Wynn Williams House: A show of cost-effective construction

Wynn Williams House is a new 6-storey building on the edge of Christchurch’s CBD, showcasing how mid-rise buildings can utilise engineered wood products—which are considered by many to be expensive—to result in very cost-effective construction.

Wynn Williams House in Christchurch. Photo Credit: Skycam Ltd.

Erection of the post-tensioned concrete and timber frames. Photo: Ruamoko Solutions.

Wynn Williams House replaces the 1930s lightly reinforced concrete 8-storey building known as St Elmo Courts, which was demolished in April 2011 after suffering significant damage in the Canterbury Earthquake Sequence.

The structural design of Wynn Williams House combines base isolation and post-tensioned timber and concrete two way seismic frames to mark a world first in seismic design. During development of the design, base isolation was considered as a cost-saving alternative to providing individual dissipative devices at the beam column joints, typically detailed in ‘hybrid’ post-tensioned timber frames. The post tensioned LVL beams form a major part of the primary structure, providing seismic resistance through the use of rocking connections at the ends of the beams, as well as gravity load balancing through the use of harped tendons. The LVL beams presented Ruamoko with a number of unique challenges that required the development of innovative design solutions for numerous aspects of design, fabrication and construction.

The LVL beams were manufactured by Timberbuilt Solutions using Carter Holt Harvey LVL sourced from their Marsden Point factory. The prefabrication of the complex LVL box beams meant that construction of the bare post-tensioned frames was relatively quick. The LVL beams are partially exposed in the building, giving an aesthetic appeal to the internal office space.

The Wynn Williams House won the NZ Timber Design Awards under the Engineering Innovation & Excellence in EWP category.