More about wood in the Bullitt Center
By Nina Smith-Gardiner, AIA, LEED AP
When it comes from a responsibly managed forest, wood is one of the most sustainable building materials. In the Pacific Northwest, it is an abundant, renewable resource, produced with the sun’s energy. So wood is a logical building material for Seattle – part of our regional “vernacular” for designers and builders.
In the Bullitt Center, Forest Stewardship Council (FSC) certified glued-laminated timbers (“glulams”) were used in the place of traditional heavy timbers derived from large diameter logs (frequently old growth). Glulams makeefficient use of wood by bonding smaller pieces together to form larger components. This creates a strong, dimensionally stable and consistent product with the ability to span great distances. Using glulam timbers allows for a larger final product than using dimensional lumber, and they can be produced from lower grades of timber. During the fabrication of a glulam timber, there is only a 3% material waste. Most glulams in the Pacific Northwest are made from Douglas Fir, Western Larch and Alaskan Yellow Cedar.
At the Bullitt Center, the glulams come from Calvert Company in Vancouver, Washington. Theglulams are Industrial grade rather than Architectural or Appearance grade, to reduce costs, minimize waste and avoid the putty that is used to conceal knots in the higher grades.
To calculate the exact length of each glulam member so the precision end trim cuts could be made by Calvert instead of at the construction site, Lee Zulch of Schuchart and Mary Koenig of Calvert sent eight versions of the measurements back and forth over the course of one and a half months of detailed checking. Thanks to their meticulous calculations the glulams have been exact to within an 1/8th of an inch over long spans. The crane lowers each in to the steel buckets and helmets and all have been a snug fit. In using glulams, Lee Zulch of Schuchart said there were two key design decisions: to use steelbuckets and SDS screws instead of knife plates to connect the beams to the columns and to use 2x6’s on edge to span between the beams for the floor decks instead of tongue and groove.
One big challenge was sourcing FSC 100% (formerly “FSC Pure”) products, since they are not as easily available as the FSC Mix products. The dimensional lumber, such as the 2x6’s on edge for the flooring, came from forests in Idaho owned by Potlatch. The plywood decking – sitting atop the 2x6 flooring – came out of Northern California and was made by Roseburg Forest Products.
Part of the challenge, beauty, and success of the Bullitt Center is that the structure is also the finish material. The building occupants will enjoy the beauty of the wood structure. Thanks to the commitment of the project team, the elegant structure is a striking example of efficient building design, demonstrating how a traditional six-story office building can be transformed through innovative design solutions and high-performance materials.