Mould in the House: What Causes It and How to Avoid It

If you’ve suffered damage from floods or consistently experience wet and humid conditions, mould could be lurking in your home. 

Unfortunately, here in Australia, our homes are prone to mould, given our climate.

The good news is that removing and preventing mold in house is relatively simple. 

In our guide, we’ll explain what mould is, why it’s a health hazard, how to get rid of it, and how to prevent it from returning.

What is Mould?

At one time or another, most of us have lived (or now live) in a house or apartment where we noticed a nasty black substance growing on the wall or ceiling.

One that seemed to get bigger each time we looked at it.

That nasty splodge would be mould, which is a type of fungus. 

And it’s everywhere.

Not just where you can see it.

Mould can also be found in the air and in food.

That’s right. Food. 


We’re talking cereals, spices, coffee, dairy products and nuts – especially those you buy from supermarket tubs because you want to save some dough.

Mould can even hitch a ride home with you after attaching to:

  • Clothing
  • Shoes
  • Pets
  • Reusable shopping bags

And if its final destination is somewhere even slightly damp, it will grow and multiply.



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How can I tell if I have a mould problem?

Any part of your home that gets wet is likely to be mouldy. 

Look for:

  • Leaks in your roof or plumbing. If water is trapped inside your walls, mould may be growing there, although you won’t always be able to see it. Check if your walls have light stains or a strong, musty smell.
  • Outside water damage around your windows or doors. In winter, damp air can convert to water, causing mould to grow.
  • Mould on the walls, ceilings, floors, carpets, books or hoarded newspapers. Take a good whiff of these areas, as a musty smell is often your only clue that you have a mould problem.

If you’ve got a dark spot in your home and aren’t sure if it’s just a splodge of dirt or an old stain, here’s how to tell if it could be mould:

  • It smells musty and earthy.
  • There’s a nearby source of moisture but not much light.
  • The material the mould is growing on is warping, cracking, or peeling.
  • Applying bleach lightens its colour in a couple of minutes.
  • Unchecked mould will spread. Dirt and old stains will not.

Causes of moisture and mould

A damp home is a breeding ground for mould. 

If you allow moisture to build up in your indoor spaces, mould takes that as an invitation to move on in. 

Mold in house is more than just a cosmetic problem. It can damage your home and contribute to health issues. 

Sometimes mould is obvious, but it can also be hard to recognise. 

It resembles a stain, smudge, spots, fuzz, or discolouration. It’s typically black, green or white, but you may also find it in grey, orange, pink and brown. 

The big giveaway is the smell.

Places you’ll commonly mold in house:

  • walls or wallpaper, 
  • ceilings, 
  • bathroom tiles, 
  • carpets & rugs (especially if they’re jute-backed), 
  • insulation material, and 
  • wood. 
Causes of moisture and mould

Effects on health

Mould produces spores in order to reproduce. 

These spores are carried in the air and can cause serious health problems. 

Not only can mould bring on its own symptoms, but it can also make you more susceptible to other illnesses.

For most people, just touching or inhaling mould spores can cause:

  • a runny nose,
  • eye irritation,
  • skin rashes,
  • respiratory problems and infections,
  • wheezing or asthma attacks, and
  • allergies.

Some people need to be extra careful. People who may be ultra-sensitive to mould are:

  • Babies and children.
  • The elderly.
  • People with existing skin conditions such as eczema.
  • People with respiratory problems such as allergies and asthma.
  • People with a weakened immune system and have:
  • HIV infection, 
  • Cancer and are undergoing chemotherapy,
  • Received an organ transplant,
  • Chronic lung disease (i.e., Chronic Obstructive Pulmonary Disease (COPD) and emphysema).

But, before you whip out the cleaning supplies, first:

  1. Open any windows.
  2. Pop on long sleeves and pants, protective eyewear,
    nonporous gloves, and a face mask or N95 respirator.
  3. Make sure you always use a different cloth or sponge
    with each process and throw them away afterwards. If you don’t,
    the mould spores will spread, and the mould will reappear.
    If you use a brush, disinfect it if you want to keep it.
  4. Avoid dry brushing the area with a broom or brush, as this can spread mold in house.
  5. Ensure all the mold in house is gone before painting or caulking.

Suited up and ready to kick that nasty mould to the curb? 
Then use these simple cleaning tips to remove mold in house.

Products that kill mould

How to get rid of mould

Removing mould on the walls

  1. To clean mould from porous surfaces such as wood and drywall, mix 1 part dishwashing detergent, 10 parts bleach, and 20 parts water in a bucket.
  2. Apply the mixture with a sponge without over-saturating the surface.
  3. Allow the surface to air dry (don’t rinse!).

Removing mould from indoor fabric

  1. Combine one part vinegar and one part water in a bucket. 
  2. Sponge down the mouldy area and scrub with a sponge or brush.
  3. Repeat if necessary. 
  4. Leave to air dry, or use a fan or hair dryer on a cool setting.

