Timber’s Transformation: An Old Building Material Reborn

Highly engineered timber may very well prove to be the material of 21st-century architecture.

Mass construction timber (MCT) was employed for the building of the University of Massachusetts Amherst Design Building. Above is an interior view of the Commons.

Courtesy Leers Weinzapfel Associates

We ask: If the 19th century modern building technology was associated with steel and the 20th century with concrete, could the 21st be the century of “MCT,” mass construction timber? Wood, one of the world’s oldest (and greenest) building materials, was the de facto construction material in American cities for over two centuries, falling out of favor when non-combustible materials capable of building high and wide emerged.

Today, highly engineered timber, sized to compete with these structural systems, is making a comeback in Europe, especially in Germany and in Austria, where the world’s first 8-story “ply-scraper” was recently completed. Stateside, the Boston Society of Architects recently featured Urban Timber, an exhibit showcasing innovative developments in wood technology and construction, and the U.S. Department of Agriculture is sponsoring a $2M ideas competition for the design of tall wood buildings. Given all of this hoopla, one  could assume that we are on the verge of a global timber revolution, yet the U.S. is lagging far behind our European neighbors. In fact, to date, neither the U.S. nor Canadian building codes explicitly recognize mass timber structural systems.

Deeply committed to sustainability, we made the choice to dive feet first into connecting with the past to build the future by employing MCT for the primary structural system of our University of Massachusetts Amherst Design Building. Designed with Equilibrium Consultants, one of the world’s foremost timber engineers, the building will house the university’s Departments of Architecture, Landscape Architecture, Regional Planning, and Building Construction Technology, and is now under construction.  Permitted through a variance application using the “alternative” method provisions of the building code, our 87,000-square-foot building furthers the university’s educational mission by incorporating examples of the inherent departments’ design practices. Targeting LEED Gold, it will be among the first MCT structures in the region when completed in 2017.

A cross-laminated timber (CLT) slab

Courtesy Leers Weinzapfel Associates

Laminated technologies, first developed in Europe in the 1980s, are allowing us to fabricate fairly massive timber components for the Design Building using small diameter trees sustainably harvested from managed forests. Our selected timber, black spruce, was sourced from Canada’s Boreal forest region, an area that constitutes the world’s largest land based biome. It is constituted to stand up to fire and maintain its structural integrity.

The building incorporates a hybrid structural system of cross-laminated timber and concrete that includes some steel components—glulam columns and beams with cross-laminated timber (CLT) slabs and core walls. CLT acts like plywood but on a much larger scale. The panels are made from dried lumber glued together and stacked at right angles to create strength which is comparable to steel. Ours have 5-layers for slabs and 7-layers for its core “shear” walls, which provide lateral structural support.

A sectional perspective of the University of Massachusetts Amherst Design Building.

Courtesy Leers Weinzapfel Associates

The building’s multi-disciplinary program, which is organized around an interior courtyard of exposed timber and an exterior landscaped courtyard and outdoor classroom, will foster collaboration across its inherent disciplines. With its glue-laminated wood frame, floor slabs of composite, exposed cross-laminate timber (CLT) plank, and cast-in-place concrete, the Design Building will demonstrate leading-edge timber engineering, informed by the school’s own building technology research initiatives. The structure will also incorporate a high-performance metal-clad building envelope integrated with a landscape featuring native plants and paving materials, making it a model for the integration of landscape and architecture for the entire campus, as well as one for sustainability.


This blog series, part of our “voices from inside the profession”, is written by the staff of Leers Weinzapfel Associates, Boston. It explores the firm’s mission of “making connections” across all aspects of design. A ubiquitous concept today, collaboration on every front has been the essence of the firm’s DNA for more than three decades. Posts provide a behind-the-scenes look at the ways the firm’s work serves the public realm by connecting people to place; building to urban context, landscape, and infrastructure; and past to future. Unexpected writing pairs will connect to reflect on the practice’s goals, decisions, outcomes, and learnings across typologies and design challenges, with an emphasis on how connectivity serves the greater good. 

Categories: Building Products, Sustainability

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