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The Timber Revolution Reaches New Heights | Part 1

An In-Depth Report on Mass Timber Innovation in 2025 so far

I. Introduction: Wood Re-imagined for the Urban Skyline

On June 16, 2025, a groundbreaking ceremony in downtown Milwaukee marked a pivotal moment in the evolution of urban construction.1 The project, known as “The Edison” or Neutral 1005 N Edison St., is not just another high-rise. It represents the next leap forward in rethinking the materials used to build our cities. It is to become the tallest mass timber tower in the Western Hemisphere upon its completion in 2027. The Edison symbolizes the arrival of wood and mass timber as a high-performance, engineered material that is a serious contender for the urban skyline of the future.1

The Edison, the tallest mass timber building in the US, as seen from the Milwaukee River
Photo courtesy of Neutral.

This development is a far cry from the historical trajectory of wood in architecture. Following a series of devastating city fires in the late 19th century, wood was largely dismissed as a primary structural material for large-scale buildings, ceding dominance to the perceived safety and strength of concrete and steel.4 Today, however, a new generation of engineered wood products is enabling a resurgence. These materials are challenging long-held assumptions and proving their viability in applications once thought impossible for wood, from multi-story residences and offices to rising approvals for towers and long-span arenas.5

A convergence of advanced material science, rigorous performance testing that validates its safety, and a sustainability narrative that aligns with global decarbonization goals drives the ascent of mass timber. A maturing technological ecosystem, featuring specialized connectors, advanced fabrication techniques, and streamlined construction processes, supports this transformation.

The Edison Building mockup in front of the river
The Edison. Rendering by Hartshorne Plunkard Architecture.

Yet, for mass timber to transition from a niche innovation to a mainstream construction method, it must navigate significant hurdles in regulatory adoption, industry acceptance, and market logistics. This report provides an analysis of the state of mass timber in 2025 so far, examining the technical foundations of its core products, showcasing the record-breaking structures that define its potential, and delving into the scientific research that underpins its performance. It further examines the crucial role of mass timber in climate-conscious construction and evaluates the market forces and systemic challenges that will shape its future.

The very location of The Edison tower is telling. Milwaukee is already home to the current world-record holder for a timber-concrete hybrid building, the 25-story Ascent MKE, completed in 2022.8  The decision by developers to build an even taller mass timber structure in the same city points to the emergence of regional innovation. This pattern suggests that a successful project creates a localized ecosystem of expertise of manufacturers, design firms, specialized contractors, and supportive municipal authorities. This concentration of knowledge and confidence reduces the perceived risk for subsequent projects, creating a cycle that accelerates adoption and solidifies a region’s leadership in this advanced construction methodology.1

 

 

II. The Mass Timber Toolkit: A Guide to Engineered Wood Products

At its core, mass timber is a category of engineered wood products characterized by large, solid wood panels, columns, and beams.11 These components are manufactured by laminating, nailing, or doweling together layers of wood to create structural elements with exceptional strength and dimensional stability, far exceeding those of traditional lumber.4  Understanding the distinct properties of each product is essential to appreciating their specific applications in modern construction.

 

Panel Products (for Surfaces and Shear)

Panel products form the surfaces of a building (its floors, walls, and roof) and are critical for resisting shear forces.

