Not every patch of mold needs a professional. Health Canada’s own guidance is clear that small amounts of mold can be cleaned by homeowners, as long as it’s done safely and the underlying cause is fixed. The trouble is that most people don’t know where that line is, or what “safely” actually means in practice. This guide walks through how to decide, and exactly how to do it if you’re in the clear to handle it yourself.
How to decide if you can clean it yourself
Health Canada classifies mold by size, and the size of the problem is what determines whether it’s a DIY job:
- Small (do-it-yourself territory): Three or fewer patches, with a combined area of less than 1 square metre (about 10.75 square feet — roughly the size of a bathroom vanity or a single damp patch on a wall).
- Medium (a judgment call): More than three patches, or a combined area of 1 to 3 square metres. Health Canada recommends having this assessed by a qualified professional first, though it may still be cleanable by a homeowner once assessed.
- Large (call a professional): A single patch larger than 3 square metres (about 32 square feet — roughly the size of a full wall in a small room). This is beyond the scope of DIY cleanup.
Size isn’t the only factor, though. Call a professional regardless of size if any of the following apply:
- The mold keeps coming back after you’ve cleaned it before.
- You suspect hidden mold growth inside walls, above ceilings, in ductwork, or under flooring — if you can smell mold but can’t see where it’s coming from, that’s a sign there’s more than what’s visible.
- Anyone in the home is an infant, senior, pregnant woman, or has a respiratory condition like asthma — Health Canada specifically advises these individuals stay away from mold cleanup entirely, which in practice often means the job should go to someone else.
- The mold followed a flood, sewage backup, or significant water damage, rather than everyday condensation.
- The affected material is porous and can’t realistically be salvaged (see below) — at that point it’s often more of a removal and replacement job than a cleaning one.
What you’ll need
- Safety glasses or goggles
- A disposable, well-fitting N95 respirator (a regular dust mask isn’t enough)
- Household disposable gloves
- An unscented soap solution (dish soap works)
- Clean cloths or sponges
- A garbage bag for disposal
- A fan and, ideally, a portable dehumidifier
Health Canada specifically advises against using bleach— bleach does reliably kill mold on surfaces but is can also produce harmful fumes especially when mixed with other cleaners. Bleach requires extra caution and should be used only when necessary. Plain unscented soap and water is what’s actually recommended at least as the first step. And make sure anyone in the household who shouldn’t be exposed to mold — infants, seniors, pregnant women, anyone with asthma or another respiratory condition — is out of the area for the entire job, not just while you’re actively scrubbing.
Step-by-step: cleaning mold off hard surfaces
- Ventilate the room. Open windows and exterior doors to bring in fresh air before you start.
- Isolate the area if you can. If the space connects to the rest of the home, cover doorways with plastic sheeting secured with tape to keep spores from spreading while you work.
- Put on your PPE. Goggles, N95 respirator, and gloves — every time, even for a small patch.
- Scrub the surface. Using a cloth with an unscented soap solution, scrub the moldy area until the discoloration is gone. Don’t just wipe — mold can be embedded in the surface texture, not just sitting on top of it.
- Dry the area completely and quickly. This is the step people skip, and it’s the one that matters most. Use a fan, and a dehumidifier if you have one, to get the surface and surrounding air dry as fast as possible — mold needs moisture to grow back, so a damp surface left to air-dry slowly is inviting it to return.
- Dispose of anything you used. Cloths, gloves, and any porous material you removed should go straight into a garbage bag, sealed, and out of the house.
- Keep the room ventilated and monitor humidity. Aim to keep indoor relative humidity below 50% while the area finishes drying and going forward.
What to do about porous materials
Hard, non-porous surfaces — tile, glass, sealed countertops, painted drywall in many cases — can usually be cleaned as above. Porous materials are a different story: Health Canada is direct about this one — fabrics, carpet, upholstery, ceiling tiles, and paper products with mold growth often can’t be properly cleaned, and should be discarded rather than cleaned and reused. Trying to salvage a moldy mattress, carpet, or stack of water-damaged boxes isn’t worth the risk of leaving spores embedded where you can’t reach them.
The step people miss: fixing the moisture source
Cleaning the mold you can see doesn’t fix the reason it grew there in the first place. Health Canada’s guidance is blunt on this point: unless the underlying moisture problem is identified and solved, the mold will come back — often in the same spot. Before you consider the job done, work out why that area was damp or humid enough for mold to take hold: a leak, condensation from a cold surface, poor ventilation in a bathroom, a grading issue outside a foundation wall, and so on. If you can’t pin down the cause, or the mold returns after you’ve cleaned it once, that’s a sign it’s time to bring in someone who can assess the moisture source properly rather than repeating the same cleanup every few months.
Safety precautions, in summary
- Never skip the N95 respirator, goggles, or gloves, even for a small patch.
- Keep infants, seniors, pregnant women, and anyone with a respiratory condition out of the area entirely during cleanup.
- Ventilate the space throughout the job, not just at the start.
- Never mix cleaning products, and skip the bleach — an unscented soap solution is what’s actually recommended.
- Dry the area completely and as quickly as possible once it’s clean.
- If you start the job and the affected area turns out to be larger than it looked, or you find mold behind a wall or under flooring once you open things up, stop and call a professional rather than continuing.
Frequently Asked Questions
Can I clean mold myself, or do I always need a professional?
Health Canada’s guidance says small amounts of mold — three or fewer patches totalling less than 1 square metre — can generally be cleaned by a homeowner with proper precautions. Larger areas, recurring mold, or mold affecting anyone with a respiratory condition or other vulnerability should go to a professional.
Is it safe to use bleach on mold?
Health Canada specifically advises against using bleach to clean mold. Use an unscented soap solution or baking soda instead.
How big of an area is considered “small enough” to clean myself?
Less than 1 square metre (about 10.75 square feet) in total, across three or fewer patches. Anything larger, or a single patch over 3 square metres, is outside the scope of DIY cleanup.
Why does mold keep coming back after I clean it?
Because the moisture source that allowed it to grow hasn’t been fixed. Cleaning the visible mold without addressing the underlying dampness — a leak, condensation, poor ventilation — almost always means it returns.
What should I do if I find mold inside a wall or under flooring?
Stop and call a professional. Hidden mold behind walls, above ceilings, or in ductwork isn’t something a surface cleaning can address, and opening up building materials without proper containment can spread spores through the rest of the home.
Can I just paint over mold instead of cleaning it?
No. Painting over mold doesn’t kill it or remove the moisture source — it will continue growing underneath the paint and can resurface, and it hides a problem that needs to be dealt with rather than solving it.
If your mold problem is larger than a small patch, keeps coming back, or you’re not sure what you’re dealing with, it’s worth having it assessed properly rather than guessing. See our guide to choosing a mold remediation company, or call ABM Environmental at (604) 568-5177 for a free phone consultation.
Written by Brian Mackenzie, Senior Project Consultant at ABM Environmental, with over 18 years of experience in indoor environmental consulting.