Mold remediation in Ottawa costs roughly $600 to $1,800 for a small, contained patch under about 30 square feet, and $2,500 to $8,000 for a typical mid-sized job such as one wall of a finished basement or a bathroom behind the tile. Large or whole-basement remediation involving containment, HEPA filtration, and significant demolition commonly runs $8,000 to $25,000 in 2026, and severe cases with structural rot can exceed that. Priced by area, most Ottawa remediation firms land between $20 and $45 per square foot of affected surface once containment, removal, disposal, HEPA cleaning, and antimi...
Remediation companies scale pricing by the size of the contaminated area and how much containment the job demands. A small job — under roughly 30 square feet, such as mould on a section of drywall behind a leaking washing machine — typically runs $600–$1,800 and can often be completed in a single day. A medium job of 30–100 square feet, like a bathroom wall cavity or a strip of finished basement wall, generally costs $2,500–$8,000 because it requires poly containment, negative air machines, HEPA vacuuming, and disposal of contaminated drywall and insulation. Large-scale remediation above 100 square feet — a flooded basement, a chronically damp crawl space, or widespread attic sheathing mould — commonly costs $8,000–$25,000. Attic mould from bathroom fans venting into the attic, a very common Ottawa problem in 1970s–1990s homes, usually runs $2,500–$7,500 to treat, plus $600–$1,500 to reroute the fans and correct the ventilation that caused it.
If mould follows a burst pipe or sewer backup, water extraction and drying come first and are billed separately, usually $1,200–$4,000 for a basement. After-hours or weekend emergency callouts typically carry a 1.5x labour multiplier.
A legitimate Ottawa remediation quote is not just "spray and wipe." It should itemize containment (poly barriers and zippered access), negative air pressure with HEPA-filtered air scrubbers, removal and bagged disposal of porous materials like drywall, insulation, carpet, and underlay, HEPA vacuuming of all surfaces, damp-wiping with an antimicrobial, and controlled drying. Non-porous materials such as concrete, framing lumber, and steel can usually be cleaned and treated rather than removed. Encapsulant sealer on cleaned framing is common and adds a modest amount. What is generally not included is reconstruction — replacing the drywall, insulation, flooring, and paint after the mould is gone. That rebuild often costs as much as the remediation itself, commonly $2,000–$8,000 for a basement section, so ask whether the company handles it or whether you'll be hiring a separate renovator afterward.
A visual mould inspection from an independent Ottawa building science or indoor air quality consultant typically costs $300–$600. Adding air sampling with lab analysis runs $150–$300 per sample, so a typical inspection with two indoor samples and one outdoor control comes to $600–$1,200 all in. Surface tape-lift or swab samples are cheaper at roughly $75–$150 each. Health Canada's guidance is that visible mould should be removed regardless of species, so testing is not always necessary for a small, obvious patch — you can usually skip it and go straight to remediation. Testing does make sense when you smell musty odours but can't find the source, when someone in the household has respiratory symptoms, during a real estate transaction, or when you want independent post-remediation verification that the job worked. Critically, use a separate company for testing than the one doing the removal; a firm that tests and then quotes its own remediation has an obvious conflict of interest.
For larger jobs, budget $400–$800 for independent clearance testing after the work is done. It confirms spore counts are back to normal and gives you documentation for insurance or a future home sale.
Ottawa's climate creates a near-perfect mould environment twice a year. Spring meltwater saturates clay soils around foundations, and homes with poor lot grading, disconnected downspouts, or clogged weeping tile take on moisture in the basement. Then in July and August, warm humid air enters cool basements and crawl spaces and condenses on cold surfaces. Add the winter side: interior humidity from cooking, showers, and drying clothes migrates into attics through poorly sealed ceiling penetrations and pot lights, freezes on the roof sheathing, and then melts and feeds mould in the spring thaw. Older neighbourhoods with rubble or fieldstone foundations — Sandy Hill, the Glebe, New Edinburgh — see chronic basement dampness. Newer builds aren't immune either; tightly sealed homes with undersized or unbalanced HRV systems can trap humidity. Remediating without correcting the moisture source virtually guarantees the mould returns within a year or two, which is why any competent quote starts with a moisture diagnosis.
Sometimes, and the distinction matters. Most Ontario home insurance policies cover mould damage when it results from a sudden and accidental covered event — a burst pipe, an appliance supply line failure, or water damage from putting out a fire. What is almost never covered is mould caused by gradual seepage, long-term humidity, poor maintenance, or groundwater intrusion, and many policies explicitly exclude flooding unless you carry an overland water or sewer backup endorsement. Coverage limits for mould are also frequently capped, often at $10,000–$25,000 even when the claim qualifies. If you think you have a claim, photograph everything before any material is removed, keep all invoices, and notify your insurer before demolition begins. Ask your remediation contractor whether they work directly with insurers and can provide the moisture readings and documentation adjusters require — it materially improves the odds of a claim being approved.
Mould remediation is not a licensed trade in Ontario, which means anyone can advertise the service — so vetting is entirely on you. Look for technicians certified through IICRC (Institute of Inspection, Cleaning and Restoration Certification), particularly the Applied Microbial Remediation Technician designation, and confirm the company carries general liability insurance and WSIB coverage. Ask them to show you their containment and negative air setup plan in writing, and ask what happens if the contamination turns out to be larger than expected once the wall is opened — a fair contract has a defined change-order process, not an open-ended hourly rate. Get three written quotes and be sceptical of both the outlier low bid and the high-pressure scare pitch. Also insist the quote addresses the water source: if nobody has explained why the mould grew, the job isn't finished. Comparing quotes side by side quickly reveals who did a real diagnosis and who just walked through with a flashlight.
In 2026, small contained jobs under about 30 square feet run $600–$1,800, mid-sized jobs of 30–100 square feet run $2,500–$8,000, and large or whole-basement remediation runs $8,000–$25,000. Priced by area, most Ottawa firms charge roughly $20–$45 per square foot of affected surface including containment, removal, HEPA cleaning, and disposal.
A visual inspection from an independent consultant runs $300–$600. Adding air sampling with lab analysis costs $150–$300 per sample, so a typical inspection with two indoor samples and an outdoor control totals $600–$1,200. Use a different company for testing than the one performing removal to avoid a conflict of interest.
Usually only when the mould results from a sudden, accidental covered event such as a burst pipe. Mould from gradual seepage, chronic humidity, groundwater, or poor maintenance is typically excluded, and even covered claims are often capped at $10,000–$25,000. Overland water and sewer backup endorsements matter, so check your policy before assuming coverage.
Attic mould treatment generally runs $2,500–$7,500 depending on the sheathing area affected. Budget another $600–$1,500 to correct the cause, which in Ottawa homes is usually bathroom fans venting into the attic or blocked soffit ventilation. Without fixing the ventilation, the mould comes back.
Health Canada guidance suggests small areas — roughly under one square metre of hard, non-porous surface — can often be cleaned by a homeowner with soap and water and proper protective equipment. Larger areas, anything inside wall cavities or insulation, and any situation involving sewage or a household member with respiratory issues should go to a certified professional with proper containment.
Remediation and cleaning alone typically don't require a building permit. However, if the work involves removing load-bearing elements, structural repairs to rotted framing, or a substantial rebuild of the space, a City of Ottawa building permit may be required. Confirm with the City before demolition begins.