, the job is remediation. That means containing the area so spores do not spread, removing the affected material rather than painting over it, filtering the air, and fixing the moisture source so it does not return. Killing mould with bleach on the surface does not remove it, and it does nothing about the moisture that grew it.
We assess and remediate mould across Toronto, North York, Scarborough, Etobicoke, Mississauga, Vaughan, Thornhill, Richmond Hill and Markham. For water damage in progress, call our 24/7 emergency line. For a suspected mould problem, book an assessment and we will tell you whether it is a small cleanup or a full remediation.
What we do on site
- Inspect the area with a moisture meter and borescope, and take samples for lab analysis when the scope is unclear or an insurer requires it.
- Build containment with sealed plastic and a HEPA negative air machine, and protect the path to the exit.
- Remove and bag porous materials with growth: drywall, insulation, carpet, ceiling tile and affected contents.
- HEPA vacuum and clean framing, concrete and other hard surfaces with an antimicrobial, and sand or abrasive-clean embedded growth.
- Identify and correct the moisture source, whether a leak, condensation, foundation seepage or humidity, or coordinate the fix with DryFort Waterproofing.
- Dry the area to a measured standard and run air scrubbers until the final clean is complete.
- Document every stage with photos, arrange third-party clearance testing on larger jobs, and hand off to Rebuild Pro Contracting.
How quickly does mould grow after a flood or leak?
Growth can begin within 24 hours on wet drywall paper and wood in a warm room, and is usually visible within 3 to 12 days. A Toronto basement in July, at 24 degrees and 70 percent humidity, is close to ideal. The same basement in January is slower but still grows mould if materials stay wet. This is the reason the IICRC S500 standard treats 48 hours as the line. Clean water that has sat longer than that is downgraded to Category 2, and the drying plan changes to account for likely microbial growth.
The practical takeaway: if a water loss is extracted and drying starts the same day, mould is rarely a factor. If the house sat wet for a weekend, expect to remove more material.
How do I know if I have mould behind the walls?
Look for a musty, earthy smell that is stronger in one room or when the HVAC runs. Look for staining, bubbling or a soft spot on drywall near a past leak. Baseboards that have pulled away or discoloured at the bottom edge are a common sign in basements. If anyone in the house has allergy symptoms that improve when they leave, that is worth noting.
We confirm with a moisture meter, which shows if the wall is still damp, and a borescope through a small hole to see the back of the drywall. Where needed we take a surface or air sample for lab analysis, but in most residential cases visible growth and moisture readings tell us enough to plan the work.
- Persistent musty odour in one area of the house
- Discoloured, bubbling or soft drywall near a previous leak
- Baseboards separating or dark at the bottom edge
- Condensation on windows and cold walls through winter
- Allergy or respiratory symptoms that ease when away from home
What does mould remediation actually involve?
First, containment. Plastic sheeting seals the work area and a HEPA negative air machine keeps it under negative pressure so spores move toward the filter, not into the house. Technicians wear respirators and disposable suits. Then, removal. Porous materials with growth, such as drywall, insulation, carpet and ceiling tile, are cut out, bagged inside the containment and removed. Non-porous and semi-porous surfaces like framing and concrete are HEPA vacuumed, cleaned with an antimicrobial, and in some cases sanded or abrasive-blasted to remove embedded growth.
Finally, the moisture source is fixed and the area is dried to standard. Without that step, remediation is temporary. Air scrubbers run throughout, and a final HEPA vacuum and wipe-down of the containment area completes the job. For larger jobs an independent post-remediation inspection confirms the air and surfaces are back to normal before rebuild.
How do I prevent mould in a Toronto basement?
Control humidity and stop water at the source. Run a dehumidifier in the basement from May to October and keep humidity under 50 percent. Insulate cold water pipes and exterior walls to prevent condensation. Extend downspouts at least 1.8 metres from the foundation and make sure grading slopes away. Fix foundation cracks and seepage rather than living with a damp corner. Do not store cardboard and fabric directly on a concrete floor.
If the basement has ever flooded or has chronic seepage, DryFort Waterproofing can address the foundation and drainage. The City of Toronto subsidy for backwater valves and sump pumps applies to many of the measures that also reduce basement moisture.
Is black mould more dangerous than other kinds?
Colour does not tell you the species or the risk. Stachybotrys, often called black mould, is one of many dark-coloured moulds, and many common household moulds like Cladosporium and Aspergillus can also appear black or green. Health Canada's position is that any indoor mould growth should be removed regardless of type, and that people with asthma, allergies or weakened immune systems are most affected. We do not test to identify species unless a doctor or insurer asks for it. We remove it.
Mould coverage in Ontario is limited. Most home policies cover mould only when it results directly from a covered sudden water event, such as a burst pipe, and many cap mould remediation at a sublimit. Mould from long-term leaks, humidity, seepage or neglected maintenance is generally excluded. The key is to report the water event promptly and dry quickly, which keeps mould within the original covered claim. When it is covered, we bill your insurer directly through a Direction to Pay. When it is not, we quote a fixed price before starting.
Frequently asked questions
Can I clean mould myself with bleach?
For a small patch on a hard, non-porous surface like tile or a painted metal frame, a detergent solution and a scrub will handle it. Bleach is not recommended on porous materials because the water in it soaks in and feeds the mould while the chlorine stays on the surface. Health Canada suggests professional remediation for any area larger than about one square metre or for any mould inside walls or on drywall.
Do I need to have the mould tested before you remove it?
Usually not. Visible growth on a wet or previously wet surface is enough to plan remediation, and testing adds cost without changing the work. We take samples when the scope is unclear, when a tenant or buyer dispute is involved, or when an insurer or physician requests it. Post-remediation clearance testing is more useful, because it confirms the job is done.
Will the mould come back after remediation?
Not if the moisture source is fixed. Mould returns when the leak, seepage or humidity that caused it is left alone. That is why every remediation we do includes identifying the source and either fixing it or bringing in DryFort Waterproofing for foundation and drainage work. Keeping basement humidity under 50 percent is the most important ongoing step.
Is it safe to stay in the house during remediation?
For most residential jobs, yes. The work area is sealed under negative pressure, so spores are pulled toward the filter rather than into living spaces. People with asthma, severe allergies or compromised immunity may prefer to stay elsewhere for the day or two of active removal. We let you know the schedule and when the containment comes down.
Does my insurance cover mould in Ontario?
Only when the mould is a direct result of a covered sudden water event, and often only up to a sublimit. Mould from slow leaks, condensation, seepage or poor maintenance is usually excluded. Reporting a water loss quickly and having it dried properly is the best way to keep any mould inside the original covered claim.