Looking back at the past 10 years in mass timber design - since our firm’s first mass timber building, the John W. Olver Design Building at the University of Massachusetts Amherst - it’s evident that as a building material mass timber and especially cross laminated timber (CLT) has come a long way. Designed in 2014 and completed in 2017, the 87,500-square foot Design Building was one of the first large-scale mass timber buildings in the U.S. It demonstrated the possibilities of mass timber with both gravity and lateral systems in CLT and a cutting-edge concrete-CLT composite floor system.
The safety, reliability, and durability of mass timber buildings to replace steel or concrete buildings of scale and size has been proven many times over, especially in large office buildings and housing projects.
The distinction of the LWA-designed Adohi Hall Student Housing at the University of Arkansas in Fayetteville as being the largest CLT building in the U.S. at the time of its completion in 2019 has long been surpassed. It became a “proof of concept” for many projects, notably the headquarters of Walmart and its entire campus planned and now being built with mass timber in nearby Bentonville.
The early decades of this innovative material had three common sets of details across most projects: a mass timber floor panel in conjunction with a post and beam structure of glulam columns and beams, a concrete or other “wet” topping with a thin acoustic mat above the mass timber floor panel for vibration and acoustic control, and a type of metal hanger for column-to-beam connections.
These three common components—paired with a concrete core or a braced steel lateral structural system—solve a vast majority of architectural and structural conditions necessary for mass timber buildings. As mass timber evolves from this first decade of “common” projects, we’re finding an increasing variety of mass timber solutions. I’d like to mention one.
When Le Corbusier introduced his “Maison Dom-Ino” in 1914, it ushered in a century of modern architecture influenced by his five points of architecture - freeing architectural expression from structural necessity by allowing for the free plan and free façade made possible by the revolutionary new structure of reinforced concrete.
A century later in 2024, the combination of Cross Laminated Timer (CLT) and its inherent two-way spanning capability along with advancements in gluing technology promises to advance mass timber beyond its initial use and offer the freedom that flat slab reinforced concrete did.
Efforts to more fully make use of the inherent two-way span capability of certain mass timber floor panel types such as CLT and MPP (mass plywood panel) are increasing. An early example of such an approach was the Brock Commons Tallwood House at the University of British Columbia. While best known for being the tallest mass timber building at 18 stories at the time of its completion, it also featured a unique system of highly repetitive and closely spaced CLT panels point supported on glulam columns without beams.
Its column spacing was relatively limited to about nine-foot widths given the production capability of CLT panel widths, resulting in very closely spaced columns (but applicable for student housing with many narrow dorm rooms). However, cutting edge research in gluing technology, especially in Europe by Timber Systems 3, is allowing for much greater spans and a truer realization of the potential of mass timber to replicate the “Maison Dom-Ino.”
Intrigued by this potential, at LWA we are exploring this point-supported, two-way span capability of CLT at our Woodland Wonders Preschool at Auburn University (2022 WAN Future Projects Gold Award Recipient.) Here, we are cantilevering CLT panels on glulam columns without beams to maximize the effect of a flat slab mass timber roof without the visual barrier of beams below. It facilitates the connection of interior spaces to the forest preserve outside and allows for the butterfly roofs to extend and soar towards the trees and the sky.
There is joy in this freedom, as evidenced by the children who play, grow and learn to be good stewards of our natural environment. That inspired us to conceptualize the project as a “learning trail”, a metaphor for the trails that enable the children’s exploration of the forest and organized along a zig-zag shaped open corridor leading to the classrooms and support spaces that facilitate their learning. We hope our building, while showcasing technical advancements in wood structure, will also inspire and connect us to our environment as a model of sustainable and biophilic wood architecture.