  • Cross-Laminated Timber (CLT): CLT is arguably the most versatile and well-known mass timber product. It is manufactured from layers of kiln-dried dimension lumber (typically three, five, seven, or nine layers) that are stacked at 90-degree angles to one another and bonded with structural adhesives under high pressure.5  This orthogonal arrangement is the key to its performance; by alternating the grain direction, the panel gains exceptional structural rigidity and dimensional stability in two directions.6  This biaxial strength allows CLT panels to be used for floors, load-bearing walls, and roofs, and they have even been employed in elevator shafts.6  Their strength and stability make them particularly suitable for mid- and high-rise construction.14
  • Nail-Laminated Timber (NLT): NLT is a legacy product experiencing a modern renaissance.14  It is formed by stacking dimensional lumber on edge and fastening the individual laminations together with nails or screws.6  Unlike CLT, the grain of all laminations runs in the same direction. NLT is commonly used for floor and roof decks and is often prized for the rich, natural aesthetic it provides when left exposed.6  Because it is composed of individual boards, NLT can be used to create unique, curved roof forms by slightly offsetting and rotating each board relative to the next.15
  • Dowel-Laminated Timber (DLT): DLT represents a newer, adhesive-free approach to panel manufacturing. It is constructed from softwood lumber boards stacked on edge, similar to NLT, but they are joined using hardwood dowels instead of metal fasteners or glue.5  The dowels are kiln-dried to a lower moisture content than the softwood lumber; after insertion, the dowels absorb ambient moisture and swell, creating a tight friction fit that locks the panel together.7  This all-wood composition is a key advantage for projects seeking to maximize natural materials.16  Furthermore, because DLT contains no adhesives or nails, it is exceptionally easy to mill with Computer Numerical Control (CNC) machinery, allowing for the seamless pre-integration of electrical conduits and other services (MEP) and the creation of unique acoustic profiles on the exposed face.6  It is best suited for horizontal spans such as floors and roofs.7

 

Linear Elements (for Frames and Spans)

Linear elements form the structural skeleton of a building, including its columns and beams.

  • Glue-Laminated Timber (Glulam): Glulam is an engineered wood product composed of multiple layers of dimensional lumber oriented with the grain running in parallel.7  These laminations are bonded together with durable, moisture-resistant adhesives to create large structural members.18  Glulam is exceptionally versatile and is typically used for beams, columns, purlins, and arches.6  Its high strength-to-weight ratio allows for the creation of long spans and dramatic, open spaces, and it can be manufactured into curved and arched shapes, offering significant design flexibility.6

 

Structural Composite Lumber (SCL) Family

The mass timber family also includes various types of structural composite lumber, which are produced by bonding together wood strands or veneers. Products like Laminated Strand Lumber (LSL) and Parallel Strand Lumber (PSL) are utilized in applications such as headers, beams, and columns, where dimensional uniformity and high strength are crucial.6

The following table provides a comparative overview of the primary mass timber products, outlining their composition, applications, and key advantages to aid in material selection.

Product Name Composition / Manufacturing Primary Structural Application Key Advantage(s) Notable Considerations
Cross-Laminated Timber (CLT)
Layers of lumber stacked at 90-degree angles and bonded with adhesive.5
Floors, walls, roofs, elevator/stair shafts.6
Excellent two-way structural rigidity and dimensional stability; high load-bearing capacity.5
Requires adhesives in manufacturing; two-way span capability is a key design feature.6
Glue-Laminated Timber (Glulam)
Parallel layers of lumber bonded with adhesive.7
Beams, columns, arches, long-span structural frames.6
High strength-to-weight ratio; design flexibility for long spans and curved shapes; aesthetic appeal.6
Primarily a unidirectional spanning element; manufacturing is adhesive-dependent.18
Dowel-Laminated Timber (DLT)
Softwood lumber boards joined by hardwood dowels (friction fit).5
Floor and roof systems.7
Adhesive-free (all-wood); easy to mill with CNC for MEP integration; good acoustic properties.6
Primarily a unidirectional spanning element; a relatively newer product in North America.16
Nail-Laminated Timber (NLT)
Dimensional lumber stacked on edge and fastened with nails or screws.6
Floors, roofs, and decks.6
Cost-effective; long history of use; natural aesthetic; can be used to create curved forms.11
Primarily a unidirectional spanning element; can be fabricated on-site or prefabricated.15

III. Touching the Sky: Record-Breaking Mass Timber Structures

The theoretical potential of mass timber is being realized in a new generation of “plyscrapers” that are pushing the boundaries of wood construction. These landmark projects not only set new records for height but also serve as powerful demonstrations of innovative structural systems and sustainable design principles.

