Mould is a common household problem, particularly in damp or poorly ventilated spaces. While mould may start as a small patch, if left untreated it can spread quickly, damage your property, and pose potential health risks.
Understanding the different types of mould, what they look like, and how to deal with them is the first step in protecting your home.
What Is Mould?
Mould is a type of fungus that thrives in moist environments. It spreads by releasing tiny spores into the air, which settle and grow when they find suitable conditions, typically moisture, warmth, and organic material.
Mould often appears on walls, ceilings, windows, bathrooms, kitchens, basements, and around leaks.
Common Types of Mould by Colour
Black Mould
What it looks like:
Black mould appears as dark black or deep green patches. It often looks slimy or spotty and is commonly found around windows, bathrooms, ceilings, and damp walls.
What causes it:
- Condensation
- Leaking pipes or roofs
- High humidity and poor ventilation
Risks:
Black mould is one of the most well-known types due to its potential health effects. It can:
- Trigger allergies and asthma
- Cause respiratory irritation
- Weaken plaster, paint, and wood over time
How to get rid of it:
- Improve ventilation (extractor fans, open windows)
- Use a mould-killing solution or professional-grade treatment
- Address the moisture source permanently
Green Mould
What it looks like:
Green mould can appear fuzzy or powdery and ranges from light green to dark green. It commonly grows on walls, food, carpets, and damp surfaces.
What causes it:
- High humidity
- Water damage
- Poor airflow
Risks:
Green mould can:
- Cause coughing, sneezing, and eye irritation
- Spread quickly if moisture remains
- Damage soft furnishings and wall surfaces
How to get rid of it:
- Remove affected materials if heavily contaminated
- Clean surfaces with anti-mould products
- Reduce indoor humidity levels
White Mould
What it looks like:
White mould often appears powdery or fluffy and can be mistaken for salt or efflorescence. It is commonly found on wood, basements, and crawl spaces.
What causes it:
- Persistent damp conditions
- Poor air circulation
- Moisture trapped in porous materials
Risks:
White mould can:
- Weaken wooden structures
- Cause allergic reactions
- Indicate underlying moisture problems
How to get rid of it:
- Identify and fix moisture sources
- Dry affected areas thoroughly
- Treat surfaces with mould inhibitors
Blue or Grey Mould
What it looks like:
This mould appears in shades of blue, grey, or bluish-green and often grows on walls, insulation, and damp furniture.
What causes it:
- Water damage
- Poor ventilation
- Long-term dampness
Risks:
- Structural damage to walls and furnishings
- Potential respiratory irritation
- Unpleasant musty odours
How to get rid of it:
- Dry out the affected area
- Clean with appropriate mould treatments
- Improve airflow and ventilation
Yellow or Orange Mould
What it looks like:
Yellow or orange mould may appear slimy or powdery and is often found in bathrooms, kitchens, or on damp wood.
What causes it:
- High moisture levels
- Organic materials such as wood or drywall
Risks:
- Can spread rapidly
- May cause allergic reactions
- Can damage decorative finishes
How to get rid of it:
- Remove moisture sources
- Clean thoroughly with mould-specific cleaners
- Monitor for regrowth
What Mould Can Do to Your Home If Left Untreated
If mould is ignored, it can lead to serious long-term problems, including:
- Structural damage to walls, ceilings, timber, and insulation
- Persistent damp smells that are difficult to remove
- Reduced property value
- Health concerns, especially for children, elderly individuals, and those with respiratory conditions
- Increased repair costs the longer the issue is left unresolved
How to Prevent Mould in Your Home
Prevention is always better than cure. To reduce the risk of mould:
- Keep your home well-ventilated
- Use extractor fans in kitchens and bathrooms
- Address leaks immediately
- Maintain consistent heating
- Control indoor humidity levels
Small surface mould can sometimes be treated with household products, but recurring, widespread, or severe mould problems should be assessed by a professional. This ensures the root cause is addressed, and the mould is removed safely and effectively.