Weathertightness
A building's ability to prevent water from entering the structure through its exterior envelope — the roof, walls, windows, and other external elements.
What is a Weathertightness?
Weathertightness refers to how effectively a building keeps moisture out. In New Zealand, this issue became a national crisis in the early 2000s when thousands of homes built between the mid-1990s and mid-2000s were found to have serious moisture ingress problems — commonly known as the 'leaky building crisis'.
The crisis was caused by a combination of factors: monolithic cladding systems (plaster-style exteriors with no drainage cavity), inadequate flashings, flat or low-pitch roof designs, untreated timber framing, and poor quality construction. When water penetrated the cladding and couldn't drain away, the timber framing rotted, often invisibly behind the walls.
The New Zealand Building Code clause E2 (External Moisture) sets the performance requirements for weathertightness. Changes made after the leaky building crisis include mandatory use of treated timber, requirements for drained and ventilated cavities behind claddings, and improved flashing details.
Why It Matters for Due Diligence
Weathertightness failures can cost $100,000-$500,000+ to repair and can make a property structurally unsound. Any property built between 1995 and 2005 with monolithic cladding, Mediterranean-style design features, or flat roofs should be considered higher risk.
Get a thorough pre-purchase building inspection with specific attention to weathertightness. For higher-risk properties, consider an invasive moisture test where the inspector takes moisture readings from within the wall cavity. Check the LIM report for any weathertightness-related building consents or WHRS claims.
How to Check
A qualified building inspector should assess weathertightness as part of a pre-purchase inspection. Non-invasive moisture meters can detect moisture behind cladding. For higher-risk properties, invasive moisture testing (drilling small holes to test inside the wall) provides more definitive results. Check the LIM report for any Weathertight Homes Resolution Service (WHRS) claims or remediation consents.
Frequently Asked Questions
How can I tell if a house has weathertightness issues?
Warning signs include musty smells, staining around windows, swelling or bubbling of interior linings, and soft spots in walls or flooring. However, many weathertightness problems are invisible from inside. A professional inspection with moisture testing is the only reliable way to assess the risk, especially for homes built between 1995 and 2005.
Are all monolithic-clad houses leaky?
No. While monolithic cladding is a risk factor, not all monolithic-clad houses leak. The risk depends on the specific cladding system, how it was installed, the building's design (flat roofs and complex junctions increase risk), and how well it's been maintained. A professional moisture assessment can determine whether a specific house has issues.
Related Terms
Leaky Building
GlossaryA building that suffers from moisture ingress through its exterior envelope, leading to hidden rot and structural damage — a widespread problem in New Zealand known as the leaky building crisis.
Monolithic Cladding
GlossaryA type of exterior wall cladding that presents a seamless, plaster-like finish with no visible joints — strongly associated with New Zealand's leaky building crisis.
Building Code
GlossaryThe New Zealand Building Code — a set of minimum performance standards that all building work must meet, covering structure, fire safety, moisture, energy efficiency, and accessibility.
Code Compliance Certificate (CCC)
GlossaryAn official council certificate confirming that completed building work meets the requirements of the building consent and the Building Code.
Remediation
GlossaryThe process of repairing, restoring, or cleaning up a building or land to fix defects, remove contamination, or bring it to a safe and compliant standard.
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