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Weathertightness is a building's ability to prevent water from penetrating the building envelope. It depends on the building's location, design, materials, construction and maintenance. Preventing damage caused by moisture makes it safer and healthier for occupants.

From the mid-1990s to around 2005, thousands of Aotearoa New Zealand homes were constructed with designs, details, materials and methods that resulted in leaks. In many cases a lack of maintenance made the problem worse. Where rainwater couldn’t drain away, it frequently led to damage in the wall assemblies.

BRANZ research has found that problems with weathertightness still exist in some new buildings today.

Resources for designers and builders

When building a new home, it is up to designers, builders and engineers to ensure that it is weathertight. BRANZ provides information in many different formats about designing and constructing weathertight homes.

Services for manufacturers and distributors

BRANZ can evaluate the weathertightness of different construction systems and building materials through laboratory-based and on-site tests of air permeability, watertightness and wind resistance.

Updated: 4 June 2024