Does Healthy Homes compliance mean a rental will remain mould-free?

No. New Zealand’s Healthy Homes standards do not provide a general certification that a property is, or will remain, mould-free.

The standards cover five areas:

1. Heating
2. Insulation
3. Ventilation
4. Moisture ingress and drainage
5. Draught stopping

These measures help create warmer, drier rental homes. However, mould can still develop where moisture accumulates and surfaces remain damp for long enough.

A property may have compliant insulation, an appropriately sized heater and the required extractor fans, but still experience mould because of a leak, blocked drainage, a failed fan, insufficient air movement or another moisture source.

Compliance is an important baseline, not a substitute for maintenance and ongoing observation.

Why can mould appear in a compliant rental property?

Mould needs moisture, suitable temperatures and a surface on which to grow. The key question is not simply whether mould is present, but where the moisture is coming from.

Possible contributing factors include:

• Leaking roofs, gutters, pipes or windows
• Ground moisture entering beneath or through the building
• Damaged cladding, sealants or flashings
• Blocked or inadequate drainage
• An extractor fan that is damaged, disconnected or no longer performing effectively
• Condensation forming on cold surfaces
• Furniture or stored belongings restricting air movement
• Steam from cooking, showering or drying clothes indoors
• Rooms that are difficult to heat or ventilate effectively
• Changes to the property since its last Healthy Homes assessment

More than one factor may be involved.

Visible mould alone does not establish the cause, when it developed or who is responsible. Those conclusions require information about the property, the location of the mould and the surrounding moisture conditions.

Does mould automatically mean the property has failed the Healthy Homes standards?

No. Mould does not automatically prove that a rental property is non-compliant.

New Zealand’s Healthy Homes legislation does not establish a separate mould standard or a universal pass-or-fail mould measurement for residential rentals.

However, mould may be evidence of a problem associated with one of the regulated standards. For example:

• A failed bathroom extractor fan may raise a ventilation issue.
• Water beneath the property may indicate a moisture-ingress or drainage problem.
• Gaps allowing significant uncontrolled airflow may relate to draught stopping.
• Changes to insulation may affect the property’s continued compliance.

Mould may also indicate a repair or maintenance problem that sits outside the five Healthy Homes standards.

Under section 45 of the Residential Tenancies Act 1986, landlords have broader obligations to provide and maintain rental premises in a reasonable state of repair and to comply with applicable building, health and safety requirements. Compliance with the Healthy Homes standards does not replace those obligations.

Who is responsible when mould appears?

Responsibility depends on the cause and should not be assumed from the appearance of mould alone.

Landlords are responsible for maintaining the property, attending to necessary repairs and continuing to comply with the Healthy Homes standards.

Tenants have legal duties under section 40 of the Residential Tenancies Act, including keeping the premises reasonably clean and tidy and notifying the landlord as soon as possible when repairs are needed.

Tenancy Services also recommends practical measures such as using available extractor fans, airing the home and managing indoor moisture. These are useful occupancy practices, but they should not be presented as proof that a tenant caused a mould problem.

Before responsibility is assigned, the property should be examined for:

• Water entry
• Plumbing or drainage faults
• Ventilation performance
• Condensation patterns
• Heating and insulation conditions
• Maintenance problems
• How and where moisture is being generated

A neutral investigation protects both the property owner and the tenant from conclusions that are not supported by evidence.

Cleaning mould may not solve the underlying problem

Cleaning visible mould can improve the affected surface, but it may not remove the reason the mould appeared.

If moisture continues to enter or accumulate, the mould may return.

Repeatedly treating the surface without investigating the moisture source can allow a maintenance issue to continue. It can also make it harder to understand whether the property’s condition is improving or deteriorating.

Recurring mould is a signal to look beyond the stain.

What should a landlord or property manager do next?

1. Record the problem

Photograph the affected area and note:

• The date it was reported or observed
• The room and surface affected
• Whether the mould is localised or widespread
• Any visible condensation, staining or water damage
• Whether the problem has occurred before

Good records help identify patterns and support later decisions.

