Understanding Plaster Cladding Risks in New Zealand Homes: A Home Inspector's Perspective

How to Identify, Prevent, and Address Water Ingress Issues?

The History Behind New Zealand’s Plaster Cladding Crisis

Between the 1990s and early 2000s, plaster (or monolithic) cladding systems became widely used in New Zealand homes. This period, now known as the "leaky homes crisis", was fueled by four critical factors:

1. Design Flaws

   • Mediterranean-style internal balconies (set within the wall line)

   • Flat roofs lacking eaves

   • Complex junctions without flashings

2. Material Shortcomings

   • Plaster cladding installed directly onto timber frames (no drainage cavity)

   • Untreated timber permitted until 2004

3. Construction Errors

   • 78% of cases involved improper waterproofing installation (MBIE 2022 Report)

   • Poorly sealed penetrations for services

High-Risk Indicators:

• Built between 1994–2004

• Flat roofs with no eaves

• Cladding in direct contact with soil

• Internal balconies (balconies that are set within the wall line)

• Plaster monolithic cladding with no cavity between the cladding and the timber frame

High-Risk Indicators

Feature	Risk Level	Regional Hotspots
1994–2004 construction	⚠️⚠️⚠️	Hamilton Rototuna, Auckland North Shore
Internal balconies	⚠️⚠️⚠️	Auckland CBD apartments, Hamilton townhouses
Plaster cladding with no cavity	⚠️⚠️⚠️⚠️	89% of leaky homes nationwide
Flat roofs	⚠️⚠️	Coastal Auckland properties

Critical Note: The combination of internal balconies + cavity-free plaster cladding accounts for 63% of severe leaky home claims in Hamilton (Waikato Building Surveyors 2023 Data).

4D Weatherproofing Principles Addendum

For homes with these high-risk features:

1. Deflection

   • Install extended flashings around internal balconies

   • Add drip edges to cavity-free plaster joints

2. Drainage

   • Retrofit cavities (150–150–200/m²)

   • Clear weep holes quarterly

3. Drying

   • Install ventilation grilles near problem areas

   • Use breathable plaster sealants

4. Durability

   • Replace untreated framing with H3.2 timber

   • Apply anti-capillary breaks between materials

Regional Repair Strategies

For Auckland Internal Balconies:

• Remove embedded structures

• Rebuild as protruding balconies with 1.5° slope

For Cavity-Free Hamilton Homes:

• Install drained cavity system + ventilated base track

• Monitor with wireless moisture sensors

Further Reading

• MBIE Weathertightness Guidelines

• BRANZ’s Cladding Maintenance Handbook

• Consumer NZ’s Pre-Purchase Inspection Checklist