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Mould vs mildew: What are their key differences?

Comparing mould and mildew based on appearance, smell, and more

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Key Facts

  • Mould is a type of fungi with a raised, fuzzy, patchy texture. Its colours can range from black to white and dark green, and it emits a musty, earthy odour. It is commonly found in damp, wet places with high humidity, although some grow in dark, cold environments.
  • Mildew is a type of mould known for its flat growth. Its colour is usually white or grey, which sometimes turns brown. Its smell is similar to mould’s, only less intense. It thrives in places with high moisture but cannot go deep into porous materials.

At first glance, it seems mould and mildew are the same. These microscopic fungi often lead to allergic reactions, such as sneezing or eye irritation. They also grow and spread new spores in hours, thrive in damp and humid places, and smell similarly. 

However, when you look closely, you see telltale signs of the differences between mould and mildew. This mould vs mildew guide will spell them out for you and share how to hire a mould removal expert for your safety and convenience.

If you are ready to be a more knowledgeable homeowner, read the mildew vs mould primer below!

What is mould?

a wall with black mouldMould is a type of fungus that develops multicellular filaments called hyphae. These fine threads develop at the tip and then divide over and over until they grow longer and branch out. By then, they create chains that can intertwine, forming a network called mycelium.

As organisms, these fungi need a food source, such as soil, and organic matter, like wood. This explains why you can find them in walls and ceilings, as well as food such as bread. They also thrive in places with high humidity because of high water vapour and oxygen. With the right environmental conditions, mould spores can multiply within 24 to 48 hours. Within a week, they become visible.

The types of mould you can see in your home can also vary. These include Stachybotrys chartarum, which is also known as black mould. Other examples are Aspergillus, which can thrive indoors and outdoors, and Cladosporium, which prefers painted surfaces and areas with cooler temperatures. A popular type of mould is Penicillium, which scientists use to make antibiotics.

What is mildew?

a wall with mildewMildew refers to a type of fungus or mould, which means it can also develop hyphae and mycelium. Mildew also grows in damp environments, such as shower walls. In fact, they are so much alike that some refer to this as early-growth mould.

What does mildew look like? It varies from its closely related cousin by its appearance, especially the colour and texture. It is also easier to clean or remove than mould because of its penetration depth, growth structure, and visibility.

Mould vs mildew: How different are they?

a bathtub with mould and mildew buildup

Both mould and mildew are disgusting and damaging to health and property, so if you have mould problems, get cleaners to deal with them. However, it still pays to know the difference between mould and mildew to better describe your problems and hire the right removal expert.

In terms of appearance

What does mould look like? Its physical characteristics vary according to the age of the colony and type.

Usually, the colours of the fungus can range from black to deep green, yellow, and sometimes even blue and purple. It also appears fuzzy and slimy, especially during its early stages when its hyphae are still growing and dividing. The colony can begin as a small spot, measuring only a few inches across, until it grows and covers an entire surface. Mould also features a 3D or raised texture, such as when it develops in bread.

Mildew is more known for its flat-growth habit, so it does not look puffy or raised as regular mould. The texture is also powdery, and the colour is usually grey or white, which can turn brown.

In terms of smell

What does mould smell like? People often describe it as earthy or musty. It is similar to the odour of rotting wood, wet socks, damp areas, and unaired spaces, such as basements. Sometimes, the scent reminds you of old paper, such as books, kept inside a cabinet for decades.

What does mildew smell like? Because it is also a type of mould, the scent is almost the same, except it is less intense. You can compare it to improperly dried fabric or clothing.

Either way, the smell is often the first sign of mould growth. It happens because the organisms release microbial volatile organic compounds during metabolism. If any part of your home does not feel right, start investigating for mould and mildew infestation, even if you cannot see them yet.

In terms of texture

a man touching black mouldBecause there are different types of mould, their texture can also widely differ. As mentioned, they usually start off appearing fuzzy and patchy as they build their network or mycelium. As they reproduce more spores and create denser chains, they can look cottony.

Typical mould is also slimy, mainly due to the wet environment where it grows. When it comes to patterns, mould and its substrates can form a circle that expands outwards as it spreads across a surface.

How about mildew? It can be powdery (feels like fine powder when touched) or downy, which means fluffy.

In terms of location

As fungi, both mildew and mould require food sources to grow and reproduce. They thrive on wet surfaces and moist environments with high humidity. They also feed on organic materials. So expect them to be in bathrooms and kitchens, particularly plumbing pipes prone to leaks. They can also likely appear after a flood.

