The much-anticipated New Zealand International Convention Centre (NZICC) in Auckland is now open, and one of the project’s less visible but highly significant elements is the high-performance low-slope roof assembly engineered by RoofLogic and installed by SWP Commercial Limited.

The roof system utilised RoofLogic’s Ultratherm Xtreme warm roof assembly incorporating Fibertite XT membrane, installed over a proprietary Durra Beam structural purlin system. The completed assembly comprised a steel base deck, vapour control layer, rigid PIR insulation, high-density roof board, and Fibertite XT membrane.

While the finished roof presents as a clean and efficient solution, the engineering behind it was far from straightforward. One of the primary challenges was structural. The original roof design had been based on a plywood diaphragm substrate fixed to closely spaced timber sub-framing, whereas RoofLogic’s system required a steel base deck fixed directly to steel purlins at 1200mm centres. To achieve the required diaphragm performance, RoofLogic developed a project-specific structural testing programme and undertook testing at Scion’s structural testing laboratory in Rotorua. This work ultimately resulted in a new fixing and installation methodology being developed specifically for the project.

The roof assembly also required careful design to address hygrothermal performance, wind uplift resistance, trafficability, and fire performance. A high-performance vapour control layer was specified to help manage condensation risk within the roof build-up, while the inclusion of a 13mm high-density roof board improved roof trafficability and helped the assembly satisfy the project’s demanding ultimate and serviceability wind load requirements.

Fibertite XT was selected as the roof membrane for its proven long-term durability, puncture resistance, and fire performance. Introduced to the commercial roofing market in 1979, Fibertite has an almost 50-year in-service history, with recent ASTM verification recognising minimum 40-year in-service performance.

For a project of this scale and profile, the NZICC roof demanded more than a standard roof build-up, it required a carefully engineered system designed specifically to meet the project’s unique structural and performance requirements. The result is a robust, high-performance roof assembly suited to one of New Zealand’s most significant new public buildings.