Removing mould from brick, concrete and stone

  1. Mix 1 cup of chlorine bleach with 4.5 litres of water.
  2. First, wet the mouldy areas with plain water using a garden hose or by hand, then apply the bleach and water solution with a sponge. 
  3. Allow it to sit on the surface for several minutes.
  4. Scrub with a soft- or hard-bristle brush, depending on the surface. 
  5. If the stain remains, the area may require multiple treatments.
  6. Hose surrounding areas (especially plants) that may have been splashed inadvertently with bleach.

Removing mould from carpets

  1. Mix equal parts vinegar and water in a spray bottle and apply to the affected area.
  2. Dab excess moisture with a dry cloth.
  3. Sprinkle with baking soda.
  4. Allow it to sit overnight. 
  5. Vacuum.

Removing mould from tile and grout

  1. Mix one cup of bleach with 4.5 litres of water.
  2. Liberally apply the mixture to the mould-affected areas with a sponge. 
  3. Allow the bleach mixture to sit for at least 15 minutes before scrubbing with your brush.
  4. Rinse off with water and wipe dry. Check to make sure all the spores are gone.
  5. Re-apply if necessary. Leave any windows open if you can to allow the space to breathe.

Hello Breeze Pro Tip! 

If you’ve used bleach at any time, allow surfaces to air dry to maximise their contact time with the bleach.

When should I seek professional help to remove mould?

Sometimes a mould infestation is too much for us to tackle alone. 

Don't take a chance with the potential health risks that mould can cause you and your family.

Seek out a professional contractor with experience in the safe removal of mould if:

  • The mould covers a wide area, or it’s hard to reach.
  • You’ve had severe water damage.
  • It’s spread into the floorboards or wood on the walls.
  • You’re at high risk of symptoms from mould spores.

What’s the best way to prevent mould and moisture?

Keeping indoor humidity levels below 50% will prevent moisture build-up. The best way to do that, is with a reverse-cycle ducted or split system air conditioner.

Not only will you have a sweet-as climate-controlled home year-round, but an air-conditioning system will remove excess moisture in the air through dehumidification.

Your home will also be:

Asthma Tip Caffeine


Dehumidification helps you feel more comfortable without the need to set the thermostat to ‘arctic’. 

You’ll feel less clammy, sweaty and tired as the air feels lighter.

Asthma Mint DIY


Dehumidification maintains a reasonable humidity level indoors, helping every family member breathe easier.

If you or any family member suffers from allergies or asthma, shop for an air conditioner approved by the National Asthma Council of Australia, such as the Daikin reverse-cycle split system.

Plus, bread and cereals will remain fresher for longer without going stale.

Spice in Treatment for Asthma

Nicer smelling

Indoor air that’s free from dampness, mould and mildew smells fresh and inviting. Dehumidification helps remove the musty smell that can accompany mold in house.

Nicer smelling
Better protected

Better protected

Excess moisture or humidity in your home increases the potential to develop mould on your clothing, furniture, curtains, bed linen, towels and other fabrics. 

Dehumidification alleviates this problem and helps prevent tools, computer equipment and electronic equipment from rusting or corroding.


Switch on the dehumidification setting to reduce dust in your home. Less dust means less time spent with the feather duster and Hoover.

More energy-efficient

More energy-efficient

High humidity makes rooms feel warmer than the actual temperature, and you’ll naturally reach to lower the thermostat to cool your home faster. 

However,  with the flick of a switch to a dehumidification setting, your AC will run more efficiently, reducing energy costs. 

Other tips for keeping surfaces clear of mould for longer

  • Use energy-efficient, low-emissions heaters. 
  • Allow space between furniture and walls so air can flow, especially during winter. 
  • Limit the number of fish tanks and indoor plants. 
  • Clean your carpets and rugs using a HEPA (High-Efficiency Particulate Air) filter vacuum cleaner. 
  • Be mindful of stacking boxes or other items against outside walls – especially walls that don’t get a lot of sunlight.
  • Use waterproof paint, which creates a seal and prevents moisture from seeping through the walls.   
  • Clean your gutters regularly, as gutters full of debris can cause leaks, leading to mould.
  • Clean evaporation trays in air coolers, dehumidifiers and refrigerators frequently. 

Upgrade your comfort now

Make your life a little easier and cooler, and install a kick-ar*e air conditioning system from Hello Breeze. Take a look at our split systems and ducted systems now. 

If you’re unsure which type suits your home, lifestyle or budget, no worries – this is where we shine! Our climate control Specialists are more than happy to talk you through it.

So, c’mon, mate! Get on the blower and have a mag with us on 1300 712 732, and ask us for a quote on a world-class air conditioner installation for your home.

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