The Rise of the 'Plyscraper': How Mass Timber is Rewriting the Rules of Architecture

The skyline of Milwaukee is changing, and it smells like pine. The Ascent tower, standing 25 stories and 284 feet tall, currently holds the title of the world's tallest completed mass timber building.[2]

But its record won't last long. Just blocks away, developers are preparing to break ground on The Edison, a 31-story "plyscraper" that will utilize nearly 100,000 cubic feet of lumber. Meanwhile, in Sydney, the 42-story Atlassian headquarters is rising, showcasing how timber and steel can integrate on a massive scale.[1][2]

For over a century, the recipe for a skyscraper has been rigid: pour concrete and forge steel. But a quiet revolution is replacing those heavy, carbon-intensive materials with engineered wood, fundamentally rewriting the rules of modern architecture.[7][9]

The shift is driven by a pressing environmental reality. Concrete and steel production are responsible for roughly 15% of global carbon emissions. Mass timber offers a radically different math: because trees absorb carbon dioxide as they grow, buildings constructed from wood act as massive carbon sinks, locking away emissions for the lifespan of the structure.[3][4]

Studies indicate that swapping concrete and steel for mass timber can reduce a building's embodied carbon footprint by 35% to 50%. But to build a skyscraper out of wood, you cannot simply stack traditional two-by-fours. You need mass timber.[4]

"Mass timber" is an umbrella term for a family of engineered wood products designed to carry heavy structural loads. The most prominent of these materials is Cross-Laminated Timber (CLT).[5]

CLT is manufactured by taking solid wood boards and gluing them together in alternating, perpendicular layers—typically three, five, or seven plies thick. This crosswise arrangement gives the resulting panels exceptional two-way strength and rigidity, effectively creating a "super plywood" capable of serving as floors, walls, and elevator cores.[5][6]

For columns and beams, engineers rely on Glue-Laminated Timber (Glulam), where the wood grain of all layers runs parallel, maximizing strength in a single direction. Together, these components form a structural system that rivals traditional heavy materials.[5]

The most common question architects face when proposing a plyscraper is instinctual: won't it burn? The Great Chicago Fire casts a long psychological shadow over urban wood construction, making fire safety a paramount concern for regulators and the public alike.[1][9]

However, mass timber behaves very differently than the light-frame wood used in single-family homes. It has inherent fire resistance due to its sheer density and a chemical process called charring.[3]

When exposed to intense heat, the outer layer of a mass timber beam chars at a predictable rate of about 1.5 inches per hour. This charred layer acts as a thermal insulator, starving the fire of oxygen and protecting the structural integrity of the unburned wood inside.[3][8]

In rigorous testing conducted by the International Code Council, a seven-inch-thick CLT wall subjected to a continuous blaze lasted over three hours—exceeding current fire code requirements by a full hour.[8]

Beyond fire safety, mass timber fundamentally changes how a building is constructed. It shifts the process from on-site fabrication to off-site manufacturing, bringing factory precision to the construction site.[7]

Using detailed 3D models, structural elements are milled in factories by computer-controlled machines with millimeter precision. Openings for doors, windows, and plumbing are pre-cut before the wood ever leaves the facility.[5]

When the panels arrive on-site, they are hoisted by cranes and bolted together like a giant piece of flat-pack furniture. This prefabrication drastically reduces construction timelines, requires fewer site deliveries, and minimizes noise and neighborhood disruption.[3][6]

The timber boom also offers a surprising lifeline to rural forest economies. Sustainable mass timber is often sourced from smaller-diameter trees that are less commercially desirable for traditional lumber.[4]

Forestry experts note that selectively thinning these smaller trees is a standard practice for mitigating wildfire risks in overgrown forests. By creating a lucrative market for this thinned wood, mass timber incentivizes responsible forest management and helps fund conservation efforts.[4][7]

Despite the momentum, the plyscraper revolution faces headwinds. Wood is naturally susceptible to moisture, requiring meticulous weatherproofing during the construction phase to prevent warping or rot before the building is sealed.[6]

Furthermore, while building codes like the International Building Code have recently updated to allow timber structures up to 18 stories, local municipal codes often lag behind, requiring developers to undergo lengthy variance approval processes. Insurance underwriters, too, are still gathering actuarial data on long-term water damage, which can lead to higher premiums.[5][9]

Ultimately, the future of the skyline is likely hybrid. The tallest proposed timber towers utilize concrete foundations and steel exoskeletons paired with mass timber floors and walls. By placing the right material in the right role, architects are proving that the cities of tomorrow can be grown in the forests of today.[2][9]