How Mass Timber is Replacing Concrete to Build the Next Generation of Skyscrapers

The skyline of the 21st century is being fundamentally reimagined, and the material of choice for the next generation of high-rises isn't a futuristic titanium alloy or a new iteration of reinforced steel. It is wood. After more than a century of concrete dominating urban architecture, a renaissance of timber construction is sweeping through the world's major cities. Across the globe, from the industrial corridors of the American Midwest to the suburbs of Paris and the bustling center of Sydney, developers are racing to build the world's tallest timber skyscrapers, promising to alter both the aesthetics and the environmental impact of the built environment.[8]

This architectural revolution has nothing to do with the traditional 'stick-frame' lumber used to build sprawling suburban homes or low-rise apartment complexes. The current high-rise boom is driven entirely by 'mass timber,' a category of highly engineered wood products specifically designed to rival the compressive strength of concrete and the tensile flexibility of steel. By rethinking how wood is processed and assembled, engineers have unlocked the ability to build massive, load-bearing structures out of a renewable resource, fundamentally challenging the long-held assumption that skyscrapers require carbon-intensive materials to safely reach the clouds.[3]

The crown jewel of this structural movement is Cross-Laminated Timber, universally known in the commercial construction industry as CLT. To manufacture a CLT panel, massive boards of raw timber are stacked in alternating directions—each layer resting at an exact 90-degree angle to the one below it—and bonded together under immense industrial pressure. By crossing the direction of the natural wood grain, CLT achieves a profound level of structural rigidity along both the vertical and horizontal axes. The complex physics involved in this perpendicular lamination results in a wooden panel that performs remarkably like reinforced concrete, capable of bearing immense loads and resisting severe seismic forces without fracturing.[3]

While CLT forms the rigid floors and walls of these new towers, it is typically paired with Glulam, or glued laminated timber. Glulam complements CLT by aligning the wood grain in a single, continuous direction to form the massive, load-bearing columns and beams that hold the skyscraper aloft. Together, these two engineered materials form a structural skeleton that is significantly lighter than a traditional concrete frame, allowing for faster construction times and requiring less extensive foundation work deep underground.[3][8]

But why are the world's top architecture firms suddenly abandoning the steel-and-glass orthodoxy that has defined urban centers since the late 19th century? The answer lies in the atmosphere. The built environment is responsible for nearly 40 percent of global carbon emissions, with the energy-intensive production of cement alone accounting for roughly 8 percent of the world's total carbon footprint. As the climate crisis accelerates, the architectural industry is under immense pressure to decarbonize its supply chains.[1]

Mass timber fundamentally flips this environmental equation, offering a rare opportunity to turn massive infrastructure projects into ecological assets. Trees naturally sequester carbon dioxide from the atmosphere during photosynthesis, locking the carbon into their cellular structure as they grow. When those trees are harvested from sustainably managed forests and engineered into mass timber products, that captured carbon remains trapped inside the building's physical frame for decades or even centuries. Furthermore, the manufacturing process for mass timber requires a mere fraction of the fossil fuels needed to forge steel beams or mix industrial concrete, drastically lowering the 'embodied carbon' of the construction phase.[1][8]

The global race for the sky is accelerating rapidly, and Milwaukee, Wisconsin, has emerged as an unlikely global capital for timber architecture. The Midwestern city already boasts the 87-meter Ascent tower, which was completed in 2022 and currently holds the official record for the world's tallest mass timber building. However, that record is already in jeopardy. Construction is currently underway just blocks away on The Edison, a 110-meter, 31-story timber high-rise slated to open its doors to residents and commercial tenants in 2027, proving that the scale of these projects is growing exponentially.[4]

Not content with those impending records, the Vancouver-based firm Michael Green Architecture recently proposed a staggering 55-story timber tower for Milwaukee. Representing a massive $700 million investment, the proposed development aims to set a completely new global benchmark for regenerative development and urban density. If approved and completed, a 55-story wooden skyscraper would shatter the psychological and engineering barriers that have historically limited timber construction, proving that wood can compete with steel at the absolute highest echelons of urban design.[1]

In Europe, the push toward mass timber is driven by a potent mix of engineering ambition and strict new climate regulations. France, for instance, has mandated strict carbon limits on new construction and required that new public buildings utilize sustainable materials. This regulatory environment has sparked a wooden skyscraper boom in cities like Bordeaux and Paris, where towers like Hyperion and Wood Up are proving the material's viability. By forcing developers to account for the embodied carbon of their materials, European regulators are effectively pricing concrete out of the market for environmentally conscious urban developments.[6]

Meanwhile, Switzerland is pushing the engineering boundaries of what is possible with Rocket&Tigerli, a 100-meter residential tower expected to complete construction in 2026. Unlike many of the 'hybrid' timber towers currently rising around the world—which still rely on a traditional concrete core to house elevator shafts and provide lateral stability—Rocket&Tigerli features a pioneering all-timber core. By replacing the heavy concrete core with an innovative wooden structural system, the Swiss engineering team has significantly reduced the overall weight of the building, allowing it to reach unprecedented heights without requiring massive, carbon-intensive foundation work.[5]

Despite the widespread enthusiasm among architects and environmentalists, the most persistent question from the general public, city regulators, and insurance underwriters remains inevitable: What happens when a wooden skyscraper catches fire? It is a visceral fear rooted in centuries of urban conflagrations, but modern engineering has a highly technical answer.[2]

Fire safety engineers point to a well-documented and heavily tested phenomenon known as 'charring.' When mass timber is exposed to the intense heat of a structural fire, the outer layer of the wood burns and rapidly turns to charcoal. This charred layer acts as a highly effective thermal insulator, protecting the unburned wood deep inside the beam and maintaining its structural load-bearing capacity even as the fire rages around it. Because mass timber panels are so thick and dense, they do not ignite easily or burn rapidly like traditional lumber.[2][7]

Unlike structural steel, which can rapidly weaken, buckle, and melt under extreme temperatures, or concrete, which can violently spall and crack as trapped moisture expands, mass timber burns at a slow, highly predictable rate. This predictability gives occupants crucial time to evacuate and allows firefighters to calculate exactly how long the structure will hold before a catastrophic failure becomes a risk.[7]

Still, leading fire experts caution against overconfidence. The behavior of exposed timber in a massive, multi-story fire is incredibly complex, and unlike inert concrete, the wooden structure itself becomes a potential fuel source if the fire manages to breach the protective char layer. Experts warn that the industry must not rely on charring alone, emphasizing that the consequences of a high-rise fire in a timber building could be devastating if proper precautions are ignored.[2]

To mitigate these inherent risks, modern building codes have evolved to mandate strict safety redundancies. The International Building Code (IBC), which recently expanded its allowances to permit mass timber buildings up to 18 stories tall without special variances, requires rigorous encapsulation techniques. In many tall timber buildings, significant portions of the wood are covered in fire-resistant drywall, and the structures are outfitted with advanced, highly reliable sprinkler systems. Engineers must utilize performance-based fire modeling to prove to local authorities that the building can withstand a worst-case scenario burnout.[7]

Ultimately, the immediate future of the ultra-tall timber skyscraper will likely be hybrid. Projects like Sydney's Atlassian Central—which is currently under construction and aims to be the tallest hybrid timber tower in the world—use a combination of steel exoskeletons, concrete cores, and mass timber floors. This hybrid approach balances wind loads, fire safety, and carbon reduction, utilizing each material for its specific strengths. As the mass timber revolution matures, it promises to transform our cities from massive carbon emitters into towering, habitable carbon sinks, proving that the oldest building material on earth might just be the blueprint for a sustainable future.[4][8]