Mention the word “urban,” and many people think of “the concrete jungle” — tightly packed cities with tall buildings made of concrete and steel, and the sizzling surfaces of streets and sidewalks instead of cool grass. But that perception is changing. Worldwide, mass timber is bringing the warmth, beauty, and strength of wood to the urban landscape, making it a more desirable place for people to live.
According to the most recent United States Census, over the last decade, the country’s overall population grew at the slowest rate since the 1930s. However, urban areas continued to experience steady growth:
- Approximately 86% of the US population lives in large metropolitan areas.
- 8% of the population lives in cities.
- The most populous cities are New York City, Los Angeles, Chicago, Houston, Phoenix, Philadelphia, San Antonio, San Diego, Dallas, and San Jose.
With the world’s population continuing to grow, and more people choosing to live in cities, urban building is on the rise. Many cities don’t have space to build outward — but they can build up. And mass timber is opening exciting new possibilities for high-rise structures and multi-family homes.
What is Mass Timber?
Mass timber is a framing style that uses large solid wood panels — typically engineered into multiple layers — for wall, floor, and roof construction. These panels are extremely strong and rigid and create a surprisingly sustainable and fire-resistant building material. Mass timber is perfect for projects such as office and mixed-use buildings, multi-unit residential structures, public and institutional buildings, hospitality buildings, and schools and universities.
While mass timber is the common catch-all term, it actually refers to a family of different wood products, each with its own unique qualities and best areas of use. Mass timber is divided between cross-laminated timber (CLT) and glued laminated timber (glulam).
CLT consists of layers of lumber that are orientated perpendicular to one another and then glued together to form structural panels. These panels provide exceptional strength, dimensional stability, and rigidity, as well as a more organic look when compared to other building materials. CLT is most commonly used to create floors, walls, and roofing in a commercial building or multi-family structure.
Glulam is a structurally engineered wood product composed of individual wood laminations bonded together by durable, moisture-resistant adhesives. Glulam panels have excellent strength and stiffness, making them ideal for applications such as columns and beams. Glulam is generally used to create the skeleton of a commercial structure, specifically beams, columns, and roof trusses.
Mass timber products can also be used in conjunction with other building materials, such as steel, concrete, and/or glass. The resulting structure is called a hybrid timber building. Mixing materials can help to reduce costs, but moreover, the blend of natural timber with “harder” materials can create very striking building designs.
The popularity of CLT and glulam in commercial building has been growing, and these materials are bound to be used in cities and towns across the country more frequently in the coming years. A major code revision in the 2021 International Building Code included new mass timber specifications, paving the way for even more mass timber projects in the future.
History of Mass Timber
Although wood has been used as a building material for thousands of years, turning wood into mass timber is a relatively new and cutting-edge technology.
Mass timber was developed in Europe only about thirty years ago. It was initially used to build smaller structures, but as it became more difficult to source old-growth timber, mass timber started to be used in larger buildings as well. Mass timber’s popularity in the United States has been growing as architects and engineers learn more about its benefits. And as building officials learn more about mass timber, codes continue to change to allow for its use in a wider range of applications, including tall wood buildings.
Benefits of Mass Timber Compared to Other Building Materials
It’s easy to see why architects, builders, and officials have been won over by mass timber. Its benefits include:
- Aesthetics: There’s no denying the beauty of wood. And with different species, stains, and paints, its design flexibility is unrivaled.
- Sustainability: When sourced responsibly, timber provides a sustainable and renewable building material that creates fewer carbon emissions when compared to the production of steel and concrete. Timber is the only building material that is a carbon sink — as opposed to releasing carbon into the atmosphere. It is also completely renewable, as new trees are planted to replace those that are cut down. Also, smaller trees, and even diseased or dead trees, can be harvested to engineer CLT and glulam for mass timber projects.
- Resiliency: If you plan to build in an area that frequently experiences seismic events, mass timber is a safe build option due to its strength-to-weight ratio. Although it weighs between one-third and one-fifth less than concrete, it maintains the same structural capacity. It is also more flexible than other building materials. Consider how a tree moves in a windstorm. It can bend pretty far without breaking. Plus, the types of connections used in a mass timber structure help the building move and sway instead of remaining rigid and breaking.
- Integrity: Because of timber’s natural tendency to char, mass timber construction maintains its structural integrity well in the event of a fire. Wood is an excellent heat insulator and develops a char layer when exposed to fire. After the heat source is removed, wood extinguishes itself and retains a significant amount of strength.
- Efficiency: Mass timber is cut to size and often modularized into large components in a manufacturing facility, which can shorten the amount of time a construction team needs to be on the job site. Onsite construction time for mass timber buildings is often shorter than when using other materials, resulting in less impact to job sites and faster return on investments.
- Higher Income Potential: Mass timber buildings are easily differentiated from others because of their more natural look and feel and also because of the sculptural quality they tend to take on. People are willing to pay premium rents for these upgraded aesthetics.
Current Status of Mass Timber
International Building Code amendments are making it easier to build with heavy and mass timber. For example, the 2021 IBC includes special inspection requirements to address the anchorage and connection of mass timber structural elements. In addition, three new types of construction (Types IV-A, IV-B, and IV-C) allow mass timber buildings of taller heights, more stories above grade, and greater allowable areas compared to existing provisions.
As of October 2021, hundreds of multi-family and commercial mass timber structures have been built or are being built worldwide. A few fine examples of the possibilities of mass timber construction include:
- Atlassian headquarters, Sydney, Australia (a hybrid timber building)
- The Toronto and Region Conservation Authority headquarters, Toronto, Canada (an 87,000-square-foot office building)
- Dalston Works, London, England (a 10-story residential building)
- Carbon12, Portland, Oregon (luxury condominiums)
- The Beam on Farmer, Tempe, Arizona (a mixed-use mass timber building)
- Hotel Magdalena, Austin, Texas (America’s first mass timber hotel)
- Ascent, Milwaukee, Wisconsin (at twenty-five stories, this will be the tallest mass timber hybrid building in the world once it is completed)
The Future of Mass Timber
Proprietary technology and innovation are still being explored in the mass timber realm, so it is safe to say that we can still look forward to new and exciting possibilities. Areas of innovation that we’re keeping an eye on include:
- Helping builders increase the efficiencies of building with CLT and glulam
- Increased modularization and pre-building components
- CNC fabrication to transform commodity products into custom building components
- BIM modeling for prefabricated elements
- Decreased costs (as the popularity of mass timber increases, we might see more manufacturing facilities being built, bringing down the cost of CLT and glulam)
- Optimizing the amount of wood fiber used
Are You Ready to Build with Mass Timber?
At Mid-Atlantic Timberframes, we’ve reinvented our old-world craftsmanship for the future of mass timber. Drawing on our heritage of quality custom timber framing using fine wood materials, centuries-old techniques, and the latest CNC technology, we’ve expanded our services to include working with mass timber. To learn more about using mass timber in your next construction project, contact us today!