New Zealand's leaky homes crisis is one of the largest construction defect events in the country's history. Tens of thousands of properties — primarily those built between 1992 and 2004 — were constructed with weathertightness systems that failed to keep water out of the building structure. The consequences have been devastating: structural decay, widespread mould, health impacts on occupants, and remediation costs that have bankrupted developers, insurers, and homeowners.

The worst of the crisis peaked over a decade ago, but leaky homes remain a significant risk in the Auckland property market today. Many affected properties have been repaired — some well, some inadequately. Others have never been remediated and continue to deteriorate behind freshly painted surfaces. Knowing what to look for, and commissioning the right inspection, is the only reliable way to protect yourself.

What are leaky homes?

A "leaky home" is a property in which the exterior cladding system has failed to prevent water from entering the wall cavity and reaching the structural timber framing. The water enters — typically through failed flashings, inadequate sealants, or poor detailing at penetrations — and becomes trapped inside the cavity with no path to drain or dry out.

Trapped moisture then enables two damaging processes:

  • Timber decay — wet timber framing loses structural strength over time. In severe cases, wall framing, floor joists, and even structural posts can become so degraded that the building is unsafe. The damage is invisible from the interior; the wall lining looks normal while the framing behind it is rotting.
  • Mould growth — the dark, moist interior of a wall cavity is ideal for mould colonisation. Mould spores enter the living environment through gaps in linings and through ventilation systems, causing respiratory illness, allergic reactions, and in some cases serious long-term health effects.

The term "leaky home" is technically a misnomer in many cases — the issue is not that water leaks visibly into the living space, but that it enters the structure invisibly and remains there. Many occupants of severely affected homes do not know they have a problem until a building inspection reveals it.

The New Zealand leaky homes crisis

The leaky homes crisis in New Zealand was caused by a convergence of regulatory, architectural, and construction factors in the late 1980s and 1990s.

The Building Act 1991 moved New Zealand's building controls from a prescriptive system — specifying exactly how buildings had to be constructed — to a performance-based system. The intent was to allow innovation, but the practical effect was that new cladding systems were introduced to the market without adequate long-term performance testing.

Simultaneously, an architectural trend toward Mediterranean-influenced designs led to the widespread use of monolithic plaster cladding systems: seamless plaster applied directly over a timber frame, often without a drainage cavity. These systems looked attractive but had no tolerance for moisture — any failure in the system (a failed sealant joint, a poorly flashed penetration, an inadequate junction at a deck or balcony) allowed water to enter the structure with no means of escape.

The government's own estimates suggest around 42,000 properties were affected. Independent experts have consistently placed the figure higher — at 89,000 or more. Total remediation costs have been estimated at between $11 billion and $22 billion NZD.

Which properties carry the highest risk?

The risk of leaky home defects is concentrated in a specific era of construction and a specific set of cladding types. However, no property type is immune — water ingress can occur in any building with a failed or ageing weathertightness system.

Highest risk (require specialist weathertightness assessment before purchase):

  • Monolithic plaster or stucco cladding over a timber-framed wall, built 1992–2004, without a drainage cavity
  • EIFS (Exterior Insulation and Finish Systems) — foam board with a thin plaster coating, often called "synthetic plaster"
  • Fibre-cement sheet cladding (Harditex, Monotek) installed without cavities and with inadequate flashings
  • Multi-unit apartments and townhouses of this era — shared weathertightness components amplify individual unit risk
  • Buildings with complex roof lines, multiple penetrations, flat or low-pitched roofs, parapets, and deep balconies or decks

Moderate risk (standard pre-purchase inspection recommended):

  • Properties built before 1992 with ageing weathertightness systems — roofing, flashings, and sealants approaching end of life
  • Properties built after 2004 with high-risk cladding types — the Building Code was updated, but not all builders complied equally
  • Any property that has had significant cladding or roofing repairs — particularly important to verify that repairs were consented and correctly executed

Visual warning signs at an open home

Most leaky home damage is not visible at an open home. The point of a professional building inspection is precisely to find what you cannot see. However, there are visual and olfactory cues that should prompt you to investigate further:

On the exterior:

  • Cracking or crazing in plaster or stucco cladding — particularly at corners, around window reveals, and at horizontal joints
  • Staining or discolouration of cladding below windows or at wall-to-deck junctions
  • Failed or missing sealant at window joinery, at penetrations (pipes, cables, vents), or at changes of cladding material
  • Evidence of previous repair patches — look for slight colour variations, texture differences, or patchwork sealant application
  • Decks or balconies that drain toward the building, or where the deck-to-wall flashing is not visible
  • Parapets, butterfly roofs, or internal gutters — these are high-risk design features

On the interior:

  • A musty or damp smell — particularly in rooms adjacent to exterior walls, in subfloor areas, or in roof spaces
  • Water staining on ceilings or upper walls — even if old and dry, staining indicates a past ingress event that may be ongoing
  • Corrosion on metal fixings visible at skirtings or trims — suggests prolonged elevated moisture at floor level
  • Uneven or springy floors — can indicate subfloor framing damage
  • Condensation on interior wall surfaces in rooms that are otherwise adequately heated
  • Evidence of fresh paint or lining work inconsistent with the general condition of the property

None of these signs are conclusive on their own. But any combination of them should be treated as grounds for a thorough professional inspection before proceeding.

