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How to get rid of mould

How to clean mould yourself, and when you should call the pros.

sponge cleaning bathroom tiles
Last updated: 07 March 2022

Getting rid of mould in your home takes time and elbow grease – and you probably won't be using that 'miracle' mould killer you picked up at the supermarket.

It's important you don't just ignore mould growing in your home. It can give off toxic spores and vapours which can be dangerous to your health – possibly resulting in allergic reactions, asthma and flu-like symptoms.

How to remove mould yourself

Step 1: Assess the damage

Before starting, work out what kind of surface the mould has attached to:

  • If the mould is on something that's super-porous, like a textile, clothing or furniture, there's a good chance it can't be completely removed and it may need to be thrown out. Anything like wicker baskets, textiles, paper and cardboard or carpet needs to be chucked away – don't even bother with these surfaces. (And don't just let carpet dry out if there's been water damage, as mould spores will be left behind, buried in the carpet fibres.)
  • Non-porous surfaces such as hard plastics should be relatively easier to clean.
  • Semi-porous surfaces will be variable.
mould in silicone

Mouldy grout can be very difficult to clean.

Mould in bathroom grout or silicone

These areas deserve a separate mention. Once mould gets its grip here, getting rid of it is almost impossible. When mould grows, it develops hyphae, or roots, which grow into the grout or silicone. You can clean the surfaces of the grout or silicone, but not deep into it. In those cases you have to replace the silicone or re-grout your bathroom.

Step 2: Vacuum the mould

The next step is to vacuum up the mould, but your vacuum cleaner needs a good HEPA filter, otherwise you could be making the problem worse by spreading the mould around.

Step 3: Remove the mould

Our experts recommend using diluted vinegar, which causes mould to overeat and die.

How to use vinegar to clean mould

  • Pour a concentration of 80% vinegar to 20% water into three buckets.
  • Grab a microfibre cloth, dip it into the first bucket, then use it for cleaning a patch of mould.
  • The same microfibre cloth should then be rinsed in the second bucket, then rinsed again in the third to ensure cross-contamination doesn't occur.
  • Microfibre cloths, which reach deep into tiny crevices and have a slight electric charge, can be bought cheaply and washed on a hot cycle in the washing machine with vinegar up to 100 times.
  • After using vinegar there may still be streaks or discolouration on surfaces which you should be able to remove with bleach.
vinegar scourer brush

Diluted vinegar can be more effective than bleach or commercial products.

Does bleach kill mould?

Experts we spoke to say there's evidence that bleach can kill fungi, but it needs to be at a 10% concentration to work.  

Even at a higher potency, bleach won't penetrate porous materials, so if the mould is growing on plaster, grout or wood, it will kill mould on the surface, but not below it. 

Also, several experts told us that bleach can be a masking agent. Bleach takes the colour, or melanin, out of fungi, making it invisible. You can't see it anymore, so you think the bleach has done its job, when that's not necessarily the case. 

Strong bleach is also harmful to grout and tiles as it erodes and corrodes the surfaces, making them more porous, which in turn makes them more vulnerable to further fungi growth.

Warning: Never mix bleach and vinegar together  it creates toxic chlorine gas.

Do commerical mould cleaning products work?

Commercially available mould cleaning products may look like they're doing the job, but it's probably an illusion. 

Most of them use bleach (often listed as sodium hypochlorite) as an active ingredient. But the concentration of bleach in these products marketed as 'mould killers' is often five percent or less. 

Bleach has a short shelf life and loses potency quickly, so if products have been on shelves for an extended period of time, they become even more ineffective.

When to call in the professional mould removalists

If mould covers a large area of your home – experts say a rough guide is one metre square – and is dense, if you've had flooding, or if householders are asthmatic, it's best to call in the experts.

The cost of professional help varies. An initial investigation can cost around $1500 for an expert to test the site and find the cause of the mould and write a plan for removal of mould. After that, it's a question of the extent of the problem.

Actual removal of mould can range from $2000 to $90,000, depending on the contamination level and size of the property. Mould removalists need to be certified, have the right equipment, get special training, maintain a high level of fitness and have the ability to sustain thermal stress. They're not just cleaners, so their hourly rate can be $80 – $110.

How to prevent mould from coming back

Here are some tips for preventing mould from growing in the home:

  • Fix any external entry points for moisture in your home, for example, a leaky roof or broken pipes.
  • Install a good exhaust fan in the bathroom and prevent moisture build-up on surfaces. Squeegee or towel-dry your tiles and floors immediately after showering, and make sure you clean bathroom scum, which mould feeds on.
  • Ventilate your home. Inadequate ventilation is one of the main reasons homes become vulnerable to mould growth. When the air stops moving, you can get a build-up of humidity and moisture in those areas. If you can't ventilate, think about a dehumidifier for the room.
  • Avoid air drying clothes indoors, especially without adequate ventilation.
  • Be careful about extreme differences in heat between indoors and outdoors (for example, having super cold air conditioning when it's 40°C outside) as condensation will form if there's a gap in the window or you open the door.
  • Make informed heating and cooling choices – several experts we consulted warned against the use of unflued gas heaters, which release moisture into the air.
  • Mould needs organic matter – such as dust or dead skin cells – to thrive, so it's important to keep up with regular vacuuming and dusting.
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