Water damage is one of the most common and costly building defects, leading to issues such as timber rot, concrete spalling, and long-term structural deterioration. The National Construction Code (NCC) references AS4654 Parts 1 and 2 as a Deemed-to-Satisfy solution for external above-ground waterproofing.
Understanding these standards can help builders, architects, and property owners implement effective and durable waterproofing systems. In this blog, we explain the key sections of AS4654 and outline its main requirements.
What is AS4654?
In Australia, AS4654 (2012) is the standard for waterproofing membranes used in above-ground external areas. AS4654.1 (Part 1) covers material requirements, while AS4654.2 (Part 2) covers design and installation practices. These standards, developed by Standards Australia, provide current guidance for materials, design, and installation in line with industry best practices.
AS4654.1: Materials
Part 1 specifies the performance requirements and test methods for materials used as external waterproofing membranes. This includes verifying that materials meet durability, flexibility, and environmental resistance requirements, such as UV exposure and temperature variations.
AS4654.2: Design and Installation
Part 2 specifies the design and installation requirements for external waterproofing systems. It lays out requirements for applying compliant materials to achieve watertightness, including considerations for falls, drainage, penetrations, and terminations.
Where Does AS4654 Apply?
The standard applies to external horizontal surfaces above internal spaces, such as balconies, decks, rooftop terraces, and podium levels. These areas are exposed to rain and other environmental factors, making proper waterproofing essential.
Balconies
Balconies are suspended structures attached to a building. Because they sit directly above other habitable spaces or structural supports, failing to waterproof them properly can lead to internal water damage.
Decks
Decks located above enclosed spaces demand careful waterproofing to prevent water ingress. The Queensland Building and Construction Commission (QBCC) enforces strict compliance for these areas.
Rooftop Terraces
Rooftop terraces, which often function as flat roofs for the spaces below, are exposed to UV radiation, rain, and pedestrian traffic. Waterproofing membranes act as the primary defence against water entering the building’s top floor.
Podium Levels
Podium levels are large, open spaces often found in commercial or high-density residential buildings, usually situated above basements or car parks. These large external areas require complex drainage falls and robust membrane systems to manage significant volumes of water.
Key Requirements of AS4654.2 External Waterproofing
To prevent water leakage, AS4654.2 outlines several strict requirements for the design and installation of drainage and membranes.
Falls and Drainage
Water must be directed away from the building and toward designated drainage points. The substrate must be prepared with an appropriate fall (usually 1:100, although it depends on the surface finish) to direct water toward designated drainage points and prevent pooling.
Membrane Installation
The membrane must be applied strictly in accordance with the manufacturer’s specifications and the standard’s guidelines. This process includes appropriate surface preparation, priming, and applying dry film to the correct thickness.
Upturns and Membrane Terminations
Where a horizontal surface meets a vertical wall, the waterproofing membrane must extend up the wall to a height sufficient to prevent water ingress. The required termination height varies depending on wind class and exposure, as indicated in AS4654.2 Appendix A.
Doorway Detailing
Doorways opening onto external areas are common failure points. AS4654.2 provides doorway detailing options, including sub-sill flashing and careful level transitions, to prevent water ingress.
Key Takeaway
Effective waterproofing is essential to maintaining a building’s structural integrity and longevity. By adhering to its requirements for materials (Part 1) and design and installation (Part 2), construction professionals can avoid costly repairs, safeguard structural integrity, and deliver reliable results for every project.
If your building project requires inspection for standards compliance, contact PCG today to request a quote.