What are the Signs of Mould in Your House?

What are the Signs of Mould in Your House?

Mould is a type of fungus that has been in existence for millions of years. It can easily reproduce, especially if conducive conditions are present. Outdoors, mould can be found feeding on decomposing organic matter, such as rotting wood, fallen leaves, compost piles and even on grass and grains.

Indoors, mould thrives in damp, dark and humid areas, such as the kitchen, laundry and bathroom. Mould may also enter a property through open doors, windows or poorly maintained ventilation systems.

According to the Centers for Disease Control and Prevention (CDC), some of the most common types of indoor mould found in the home are:

  • Cladosporium
  • Penicillium
  • Aspergillus
  • Alternaria.

In some homes and buildings, black mould or Stachybotrys may also rapidly grow and multiply.

Not all types of mould are toxic or produce toxic byproducts. However, when allowed to grow indoors, mould can potentially pose health risks, especially if a person is allergic to mould or experiences respiratory problems. In addition to possibly affecting one’s health, mould can also weaken the internal structure of the property, resulting in expensive maintenance costs further down the road.

Mould Warning Signs

Some types of mould may be visible, but others are not always so easy to spot. If you’re worried that mould might be growing inside your house, below are some of the most common warning signs that you should look for.

Visible Mould

Mould sometimes looks like soot or dirt stuck to walls, window frames and ceilings, so it’s easy to mistake mould in your house for surface dirt. Some molds appear white and thread-like, while others appear in clusters of black, dark green, grey or brown rings or spots.

mould in the backside of a portrait

Musty Odour

While not all moulds produce a smell, those that do often release a stale and musty odour, similar to what you would smell when you open an old book. If the pungent odour persists, it can cause headaches, nasal and throat irritations, dizziness, nausea or trigger allergic or asthmatic reactions. It’s not so much the odour that’s to blame here, but the fact that it’s a telltale sign that unwanted mould is somewhere in your home.


If you see condensation or moisture build-up inside your home, it is a sign that you may have an indoor humidity problem. Condensation may appear as fog or beads of water on glass doors or windows. However, when it comes to walls, floors, ceilings and furniture, condensation may not be so easy to spot. Rusty metal fittings and fixtures such as curtain rods and window frames are also an indication that there’s a lot of condensation in your home. Mould loves moistures, so a damp or wet interior can become the perfect breeding ground for it.

Past Flooding

Mould can start growing as quickly as just a day or two after your house has been flooded, so it is important for you to remove floodwater and clean the area immediately. Floods create perfect conditions for mould to grow, especially under floor coverings or within wall cavities of the rooms where flooding occurred. Not only does flood water create the right environment for mould but it may also bring it into your property, creating a problem starting in the lowest structures of your property.

Water Damage

Water damage may appear as bubbles, cracks or peeling in your wallpaper or painted walls. Bulging or warped ceilings and walls are also tell-tale signs that there is mould growth under the surface. If you notice that there are areas of discolouration or water stains on walls, ceilings or floorboards, it could be a sign that you have high humidity inside your house. They could also be a result of ventilation problems or leakages in your plumbing system.

Places to Check for Mould

When mould spores begin to grow and reproduce, they become visible to the human eye. However, some mould grows in areas hidden away from sight, so knowing where to check for mould growth can help with mould prevention and removal. Here are the most common places molds like to set up home.

black mould on corner


You may love to take a long hot shower or a relaxing soak in the tub. Unfortunately, so does mould. Mould loves warm, damp areas, just like your bathroom. And if your bathroom lacks proper ventilation, the higher the possibility that it will take hold and spread to other parts of the building.

As steam has a lower molecular weight than air, it rises – causing ceilings and walls to become saturated. These are the first places most people notice a problem occurring.

Mould may also be present on the surface of sinks and counters, so it is important to clean them down and wipe them dry. Bathroom floors and tile grout are also areas where visible mould can grow. You may also need to inspect for mould behind the toilet and inside the toilet tank. Your bathroom essentials and accessories such as toothbrush caddies, shampoo bottles, loofah, washcloths and shower curtains are places to check.


Humidity in your kitchen creates an inviting atmosphere for mould infiltration. Mould usually grow on or under the kitchen sink, in leaky pipes and even in wet sponges that sit in the caddies.

If you have laundry machines in the kitchen area or cupboards within the kitchen, condensation can make its way inside. Check connecting water pipes, drainage hoses and ventilation tubes for mould growth. If you find any, then you need to look at ways to decrease moisture content in the area.

Living Room

The living room is often the most used room in the home, but that doesn’t mean its safe from mould infestation. Fabric, upholstery, window curtains and even indoor plants can provide perfect surfaces for mould, especially if they become moist.

When not in use, mould may also grow in a painted fireplace or chimney because they tend to be extremely porous, damp and dark. The average person breathes out 70 grams of water per hour when sitting down, multiply that by the average family and you are looking at several litres a day – and that’s not including perspiration. Easy to see how living rooms and lounges become prime targets for mould.


All indoor spaces are susceptible to mould infestation, including your bedroom. Always check your window sills, wardrobes, bed frames and mattress. Don’t forget to look behind cabinets and drawers as mould can grow there, too.

While your AC or heating vents can help control humidity, you may also need to inspect them regularly to check if mould is growing in or around them. If you do notice mould in these places, it could be a sign that some upkeep or repairs are needed.

Subfloors, Roof Cavities and Garage

The cold, dark and damp atmosphere in these areas, combined with moisture build-up, water intrusion and poor ventilation make them a haven for mould growth. And since you don’t spend a lot of time in these places, you likely won’t notice any mould growth.

Inspecting for Mould

Once you notice the telltale signs of mould in your home, you should take swift action and contact a mould remediation company. Unlike DIY mould testing kits, expert mould remediators should focus on identifying the moisture sources and developing a remediation plan to remove the mould growth.

Our knowledgeable experts at Mould Cleaning Australia will perform a detailed inspection of your property to determine what steps to take to get rid of mould permanently. Our mould removal and remediation service can be completed in as little as a day.

Worried that you have mould growing in your home? Worry no more. Contact us today to arrange your free inspection and let us take care of your mould problem the right way.

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