How do you build a theater in a park without taking up valuable park land? Build it into the side of a hill and let the children play on top.
This was the basic design idea behind the Bellevue Youth Theatre in Bellevue, Washington, says Robert George Becker, principal and owner of Becker Architects in Bellevue. The theater includes a living roof comprised of lawn, soil, irrigation and a waterproofing system, which are all placed on top of a structural precast concrete roofing system. “One of the main aesthetic design goals was to have an exposed concrete roof and wall structural system because it allows the building to appear as if it is extruded out of the ground.”
Coming up with a visually integrated design that both showcases the theater from the front, and obscures it from the back, was only half the challenge on this project. The designers also had to address practical issues, like how to design a waterproof roof that could handle the weight of landscaping and associated traffic while contributing to effective sound attenuation and insulation within the building. “Together all these challenges contributed to the final design approach and mandated a precast concrete roofing system that would easily join up with concrete structural and retaining walls,” Becker says.
The roof system consists of precast concrete beams, hollow-core planks, and a precast concrete exhaust dome hub that was cast off-site then lifted into place over the span of a couple of weeks. “That is just a fraction of the time a cast-in-place system would have required,” Becker says.
The project architect Tanja Reiners explained that the precast concrete beams were curved at the top with projecting steel reinforcing to engage the precast concrete hollow-core planks. She says, “By end-supporting the precast concrete beams on the outside concrete wall and then supporting the beams on the interior concrete wall, surrounding the main theater, we were able to cantilever the beams to the center precast concrete hub, where they are all joined together.”
The precast concrete compression hub at the center of the theater was placed after all the critical cantilevered beams were in place. The hub, which is hollow, allows unwanted air to be exhausted directly to the outside, thereby eliminating the need to use energy to re-circulate the air back into the theater where it would be cooled before re-circulating it back to the theater. Because the cantilevered precast concrete roof beams and hub system needed only two main concentric load-bearing concrete walls to support them, it created a wide open theater space optimizing capacity and viewing for performances.
The resulting structure is a durable building that has become a unique part of the broader park design, Becker says. “This theater was designed as environmental sculpture seamlessly integrated into the park’s surrounding hillside lawn area.”