External water ingress is a contributing factor in most serious building failures. New Zealand knows this better than most countries — the leaky buildings crisis of the 1990s and early 2000s, caused by a combination of design decisions, material choices, and construction practices, resulted in billions of dollars of remediation costs and enormous distress for homeowners.
Yet BRANZ research published in 2020 found that weathertightness failures are still occurring in new residential construction. The industry has not fully absorbed the lessons of what went wrong, and some of the same risk factors — complex designs, inadequate detailing, poor material compatibility, and cultural pressure to build fast — remain present.
What the BRANZ Survey Found
A 2020 BRANZ industry survey on weathertightness found that builders, designers, and developers broadly agree on what needs to change: better quality design, improved control processes, and a shift in industry culture toward taking weathertightness seriously from the very beginning of a project.
Specific improvements cited included more detailed construction plans (particularly for junctions and penetrations), improved training for builders and subbies on water management, and better awareness of material compatibility. Several respondents noted that products that look similar are not always interchangeable — and that getting this wrong at the flashing or cladding stage can mean years of latent defects.
Where the Risk Is Highest
Weathertightness risk is highest in buildings with complex geometry — multiple roof planes, integrated decks, curved walls, and penetrations for windows, doors, services, and features. Every junction is a potential entry point for water if the detailing is wrong or the installation is rushed.
The research consistently shows that weathertightness must be designed in, not inspected in. Waiting until the building is up to check for issues is too late. The critical decisions happen at design stage — cladding system selection, eave overhangs, drainage planes, cavity construction, and window/door head flashings.
Practical Steps for Builders
For builders on the tools, the key habits are:
- Never allow water to sit or pond at any junction — design for drainage at every detail.
- Follow the manufacturer’s installation requirements for every cladding system — warranties depend on it, and so does performance.
- Check flashing sequences: water management is a sequence, and any step missed can compromise the whole system.
- Document what you’ve built. Photographs of flashing and waterproofing details before they’re covered are valuable protection if questions arise later.
New Zealand’s climate — particularly in Auckland and along the West Coast — is genuinely demanding. Buildings that wouldn’t leak in a dry climate will leak here if they’re not designed and built to a high standard. The leaky buildings crisis was expensive enough. The industry cannot afford a repeat.