Three Key Takeaways
- Mass timber products save construction time because of its prefabrication.
- The materials sequester carbon rather than emit it as concrete and steel do.
- Wood exposed on the interior provides a biophilic effect, a boon to aesthetics and healthfulness.
In the multifamily space, the need for new building processes and materials and the possibility of paring construction and labor costs are generating a buzz. This is especially true as rising costs and inflation, labor shortages and an increased concern for the environment continue to impact the industry.
Among a few, one solution, mass timber, stands out as a viable option that could help alleviate builder woes. The “large pre-manufactured, multilayered, solid wood panels” check many of the boxes for developers, according to the American Wood Council. They’re fire resistant, strong, sustainable and reduce construction and labor costs.
Though it took a while to gain traction in the United States, the use of mass timber is on the rise, which means more real estate clients might make the choice to live in a building with this construction.
The Emergence of Prefabricated Wood
Wood has long been used to construct multifamily residential and commercial buildings, but in the 1800s and 1900s, concrete and steel replaced it in many cases. The reason? So buildings could rise higher. European architects and builders focused again on wood as a smart, renewable environmental choice that could take carbon from the air and sequester it versus concrete and steel that emit it, says architect Zac Miles, AIA, with architecture firm KTGY.
In factories overseas, Europeans were first to engineer mass timber pieces into large wood panels for floors and walls, and they attached them through cross-laminated timber layers (CLT), nail laminated timber (NLT), or dowel laminated timber (DLT), says Dan Getz, structures global practice director at global design firm HKS architects. These prefabricated panels provide strength comparable to concrete and steel floor systems and got the code approval go-ahead for use in buildings taller than those constructed from non-engineered wood members, Getz says.
Interest in the U.S. developed slower due to resistance because of building codes that capped heights at six stories and fear of fire. Still, several developers, including architect Jason Korb and his company, Korb + Associates Architects, pushed the envelope and sought approval through variances from local authorities or by showing that their designs would perform successfully. “In all building codes, there’s a paragraph that says the purpose is not to stifle innovation but allow the applicant to proceed if it can prove equivalencies through third-party testing for fire safety. We did that,” he says.
In 2016, the seven-story T3 Minneapolis office building became the tallest U.S. mass timber structure, followed two years later by the 12-story condo complex Carbon 12 in Portland, Ore. Ascent at 284 feet was next, approved despite going higher than the code limit because it met performance tests, Korb says.
Around the same time, the International Code Council (ICC) approved proposals that would allow other mass timber buildings to go up to nine, 12 or 18 stories as part of its 2021 International Building Code (IBC).
Volatility in lumber and resin prices due to the pandemic, bad weather where plants were located, and other challenges caused some issues in 2021. “Supply chain disruptions caused a step backward,” says Christian Beard, director of building products research at John Burns Real Estate Consulting. Once prices stabilized, however, interest was reignited, he says.
Already 1,571 residential and commercial multifamily mass timber buildings have been constructed, according to WoodWorks, a nonprofit that tracks these numbers and provides education and other support related to U.S. wood buildings, says Bill Parsons, chief operating officer. Almost 200 are under development with the majority in the seven to 12-story range and designed for multifamily housing. While there were once few factories in North America, the domestic numbers are increasing, says architect Susan Jones, FAIA founding architect of atelierjones LLC. Among her current projects is the eight-story Heartwood building in Seattle for the nonprofit Community Roots Housing. Jones and others point out that tall wood, mass timber buildings will appeal more to others as their benefits are recognized:
Shorter Timetables and Lower Costs
Because these buildings are comprised of prefabricated members, construction time is less, and labor costs are lower. Korb estimates the installation time for Ascent was cut by one quarter versus other construction. The project also required a crew of 11 versus a typical team of 40 for a comparable concrete building. The shorter time cycle also means that these buildings generally get to market and into the revenue stream faster, says architect Rockland Berg, AIA, NCARB, principal and director of business development at the Dallas-based architecture firm, three. This appeals to developers watching timelines because of higher interest rates, says Vaughan Buckley, CEO of Volumetric Building Companies, a vertically integrated volumetric modular construction technology company. To boot, work at sites to lift panels is also quieter, Jones says.
