Moisture ingress and drainage standard
Rental properties must have efficient drainage for the removal of storm water, surface water and ground water. Rental properties with an enclosed sub-floor space must have a ground moisture barrier.
Moisture can be a large source of dampness in a home. This dampness can lead to poor health outcomes for tenants and can be destructive to the quality of a house.
Between 1 July 2021 and 1 July 2025, all private rentals must comply with the healthy homes standards within certain timeframes from the start of any new, or renewed, tenancy.
Use the compliance timeframes decision tool to find out when your rental property needs to comply
All boarding houses must have complied by 1 July 2021. All houses rented by Kāinga Ora (formerly Housing New Zealand) and registered Community Housing Providers must comply by 1 July 2024.
Landlords that don’t meet their obligations under the healthy homes standards are in breach of the Residential Tenancies Act 1986. They may be liable for exemplary damages of up to $7,200.
What is the moisture ingress and drainage standard?
Rental properties must have efficient drainage for the removal of storm water, surface water and ground water, including an appropriate outfall. The drainage system must include gutters, downpipes and drains for the removal of water from the roof.
If the rental property has an enclosed subfloor, a ground moisture barrier must be installed if it is reasonably practicable to do so.
Our guidance document has more specific information on the moisture ingress and drainage standard.
Download the moisture ingress and drainage guidance document. [PDF, 2 MB]
Ground moisture barrier
A ground moisture barrier is generally a polythene sheet that can be bought from most building retailers. It can be installed by a house owner or a building professional.
Ground moisture barriers must either:
- be a polythene sheet and installed in accordance with section 8 of New Zealand Standard NZS4246:2016(external link), or
- have a vapour flow resistance of at least 50MNs/g and be installed by a professional installer.
Exemptions to the moisture ingress and drainage standard
There is one specific exemption to the moisture ingress and drainage standard. This exemption covers properties where it is not reasonably practicable to install a ground moisture barrier.
It is not reasonably practicable to install something if a professional installer can’t access the area without:
- carrying out substantial building work
- causing substantial damage to the property
- creating greater risks to a person’s health and safety than is normally acceptable
Or it is otherwise not reasonably practicable for a professional installer to carry out the work.
Landlords are not required to install alternative moisture barriers where installation of a polythene barrier isn’t reasonably practicable in the subfloor area.
Managing asbestos risks
Landlords must manage any asbestos-related risks when work is being done at their property.
This is to protect the health and safety of tenants, neighbours, contractors and anyone else who may be affected.
Further information
The moisture and drainage standard is one of five healthy homes standards. Find out about the other healthy homes standards:
