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What is Mould – Types, Risks, Causes & How to Remove it

technician investigating mould on roof of home with homeowner

Mould can be found in most areas around the home and property. Not only can mould quickly become an inconvenience, but it can also cause serious health problems if left untreated. With thousands of strains in existence, mould can come in different colours and textures, and some are classified as more dangerous than others.

Understanding what mould is, how it grows, and what to do when you find it will help you plan out a course of action to eradicate mould from your property. We’ve compiled the ultimate guide about everything you need to know about mould, common species, and what to do if you believe you have a mould problem.

What is mould?

Mould is a fungus with a significant function within the ecosystem by releasing enzymes to break down dead organic matter such as plants, or any natural biodegradable substance. As a living organism, mould needs moisture to survive and will release airborne spores to spread, attaching itself to any areas of above average humidity, or areas with inadequate ventilation.

Most mould species cannot be accurately identified from a visual inspection and require a lab analysis, making it difficult to discern what mould you are dealing with. With that being said, mould usually ranges from dark green to black, while also appearing as white, grey, pinkorangeyellow or brown depending on its maturity. It is also known to appear in a range of textures spanning from slimy, fuzzy, powdery, or even vomit-like.

Where does mould grow?

While warm, moist environments are the ideal conditions for mould to grow, it also thrives in dark, damp and sometimes cold environments with little to no natural light. Bathrooms, showers, kitchens, ceilings and wardrobes are common areas for mould to grow and spread due to its naturally high levels of moisture and condensation buildup and can easily spread on inorganic surfaces as long as there is enough moisture to prompt its growth.

Mould tends to make its way through surfaces and eats its way down underneath areas, continuing to spread until it eventually breaks down organic matter. Because of this, the extent of mould infestation is usually more severe than what meets the eye and can be incredibly difficult to eradicate. In many cases, removing mould in its entirety requires a professional mould removal specialist for an inspection, treatment and further prevention plan.

How does mould grow?

The growth of mould is an important part to keep our ecosystem functioning, however, it is not uncommon for mould to spread indoors and attach itself to non-organic materials where excess moisture is available.

Because of this, mould can grow throughout any area with high moisture levels and can begin its process within 24-48 hours. This means mould can easily become an infestation making its way through wood, fabrics, carpet, furniture and food. Furthermore, its airborne spores make it easier for mould to spread around the home or property.

What causes mould?

Warm, moist, humid, dark and damp areas with inadequate ventilation create the perfect conditions for mould to grow and spread.

The combination of inadequate ventilation, lack of light, and high moisture levels enhances mould growth, and as a result, causes it to spread in hard to notice places. This often means that by the time you notice mould growing, its damage can be more severe than what you can see.

Other common occurrences that can cause mould to grow can include:

  • Inadequate ventilation in bathrooms and kitchens
  • Buildup of condensation around window frames
  • Damp, dark areas such as basements or crawl spaces
  • Water damaged or flooded areas
  • Not cleaning wet areas or spills
  • Moist foods left at room temperature
  • Wet clothes left in the washing machine
  • Leaking/plumbing problems left untreated
  • Buildup of soap scum in showers or baths
  • Airborne spores spreading throughout the property as a result of cross contamination or when left untreated overtime

To avoid mould growth becoming an issue throughout your home or property it is important to ensure there is regular fresh air circulation, while making a conscious effort to keep all areas dry and well-ventilated.

Common mould types

There are thousands of mould strains that can be found either indoors or outdoors, anywhere around the property. Here are a few of the most common mould types in Australia:


Aspergillus is usually found in bathrooms and window frames, and will appear green, grey, or white with dark spots. This is one of the most common mould strains and is known to cause respiratory discomfort from its airborne spores spreading around the home and property.

Stachybotrys Chartarum (Toxic Black Mould)

Greenish-black in appearance, toxic black mould thrives in warm environments and above average levels of humidity such as bathrooms, kitchens or ceiling. It can easily grow and spread on materials with a high cellulose content such as fiberboard and paper. Black mould is more commonly known for its release of airborne mycotoxin spores that can create respiratory discomfort and a burning sensation in the throat and nasal passages.


Appearing with a blue, green or yellow tinge, Penicillium usually grows in overly damp and wet conditions and will spread under carpets and spoiled food. Finding Penicillium usually means that there are excessive moisture levels in the home or property.


Alternaria is fuzzy and white with black spots and tends to grow and spread in fabrics, clothing, furniture and wallpaper. It can also appear near and around windows, bathrooms and air-conditioners.


Requiring intensely high levels of moisture to thrive, Acremonium thrives in water damaged buildings or areas of excess flooding. It can also appear in air-conditioners or dehumidifiers where there is a high level of moisture exposure.


Basidiospores are most commonly found outdoors and are known to grow and spread after rainfall or in humid environments in gardens, soil, wood and plants. They can also spread indoors in spoiled food, wood, and wallpapers and any organic matter causing dry rot.


Warm, humid, or wet conditions such as flooding and water damaged areas are the ideal conditions for Cladosporium to grow and spread. This strain can be green, brown or black in colour and is known to grow under carpets, wood, and clothing.


This mould strain thrives in tropical or humid climates, however, can be found either outdoors or within the home in the bathroom, tiles, or ceilings. Because of its airborne spores, Ascospores can cause allergy symptoms such as hay fever, coughing and respiratory discomfort.


Chaetomium is commonly found indoors in materials with a high cellulose content that have been subject to water damage, such as paper, sheetrock and wallpaper. This strain can often appear with a cotton-like texture before maturing into a grey to olive colour and can be known to cause asthma affects and respiratory issues if left untreated.

Mould vs Mildew: What’s the difference?