However, some types of mould can also prefer dark and warm places, such as basements and attics. (Note that humidity is also often high in these parts of the house due to poor ventilation.) Others like the cold, which is why you can see them in refrigerators. Mould growth can also be sneaky because it can penetrate deeper into more porous materials and spread in well-hidden areas.

On the other hand, you usually find mildew in flat, less-porous surfaces with better airflow, such as shower walls. It is also in areas with temporary or intermittent moisture, like when dew forms on plants in the morning.

In terms of health impact

Can mould spores and mildew cause health concerns? Yes, but probably not as extreme as you think. 

In general, many types of mould live harmoniously with humans and animals, which means they do not cause disease. In fact, a 2017 research in the Clinical Reviews in Allergy & Immunology said that claims of ‘toxic black mould’ and ‘sick-building syndrome’ are more likely media hype than anything.

However, most studies cite how they can trigger allergic reactions, like itchy eyes, sore throat, and sneezing. For people overly sensitive to spores, one of the health problems to watch out for is anaphylaxis. It is a life-threatening situation wherein the person suffers from difficulty in breathing, low blood pressure, and irregular heart rhythm.

Because mould and mildew are minuscule, they can easily enter the lungs, causing respiratory illnesses such as asthma attacks. In rare but severe cases, some types of mould release mycotoxins. These can be dangerous for people with compromised immune systems.

In terms of removal cost

In Australia, the average cost of removing mould and mildew starts at $100. However, if they need to clean the mould all over the house, the specialists can charge up to $6,000 for the whole work. The fee can already cover their protective gear and cleaning supplies.

However, since mildew is easier to clean, the removal price could be lower. You can get free quotes, proposals, or consultations to get a better idea of the charges.

In terms of prevention measures

Unlike mould, whose spores can fill in the spaces of porous materials, mildew is often superficial. It is, therefore, easier to eliminate. Usually, you just need a scrub brush, regular mildew cleaner, and elbow grease.

Mould is more challenging because you cannot see it immediately. By the time it becomes visible, it has already built a colony. The good news is that it often dies with bleach or undiluted white vinegar.

But getting rid of these spores by yourself is not ideal. The job requires extensive knowledge about mould and mildew, the right equipment and cleaning supplies, and skills in handling spores. 

Restore mouldy and mildewy surfaces with Airtasker

removing mould from a wall

Whether you have mould or mildew or both, hiring a removal expert is the best way to deal with the problem. Besides technical expertise, they can:

  • Perform house fungus identification via a thorough inspection to accurately determine the best solution.

  • Measure and help you manage the moisture levels to prevent fungal growth.

  • Provide other related services, such as waterproofing your home or fixing your plumbing.

Airtasker connects you with mould and mildew removal specialists near you in three steps:

  1. Open a free account.

  2. Log in and post a task detailing the severity of the mould or mildew in your home.

  3. Receive quotes from Taskers, narrow down your options, and pick the best from the pool.

Overall, mould and mildew are slightly different, but their effects are the same: They harm you and your home. The sooner you can get them out of the house, the faster you obtain peace of mind. Sign up on Airtasker and find a nearby mould removal expert today.

Mould vs mildew

Often black or dark green; others are yellow, blue, or purple
Grey or white that sometimes turns brown
Musty and earthy
Similar to mould but less intense
Raised, fluffy, or cottony
Damp places with high humidity; cold dark places like refrigerators; and areas with poor ventilation
Environments with high levels of moisture but better airflow; less-porous materials such as shower tiles
Health Impact
Can cause allergic reactions, asthma attacks, or, in rare but severe cases, anaphylaxis and complications from mycotoxins
Can cause allergic reactions, asthma attacks, or, in rare but severe cases, anaphylaxis and complications from mycotoxins
Removal Cost
Starts at $100 an hour or around $6,000 for an entire home
Charged along with mould removal but could be cheaper on its own 
Prevention Measures
Sneakier than mildew because it takes a while to see the colony; can die with bleach or undiluted white vinegar
Easier to see because it almost always does not grow on porous materials; can react to regular mildew cleaner

FAQs on mould and mildew

One of the earliest signs of a mould problem is smell, which is musty or earthy. If you are sensitive to the fungi, you will also develop allergic reactions, such as runny nose, watery eyes, and sneezing. Eventually, both mould and mildew will become visible, forming colonies that spread across surfaces.

No. While they are related as types of fungi, mould and mildew have distinct behaviours and effects, and one does not transform into the other.

Yes, these fungi can grow together as long as they have the right environment to thrive in. These include places with dampness, high moisture levels, or high relative humidity.

Yes, to minimise mould exposure and health risks. Professional mould and mildew experts have the proper gear, tools, and skills to remove these fungi as safely as possible from your home.

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