Mould and damp in a rental property: NZ landlord checklist before winter

If you want the short answer, here it is: when mould or damp shows up in a rental property, NZ landlords should first check whether the building systems are doing their job. Start with water entry, drainage, ventilation, heating, insulation, draughts, and records before treating it as only a tenant-behaviour issue.

That matters more before winter. Cold weather, closed windows, heavier rain, and weaker drying conditions can turn a small damp clue into a maintenance job, a Healthy Homes pressure point, or a tenant dispute.

This guide is general information for NZ landlords, not legal advice. For official rules, use Tenancy Services as the source of truth.

What should a landlord check first when mould or damp is reported?

Start with the cause, not the stain. Clean-up matters, but the landlord risk usually sits in the system that allowed the dampness to keep returning.

Use this order:

1. Is water getting in from outside or plumbing?
2. Are gutters, downpipes, drains, and subfloor moisture controls working?
3. Are bathroom and kitchen extractors clearing moisture to the outside?
4. Can tenants ventilate rooms using openable windows or doors?
5. Is the main living room heating working well enough in real conditions?
6. Are draughts, gaps, cold surfaces, or weak insulation making moisture worse?
7. Do you have photos, receipts, reports, and tenant communications in one place?

That order keeps the response practical. It separates immediate cleaning from the bigger question: what has to change so the issue does not come back.

1. Check for water entry before blaming condensation

Visible mould can come from condensation, but dampness often starts with water entering where it should not.

Check:

• roof leaks, flashing, gutters, and downpipes
• window frames, external doors, cladding joins, and wet-area sealant
• plumbing drips under sinks, vanities, laundries, cylinders, and toilets
• musty smells near wardrobes, subfloors, corners, and rooms against external walls
• staining, bubbling paint, swelling skirting, or soft flooring

If you find active water entry, treat that as a maintenance issue first. Cleaning the mould without fixing the moisture source is just resetting the clock.

2. Check gutters, downpipes, drainage, and the subfloor

Tenancy Services' Healthy Homes guidance says rental properties need efficient drainage, including gutters, downpipes, and drains for stormwater, surface water, and ground water. Where there is an enclosed subfloor, a ground moisture barrier can also be required.

Before winter, check:

• gutters are clear and not overflowing
• downpipes are connected and moving water away from the building
• ground drainage is not pooling around foundations
• subfloor areas are reasonably dry where accessible
• any ground moisture barrier is present and intact where required

This is one of the most common places a cheap maintenance task becomes an expensive winter problem. A blocked gutter can become internal dampness. Poor drainage can become subfloor moisture. Subfloor moisture can become cold rooms, smells, and recurring mould.

3. Test ventilation, not just windows

Ventilation is not a vague instruction to "open a window". Under the Healthy Homes ventilation standard, each liveable space needs an openable window or door to the outside, and kitchens and bathrooms need extractor fans to remove moisture.

Check:

• bathroom fans switch on and pull air strongly
• kitchen extraction vents outside rather than recirculating
• windows open, close, and can be fixed open where required
• tenants know how and when to use the fans
• steam-heavy rooms dry out after normal use

If a bathroom fan is weak, noisy, disconnected, or venting into a roof space, it can make a damp issue look like tenant behaviour when the system itself is failing.

4. Confirm heating works in real conditions

Healthy Homes requires fixed heating in the main living room that meets the required capacity for that room. But landlords should also think operationally: does the installed heater still work well enough when tenants actually need it?

Check:

• heat pump filters and servicing
• thermostat settings and error codes
• whether the main living room warms properly
• whether tenants are relying on portable heaters because the fixed heater feels inadequate
• whether cold rooms point to insulation, draught, or moisture problems elsewhere

Heating does not solve all dampness. But weak heating makes condensation, drying, and tenant comfort harder to manage.

5. Look for draughts and heat-loss clues

The Healthy Homes draught stopping standard requires landlords to block unreasonable gaps or holes that cause noticeable draughts. In practice, draughts also make mould and damp problems harder to control.