Mould and mildew share many of the same characteristics: both have the ability to thrive in warm, moist environments, both are classified as fungi, and both are found in similar areas around the home and property.

While mould and mildew are often confused with one another, its main distinction is its maturity stage. Mildew is commonly referred to as the “early” or beginning stages of what will eventually evolve into its matured version, mould. In saying this, mildew is often seen on bathroom tiles and grout, however, will remain on the surface level without working its way down underneath to eat through the material in the way that mould does.

In any case, it can still be difficult to visually distinguish between the two, as both can appear fuzzy or powdery in texture.Mould can appear as green or black, while mildew can present as white or grey. Furthermore, both mildew and mould can carry throughout the home or property via airborne spores and attach themselves to any areas in which it is likely to grow, spread, and mature.

It is important to keep your home or property as dry as possible to prevent the spread of mildew and mould. If left untreated both can cause serious health problems, especially for those with underlying respiratory conditions.

Is mould dangerous?

There are thousands of mould species in existence and some are considered more dangerous than others. While finding mould in small patches or spots is not considered harmful, if left untreated mould can cause health problems as it spreads throughout the home or property. Common symptoms of mould exposure can include:

  • Headaches
  • Coughing/wheezing
  • Rashes and inflammation
  • Dizziness
  • Eye irritations

Mould exposure can pose more serious health conditions for those with existing respiratory conditions and weaker immune systems, as well as in children and the elderly. Furthermore, there are particular mould species that have been linked to more serious health problems, including:

  • Internal infections, such as mucormycosis
  • Allergy symptoms
  • Some mould can be fatal, in the case of Ulocladium (a strain of brown mould)

Mould can turn harmful in the case of overexposure if left untreated or if it is ingested. If you find mould in your home or property, it is important to wear protective masks and gloves when attempting removal to prevent making contact or inhalation. If you find a larger mould infestation, do not attempt removal as this might aggravate its spores, causing it to spread. If you find mould on your food, throw it away in its entirety to avoid indigestion.

Most moulds cannot be accurately identified from a visual inspection, so if you are concerned about finding mould in your property, seek out a professional service for an inspection. If you are experiencing mild or severe reactions due to mould exposure, it is recommended that you seek a GP or healthcare professional to discuss your symptoms and treatment.

How to get rid of mould?

The removal of mould can be a tedious, tricky process and is very difficult to eradicate completely, especially if it is the result of a larger plumbing problem or the result of severe water damage.

Any attempt to remove larger mould infestations can put you at risk of aggravating the spores to travel around the home or property.

However, if you do attempt to remove small areas of mould yourself, make sure you are wearing a protective mask and gloves to prevent breathing in spores.

Because mould can grow behind walls, and in dark, hard-to-notice places, it can be difficult to see the severity of its growth, so if you believe you have a mould problem, it is recommended to book a professional mould inspection first.

Read more: What do to if you find mould in your home.

How to remove mould naturally

There are several species of mould that require a professional mould removal specialist, especially in the case of brown, yellow, and toxic black mould. For small mildew and mould patches and spot removal, however, here are a few ways to naturally remove it from the surface:

Vinegar: Mix a 50/50 ratio of water and vinegar into a spray bottle, shake well, spray onto the mould and allow to sit for at least 10 minutes before scrubbing it clean.

If mould is found on your clothes or shower curtains, wash them (preferably on a heavy duty cycle) with a solution including vinegar, bleach and your regular washing detergent.

Baking Soda: In a 250ml measuring cup, mix 125ml baking soda with 62ml white vinegar and 62ml water (2:1:1 ratio) to make a thick paste. Spread the paste onto the mould affected area and allow to dry. Scrub off any mould or stains and wipe down with a wet cloth to remove tough or stubborn mould growth.

Removing mould naturally may not eradicate the problem entirely, however, especially if the area is exposed to inadequate ventilation and high levels of moisture. If you are seeking a permanent removal technique, it is recommended to seek out a professional mould removal service.

How to prevent mould? 

In any variety, mould relies on moisture and inadequate ventilation to grow and spread. The key to preventing mould spreading throughout your home and property is to ensure that each area receives fresh, regular circulation of air. In addition to this, here are some of the most effective ways to prevent mould:

  • Use a dehumidifier, especially in above average humidity climates
  • Ensure your bathroom is well ventilated
  • Keep all areas of the home dry
  • Circulate the air regularly, especially in dark, naturally damp areas
  • Clean and dry any flooding, spills or water damage promptly
  • Regularly clean out external drainage, guttering, downpipes and eaves
  • Fix any leaking or plumbing problems promptly
  • Hang out wet clothes to dry outdoors
  • Do not leave wet or damp fabric or clothing around the home or property
  • Regularly clean and dry water excess trays from air conditioners and dehumidifiers

What are the methods of mould removal?

The process of mould removal and remediation begins with an extensive inspection to determine the severity of the mould infestation, distinguish mould strains, and determine an effective treatment plan. The methods of treating mould include:

  • Mould Removal: All visible mould will be removed as part of a professional mould removal treatment. This includes any contaminated areas and surfaces such as walls, doors, windows, and ceilings.
  • Misting: Once the visible mould has been removed, a misting treatment is used throughout the property to eliminate any airborne mould spores and ensure that any remaining spores or odours are eradicated.
  • Management and Prevention Plan: A management plan will further protect and prevent mould from reappearing throughout the property, including a tailored guide to keep your property mould-free.

When to call in a mould removal professional? 

With thousands of strains in existence, mould can pose a harmful risk if left untreated.

If you suspect you have a mould issue in your property, the first step is a free inspection with MouldMen. Over the last decade, we’ve helped 1000’s of Australians resolve their mould issues for good with our effective & safe remediation process. Call us on 1300 60 59 60 or book your free inspection today.

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