Chilliwack Secondary School
The public areas of this 3-storey secondary school - atrium, library, gymnasium and entrance canopies - all feature a wide range of architectural exposed timber structures: fluted Nail-Laminated Timber (NLT), built-up Mechanically-Fastened CLT (MF-CLT), hybrid timber-steel kingpost trusses and lathe-turned timber columns. We were invited in September 2010 by the Graham-Dialog design-build team to engineer and build the timber structures: the roofs of the atrium/multi-purpose room and library, the main entrance canopy, later on the gym trusses, and then the low canopy and bus & bike shelters. All told, a total of 34,000sqft of unique timber structure.
As a design-build project, close collaboration was needed between the architect, general contractor, and ourselves in order to ensure a cohesive design process which took into account the client's and architect's design intent while ensuring the project was constructible and remained on budget. Graham and Dialog depended upon us specifically for our experience in design, engineering, and building with wood. Our past projects had demonstrated that the solutions we came up with would not only be feasible to construct, but would also meet the structural and architectural intent, and be aesthetically complimentary to the entire school.
Examples of our responses to the challenges we faced:
- Early in the project we created a full 3D parametric model of the project. This model was a true building information model (BIM) used for quantity takeoffs, for procurement, to drive our shop drawing and manufacturing process, and to coordinate with other disciplines.
- The atrium/multipurpose room needed to fit between two buildings that were not parallel and had different edge conditions, requiring in a warped roof, with every truss unique.
- The constantly changing roof geometry meant that creating a standard casting for the connections in the trusses would not suffice. Instead, we came up with a unique casting design which accommodated the various angles of the structural members.
- The necessity for a large 2-way cantilever at the corner of the library and the long spans between trusses required us to design and develop a special deep version of our mechanically fastened MF-CLT panel.
"The Chilliwack secondary school project triggered two silver winners, which is really, really impressive" Fiona Famulak, president of VRCA
Fabrication & Installation
We approached this project understanding the complexities which were inherent in the tight schedule and complex designs, and so moved quickly towards a system of prefabricating components, for example:
- Both the NLT and MF-CLT panels were prefabricated by our shop crews and shipped directly to site for installation.
- The multi-purpose room/atrium and library trusses were carefully shop-fabricated, shipped to site and erected by our crews.
- The length of the kingpost gym trusses required special handling in the shop and on site - we staged the prefabricated truss components on site until near time of installation, then completed the cable installation and erected the trusses.