Water damage and mould go together. Mould spores are present in every Mississauga home. All they need to grow is moisture, a food source like drywall paper, wood or carpet backing, and time. After a leak or flood, that time is short: mould can begin growing within 24 to 48 hours, and visible colonies can appear within a week or two. Here’s how to tell if you have a problem and how to stop it.
How Fast Does Mould Grow After Water Damage?
| Time after water damage | What’s happening |
|---|---|
| 0–24 hours | Water wicks up drywall; carpet pad saturates; humidity rises. |
| 24–48 hours | Mould spores start germinating on wet organic materials. |
| 3–7 days | Musty smell; colonies form inside wall cavities and under flooring. |
| 1–3 weeks | Visible spotting on drywall and baseboards; materials start breaking down. |
This is why professional water damage restoration in Mississauga focuses on drying fast. Getting materials below their dry standard quickly is the best mould prevention there is.
Stop mould before it starts. Get your home dried professionally.
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Signs of Mould After a Leak or Flood
- A musty, earthy smell, especially in basements and closets
- Black, green, grey or white spotting on drywall, baseboards or ceiling
- Paint bubbling or peeling
- Warped baseboards or soft drywall
- Condensation on windows and high indoor humidity (over 60%)
- Allergy-like symptoms that improve when you leave the house
Why Household Fans Aren’t Enough
Box fans move air across the surface, but water hides in wall cavities, under baseboards, inside subfloors and beneath laminate. Surfaces can feel dry while the inside of the wall is still wet. Professionals use moisture meters and thermal cameras to find hidden water, and commercial dehumidifiers pull moisture out of the air so materials can actually dry. Learn more in how long water damage takes to dry.
How Mould Is Prevented During Restoration
- Fast extraction of standing water
- Removal of materials that can’t be dried in time (wet insulation, carpet pad)
- Antimicrobial treatment on framing and exposed surfaces
- Structural drying with daily moisture monitoring
- Final moisture verification before walls are closed up
What If Mould Is Already There?
Small spots (under about 1 square metre) on hard surfaces can often be cleaned by a homeowner with detergent and water while wearing gloves and an N95 mask. Larger areas, mould inside walls, or mould after a sewage backup should be handled by professionals using containment, HEPA air filtration and removal of affected materials. Health Canada recommends fixing the moisture source first, because cleaning mould without fixing the water problem doesn’t work.
Does Insurance Cover Mould?
Mould that results from a covered, sudden water loss that was reported promptly is often covered as part of the claim. Mould from a long-term leak or high humidity usually isn’t. See our Ontario insurance claim guide.
Prevent Mould in Your Mississauga Home
- Keep indoor humidity between 30% and 50%. Run a dehumidifier in the basement in summer.
- Use bathroom fans during and 20 minutes after showers.
- Fix drips and leaks right away.
- Keep gutters clear and downspouts pointed away from the foundation.
- Don’t store cardboard boxes directly on basement floors.
Related: flooded basement checklist · water damage cost guide
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