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Weathertightness

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. 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.

  • BRANZ Weathertight website

    This comprehensive website covers the background to the issues and provides extensive advice on design and construction to ensure houses are weathertight.

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  • Weathertight: New buildings

    Making sure a new house is weathertight begins with carefully evaluating the site. From there, it is important to understand and apply basic design principles and choose the appropriate materials, techniques and detail solutions.

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  • Weathertight: Fixing leaky buildings

    Making leaky buildings weathertight is a complex job that requires expert input to assess the extent of the problem, select the appropriate repair option and design the appropriate solutions.

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  • Weathertight: Why buildings leak

    Knowing how water behaves can help you understand why some designs and details leak while others remain weathertight.

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  • Weathertight: Getting it right on site

    Following the design carefully on site and using the right techniques are just as important as getting the design itself right.

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  • Building Basics: Weathertightness

    This book aims to provide guidance for builders and associated subtrades in the basics of weathertight construction of light timber-framed residential buildings.

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  • Seminar: Keeping water out

    Guidance on minimising the risk of water entry and/or migration to adjacent spaces in basements, bathrooms (particularly tiled showers) and decks.

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  • Industry perceptions of weathertightness failure in residential construction

    This study report (SR442, July 2020) investigates industry beliefs about why weathertightness issues persist in new residential builds and how these issues can be mitigated.

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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.

  • Weathertightness testing

    We use a range of methods to evaluate the weathertightness of roofs, wall claddings and other external openings such as windows, doors, meter boxes and pipes.

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  • Building materials performance testing

    We use accelerated weathering, ultraviolet (UV) light and moisture exposure to test the mechanical strength retention and durability of building materials and products, including plastics, metals, cement, timber and wood-based materials.

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  • Building materials durability testing

    BRANZ tests the durability of building materials, components, and construction methods to determine if they will remain functional over the 5, 15 or 50 year period required for compliance with New Zealand Building Code clause B2 Durability.

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