The purpose-built extension to Waitakere Hospital's Emergency Department increases capacity while also provides refurbishment to the existing part of the department. Housed in the 1800m² extension are a waiting area; triage zone; consultation spaces; acute bays; whanau support; a 4-bay ambulance drop off zone; 3 resuscitation spaces; procedure and plaster rooms; and staff support spaces.

The original concept design had proposed a further new build to the east of the extension to include a new paediatric treatment area and a lower ground floor staff area. These will be provided at a later date as part of a staged masterplan.

A key health planning feature is to improve circulation routes to strengthen the key connections to other parts of the hospital. To achieve this, a new internal corridor was provided to the department to ensure patients or visitors from paediatrics, resuscitation and consultation do not need to travel through the adult treatment area unless absolutely necessary, thereby reducing traffic and crossovers.