Mass Timber in North America 1

EDUCATIONAL-ADVERTISEMENT EDUCATIONAL-ADVERTISEMENT MASS TIMBER IN NORTH AMERICA 1

Mass Timber in North America Expanding the possibilities of wood building design Sponsored by reThink Wood CONTINUING EDUCATION CONTINUING

Albina Yard CONTINUING EDUCATION Location: Portland, Oregon Architect: LEVER Architecture Structural Engineer: KPFF Earn 0.1 ICC Consulting Engineers Continuing Developer: reworks Education Unit (CEU)

Photo courtesy of LEVER Architecture Learning Objectives After reading this article, you should be able to: t’s been a while since a major category of Construction efficiency: Mass timber 1. Examine the trend toward mass timber building materials inspired the kind of construction is fast, and speed correlates buildings in the context of carbon footprint, widespread enthusiasm currently being to revenue, whether the project is an office, construction efficiency, fire and life safety, I occupant well-being, and other potential shown for mass timber. Around the world, school, student residence, condominium, advantages. designers are leveraging the strength, stability, or hotel. Bernhard Gafner of structural 2. Identify a range of mass timber products and design flexibility of products such as engineering firm Fast + Epp, says that, available to North American building cross-laminated timber (CLT) to push beyond in his firm’s experience, a mass timber designers. wood’s perceived boundaries, achieving project is approximately 25 percent faster to 3. Discuss research and resources related building heights and spans that would have construct than a similar project in concrete. to the structural performance and fire/life once required concrete, steel, or masonry for Noting the advantages for urban infill sites safety of mass timber products. structural support. in particular, he says it also offers 90 percent 4. Based on examples of mass timber buildings For many, it’s the combination of aesthetics, less construction traffic (trucks delivering either built or under construction, describe structural performance, and opportunity materials) and requires 75 percent fewer how all-wood and hybrid systems are for innovation that have proven irresistible. workers on the active deck, making for a expanding the options for wood design. But mass timber also offers a host of other much quieter job site. advantages: The fact that mass timber weighs less To receive credit, you are required to read the Lighter carbon footprint: Mass timber than other materials also has a number entire article and pass the test. Go to www.awc.org for complete text and to take the products allow the use of a renewable and of potential benefits, including smaller test for free. sustainable resource as an alternative to more foundation requirements and lower forces fossil fuel-intensive materials. Designers of ‘tall for seismic resistance. Discussing the wood’ buildings have been especially focused new Design Building at the University of on the reduced carbon footprint achieved by Massachusetts, for example, structural using wood, which aligns with the goals of engineer Robert Malczyk of Equilibrium AWC Course #DES610-A Architecture 2030. Reducing carbon is also a Consulting, says, “The seismic force is ICC#9766OL priority for many public buildings and schools. proportionate to the weight of the building. 2 MASS TIMBER IN NORTH AMERICA EDUCATIONAL-ADVERTISEMENT

Image courtesy of Fast + Epp CONTINUING EDUCATION CONTINUING

Mass timber systems are a complement to light wood-frame and post-and-beam construction.

