It was one of those moments. You encounter an idea so simple and easy to understand, so widely applicable and yet never done before. Your jaw drops. “Why didn’t I think of that?” Dimensional lumber, laminated in opposite directions, manufactured in panels about 10’x40’. It is a pumped-up plywood-like concept that spans and provides shear strength in one, engineered, non-proprietary solution. Sustainably harvested wood, notable thermal performance, fast installation, minimal construction waste, and fire resistant, Cross-Laminated-Timber (CLT) was developed in Europe in the 90s and is starting to make an appearance in the US.
It was brilliant! It also happened to solve a design problem on a building we were currently working on: a small but prominent visitor “hub” building at the Oregon Zoo, comprising one edge of a gateway space to the new elephant habitat (opens 2015). Using this system, we could cantilever the roof deck in two directions, which eliminated the need for clunky eave outriggers and provided a very clean, continuous plane of luminous wood that we were previously achieving with standard wood decking. It also greatly cleaned up the roofline of a small kiosk structure nearby, detailed to match.
Our structural engineer was excited, too. She had never worked with CLT before and jumped right in to the calculations. But there was a hang up. It was also new to the city of Portland; they had never before permitted a CLT structure. We set up a meeting to discuss feasibility. Fortunately, the reviewers were also very interested in the material and regarded this project, rectangular in floor plan and otherwise standard in lateral strategy, as a perfect introduction to the municipality. With their trademark caution, they advised that it was probably worth giving it a shot.
This month the city approved the design, and the building will be completed mid-2014.