The Hidden Dangers of a "Simple" Mould Clean: Why Your DIY Fix Could Cost You Thousands

Michael Nguyen
3 days ago
5 min read

One of our mould inspector onsite performing a free mould inspection for a client in Sydney

You’ve seen it. That creeping black or green smudge in the corner of the bathroom, behind a piece of furniture, or on a window sill. The immediate reaction for most homeowners is to grab a cloth and some bleach and scrub it away. It seems simple, right? But at AAA Mould Removal, we know that what appears to be a quick fix can often lead to a much larger, more expensive disaster.

Cleaning mould is not like wiping up a spill. The biggest mistake people make is underestimating their opponent. Mould is a living organism designed to spread. Get the cleaning process wrong, and you could be accidentally seeding a contamination that spreads throughout your entire home.

This guide will walk you through the critical keys to cleaning mould, the dangers of getting it wrong, and why a professional is often the cheaper and safer choice in the long run.

What Homeowners Do Wrong: The Common DIY Mistakes

Before you tackle that mould spot, be aware of the common pitfalls that can turn a small problem into a major one:

Using Bleach Incorrectly: Bleach is the go-to for many, but it's a poor solution for mould on porous surfaces like plasterboard or wood. It often only removes the visible colour of the mould, leaving the microscopic roots alive and well beneath the surface. The mould returns, and you’re caught in an endless cleaning cycle.
Dry Scrubbing or Sanding: This is the single most dangerous mistake. Attacking dry mould with a stiff brush or sandpaper sends millions of invisible spores airborne. This is the primary cause of cross-contamination.
Painting Over It: Never, ever paint over mould. You are simply hiding the problem and providing the mould with a food source (the paint). It will continue to grow and destroy the material underneath.
Ignoring the Moisture Source: Mould is a symptom of a moisture problem. If you only clean the mould but don’t fix the leak, poor ventilation, or condensation issue, it is guaranteed to come back.
This is a mould removal that AAA Mould Removal take on recently after a cross contamination. This was in Parramatta

The Ultimate Danger: Understanding Cross-Contamination

Think of a mould colony like a dandelion head full of seeds. Now, imagine what happens when you blow on it. That is precisely what happens when you improperly clean mould. Spores become airborne and travel on the slightest air current, settling in new locations like your wardrobe, carpets, curtains, and even inside your air conditioning system.

This cross-contamination can lead to:

Widespread Growth: A single-room problem can quickly become a whole-house issue.
Health Risks: As the spore count in your home’s air increases, so does the risk of respiratory issues, allergic reactions, and asthma attacks for your family.
Increased Remediation Costs: The cost to decontaminate an entire home is exponentially higher than treating one contained area correctly the first time.

The Case of the Contaminated Unit: A Cautionary Tale from Parramatta

We recently received a call from a distressed family in a Parramatta apartment. They had noticed mould in their bathroom a month prior and had "thoroughly" scrubbed it with bleach. When our team arrived, the bathroom mould was back with a vengeance. But the real problem was far worse.

Our inspection, using moisture meters and air sampling equipment, revealed high concentrations of mould spores throughout the two-bedroom unit. The homeowner’s DIY attempt, performed without containment and with the bathroom door open, had sent spores airborne. We found mould growing on clothes inside the master bedroom wardrobe and on the living room curtains. The family had been breathing contaminated air for weeks.

What would have been a straightforward, affordable professional job to treat a small bathroom had turned into a complex, whole-unit remediation project. The final cost was nearly five times what the initial intervention would have been. This Parramatta case is a textbook example of how a DIY attempt, done with the best intentions, can go horribly wrong.

The Right Equipment and Chemicals for a (Very Small) Job

If you are determined to tackle a very small, non-porous surface (e.g., a few spots on bathroom tiles), you must act like a professional.

Required Equipment:

P2 or N95 Respirator Mask: To prevent inhaling spores.
Unvented Safety Goggles: To protect your eyes.
Rubber Gloves: To protect your skin.
Disposable Cloths: Never reuse cloths used for mould cleaning.

Recommended Chemical:

A solution of 80% white vinegar and 20% water is effective and non-toxic. Spray it on, let it sit for an hour to kill the mould, and then wipe away with disposable cloths. Bag and seal all used cloths before disposal.

Why a Professional is Cheaper and Better

When you hire a certified team like AAA Mould Removal, you’re not just paying for cleaning. You’re paying for a permanent solution.

We Find the Source: We don’t just clean; we diagnose and help you solve the underlying moisture issue.
We Contain the Area: We use specialised containment barriers and negative air pressure machines to ensure spores do not escape the work area. This prevents the cross-contamination seen in the Parramatta case.
We Guarantee Our Work: We have the equipment and expertise to do the job right the first time, providing you with peace of mind.

How to Prevent Mould From Coming Back

Prevention is always the best cure.

Ventilate: Use exhaust fans in kitchens and bathrooms. Open windows for 15 minutes each day to allow fresh air to circulate.
Control Humidity: On humid Sydney days, use a dehumidifier or your air conditioner’s dry mode.
Wipe Away Condensation: Keep a squeegee in the shower and wipe down walls and glass. Dry condensation from windowsills.
Increase Airflow: Avoid over-packing wardrobes and keep furniture a few inches away from walls.
Fix Leaks: Address any water leaks from plumbing or roofs immediately.

Before you decide to wage war on that patch of mould yourself, take a moment to consider the risks. For anything more than a tiny spot, the safest, most effective, and ultimately most affordable solution is to call in the professionals.

Contact AAA Mould Removal today for a comprehensive inspection and ensure the health and safety of your home and family.

About the Author

Michael Nguyen is the founder and lead technician at AAA Mould Removal, one of Australia's trusted mould remediation companies. With industry certifications including IICRC Water Damage Restoration, Applied Microbial Remediation, and Applied Structural Drying, Michael brings expert knowledge and proven techniques to every job.

He is also a licensed builder and carpenter, holding a Diploma in Building & Construction, which gives him a deep understanding of how moisture and structural conditions contribute to mould growth in homes and buildings. Michael specialises in residential and commercial mould removal, black mould treatment, water damage restoration, and structural drying.

Currently studying a double Bachelor’s degree in Medical Science and Environmental Science at Macquarie University, Michael combines scientific expertise with hands-on experience to deliver safe, thorough, and lasting mould removal solutions. His mission is to help homeowners and property managers maintain healthy indoor environments with professional mould remediation services across Sydney and surrounding regions.

Learn more at www.aaamouldremoval.com.au or call today for a free mould inspection and quote.