Practical guidance for New Zealand homes

Types of mould in New Zealand homes

Different moulds can look alike. Understanding the moisture, affected materials and extent of growth is usually more useful than trying to name it from its colour.

Reviewed 9 October 2026. General information, not a diagnosis of a building or a person’s health.

What types of mould occur in homes?

Mould groups include Cladosporium, Penicillium, Aspergillus and several others associated with damp materials. Most names below are genera: groups containing multiple species.

A University of Otago study of 20 homes across four seasons found Cladosporium and Penicillium dominated air samples, with a wider range of fungi in flooring dust. This is useful New Zealand evidence, not a nationwide ranking of the mould growing on walls. The guide below also draws on overseas building research and specialist fungal descriptions.

These are possible appearances, not a visual identification chart. Colour and texture vary with species, growing conditions and age. More than one mould can occupy the same patch. None of these names or colours, by itself, establishes a health risk.

Mould groups and possible locations
Mould group	Possible appearance	Where it may occur
Cladosporium	Olive-brown to almost black; sometimes velvety or powdery	Household air and damp materials, including wood
Penicillium	Often blue-green or green, sometimes white and fuzzy	Household air and dust; damp plasterboard and wallpaper
Aspergillus	Varies widely: green, yellow, brown or black; often powdery	Dust and water-damaged building materials
Alternaria	Dark olive, grey or black; may look fuzzy	Outdoor sources and damp indoor materials, including wood
Aureobasidium	May start pale or pink, becoming brown or black	Household dust and damp wood or plywood
Chaetomium	May develop dark, hairy-looking structures	Cellulose-containing materials in water-damaged buildings
Stachybotrys chartarum	Greenish-black; overlaps in appearance with other fungi	Persistently wet paper, fibreboard and plasterboard paper
Acremonium	Pale white, grey, pink or orange; may become powdery	Wet plasterboard and wallpaper
Mucor	Cottony pale growth that may become darker grey	Some water-damaged building materials

Appearance descriptions are educational examples. Laboratory-grown colonies can look different from growth on a wall. See the research and mycology references below.

Some moulds can trigger allergies, and some can produce toxins under certain conditions. These effects can overlap. Identifying a mould in a sample does not, by itself, show toxin exposure or explain someone’s symptoms. Read about mould assessment and health.

When to get specialist help

Seek appropriate advice for extensive or suspected hidden growth, significant water damage, contaminated floodwater, or mould that keeps returning after cleaning. For symptoms or concerns about exposure, especially involving vulnerable occupants, seek advice from a healthcare professional.

Is all black mould toxic black mould?

No. Not all dark mould is Stachybotrys chartarum, the species often called “toxic black mould”. Cladosporium, Alternaria and some Aspergillus species can also look dark. Colour cannot establish species or toxin production.

Some moulds can produce mycotoxins under suitable conditions. Identifying a mould does not establish that a particular patch is producing toxins, that someone has received a harmful exposure, or that it explains their symptoms. Green or white growth should not be dismissed either.

The practical response is to address unwanted growth and the moisture supporting it. For symptoms or concerns about exposure, seek advice from a healthcare professional. Read more about mould assessment and health questions.

What can a photograph tell us?

A photograph can show the visible area, the surface and signs of damage. It cannot reliably identify the species, reveal everything behind a lining, or establish that a home is medically safe.

Location and patterns help guide investigation. Growth around a stain or softened lining warrants checking for water entry. Bands or patches on cold walls may warrant checking insulation, condensation and airflow. These clues do not prove the cause.

See the laundry photograph and explanation of mould patterns and insulation.

How can mould testing help?

Laboratory testing can help identify the mould in a surface sample if you want to understand what is growing. A building assessment considers different questions: the affected materials, moisture, possible causes and work that may be needed.

Testing complements this assessment. The extent of growth and the moisture source still need attention, whatever the laboratory identifies. Results relate to the sample tested; they do not certify the whole property or diagnose health effects.

Explore nationwide DIY mould testing → · Explore assessment and testing guidance.

Nationwide DIY laboratory testing

Find out what mould is in your sample

Choose a DIY postal kit for one to 100 separate surface samples. We help you record your chosen spots, collect and label each sample using the confirmed kit instructions, and understand what the laboratory findings cover. You do not need to disclose your reasons for requesting a test.

Choose your sampling spots and kit quantity.
Collect, label and return each sample separately using the supplied instructions.
Receive the original laboratory report matched to your sample locations.

The result relates to the material sampled; it does not establish the condition of the whole property or diagnose health effects. The growth and its moisture source still need attention.

Klarna for eligible personal purchases · Afterpay coming soon

DIY Lab mould test kit

DIY surface-sampling kits are available nationwide. Choose your sample quantity and complete the kit application online, then pay securely through your Xero invoice. Your kit is prepared after payment is confirmed. See the kit page for prices, inclusions and courier arrangements.

What should I do next?

Choose the next step according to the growth, dampness and condition of the affected materials.

Prevent and monitor

Where no unwanted growth or unresolved dampness is apparent, maintain moisture control and check previously affected areas. This is not a certification that a home is mould-free.

Address the growth

For visible growth, consider the extent, surface and moisture source. A suitable small-area cleaning method may be appropriate for some surfaces; affected porous material may need replacement. Cleaning does not repair a leak or correct a cold, persistently damp wall.

Arrange specialist assessment

Get appropriate advice for extensive growth, significant water damage, suspected hidden growth, contaminated floodwater or continuing recurrence. Health concerns and the needs of vulnerable occupants may also require professional advice. Avoid disturbing affected materials while arranging help.

These are action descriptions, not species danger ratings. Do not wait for a mould’s name before addressing dampness. Read about cleaning, repairs and preventing recurrence.

Tell us about the mould

For a Taranaki property, tell us which rooms and surfaces are affected, roughly how large the area is, whether it returns after cleaning, and whether there are leaks, condensation or musty smells. Photographs can help the initial discussion without disturbing the material.

Sources and further reading

New Zealand research provides local context; overseas guidance provides supplementary information. Older research is not presented as a current regulatory standard.

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