The Current Champion: Ascent MKE (Milwaukee, USA)

Completed in 2022, the Ascent MKE building in Milwaukee currently holds the title of the world’s tallest timber-concrete hybrid building.1 Standing 25 stories and 284.1 feet (86.6 m) tall, this luxury apartment tower is a testament to the viability of mass timber in high-rise applications.8 The building’s design showcases a highly optimized hybrid structural system. A cast-in-place concrete podium forms the first six floors, housing parking and retail space, while also providing a rigid base for the tower.8 The upper 19 residential floors are constructed with a mass timber superstructure consisting of exposed glulam columns and beams supporting CLT floor panels.8
The Ascent MKE building in Milwaukee
Photo courtesy of dezeen.
Critical elements requiring high levels of fire resistance and structural rigidity, such as the elevator and stair cores, are also constructed from concrete.3 This design is not a compromise but a sophisticated engineering solution. It strategically leverages concrete for its mass and non-combustibility in the core, where it is most needed for lateral stability and fire-safe egress, while using mass timber for the majority of the structure to capitalize on its light weight, speed of construction, and low carbon footprint. This pragmatic hybrid approach has become the enabling pathway for mass timber to reach new heights. The environmental benefits of this approach are significant. The extensive use of wood is estimated to sequester roughly 7,200 metric tons of carbon dioxide.8 Furthermore, the design prioritizes biophilic principles by leaving much of the timber structure exposed on the interior, enhancing occupant wellness and connecting residents to natural materials.8

The Successor: The Edison (Milwaukee, USA)

Building on the success of Ascent, the same city is now poised to break its own record. The Edison, which began construction in June 2025, is projected to rise 31 stories to a height of 375 feet (114.3 m).1 This mixed-use tower will feature 353 residential units and is slated for completion in 2027.2  The Edison is designed to set new benchmarks not only in height but also in sustainability. The project targets some of the world’s most stringent green building certifications, including the Passive House Institute US (PHIUS) 2021 Core Standard and the Living Building Challenge 4.0 Core Certification. 1
Photo courtesy of Hartshorne Plunkard Architecture
Its design aims to reduce embodied carbon by 54% and operational carbon and energy consumption by 45% compared to a conventional building of the same size and use.1 This will be achieved through a combination of the mass timber structure and innovative building systems, such as a heat pump system that utilizes the thermal energy of up to 2 million gallons of river water per day for cooling.10

Global Context: Other Landmark Towers

The push for taller timber buildings is a global phenomenon, with several other structures demonstrating diverse approaches to mass timber design.
  • Mjøstårnet (Brumunddal, Norway): For a time, Mjøstårnet held the world record for the tallest timber building. At 18 stories and 85.4 meters, it is notable for being considered an “all-timber” structure.8 Its load-bearing system is composed of glulam, with CLT used for stairwells, elevator shafts, and balconies.8 The project also benefited from its proximity to a major forestry hub, allowing all timber to be sourced locally.8
  • HoHo Wien (Vienna, Austria): This 24-story, 84-meter tower is another prominent example of hybrid construction.8 Approximately 74% of the structure is wood, complemented by a precast concrete core.8 The design features an innovative “docked” wooden framework where CLT floor panels are supported by concrete girders, efficiently transferring loads.8
  • Sara Kulturhus Centre (Skellefteå, Sweden): Located just south of the Arctic Circle, this 20-story, 80-meter cultural center and hotel showcases the adaptability of mass timber for complex public buildings.8 The structure is made almost entirely of wood, sourced from regional forests.20 Its design incorporates a hybrid wood-and-steel system to create large, column-free open spaces, and the hotel rooms were delivered to the site as prefabricated modules, demonstrating the efficiency of industrialized construction.2
Mjøstårnet (Brumunddal, Norway) Photo credit: Ricardo Foto and Øystein Elgsaas.
The HoHo-Wien Buildng in Vienna, Austria.
HoHo Wien (Vienna, Austria) Photo courtesy of WoodWorks.
The Sara Kulturhus Haus in Sweden
Sara Kulturhus Centre (Skellefteå, Sweden) Photo Courtesy of Wonderful Engineering.
More to come in Part 2 next week!

Works cited

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