Remember those old-fashion Lincoln Logs children once played with back before they became glued to their tablets?
Today, creative design using wooden materials is no longer just for kids. Across the globe, wood-framed architecture is increasingly reaching new aesthetic and technical heights.
The move is being fueled by developments in “mass timber” – factory engineered wood made from layers of planks fused together to increase their structural strength and integrity.
Though mass timber has been manufactured for commercial use in Europe since the 1980s, it’s gained new attention from architects and builders for its promise as a sustainable, eco-friendly alternative to concrete, one of the world’s most notorious polluters.
Across the globe, mass-timber sales reached just over $1 billion last year, according to Acumen Research and Consulting, a figure that’s set to treble by 2030.
The need for innovation is clear: Building construction contributes 40 percent of the world’s carbon emissions, with cement alone responsible for nearly 10 percent of that tally.
Mass timber, meanwhile, is carbon sequestering — absorbing an estimated one ton of carbon for every three cubic feet in use, according to the University of Toronto’s Mass Timber Institute.
Better still, unlike concrete – an eco-harming cement derivative – mass timber is naturally renewing when forested sensitively.
Every few weeks, another timber architecture superlative seems to come out of the woodwork.
On Manhattan’s West Side, for instance, architecture leaders Skidmore, Owings & Merrill (SOM) recently installed a 260-foot-long Alaskan Yellow Cedar truss bridge that extends from the High Line into Moynihan Train Hall.
The cedar is actually pieces of glulam, glued wood laminations sealed tight to resist moisture.
Milwaukee is currently home to the world’s tallest timber tower, the 284-foot Ascent by Korb + Associates Architects, which barely beat out its Norwegian rival, the 280-foot-tall Mjøstårnet tower by Voll Arkitekter, last year.
More recently, London’s annual Serpentine Pavilion, which opened in June, has been designed by Beirut-born/Paris-based architect Lina Ghotmeh using cross laminated timber (CLT), a plywood-like material made of wooden planks stacked at right angles.
Most ambitiously, plans were just announced by a Stockholm real estate developer for a nearly 2.7 million-square-foot mass timber housing and retail development, which will be the largest in the world.
And the Texas-based architecture firm Lake | Flato — whose Hotel Magdalena in Austin was the first all mass-timber building in the US — is now embarking on a pair of grandiose wooden designs, the Amy Guttman Hall at the University of Pennsylvania along with Dickie Hall at Trinity University in San Antonio, the nation’s largest mass timber project.
“Both symbolically and actually, Mass Timber is the building material that our culture needs right now,” says Ryan Jones, partner at Lake | Flato. “Mass Timber transforms the structural demands of a building into a warm and tactile environment that also feels organic. In terms of carbon footprint, Mass Timber’s is less than 50% that of steel or concrete,” he adds. “All of this is crucial at this moment when we are experiencing the global impact of climate change.”
Despite the frothy accolades, mass-timber construction remains far from mainstream.
Regulations vary from country to country – and even state to state — but they’re evolving rapidly.
Take Milwaukee’s Ascent Tower. At the time of its initial design in 2018, mass timber construction was permitted to top out at a mere 85 feet.
But the project’s architect Jason Korb successfully circumvented International Building Code (IBC) regulations to push it far higher after his design exceeded expectations during a three-hour fire test conducted on its columns.
The project’s convoluted approval and design process demonstrates the lack of clarity around the use of mass-timber in New York City. Initially, 670 Union was supposed to be built from CLT, which is even stronger than glulam and has been used in Europe since the 1980s.
New York City’s Department of Buildings green-lit the CLT plan, but then decided against it because the material had not yet been approved for residential construction. Liftin quickly pivoted to glulam — which had been allowed for decades — and with the support of then-City Council member and progressive politico Brad Lander, took the project over the finish line.
All of its apartments sold out – many above asking price.
In late 2021, New York City finally approved CLT use for structures up to 85 feet in height – one of some 7,400 revisions to the city’s construction codes signed off during the first comprehensive overhaul in nearly a decade.
Meanwhile, the IBC also updated its mass timber allotment in 2021, which now permits construction of up to 18 stories.
Liften, the architect behind 670 Union, applauds the new revision, but says there remains a long way to go before mass-timber becomes the standard in New York City. “NYC has legalized CLT, but its use is still quite limited and requires conditions that can be counterproductive,” Liften says.
In the latest DOB permissions brief, for instance, CLT cannot be used for elevator cores or the types of drop ceilings that typically house mechanical equipment.
Still, in this moment of increasing eco-consciousness, mass timber’s appeal is only likely to rise.
For one thing, it’s far more sustainable than common building materials such as concrete and steel. It can be precisely prefabricated off site to save time, construction waste and — most crucially — money.
