Healthy moisture barriers

Hamish asks:
(updated on Friday, May 01st 2020)

Do you know if concrete floor in enclosed space under house installed before 1 July 2019 is sufficient moisture barrier?

For Healthy Homes, our property management company asked that we install Moisture Barrier to comply with Healthy Homes however my understanding is that we already comply as the ground is fully concreted in the enclosed space and all holes/gaps sealed.

We therefore meet standard:

"Requirements for ground moisture barriers:

If there is an existing ground moisture barrier installed before 1 July 2019, make sure it does not have any significant holes or tears that allow moisture through. Ground moisture barriers installed before 1 July 2019 do not need to be installed in accordance with NZS 4246:20163 but it is recommended you check installation against the standard to make sure the barrier is installed properly.


Our Experts Answer:

As part of the moisture ingress and drainage standard, rental properties with an enclosed sub-floor space must have a ground moisture barrier installed if it is reasonably practicable to do so. If the premise has a suspended floor (i.e. there is a cavity under the floor), and the space under the suspended floor is enclosed, then the home likely has an enclosed sub-floor and requires a ground moisture barrier unless an exemption applies.

Any alternative ground moisture barriers, including concrete, must meet certain requirements under the Residential Tenancies (Healthy Homes Standards) Regulations 2019. The landlord would need to provide reliable evidence as to whether the property meets those requirements for an alternative ground moisture barrier, including evidence that shows it meets the required vapour flow resistance and that it was installed by a professional installer. If these requirements are not met then the landlord will still need to install the required ground moisture barrier. 

There is one specific exemption to this 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, or • causing substantial damage to the property, or • 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.

It is important to remember a professional installer may be able to install a ground moisture barrier in situations where landlords could not do so themselves. If you are unsure whether it is reasonably practicable to install a ground moisture barrier, you or the property manager should speak to an experienced professional. Experienced professionals can either install a ground moisture barrier if required or provide a written compliance certificate noting installation is not practicable.

Please note, these responses apply under normal circumstances. Under the current Covid-19 lockdown, you must continue to comply with the current lockdown rules and guidelines during this period. This includes recent changes in tenancy legislation, such as a freeze on rent increases and protections against tenancy terminations.

For more information see: For more information on ground moisture barriers, go to You can also subscribe to our e-newsletter Tenancy Matters here.

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