Underground auditorium carved from bedrock delivers spacious resource for city school

The school's location on the city fringe presents significant challenges and constraints when it comes to space for expansion. This unique underground subterranean auditorium is located at the heart of the campus and has a capacity of 1500 seats, with its roof-top surface functioning as a playing ground.

The client's requirement for the playground to be built first and remain operational during the remainder of works, necessitated the use of the "top down" method of construction. The structure consists of a 23m long span steel arch roof with precast panel, and post tension slab to support the school playing ground. TTW's structural design allowed the roof of the hall to be built first and handed over to the school for use within a few months of the project start. The hall was then excavated and completed underneath.

With the internal walls carved from natural bedrock, this impressive building has garnered accolades including the 2012 AIA Sir John Sulman Medal for Public Architecture.

Client: Sydney Grammar School

Architect: PTW

Builder: Southern Cross Constructions

Value: $23M

Completion: 2012

Sector: School & Colleges

Services: Construction Engineering, Structural, Civil


  • 2012 AIA – Sir John Sulman Medal for Public Architecture
  • 2012 Engineering Excellence Awards – Finalist Building and Structures