Leaky Homes Crisis

The leaky homes crisis (also called the leaky building crisis) is the widespread failure of weathertightness in New Zealand timber-framed buildings constructed between 1988 and 2004. Water entered through claddings, junctions and roofs and could not escape, causing timber framing to rot. It became one of the most expensive building failures in the country's history and reshaped its building regulation.

Causes

Several factors combined:

• Face-sealed claddings such as fibre-cement sheet and expanded polystyrene systems, which relied on paint as the main barrier; hairline cracks let water in.
• Reduced drying: sheet claddings and insulation cut airflow, so moisture stayed in the wall.
• Untreated framing: a 1995 change allowed untreated radiata pine for wall framing, which rots quickly when wet.
• Design fashion: "Mediterranean" styles with flat or complex roofs, minimal or no eaves, parapets, recessed windows, balconies and many wall penetrations.
• Process failures: poor installation, products used outside their specifications, missing detailed drawings, fewer apprenticeships, and council inspectors without weathertightness expertise, under the self-regulating regime introduced by the Building Act 1991.

Roofing lessons

Several of the identified causes concern the roof. Minimal or missing eaves left wall tops and window heads exposed to rain, parapets and complex roof shapes multiplied junctions that depended on flashings, and flat roofs and balconies over living spaces relied entirely on membranes and their detailing. The revised E2/AS1 responded with more detailed requirements for flashings and junctions.

Scale and cost

A 2009 PwC consensus estimate put repair costs at about NZ$11.3 billion for 42,000 buildings; other experts estimated NZ$23 billion for 89,000. Schools were also affected: 73 in 2009, 157 needing repair by 2011 at a cost of at least NZ$1.5 billion, and 309 with leakiness problems by 2013.

Response

• The Building Act 2004 replaced the 1991 Act and introduced licensing of designers, builders and trades.
• NZS 3602:2003 again required treated radiata pine in external wall framing.
• The Acceptable Solution for Building Code clause E2 External Moisture, E2/AS1, was substantially expanded, with more detailed flashings and cavity construction behind many claddings.
• The Weathertight Homes Resolution Services Act 2006 set up claims resolution, and a Financial Assistance Package (2010-2016) split repair costs: owners 50%, councils and government 25% each.

Courts have generally held councils responsible for about one-third of costs, and a 10-year limit after construction applies to claims.