Mould needs three things: moisture, a food source and time. You cannot remove the food source, because it is your house. You cannot remove time. So every legitimate mould strategy is a moisture strategy - and that is a building repair problem, not a spray-bottle problem.
We locate the water. That means moisture mapping with meters and, where necessary, opening a small inspection area: a failed shower pan, a supply line weeping inside a wall, a condensation problem on uninsulated ductwork, a roof or flashing leak, negative grading pushing water toward the foundation, a blocked window weep, a dryer venting into a wall cavity, or a bathroom fan that terminates in the attic instead of outside. Every one of those has a specific fix.
Then we correct it. Then we rebuild the assembly properly - new drywall with the correct board for the location, treated or replaced framing where it was compromised, insulation that was contaminated removed and replaced, correct vapour and air sealing details, flooring rebuilt on a dry substrate, and finishes matched to the rest of the room.
For large contaminated areas, occupied homes with vulnerable residents, or anything tied to an insurance claim, containment and remediation should be performed by a certified remediation contractor with proper containment, negative air and post-remediation verification. We are a licensed general contractor, not a certified mould remediator - we will tell you when the job needs one, and we will coordinate with them and handle the reconstruction afterwards, which is the part remediators do not do.
For small, contained, non-friable areas we handle the removal and rebuild directly.
The corrections that actually stop recurrence are unglamorous: a properly sized bathroom exhaust fan ducted to the exterior with a smooth rigid duct, kitchen ventilation that vents outside, insulation and air sealing that stop condensation on cold surfaces, crawl space vapour barrier and drainage, grading and downspout extensions that move roof water away from the foundation, and sealant maintenance in wet rooms. We quote those as part of the repair, not as an upsell afterwards.
We do moisture testing, which is what actually drives the repair. Air and surface sampling for species identification should be done by an independent industrial hygienist - not by the company doing the removal, because that is a conflict of interest. We are happy to work from their report.
On non-porous surfaces like tile and glass it kills surface growth. On porous materials like drywall, wood and insulation it does not penetrate, and the water in it can make things worse. Porous contaminated material gets removed, not treated.
Small contained repairs - one bathroom wall, a vanity cabinet base, a section of ceiling - typically run $650 to $2,800 including the finish work. Larger reconstruction after a certified remediation runs on a scoped fixed price. The moisture diagnosis is a separate paid inspection so that the findings are honest.
Sudden, accidental water events such as a burst supply line are often covered, and resulting mould may be covered with limits. Long-term seepage, deferred maintenance and humidity problems are usually excluded. We document thoroughly either way so your adjuster has what they need, but we cannot promise coverage.
Almost always ventilation. Either there is no exhaust fan, the fan is too small for the room, it vents into the attic instead of outside, or the duct is a crushed flexible run that moves almost no air. Fixing that one item permanently solves a large share of the bathroom mould we see.
