Definition
Healthy Homes Moisture Ingress Standard The Healthy Homes Moisture Ingress Standard requires all residential rental properties with an enclosed subfloor to have a ground moisture barrier (polythene sheet) installed over at least 75% of the ground area, with overlaps and taping in accordance with NZS 4246:2016. Properties with open subfloors are exempt. ALLWISE auto-checks subfloor enclosure type from the assessment photos.
Compliance threshold
Polythene barrier ≥ 75% of enclosed subfloor ground
How to comply — step by step
- 1
Determine if the subfloor is enclosed
Check whether the subfloor space is enclosed by walls (e.g. concrete perimeter, brick, or sealed timber). If fully open on all sides, the property is exempt.
- 2
Measure the existing barrier coverage
Measure the area covered by polythene sheeting. Calculate the percentage of the total enclosed subfloor area it covers.
- 3
Check overlap and taping
Verify that joins are overlapped by at least 150mm and taped, edges are weighted or fixed, and the barrier is intact (no tears).
- 4
Photo-document with reference object
Take a wide-angle photo of the subfloor with a measuring tape or known-size object in frame for scale. ALLWISE auto-validates coverage.
Common moisture barriers failures
- No barrier installed in older 1960s-1980s rentals
- Barrier coverage below 75%
- Barrier torn or displaced over time
- Open subfloor incorrectly classified as enclosed
Frequently asked questions
Does every rental need a ground moisture barrier?
What thickness of polythene is required?
Skip the manual calculation
Need an assessment for this standard?
Book a certified inspection.
ALLWISE auto-fills the moisture barriers check into every statutory pack based on the property address, room dimensions, and BRANZ climate zone. Court-defensible evidence in 11 minutes.