Mass timber is fabricated from young wood so when sourced sustainably, from well-managed, repopulating forests, “it is a carbon sink,” says Korb.
By using wood rather than steel and concrete, for instance, his Ascent tower’s construction process removed the equivalent of 2,400 cars from the road for an entire year.
Mass timber is also lightweight, which allows for building additions that don’t overload existing structures and perform well during earthquakes.
This past May, for instance, the University of California, San Diego successfully tested a 10-story mass timber frame by Portland, Oregon- and Los Angeles-based Lever Architecture that withstood the equivalent of a 7.7 magnitude tremor.
Because of timber’s natural ability to char and self-insulate, it can resist fires to beyond code requirements, while burning more predictably than steel beams that twist when heated.
In the case of Ascent, Chicago-based structural engineer John Peronto of Thornton Tomasetti worked with the USDA’s Forest Products Laboratory to complete its fire testing—among the most stringent ever for glulam construction.
The tower’s seven-inch-thick CLT floor plates proved capable of maintaining their integrity while burning for a full two hours, just like traditional concrete slabs, says Peronto.
However, mass timber’s newfound architectural notoriety has not come without consequence.
Take it from one of the material’s longest-term advocates. Hermann Kaufmann, principal of Austrian firm HK Architekten, has been working with mass timber professionally for the last 35 years.
He became fascinated with wood while studying architecture at University in Innsbruck in the 1970s.
Although still bullish on mass timber, Kaufmann is highly cognizant of its limitations. “Building with wood requires a great deal of knowledge and planning,” he says, warning that when not properly constructed, timber structures become susceptible to wood’s greatest enemy—moisture, and its subsequent rot.
Then there are the structural limitations of wood, which is still outmatched by more traditional building materials. “As the load on structural elements gets larger, there are natural limitations of wood fiber strength compared to concrete or steel,” says Peronto.
Which means, at least for the moment, steel beams will continue to reign supreme on towers above a certain height. Just how tall is being constantly tested by far-sighted mass timber pioneers.
There is also the issue of geography. Architectural timber can reduce the overall embodied carbon of a project—the total carbon produced from build to operation to destruction—but most meaningfully if the material is locally sourced.
Mass timber cultivation, however, remains niche, with places like Oregon, Canada, and Switzerland responsible for much of the global production.
This becomes a problem, says SOM partner Kim Van Holsbeke, when trying to scale mass timber while still benefiting the environment.
Like Kaufmann, Van Holsbeke views mass timber as ripe for innovation, but still lacking both the proper certifications and supply-chain systems needed to meet consumer and environmental demands.
“The timber industry is not as …standardized for large-scale projects as we would like it to be,” says Van Holbeke, whose firm is currently building Stony Brook University’s New York Climate Exchange on Governors Island, where all new buildings—as well as a handful of existing former barracks — will be constructed from wood. “There is a shortage both in timber and fabrication plants that can produce the quality and customization that we have in the steel industry,” she continues. Until things change, architects will be forced to return to building methods that had them longing for new solutions in the first place.
Still, as sustainability becomes increasingly important to homebuyers, mass timber is likely to become more commonplace, says Timber House developer and Brooklyn Home Company co-founder Bill Caleo. It’s a smart investment.
“As buyers become more aware of their [carbon] footprint…mass timber will bring us one step closer to building future-proof spaces” with minimal environmental impact, he says.
Though New York’s DOB regulations still lag behind much of the world, the city’s architecture community believes that mass timber is the building block of the future—within reason.
“Mass timber is a real architect’s material: delightfully engineered, simply effective, beautiful,” says Liftin, who is now designing a row of five mass timber townhouses in Brooklyn. “But most of us don’t expect mass timber to overtake all other structural systems.”
A lack of ubiquitous timber resources will demand moderation (and iteration) at some point, if not now. “In the future… we [will] need to use wood sparingly,” predicts Kaufmann, who says recycling existing timber will become key.
Also valuable: Technologies that pair conventional building materials such as steel and concrete with mass timber.
“It’s composite systems…that are the future,” says Peronto, the structural engineer, who is currently consulting for architect Sir Norman Foster on a project to cap an active railyard at Stockholm Central Station with a bespoke mass timber system.
In the hybrid systems Peronto describes, taller buildings get the sustainability and aesthetic benefits of a mass timber structure, while benefiting from the core strength, height and construction ease that steel and concrete provide.
Structures 18 stories and shorter can totally go wooden if their locality makes it possible. “I would like to see mass timber in buildings up to nearly 20 stories, although I do not see that happening soon in New York,” says Liftin, as he laments New York’s existing timber restrictions.
“Meanwhile,” he adds bullishly, “we should be building lots of six- and seven-story timber buildings—residential, commercial, and institutional.”
Elizabeth Fazzare is a former editor at Architectural Digest