Mould – causes, symptoms and prevention

Types of mould

There are many types of mould that can develop indoors, each with different characteristics and levels of risk. Understanding the most common ones can help you identify them early and take appropriate action.

Black mould (Stachybotrys chartarum): This type is one of the most well-known and potentially dangerous moulds found indoors. It thrives in damp areas such as bathrooms, basements and around leaks, appearing as dark or black patches. Prolonged exposure can cause allergic reactions, respiratory problems and fatigue.

White mould: Typically white or light grey, this mould can grow on walls, furniture, fabrics and wooden surfaces. It often spreads unnoticed and may look powdery or fluffy in texture.

Red mould: Recognised by its red, pink or orange hues, this mould often grows in damp, poorly ventilated areas like bathrooms, kitchens and basements. It can cause allergic reactions and damage materials if left untreated.

Green mould: Often found on food, walls and bathroom surfaces, this mould is common but still problematic. It can trigger allergies and produce unpleasant odours, especially in humid spaces.

Other less common variations include pink, orange and yellow mould, which are typically colour variations of red or white mould appearing in damp bathrooms or kitchens.

By learning to recognise the appearance and conditions of these mould types, you can take faster action to remove and prevent them.

Common areas where mould appears

Mould usually develops where moisture accumulates. Typical problem areas include:

• Bathrooms and showers
• Basements and crawl spaces
• Behind wallpaper or tiles
• Around windows or roof leaks
• Inside wardrobes or storage areas

Signs of mould include a musty smell, peeling wallpaper or bubbling paint, and visible black, green or white spots on walls, ceilings or furniture. Mould may also appear under carpets or behind heavy furniture.

For more detailed information about specific species, visit our mould encyclopedia.

How to identify and test for mould

Mould is often visible, but it can also hide behind walls or under floors. A distinct musty smell is one of the earliest signs of mould.

To confirm whether mould is present and determine the type, use a mould test. These tests provide quick and reliable results, helping you take the right steps for safe removal and prevention. Early detection is key to avoiding larger infestations.

How to prevent mould growth

Prevention is the most effective way to maintain a mould-free home. Keep humidity below 60 percent, ensure good airflow and address water leaks promptly.

Here are a few key prevention tips:

• Air out rooms regularly and open windows after cooking or showering.
• Use extractor fans in bathrooms and kitchens.
• Dry wet areas immediately and avoid leaving damp laundry indoors.
• Use hygrometers and moisture meters to monitor humidity levels.
• Keep furniture slightly away from walls to allow airflow.
• Repair roof leaks and seal window gaps.

Following these steps helps maintain healthy indoor air and protects your home from future growth. For more advice, visit preventing mould.