Check:

• gaps around windows, doors, floors, wall penetrations, and unused fireplaces
• warped doors or windows that no longer close properly
• damaged seals in bathrooms, laundries, and kitchens
• rooms that feel cold even when heating is on
• areas where condensation appears repeatedly

Small draught and seal problems are often cheap to fix early. They are more expensive once they have fed winter complaints for weeks.

6. Separate tenant responsibilities from landlord responsibilities carefully

Tenancy Services says rental homes need to be free from mould and dampness before being rented out, and tenants also need to keep the home well-aired and remove mould straight away during the tenancy.

That does not mean every mould issue is automatically the tenant's fault. The practical landlord question is:

• Did the property have working systems for heating, ventilation, moisture control, drainage, and draught stopping?
• Did the tenant have clear instructions for using them?
• Was there a building fault, leak, or maintenance issue?
• Did both parties document what happened and when?

If the building system is weak, fix that first. If the system is sound and behaviour is the main driver, communicate clearly and keep records.

7. Keep evidence with the work

Healthy Homes compliance is partly a record-keeping job. Tenancy Services says landlords must keep records and documents that show compliance, and tenants can request information about compliance.

For mould and damp issues, keep:

• dated photos before and after
• inspection notes
• tenant messages
• extractor, heating, plumbing, drainage, and insulation invoices
• professional reports or assessments
• follow-up dates and unresolved items

The point is not bureaucracy. It is control. If the issue returns, you need to know what was checked, what was fixed, what remains uncertain, and who is waiting on the next step.

A simple mould and damp response workflow

Use this sequence when a tenant reports mould or damp:

1. Acknowledge the report and ask for photos, location, timing, and whether the issue is worsening.
2. Check for active leaks, water entry, drainage failure, or unsafe conditions.
3. Book urgent make-safe work if water entry or health risk is escalating.
4. Test ventilation, heating, draught stopping, and moisture-control systems.
5. Clean or remediate the affected area once the source is understood.
6. Record the decision, photos, invoices, and follow-up date.
7. Give the tenant simple guidance on heating, ventilation, condensation, and reporting if it returns.

That is the difference between reacting to a stain and managing the risk.

Where Keel fits

Keel does not replace a builder, plumber, electrician, insulation assessor, or Healthy Homes specialist.

It helps with the operating layer around the work:

• tenant reports in one place
• maintenance triage
• approval decisions
• follow-up reminders
• compliance notes
• evidence and records attached to the property

For self-managing landlords, that matters because mould and damp issues rarely stay in one tidy lane. They touch maintenance, tenant communication, compliance, and evidence. Keel helps keep those threads together so the landlord reviews the next decision instead of rebuilding the whole history from memory.

Start with Keel's Healthy Homes compliance workflow, or read the official Tenancy Services pages on Healthy Homes compliance and mould and dampness.

Frequently asked questions

Is mould always the landlord's responsibility in New Zealand?

No. Responsibility depends on the cause. Landlords need to provide and maintain a property that meets the relevant standards, while tenants also have responsibilities around ventilation, ordinary cleanliness, and reporting problems. The useful first step is to identify whether the issue comes from a building, maintenance, ventilation, heating, drainage, or use pattern.

What Healthy Homes areas relate most to mould and damp?

The most relevant areas are ventilation, moisture ingress and drainage, heating, insulation, and draught stopping. In practice, these areas work together. A house with weak extraction, poor drainage, draught gaps, and underperforming heating is much harder to keep dry.

What records should landlords keep for damp or mould issues?

Keep dated photos, tenant messages, inspection notes, invoices, professional reports, and the follow-up decision. If a compliance question comes up later, the record should show what was reported, what was checked, what was fixed, and what evidence supports the decision.

Should a landlord wait until winter to check for damp?

No. Autumn is a better time to check because gutters, drainage, heating, ventilation, draughts, and small leaks can usually be dealt with before winter demand and weather pressure make the problem harder to manage.