CLIENT Costco, Westgate, Auckland

ARCHITECT Woodhams Meikle Zhan Architects

LOCATION Westgate, Auckland

work completed

The first New Zealand Costco store opened its doors in Auckland’s Westgate in September 2022. The chain’s new megastore boasts a grocery store, a food court and bakery, and a tyre centre and pharmacy.

Sansom was brought on board to provide extensive waterproofing across approximately 14,000 sqm of the site.

The project

Due to strict fire safety standards, the waterproofing process was essential for the overall safety of the establishment.

To manage the extensive area efficiently, the site was segmented into nine distinct zones, with each zone being completed within two to three days.

The waterproofing process used a torch-on membrane automation machine, allowing for the application of 1,200 sqm in a single phase. This systematic approach enabled our specialists to finalise the project within four months.

The project waterproofing was critical to the overall project success, so Sansom were engaged early to assist with the design and then were contracted to control all aspects of the delivery from surface preparation, membrane placement, wheel stops, flashings, asphalt placement and EFVM testing.


The scale of this project presented unique challenges. A primary concern was managing space for both team members and machinery, especially when working alongside other trades. Efficient coordination became essential to ensure smooth operations.

The site’s size and strict deadline demanded precise technical knowledge and strict time management. By using specialist machinery from Europe and involving multiple teams, we made the most of every moment.

Later in the project, the main contractor introduced slight contract modifications. Sansom’s team swiftly adapted, aligning with the overarching project goals and demonstrating a flexible and solution-oriented approach.


Sansom not only met the project’s rigorous technical, and timeline demands but also ensured optimal safety standards.

Despite the inherent challenges of the project scale and external modifications, the dedication and adaptability of Sansom’s team solidified the successful execution and delivery of work for the megastore.

This collaboration underscores Sansom’s commitment to quality, precision, and excellence in large-scale projects.