Changes in modern building codes are creating even more opportunities to make mass timber structures a bigger part of the urban skyline.

What is Mass Timber?

Mass timber buildings are constructed with large pre-manufactured, multilayered, solid wood panels resulting in solid timber floors and walls typically ranging from 5 to 12 inches in thickness. Typical mass timber products include cross-laminated timber (CLT), nail-laminated timber, glued-laminated timber (glulam), and structural composite lumber—all renewable and sustainable engineered wood products.

The use of prefabricated wood panels makes for efficient construction and renovation and enables end-of–life disassembly and material repurposing. This contributes to waste reduction and to extending the lifetime of carbon stored in these wood products.

What are Tall Wood Buildings?

The 2021 International Building Code introduced three new types of construction for fire-resistance rated mass timber structures, also called tall wood buildings or tall mass timber buildings. Wood structures had previously been limited to no taller than six stories or 85 feet. These changes expanded the use of mass timber for tall wood buildings up to 18 stories.

Longer spans, taller walls, faster and safer construction.

These innovative and versatile products are providing architects, designers, and builders with new opportunities to use wood as a tall building’s main structural material. Large, open-space venues like arenas, schools, and office lobbies that require tall walls and minimal supports are ideally suited to engineered wood products like glued-laminated timber (glulam), which can be manufactured to achieve spans over 100 feet and walls reaching heights of 20 feet.

Studies show that building with mass timber can accelerate construction time and improve project safety, while further efficiencies are added through a coordinated assembly strategy using prefabricated engineered mass timber components.

• Developers of the Ascent, a 25-story mass timber hybrid building in Milwaukee, said, “Mass timber construction requires 90% less construction traffic, 75% fewer workers on-site, and is 25% faster than traditional construction. All of these reductions factor into reduced emissions associated with the construction process.”
• One design firm found that using mass timber reduced the total duration of the project by five months compared to building with conventional materials. This allowed a building to be completed in ¾ of the time that a traditional concrete structure requires.
• The mass timber frame in one project installed 13 weeks faster than traditional, cast-in-place post-tension concrete by using mass timber panels, glulam columns, and glulam beams prefabricated offsite.
• Assembling roof and wall components on the ground significantly reduces the risk of worker falls.