NZ Building Answers

How do I spot a leaky home?

Updated June 2026

Short answer

Start with the era and the design. Homes built roughly between the mid-1990s and mid-2000s with plaster-look cladding, flat roofs, no eaves and balconies over living areas carry the highest risk profile. Then look for evidence: musty smells, swollen skirtings, bubbled paint and staining around windows. None of these prove anything on their own, which is why moisture testing by a specialist matters.

Source: MBIE Building Performance. Updated June 2026.

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Key facts

The highest-risk era is broadly mid-1990s to mid-2000s
Design features to note: monolithic cladding, no eaves, flat roofs, enclosed balconies
Interior signs include musty smells, swollen skirtings and stained carpet edges
Invasive moisture testing by a qualified surveyor gives the only reliable read

Start with the era and the design

Weathertightness failures cluster in homes built from roughly the mid-1990s to the mid-2000s. During those years untreated kiln-dried timber was permitted in wall framing, and plaster-look monolithic cladding was often fixed straight to the frame with no drained cavity behind it. Water that got past the surface had nowhere to go, and timber with no treatment to resist decay. The rules changed in the mid-2000s, so the same look on a 2010s build usually sits over a cavity.

Era and design set a risk profile, nothing more. Plenty of homes from those years are sound, and a 1970s weatherboard house can still leak. The point is knowing where to look harder.

Design features that raise the risk

Risk rises when several of these appear together on a home from that era:

One of these alone says little. A flat-roofed plaster home from 1999 with no eaves and an enclosed balcony deserves serious scrutiny before you go further.

Monolithic or plaster-look cladding with no visible cavity
Flat or low-pitch roofs, especially hidden behind parapets
Little or no eaves to throw water clear of the walls
Decks and balconies sitting over living spaces
Cladding running down to the ground or onto a deck surface
Handrails, pergolas or fixtures bolted through the cladding

Signs you can see and smell

Inside, trust your nose first. A musty smell in wardrobes or south-facing rooms is moisture talking. Look for swollen or lifting skirting boards, bubbling paint around window sills, staining on ceilings and at window corners, and carpet edges with tide marks. Outside, look for cracks in the plaster, rust staining at fixings, moss along junctions, and soft spots if you press gently near the base of the cladding.

A fresh interior paint job before sale can hide most of this, and serious decay often shows nothing at the surface at all. Visible signs mean look closer. Their absence does not mean all clear.

Get it tested before you commit

A standard pre-purchase inspection is not designed for this question. Use a building surveyor with weathertightness experience and ask for moisture testing. Non-invasive meters give a first read; invasive testing, which uses small drill holes and needs the owner's permission, is the only way to know what the framing is doing.

Ask the council for the property file too. It shows the original consent, the cladding as designed, and whether the home has since been recladded or repaired with consent. A documented reclad changes the conversation entirely, and an undocumented one raises its own questions. If the readings are bad, walk away or price a reclad into your offer with professional advice behind the number.

Before you hire

Knowing the rules is half the job. The other half is knowing who you're hiring. Check any NZ builder against the public record: company status, licensing and insolvency notices, from the official NZ sources.

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Planning the project? See the costs

Cost Guide
Recladding
typical $300,000