2. Check for urgent repair issues

Look for active leaks, overflowing gutters, plumbing faults, blocked drainage or water entering through the building envelope.

Urgent maintenance should not be delayed while waiting for mould testing.

3. Inspect the relevant Healthy Homes features

Check that the features associated with the property’s compliance remain present, functional and appropriate.

This may include confirming that:

• Extractor fans are operating and venting outside
• Heating remains installed and functional
• Insulation has not been damaged, displaced or removed
• Ground moisture barriers remain intact where required
• Gutters, downpipes and drains are functioning
• Draught-stopping work has not deteriorated

An older assessment cannot confirm the current performance of a damaged or altered feature.

4. Consider how the room is being used

Occupancy information can help explain when and where moisture is produced. It should form part of the investigation, not become an automatic basis for blaming the tenant.

The practical question is whether the room can be heated, ventilated and used normally without persistent moisture accumulating.

5. Arrange further assessment where appropriate

A property assessment can help identify visible mould, moisture conditions and contributing building factors.

Testing may be appropriate where the extent or nature of contamination is uncertain, where mould keeps returning or where additional evidence is needed to guide remediation.

Testing should answer a defined question. It is not automatically required for every patch of visible mould.

6. Address the cause and document the response

Repairs, cleaning, remediation or changes to ventilation should be recorded.

Where conditions have changed since the previous Healthy Homes assessment, the property may also need to be reassessed. Landlords should retain the records used to demonstrate ongoing compliance.

What mould testing can and cannot establish

Mould testing can support an investigation, but a result must be interpreted in context.

Testing may help:

• Document conditions in a specific sampled area
• Identify mould present in the sample
• Compare selected areas of the property
• Support decisions about cleaning or remediation
• Establish a record before and after work is completed

A test result alone generally cannot establish:

• Who caused the mould
• Exactly when it developed
• The complete condition of every room
• The source of the moisture
• Whether the landlord or tenant has breached the tenancy agreement
• Whether all remediation work has been completed correctly

Testing is one piece of evidence. Moisture readings, visual observations, maintenance records and information about the building are also important.

Healthy Homes compliance is ongoing

A Healthy Homes assessment provides evidence about the property at the time it is assessed. It does not prevent future leaks, equipment failures, maintenance issues or changes in moisture conditions.

Landlords must continue to comply with the Healthy Homes standards throughout the tenancy. They must also meet their wider repair and maintenance obligations under the Residential Tenancies Act.

For property managers, that means treating a compliance record as part of the property file, not as the end of the conversation.

When mould appears, the appropriate response is to:

• Record it
• Investigate the moisture source
• Check the relevant property features
• Complete necessary repairs
• Arrange assessment or testing where appropriate
• Retain evidence of the action taken

This article provides general information about New Zealand rental-property requirements. It is not personalised legal, medical or building advice.

Frequently asked questions

Can a Healthy Homes compliant rental still develop mould?

Yes. Compliance with the five Healthy Homes standards reduces important contributors to cold and damp conditions, but it does not guarantee that mould will never develop.

Is mould a separate Healthy Homes standard?

No. The regulations contain standards for heating, insulation, ventilation, moisture ingress and drainage, and draught stopping. There is no separate statutory mould standard.

Does mould prove that a landlord has breached the law?

Not by itself. The cause, property condition, maintenance history and relevant legal obligations must be considered.

Is mould always caused by tenants?

No. Mould can result from building defects, leaks, drainage problems, failed ventilation, condensation, occupancy conditions or a combination of factors.

Does every mould problem require laboratory testing?

No. Testing should be used when it can answer a specific question or help guide the response. Visible defects and active leaks may require immediate repair without waiting for test results.

When should a property be reassessed?

Reassessment should be considered when property features change, damage occurs, compliance equipment stops working or new conditions suggest that the previous assessment may no longer reflect the property’s current state.