Under the Real Estate Agents Act 2008, licensed real estate agents have a legal obligation to disclose known material defects in a property — including known leaky home issues. Vendors also have obligations of fair dealing under the Contract and Commercial Law Act 2017.

In practice, these obligations are limited by what is actually known. A vendor who has lived in a property for years without carrying out a building inspection may genuinely be unaware that their home has significant moisture damage. Agents are not required to independently investigate defects they have not been told about.

The important takeaway: do not rely on vendor disclosure as your primary protection. A property's weathertightness history — its consenting, any repairs, any previous inspection reports — is discoverable through LIM (Land Information Memorandum) reports from the local council, but a LIM does not tell you the current physical condition of the building. Only a professional inspection can do that.

Why thermal imaging is the most reliable detection method

Visual inspection alone — even by an experienced inspector — cannot reliably detect leaky home moisture damage. The reason is fundamental: the damage occurs inside the wall cavity, not on the visible face of the lining. By the time moisture damage is visible (water staining on plasterboard, sponginess in skirting boards, visible mould on wall surfaces), the hidden damage is typically extensive.

Thermal imaging changes this. Because moisture in a wall cavity creates a measurable temperature differential on the interior lining surface, an infrared camera can detect it non-invasively — without cutting holes in the wall, without removing linings, and without any damage to the property.

In combination with moisture meters — which quantify the moisture content at specific points to confirm thermal findings — thermal imaging provides a comprehensive, non-invasive picture of a building's moisture status. This is the methodology used in a BRANZ-aligned weathertightness assessment.

Graham Walton, principal of HS Building Inspections, is an ITC Certified Level 1 Thermographer and an NZiBi Registered Building Inspector. He has inspected hundreds of leaky home-era properties across Auckland and is expert in distinguishing the thermal signature of genuine moisture from the many other causes of temperature variation in a building envelope.

What to do if you suspect a property is a leaky home

If you are considering purchasing a property that raises leaky home concerns, take the following steps before proceeding:

  1. Obtain a LIM report from the relevant council. Check for any weathertightness-related consent conditions, building consents for cladding repairs, or building report files on record.
  2. Commission a specialist weathertightness inspection from HS Building Inspections — a targeted investigation that goes beyond a standard pre-purchase inspection in its focus on the building envelope, moisture mapping, and risk rating.
  3. Ask for all available documentation — any previous building inspection reports, consent documentation for repairs, or weathertightness tribunal decisions. Vendors must provide this on request.
  4. Get a repair cost estimate — if moisture damage is found, a specialist builder or cladding contractor should provide a written estimate of remediation costs before you decide whether to proceed.
  5. Do not rely on cosmetic remediation — a fresh coat of paint or a recently resealed window does not confirm the underlying issue has been resolved. Only thermal imaging and moisture meter testing inside the wall cavity can confirm that.

Frequently asked questions

What years were most leaky homes built?

The highest concentration of leaky home risk is in properties built between 1992 and 2004. However, properties built slightly before or after this window can also be affected — the risk is tied to construction method and cladding type as much as to year of construction. Always check the cladding system, not just the date.

Can a leaky home be repaired?

Yes. Most leaky homes can be remediated — either through targeted repairs to specific ingress points (if damage is limited) or through full recladding with removal and replacement of all affected framing (for widespread damage). The key is ensuring that the remediation is comprehensive and consented, and that post-remediation testing confirms the property is dry before purchase.

Does weathertightness insurance still cover leaky homes?

The Weathertight Homes Resolution Services Act 2006 provided a resolution process for eligible homeowners. That scheme is now closed to new claims. Private insurance coverage for leaky home defects varies significantly between policies — check your specific policy wording, and consider obtaining legal advice if you believe you have a claim.

How much does a weathertightness inspection cost?

Our specialist weathertightness inspections are priced based on the property's size, age, and cladding type. Contact us for a specific quote. The cost is always a small fraction of the potential repair bill if significant moisture damage is discovered after purchase.