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How Does Mould Grow In Your Home?

Updated: May 21, 2023

How Does mould grow in your home
How Does mould grow in your home

What is Mould?

Just like yeast and mushrooms, mould is a type of fungus that grows on plants, wood, fabric, food and any other organic material.

Put simply, mould is a natural recycler of dead organic matter. Although it sounds like a nice thing to do for nature, in most cases, it is not a nice thing to do for humans. Mould can be tricky to identify, there are thousands of mould species.

Mould is an eyesore and a homeowner’s worst nightmare. However, there is much more you should know about mould because once you understand what it is, you will be better able to prevent its growth.

To begin, here are some basic facts about mould:

o Moulds are fungi.

o Moulds grow on plants, wood, fabric, soil, food, drywall, floors and ceilings.

o Moulds produce microscopic spores that germinate where moisture has accumulated.

o Mould growth threatens the structural integrity of a building.

o Mould exposure can lead to serious health problems.

What Does Mould Look Like?

Individual mould spores are very small and impossible to see without a microscope, but once a mould colony emerges, it can form visible spots on surfaces.

Mould usually comes in these colours: black, blue or green. The colour of mould is determined by various factors such as type, nutrient source, age of the colony, etc. Of all mould types, black mould (officially called Stachybotrys) is the most harmful one to the health of living beings.

Different Types of Mould

Unfortunately, not all mould types are the same, but we can roughly divide them into 3 big types:

Allergenic this type of mould is the least harmful of all mould types; however, it can

cause problems for people who are allergic to mould or have asthma.

Allergenic mould is usually not life threatening.

Pathogenic this type is often harmful, not only for people with asthma or mould

allergies, but for healthy people too. For example, this type of mould can

cause hypersensitivity pneumonitis, an acute response resembling bacterial


Toxigenic this type of mould can actually cause serious health issues, both temporary

(eye irritation or cough) and permanent (e.g. immunosuppression,

neurological disorders, or cancer). Toxigenic mould produces mycotoxins – a

toxic chemical present inside or on the surface of the mould spore, which can

be inhaled, ingested or touched.

How Does Mould Grow in Property?

Just like any other living being, mould needs water to grow. As a matter of fact, without water, mould cannot grow at all. Other factors that are crucial for mould growth are food source, oxygen and humidity.

Does that mean that by removing the main mould growth factors, we can eliminate mould once and for all?

Sadly, the answer is no. It is almost impossible to keep a place mould-free mainly because you cannot eliminate oxygen from a place and actually stay at that place, nor can you build a house without any organic materials such as wood, carpet, plants, etc.

What you can (and should do) is focus on:

o Moisture control

o Dust control

o Proper ventilation of your house

If you want to ensure a healthy living environment, it’s important to know the common causes of mould and repair them sooner rather than later.

Is it mould or mildew?

Although often considered to be the same thing, mould and mildew are better explained as two brothers with a similar feature. Both of them are frequently seen in homes, especially in moist and warm areas such as food, walls, shower, etc. That’s where the similarity ends.

Mould is a living organism that produces airborne spores and as such has harmful effects on health. Mildew is an accumulation of dirt and grime. It is not a living organism, it will not reproduce and cannot produce harmful mycotoxins, but it can potentially decrease the quality of your life. Unlike mould, which comes in much darker shades, mildew is often white or grey. While mildew is easily treated with a store-bought cleaner and a scrubbing brush, mould often requires a more professional touch.

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