How Mass Timber is Replacing Concrete and Steel in the Skyscraper Race

For over a century, the modern city skyline has been defined by the heavy, carbon-intensive silhouettes of concrete and steel. But a quiet revolution is taking root in commercial architecture, replacing the roar of cement mixers with the precision of engineered wood. Mass timber construction, once viewed as a niche environmental statement, has rapidly matured into a mainstream structural system capable of reaching skyscraper heights.[8]

The most visible symbol of this shift is rising in Milwaukee, Wisconsin. Construction is currently underway on the Neutral Edison, a 31-story mixed-use tower that will reach 362 feet and become the tallest mass timber building in the world when completed in 2027. The $133 million project will surpass Milwaukee's own Ascent tower, a 25-story timber structure completed in 2022, signaling that engineered wood is now competing directly with conventional materials for high-rise dominance.[1][2]

To understand how wood can support a 31-story tower, it is necessary to define what mass timber actually is. Unlike the light-frame two-by-fours used in residential homebuilding, mass timber relies on massive, solid panels engineered for immense load-bearing strength. The most common variant utilized in these high-rises is Cross-Laminated Timber, or CLT.[4][5]

The mechanism behind CLT is elegantly simple but structurally profound. Manufacturers take dimensional lumber—standard boards of pine or spruce—and glue them together in alternating, perpendicular layers. By crossing the grain at right angles, the resulting panel achieves extraordinary rigidity in both directions, neutralizing wood's natural tendency to warp or split. These panels, which can be up to a foot thick and forty feet long, offer a strength-to-weight ratio that rivals concrete while weighing significantly less.[4][5][6]

This lighter weight translates to a fundamentally different construction site. Because CLT panels and glue-laminated columns are prefabricated in off-site factories using computer-controlled routers, they arrive at the job site ready to be slotted into place. Builders report that mass timber projects require roughly 30 percent less time to erect and 30 percent fewer on-site workers compared to traditional concrete pours. The process is frequently compared to assembling flat-pack furniture on a massive scale, resulting in a cleaner, quieter, and highly predictable build.[4][6]

The primary driver behind the mass timber boom, however, is its environmental math. The traditional construction sector is a massive climate liability, with cement and steel production accounting for a significant portion of global greenhouse gas emissions. Mass timber flips this equation. Trees naturally absorb carbon dioxide as they grow; when that wood is harvested and locked into a building's structure, the building effectively becomes a long-term carbon sink.[5][7]

The embodied carbon savings are substantial. Developers of the Neutral Edison tower estimate that their hybrid timber approach will result in a 54 percent reduction in embodied carbon compared to a conventional concrete high-rise. Furthermore, forestry experts note that creating a high-value commercial market for timber incentivizes landowners to sustainably manage and replant their forests, rather than selling the land for carbon-intensive real estate sprawl.[2][6]

Despite these benefits, the concept of a wooden skyscraper inevitably triggers a primal question: What happens in a fire? For decades, outdated assumptions about wood's combustibility kept timber buildings capped at just a few stories. However, fire safety engineers have demonstrated that mass timber behaves entirely differently than light-frame wood when exposed to extreme heat.[3][7]

The secret to mass timber's fire resistance lies in a mechanism known as self-charring. When a massive, solid block of wood is exposed to fire, the outermost layer burns and turns to char. This charred layer acts as a highly effective thermal insulator, starving the fire of oxygen and protecting the unburned structural core inside. Unlike steel, which can rapidly lose its strength and buckle under high temperatures, or concrete, which can explosively spall as trapped moisture boils, mass timber maintains its structural integrity for a predictable duration.[3][7]

Extensive large-scale fire testing has validated this charring effect. In one rigorous test, a seven-inch-thick wall of exposed CLT was subjected to a continuous blaze and lasted for over three hours—exceeding stringent building code requirements by a full hour. Because the char rate of heavy timber is mathematically predictable, engineers can simply oversize the wooden beams by a few inches, ensuring that even after a severe fire, the remaining uncharred core is thick enough to support the building's weight.[3][7]

To reach extreme heights like 31 stories, architects do not rely on wood alone. The tallest mass timber buildings utilize a hybrid structural system. In the Neutral Edison, the cross-laminated timber floors and glued-laminated columns carry the gravity loads, while a central concrete elevator core provides lateral stability against wind and earthquakes, as well as a non-combustible fire separation zone.[1][2]

Regulatory bodies are rapidly catching up to the science. In 2021, the International Building Code (IBC) introduced sweeping updates that allowed mass timber structures to reach up to 18 stories without requiring special experimental waivers. Regional governments are pushing even further; British Columbia recently expanded its building codes to permit mass timber construction for a wider variety of commercial and institutional buildings, aiming to foster a robust local manufacturing ecosystem.[2][5]

Beyond the structural and environmental metrics, mass timber offers a distinct psychological advantage known as biophilic design. By leaving the structural wood exposed on the interior ceilings and columns, architects create spaces that feel inherently warmer and more connected to nature. Occupants of mass timber office buildings frequently report lower stress levels, improved acoustics, and a more inspiring environment compared to the sterile feel of drywall and dropped ceilings.[4][8]

The industry still faces growing pains. Managing moisture during the construction phase is critical, as prolonged exposure to rain before the building is sealed can damage the engineered panels. Additionally, the supply chain is still developing; while Europe has a mature CLT manufacturing base, North America needs more regional factories to meet surging demand and reduce transportation costs.[6][8]

Insurance premiums also remain a hurdle. Because mass timber is still relatively new to many underwriters, developers sometimes face higher builder's risk insurance rates during construction, requiring early and extensive collaboration with fire safety consultants to prove the building's resilience.[7]

Yet the trajectory is clear. As carbon taxes become more prevalent and the construction industry seeks ways to offset its massive environmental footprint, engineered wood is transitioning from an experimental novelty to a foundational material of the 21st century. With structures like the Neutral Edison proving that timber can safely scrape the sky, the future of sustainable architecture is increasingly taking root in the forest.[1][8]