Mould vs mildew: What are their key differences?

No one can fault you if you cannot tell the difference between mould and mildew. They are both microscopic fungi that can cause similar allergic reactions, such as eye irritation. Furthermore, they are fast reproducers, with hundreds of new spores growing in only two days. Many UK homes also have both mould and mildew, especially in damp or humid areas.

They are the same—for the untrained eye. In reality, they are not. This mould vs mildew guide spells out the massive differences between them and reveals one strategy for finding a mould removal professional.

What is mould?

Dark mould patches and discolouration on an interior wall near the floor (Source: iStock)

Mould is a type of fungus that develops multicellular filaments called hyphae. These fine threads develop at the tip and then divide repeatedly 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 or organic matter like wood. This explains why you can find them in walls and ceilings, as well as in 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 include Aspergillus, which can thrive indoors and outdoors, and Cladosporium, which prefers painted surfaces and cooler temperatures. A popular type of mould is Penicillium, which scientists use to make antibiotics.

What is mildew?

Visible mildew patches and moisture stains in a room corner beside a radiator and wooden flooring (Source: iStock)

Mildew 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 similar that some refer to mildew as early-growth mould.

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

Mildew vs mould: How different are they?

Dirty bathtub surface with visible mould and mildew around the tiled corner and drain area (Source: iStock)

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 colony’s age 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, and grow to cover an entire surface. Mould also features a 3D or raised texture, such as when it develops in bread.

Mildew is better known for its flat growth habit, so it does not look puffy or raised like 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 that from books kept in a cabinet for decades.

What does mildew smell like? Because it is also a type of mould, the scent is similar, though 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

Black mould growth along a white window frame and adjacent wall with a hand highlighting the affected area (Source: iStock)

Because there are different types of mould, their textures can also vary widely. 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 because of the wet environment in which 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 (fluffy).

In terms of location

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

However, some types of mould also prefer dark, 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 on flat, less-porous surfaces with better airflow, such as shower walls. It also occurs in areas with temporary or intermittent moisture, such as 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 study in 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 note that they can trigger allergic reactions, such as itchy eyes, a sore throat, and sneezing. For people who are overly sensitive to spores, one health problem to watch out for is anaphylaxis. It is a life-threatening situation wherein the person suffers from laboured breathing, low blood pressure, and an 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 the UK, the average cost of removing mould and mildew is £15 to £25 per hour. However, if they need to clean mould throughout the house, the specialists can charge up to £2,000 for the whole job. The fee can already cover the protective gear they will wear, cleaning supplies, and insurance.

However, since mildew is easier to clean, the removal price could be lower. You can get free quotes, proposals, or consultations to better understand 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 of mould and mildew, the right equipment and cleaning supplies, and the ability to handle spores. 

Restore mouldy and mildewy surfaces with Airtasker

Close-up of a blue-gloved hand holding a scraper near mould-covered walls and damaged plaster (Source: iStock)

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

• Perform a thorough inspection to identify the fungus in the house and accurately determine the best solution.

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

• Provide 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 one.
   

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.