How Do You Clean Mould Naturally in a Bathroom?

Does Health Canada really say not to use bleach on mould?

Yes, and it says it in capital letters. In Addressing Moisture and Mould in Your Home, the heading reads: “DO NOT USE BLEACH TO CLEAN UP MOULD.” The Healthy Home Guide repeats it in plainer language: “If you find small amounts of mould, clean them up with dish soap and water. You don’t need to use bleach.” (Health Canada)

This surprises almost everyone we say it to. Bleach is the default mould answer in most households, and in a wet coastal climate people reach for it hard. But the federal advice is not a compromise position or a nod to environmental preference. It is the actual guidance, and it happens to line up exactly with how we clean.

There is chemistry behind it. Bleach is sodium hypochlorite dissolved in water. On a porous material such as grout, drywall or bare wood, the water soaks into the substrate while the hypochlorite ion largely stays at the surface. The visible mould loses its colour, so the wall looks fixed, while the hyphae underneath sit in the extra moisture you have just added.

Bleach is also deactivated by dirt. In a 2015 study in BMC Research Notes, 5% sodium hypochlorite in the presence of organic soil dropped to a 4-log reduction for bacteria and only a 2-log reduction for fungi, while steam under the same soiled conditions was unaffected (Bagattini et al.). Mould grows on soil. That is the exact condition in which bleach performs worst.

And Health Canada is clear that killing the mould was never the point: “Materials damaged by mould must be physically removed and disposed of under safe conditions,” and “Painting over a mouldy surface does not kill mould and does not stop it from growing back.”

How much mould are you allowed to clean yourself?

Health Canada sorts mould into three sizes, and the dividing lines are in square metres. CMHC uses the same thresholds in its consumer guidance.

Health Canada’s own sentence: “Health Canada does not recommend that an unqualified person clean up large areas of mould.” (Health Canada) CMHC’s wording for the small category is “can clean it yourself if you are in good health, clean using water and unscented dishwashing detergent” (CMHC).

One warning about numbers you will find online. The US EPA uses 10 square feet, described as “less than roughly a 3 ft. by 3 ft. patch”, as its DIY threshold (US EPA). That is roughly 0.93 m², which is close to Health Canada’s 1 m², but it is a different agency in a different country and the two systems should not be blended. If you are in British Columbia, use the Health Canada and CMHC square-metre thresholds. A typical bathroom ceiling corner or a strip of shower grout is well inside the small category. A whole wall behind a shower is not.

What do you use instead of bleach?

Unscented soap and water, and baking soda on walls. Health Canada gives instructions by surface, and the word “unscented” appears every single time.

• Washable surfaces (window sills, wood, hard surfaces, tile): “Scrub surface using a cloth with an unscented soap solution. Sponge with a clean wet cloth and dry quickly.”
• Walls: “Clean the surface of the wall with a damp cloth using baking soda or a small amount of unscented soap solution. Do not allow the drywall to get too wet.”
• Concrete: “Scrub surface using a brush with an unscented soap mixed with warm water; then sponge with a clean, damp cloth and dry quickly.”

That is a federal government document specifying fragrance-free cleaning three times in a row, which is one of the reasons we run fragrance-free products as the default rather than as an upsell.

Be honest about what these agents are and are not. Baking soda is a mild abrasive and a weak base, not a disinfectant. Rutala’s laboratory testing of home products found baking soda eliminated fewer than 3 log10 of every pathogen tested, and vinegar fewer than 3 log10 of S. aureus and E. coli, against 5.6 to 8.2 log10 for registered disinfectants. Canada’s National Collaborating Centre for Environmental Health, hosted at the BC Centre for Disease Control, concluded that the appropriateness of vinegar, lemon juice and baking soda “appears to be limited for commercial disinfection or sanitization” (NCCEH).

None of that is a problem here, because mould cleanup is a removal job, not a disinfection job. Soap plus a cloth plus mechanical scrubbing plus rinsing is exactly the mechanism the guidance asks for.

What is the actual step by step in a bathroom?

1. Put the fan on and open the window. Keep susceptible people out. Health Canada says pregnant women, infants, children, the elderly, pets, and anyone with asthma or allergies “should not be in or near the area where the mould is being cleaned up.”
2. Wear the minimum PPE. Health Canada specifies safety glasses or goggles, a disposable N95 mask, and household disposable gloves. The label has to say N95. A paper dust mask is not the same thing.
3. Do not dry-brush it first. That aerosolises spores. Wet the surface.
4. Mix unscented soap into warm water. A small amount. You are after suds and a cloth, not a chemical reaction.
5. Scrub tile, sills and hard surfaces with the cloth. For a painted wall, use a damp cloth with baking soda instead, and keep the drywall from getting soaked.
6. Sponge with a clean wet cloth, then dry quickly. The drying step is not optional. It is half the job.
7. Vacuum only with HEPA. Health Canada: “Do not use a regular vacuum for homes with a mould problem. Instead, use a vacuum cleaner with a HEPA filter or a central vacuum system that is exhausted outside.”
8. Bag and bin the cloths. Do not put mouldy cloths back into a bucket you will use elsewhere in the house.

On grout and caulking, expect to reach a limit. If the silicone bead along the tub has black staining inside the caulk rather than on it, cleaning will not reach it. That bead needs to be cut out and replaced. That is a five dollar tube of silicone, not a remediation project.

What has to be thrown out instead of cleaned?

Porous items that got wet. Health Canada’s list is blunt, and it saves people a lot of wasted scrubbing:

• “Throw away carpets, sofas, cushions, mattresses, pillows, stuffed toys or bedding that have gotten wet, have been exposed to damp conditions or that have been stored in a wet environment.”
• “It is not possible to clean a mouldy mattress.”
• “Mouldy paper is one of the most difficult materials to clean. Throw away any books, paper, cardboard, puzzles, or other paper products that show signs of mould.”
• “Carpets and underpads that are mouldy should be cut out and discarded.”
• If the mould is underneath the paint, “the drywall will need to be removed and replaced.”

The EPA agrees on the principle: absorbent or porous materials such as ceiling tiles and carpet may have to be thrown away if they become mouldy. In a bathroom this usually means the bath mat, a cardboard box under the sink, and sometimes a section of drywall behind a leaking trap.

Why does it come back, and when do you stop cleaning?

Because mould is a symptom of water, and cleaning treats the symptom. Health Canada states that mould “will begin to grow within 48 hours” of water damage and that “unless the cause of the moisture problem has been identified and solved, mould will reappear.”

The bathroom fixes that actually hold:

• Keep indoor relative humidity between 30% and 50%.
• Run the exhaust fan for at least 30 minutes after your shower, and check it vents outside rather than into the attic.
• Squeegee the glass and wipe the walls around the tub.
• Repair cracked tile, grout and caulking.
• Stop hanging wet laundry indoors, and vent the dryer outside.

Stop and get help when the patch is bigger than the small category, when it returns within weeks of a proper clean, when it is behind or under a finish rather than on it, or when the drywall is soft. Health Canada: “Mould that comes back after cleaning is usually an indication that the source of moisture has not been removed. Seek professional assistance.”

We are a cleaning company, not a remediation contractor, and we are clear about that line on what we don’t do. If you want the small-category work done properly as part of a bathroom reset, that is what our deep cleaning service is for. If you are wondering why this keeps happening to your house in particular, we wrote about why Fraser Valley homes get mould so easily.