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Kaiser Group and Path Architecture designed Carbon 12. At the time it was built it was the tallest mass timber and cross-laminated timber building in the country. CREDIT: ANDREW POGUE Strides In Fire Safety for Mass Wood Timber Buildings Tall Mass Wood Timber buildings have captured the design imagination of North America. As these buildings are poised to go taller, the leading firestop company, Hilti North America, has stepped in with innovative ways to help promote fire safety. + www.greenbuildermedia.com “The question for Hilti became, How long can a structural wood construction element withstand a fire within a building? Hilti has focused on this gray area because no approved firestop solutions existed.” —Neal Clemens, Marketing and Product Manager, Fire Protection, Hilti North America wood-built future in tall buildings. ability to approach tall building from a From 2014 to the end of 2018, the modular standpoint results in reduced number of U.S. mass timber projects manpower and many other characteristics grew from fewer than 20 to well over that make CLT attractive to the building 400, reports nonprofit WoodWorks. And industry—and it’s not going away.” Forterra, a land conservation nonprofit, says that demand for CLT, which is used WITH INNOVATION COMES in Tall MWT projects, is expected to RESPONSIBILITY double every five years into the future. Perhaps the most important (and misun- The exponential growth of MWT derstood) aspect of MWT is its fire perfor- is good news for the building industry mance. People often think of wood as a because the technology offers faster quick-igniting object, like kindling. But CREDIT: ANDREW POGUE Carbon 12 shows off the beauty of wood with its exposed Douglas Fir panels doubling as finished ceilings. construction time, reduced on-site skilled the mass wood used in multistory build- Mass timber is the general term for labor requirements, generally lighter ings chars in the event of a fire, protecting large structural panels, posts, and beams weight potentially requiring less substan- the inner layers of wood from damage. HEN CARBON 12, A BEAUTIFUL EIGHT-STORY Cross-Laminated composed of wood. Products in the cate- tial foundations, beneficial thermal prop- In fact, according to “Mass Timber Timber (CLT) apartment complex was built in Portland, gory include CLT, Structural Composite erties, and positive environmental impact. Market Analysis,” by The Beck Group, Lumber, glue-laminated timber, and large “CLT technology is absolutely becoming “Recent laboratory burn tests of Mass Oregon, the country got excited about the future of Tall Mass section sawn lumber. The market for these more popular,” says Matthew Winston, Timber products have addressed Wood Timber (MWT) building. After Carbon 12’s 2017 debut, products in tall buildings like Carbon 12 is Testing and Approvals Engineer, Fire concerns regarding fire safety in large many on-the-boards projects got press as Portland—and growing rapidly—so rapidly, in fact, that Protection Engineering Team, Hilti North wooden structures. Mass timber struc- the building and scientific communities America. “And really that popularity tures far outperform stick framed struc- Wother cities, including Chicago, San Francisco, and Philadelphia—dreamed are struggling to keep up with the anal- started to rise in 2015, making a resurgence tures and, due to the charring effect, can of new ways to go taller with timber. Today, Portland has the country’s largest yses, best practices, and codes needed to with the green building and sustainability even outperform steel structures during ensure a smooth transition from building initiatives that design firms were looking very high temperature fires, in which concentration of mass timber buildings and has solid growth potential. with steel or post-tension concrete to a to bring into the construction world. The steel will melt, deform, and fail.” 2 Strides In Fire Safety for Mass Wood Timber Buildings Strides In Fire Safety for Mass Wood Timber Buildings 3 Hilti, the leading manufacturer of BUILDING CODES EVOLVE the use of MWT in tall buildings. worked through building code issues, Hilti While Winston points out that quite a for building designers and the inspectors internationally approved and tested fire- According to the International Code Based on favorable research results, continued to focus on firestop solutions. few Tall MWT buildings have gone up in who are tasked with signing off on fire- stop systems, monitored the growth of Council (ICC), “Tall Mass Timber” identi- ICC approved code changes to 2021 IBC “We asked ourselves, ‘How do we tie fire- places like Portland and Seattle, a large part stop systems in MWT buildings, but until MWT, and in particular CLT, and realized fies mass timber buildings constructed of allowing for Tall MWT. stop into the building of MWT, addressing of the inspection community is still waiting the assemblies are listed or certified, says its leadership in producing and testing mass timber elements that exceed current “For the 2021 IBC, ICC classified MWT these taller and bigger buildings?’ The code for a chance to review a MWT project. “For Winston, approvals will rest on project- firestop products had put the company height limits for wood buildings set by the within a Class IV building and then added gives requirements like it does for any example, I recently provided an analysis specific designs called Engineering in an excellent position to help propel the International Building Code (IBC). Until three more categories types--IV-A, IV-B, other type of construction, but you have of test data for firestops in CLT to a design Judgments. “Typically, someone who mass timber industry forward. recently, building codes were the primary and IV-C. These categories allow fully to have rated assemblies and still meet team,” says Winston. “The initial firestop needs a firestop system would refer to “The question for Hilti became, ‘How barrier to the use of Tall Mass Timber encapsulated MWT buildings (IV-A) to go up the requirements for compartmentaliza- designs were provided in 2018 and now, a listing from a third-party certification long can a structural wood construc- because they were tailored to traditional to a maximum 18 stories depending on the tion,” Goldhammer says. “We have always in 2020, the design teams are sitting with body. To date, however, no such listings tion element withstand a fire within a building systems, such as steel, stick occupancy and partially encapsulated MWT had firestop through a rated assembly, so building inspectors [to review life safety.]” exist for firestops in MWT,” he says. building?’” says Neal Clemens, Marketing frame, and concrete. buildings (IV-B) to go up to a maximum of that’s not a big change. The challenge is Hilti wants to streamline the process With the goal of developing more data In 2019, Katerra opened a 270,000-square-foot CLT factory in Spokane Valley, Wash. At full capacity, this factory will produce the highest When CLT members, such as this one being manufactured by Katerra, are tested by Hilti, they are built into mock-up assemblies with penetrations volume of CLT in North America–13,000,000 square feet of 5-ply panels annually. The factory also represents one of the largest CLT presses included. The testing plans are designed to show what happens when mechanical or electrical conduit is put through the floor to determine how to currently in operation globally, offering customers unmatched design flexibility. IMAGE BY KATERRA WWW.KATERRA.COM fire rate it. The tests include different CLT manufacturers’ products and different species of wood, which are tested in ovens. COURTESY HILTI and Product Manager, Fire Protection, “In the 2018 code cycle, wood coali- 12 stories,” Goldhammer explains. that these new assemblies are not part “There has been a big push back around fire Hilti North America. “Hilti has focused on tions put forth proposed changes to The encapsulated buildings use of a listing/certification [such as UL or safety in tall wood buildings. On the one this gray area because no approved firestop include MWT,” says Edward Goldhammer, gypsum or other noncombustible prod- Intertek] so we can not obtain a firestop solutions existed.” Director of Codes and Approvals for ucts to add passive fire resistance, which certification without a certified assembly.” hand, design firms, the mass timber “Really the question around firestop Hilti North America. “The bulk of these is why they are approved for taller struc- industry and ICC code committees have HILTI GOES TO BAT started with Oregon State University, proposals were rejected because they did tures. The partially encapsulated build- paved the way; on the other hand, fire who had contacted SmartLam to build a not have enough data on fire performance ings are still safe, Goldhammer says. “There has been a big push back around Tall MWT the University had designed,” in tall buildings. As a result ICC agreed to “Even though the IV-B structure performs fire safety in tall wood buildings,” Winston inspectors, fire departments, and city says Clemens. “SmartLam said they could create an ICC Tall Wood Building Ad Hoc well, having the gypsum just adds another says. “On the one hand, design firms, inspectors have pushed back on life safety build it but asked the important question: Committee. The committee in conjunction level of safety.” the mass timber industry and ICC code issues and the lack of assembly ‘What about life safety?’” with the wood industry conducted a series Designers can opt for the IV-B structure committees have paved the way; on the certifications.” The building industry, antsy to put of large scale fire testing to demonstrate for designs that celebrate the wood look of other hand, fire inspectors, fire depart- wood to work in buildings of scale, turned how MWT performs in a fire.

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