If this building were designed in concrete, wood panel or framing systems of six feet wherever combustible framing or heavy which was considered, the weight would or more in width or depth. Products in the timber materials are allowed. The National be six times more than the mass timber mass timber family include: Design Specification® (NDS®) for Wood design.” Construction is referenced throughout the Fire and life safety: Structurally, Cross-Laminated Timber (CLT) IBC as the standard for structural wood mass timber offers the kind of proven CLT consists of layers of dimension lumber design, including CLT. The 2012 IBC does performance—including fire protection (typically three, five, or seven) oriented at not explicitly recognize CLT, but the 2015 and seismic resistance—that allows its right angles to one another and then glued IBC provisions for CLT can be a basis for its use in larger buildings. It also expands to form structural panels with exceptional use under alternative method provisions. the options for exposed wood structure in strength, dimensional stability, and rigidity. For more information on CLT, the smaller projects. Panels are particularly cost effective for U.S. CLT Handbook is available as a free Occupant well-being: An increasing multistory and large building applications. download at www.rethinkwood.com. number of studies focused on wood’s Some designers view CLT as both a stand- biophilic aspects have linked the use of alone system and product that can be used Nail-Laminated Timber exposed wood in buildings with improved together with other wood products; it can also (NLT or Nail-lam) occupant health and well-being.1,2 be used in hybrid and composite applications. NLT is created from individual dimension This course is intended for architects and CLT is well-suited to floors, walls, and roofs, lumber members (2-by-4, 2-by-6, 2-by-8, engineers seeking current information on and may be left exposed on the interior for etc.), stacked on edge, and fastened with nails mass timber, including products, research aesthetics. Because of the cross-lamination, or screws to create a larger structural element. related to structural performance and life CLT also offers two-way span capabilities. NLT is far from new—it’s been used for safety, and available resources. It answers CLT can be manufactured in custom more than a century—but is undergoing common questions regarding strength, fire dimensions, with panel sizes varying by a resurgence as part of the modern mass protection, and durability, and highlights manufacturer. There are several CLT suppliers timber movement. Commonly used examples of mass timber buildings in in North America, with more anticipated. in floors, decks, and roofs, it offers different occupancy groups to illustrate The species of wood used depends on the the potential for a variety of textured both design trends and the extent to which manufacturing plant location. appearances in exposed applications, and mass timber has captured the imagination The 2015 International Building wood structural panels can be added to of North American building designers. Code (IBC) and 2015 International provide a structural diaphragm. NLT has Residential Code recognize CLT products also been used to create elevator and stair WHAT IS MASS TIMBER? manufactured according to the ANSI/ shafts in midrise wood-frame buildings. Mass timber is a category of framing styles APA PRG-320: Standard for Performance NLT naturally lends itself to the creation typically characterized by the use of large Rated Cross-Laminated Timber. Under of unique roof forms. Because panels are solid wood panels for wall, floor, and roof the 2015 IBC, CLT at the required size is comprised of individual boards spanning construction. It also includes innovative specifically stated for prescribed use in Type in a single direction, both singly curved and forms of sculptural buildings, and non- IV buildings. However, CLT can be used in freeform panels can be created by slightly building structures formed from solid all types of combustible construction—i.e., offsetting and rotating each board relative to EDUCATIONAL-ADVERTISEMENT MASS TIMBER IN NORTH AMERICA 3

Photo courtesy of LEVER Architecture the others. This allows the complex geometry of curved roof and canopy structures to be realised with a simple system. Advantages of NLT include the ability to use locally available wood species and the fact that specialized equipment generally isn’t necessary. An NLT system can be created via good on-site carpentry, though some suppliers do offer prefabrication, and this can have benefits depending on the scale and complexity of the project. Prefabricated NLT panels typically come in sizes up to 10 feet wide and 60 feet long, CONTINUING EDUCATION CONTINUING with wood sheathing preinstalled. When detailing NLT systems, designers need to account for moisture movement. The IBC recognises NLT and provides guidance for structural and fire design. No product-specific ANSI standard is required, as the structural design of each element is covered by the NDS and applicable grading rules. NLT can be used in all types of combustible construction.