Developer Jeff Klotz, CEO of The Klotz Group of Companies, who has built wood-framed garden-style apartments, now uses factory-built panels more since they allow for continuous work with few weather delays.
The industry has had to adapt to the faster building process, though. "You don’t have six months in most cases to decide where to place a light switch,” says Buckley. Architect Jonathan Delcambre, managing partner for BKV Group in Dallas adds, “Everyone on the team has to work on a faster track to keep up the pace.”
Better Quality Control and Savings on Materials… Maybe
Because of factory fabrication, which uses a digital building process, problems are typically resolved before installation, which is a boon to builders.
Of course, as a commodity like any other, the cost of mass timber fluctuates. “Over the last three years, there’s been a roller coaster with building material prices, including the costs of wood, resins, and other materials,” Getz says. Rather than focusing on the cost of materials, though, Getz recommends a wide-lensed view.
“It’s better to look at the holistic cost. Mass timber framing might be more expensive, but one might not need as many finishes, have lighter foundations, and have a shorter construction schedule with its prefabricated efficiency,” he says.
Also, today’s lumber is at pre-pandemic pricing and it’s readily available, Klotz says. Also, foundations are generally lighter with wood than with steel and concrete structures, often at a lower cost, Berg says.
Environmental and Climate Advantages
Mass timber presents a lower embodied carbon footprint and reduces off-gassing, which improves interior air quality. Prefabrication also minimizes construction waste at a site, and leftover pieces can be recycled for other projects or converted to mulch, Buckley says. There’s no dearth of resources. “It would take only 25 minutes of natural growth in North American forests to replenish the wood Ascent used,” Korb says. “The key to healthy buildings,” he adds, “is healthy trees that come from sustainably managed forests where trees are harvested properly to maintain the health of remaining trees. The amount of carbon sequestered is equivalent to taking 2,400 cars off the road.”
Mass timber can create an appealing repurposed industrial vibe in the interior when the wood is left exposed, Berg says. The exposed wood also contributes a biophilic effect. Architects at HKS say preliminary research shows that the exposed natural materials improve workplace productivity. Jones adds, “It offers a contemplative, calm, living-in-nature experience right in the heart of the city for residents.”
Though it seems counterproductive, mass timber’s fire resistance adds to its popularity. “Mass timber products have inherent fire resistance because they char on the outside while retaining structural strength, slowing combustion, and allowing ample time to evacuate a building,” Parsons says. “Wood’s rate of char is predictable and well established in U.S. building codes and standards.” Some remain wary. “The possibility of fire scares people but more understand that everything burns—even concrete and steel. Each material requires different ways to protect it,” Korb says
One Answer to Affordability Issues
As an example, KTGY designed a five-story, 100-percent affordable building, 330 Distel Circle, in Los Altos, Calif., the first of its kind in that city. Jeff Spiritos’s firm, Spiritos Properties, with partners Beulah Land Development and HELP Development, are developing 340 + Dixwell with state low-income tax credits, a four-story, 69-unit, affordable, passive house building in New Haven, Conn. Though the mass timber products were shipped from Austria, they emit less carbon than ones shipped to New Haven by truck, he says. Jones’ Heartwood features 126 units of workforce housing that average 400 square feet.
Throughout the country, there’s activity with U.S. developers, builders and architects playing catch-up to European counterparts, says Korb. His firm is constructing a 29-story mixed-use project in St. Louis near the new MLS soccer stadium. A key, Jones says, is for those new to the niche to take advantage of the knowledge now available. “We’ve focused on mass timber for a decade and work exclusively with it all over the country,” she says.