Building and Construction

12-Story Wooden "Plyscraper" to Grow in Portland District

08 June 2017
Architect's model of interior support structure. Credit: LEVER Architecture

Officials in Portland, Ore., approved plans for a 90,000-square-foot, 12-story, mixed-use project that will rank as one of the tallest timber high-rises to be built in North America.

The mixed-use project is called Framework and combines retail and public exhibition on the ground level, with five levels of office and 60-units of affordable housing. Framework’s commercial tenants will be certified to meet standards of social and environmental performance, accountability, and transparency. The housing component of the project accommodates residents earning less than 60% of the Area Median Income (AMI).

Detail of CLT member. Credit: StructureCraftDetail of CLT member. Credit: StructureCraftFramework is supported in part by a $1.5 million award from the U.S. Tall Wood Building Prize Competition sponsored by the U.S. Department of Agriculture, Softwood Lumber Board, and Binational Softwood Lumber Council. The award offsets the costs of testing and peer review necessary to pursue a performance-based project beyond what is permitted in current building codes.

One element of the building design led by Thomas Robinson, principal of LEVER Architecture, is to communicate at street level the project’s use of wood and engineering technology. Integrating lessons learned from tall timber structures in Canada and Europe, Robinson and his team are expected to incorporate new structural and architectural technologies that include an engineered wood core and lateral system for seismic integrity and cross laminated timber (CLT) floor panels fabricated up to 50’ in length.

The building will be constructed primarily with CLT components for the floors and the lateral force resisting system (LFRS), in conjunction with glue laminated beams (GLB) and glue laminated columns (GLC). The superstructure of what is being termed a "plyscraper" will be supported on a conventionally reinforced mat foundation.

StructureCraft is the timber structure delivery partner. Other participants include project^, KPFF, and Walsh Construction. Developers worked with scientists at Portland State University and Oregon State University to test that the materials meet building and fire safety codes.

CLT panels are formed by stacking and gluing together successive perpendicular layers of wood. The layered stacks are then pressed in large hydraulic or vacuum presses to form an interlocked panel. The panel is then sized and shaped with a Computer Numerically Control (CNC) machine into a fully construction-ready component.

The number of layers in a panel can range from three to seven or more, and panels can have door and window openings, plus routings for electrical and mechanical systems, before shipment to the building site.

By the nature of its design, CLT has load-bearing strength and can serve as material for both vertical and horizontal assembly applications. Because wall, floor, and roof sections made of CLT are formed off-site in a factory, a shorter on-site construction time is expected. CLT may be used as a structural system in Tall Wood buildings and may offer an alternative to concrete or steel.

Beneficial State Bancorp will provide site control to real estate developer project^, affordable housing investor Home Forward, and LEVER Architecture. The main community space is designed to include a public Tall Wood Exhibit, featuring resources related to the realization and design of the building.

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