Glued-Laminated Timber (glulam) Glulam is composed of individual wood laminations (dimension lumber), selected and positioned based on their performance characteristics, and then bonded together with durable, moisture-resistant adhesives. The grain of all laminations runs parallel with the length of the member. ALBINA YARD & FRAMEWORK Glulam has excellent strength and stiffness properties, and is available in a Location: Portland, Oregon Architect: range of appearance grades for structural or LEVER Architecture Structural Engineer: KPFF Consulting Engineers architectural applications. While typically Design Assist + Build (Framework): StructureCraft used as beams and columns, designers can Developer (Albina Yard): reworks use glulam in the plank orientation for floor or roof decking. With careful specification The four-story, 16,000-square-foot Albina Yard is noteworthy for being the first and design that considers the flatwise commercial building in the United States to use domestically fabricated CLT as a structural structural properties (see APA reference element. A Type III project designed under the 2014 Oregon Structural Specialty Code, it below), deep glulam sections can be placed is also interesting as a precursor to another LEVER-designed office project—Framework, flatwise as decking similar to NLT. With the the 12-story winner of the U.S. Tall Wood Building Prize Competition. flexibility of glulam manufacturing, glulam “We were very interested in exploring a mass timber/CLT project on a smaller scale ‘panels’ can be used to create complex prior to building the larger high-rise project, so it was a very fortunate coincidence,” says curvature and unique geometry. When Design Principal Thomas Robinson. Asked about lessons learned, he emphasized the need used in such innovative floor and roof for early collaboration between architectural, structural, mechanical, and installation. panel configurations, glulam is seen as an “Each discipline had a role to play; input and problem solving needed to happen together. extension of the mass timber product family As the building was essentially prefabricated off-site, the coordination and problem solving that often occurs in the field needed to be accounted for beforehand. After we and sometimes referred to as GLT. 1 were off the ground-floor slab, Albina Yard was built to a ⁄8-inch tolerance, and it went The IBC recognizes glulam products together perfectly.” manufactured in conformance with ANSI Currently in design, Framework will consist of ground-floor retail, five levels of office Standard A190.1-2012: Standard for Wood space, five levels of housing, and a rooftop community space. It is expected to include CLT Products—Structural Glued Laminated floor panels as well as a new system of post-tensioned rocking wall panels. Timber. For more information, consult the Developed for use in high seismic regions, rocking mass timber shear walls were tested Glulam Product Guide available at www. by the Network for Earthquake Engineering (NEES) as part of its CLT Planning Project. apawood.org/glulam. Seismic activity was simulated by cyclic loading that pushed and pulled the top of a 16-by- 4-foot CLT panel with an embedded vertical pretensioned rod into a rocking motion. The Dowel-Laminated Timber (DLT) wall was able to reach 18 inches of displacement, while maintaining its ability to self-center Dowel-laminated timber panels are a next- back to a vertical position. generation mass timber product commonly Framework, which is scheduled for completion in 2018, is expected to be the first used in Europe. Panels are made from application of a rocking mass timber shear wall system in the United States. softwood lumber boards (2-by-4, 2-by-6, 4 MASS TIMBER IN NORTH AMERICA EDUCATIONAL-ADVERTISEMENT

Photo courtesy of StructureCraft The manufacture of SCL is and high-end offices that would have standardized. However, while SCL is typically used concrete or steel,” said Lucas included in the NDS, design values Epp of StructureCraft, a specialty timber are provided by the manufacturers. engineering and construction company International Code Council Evaluation known for innovative wood structures. “In Service (ICC-ES) evaluation reports and addition to the warmth of exposed wood, APA product reports are available to assist people are discovering that it’s a viable with structural design capacities and option for creating high-performing and specifications. cost-competitive structures.” Thomas Robinson, whose firm is Wood-Concrete Composites designing three mass timber projects in Mass timber systems vary widely, and addition to Albina Yard and Framework, hybrids are an option for wood high-rises, sees particular potential in multifamily Pictured is a dowel-laminated timber panel very long spans, or other project-specific housing and other building types that lend with an acoustic profile integrated into the requirements. No material is perfect for themselves to modular prefabrication. exposed surface. every job, and it’s important for designers “The time spent upfront designing and to choose a combination of materials perfecting a building system can be 2-by-8, etc.) stacked like the boards of that effectively meets the performance leveraged in projects where you have NLT and friction-fit together with dowels. objectives. repeatable elements,” he says. Typically made from hardwood lumber, At a product level, most of the panels the dowels hold each board side-by-side, described above can be made into a Office/Mixed-Use similar to how nails work in an NLT panel, wood-concrete composite by applying a For office environments, the aesthetic and the friction fit lends some dimensional concrete topping in such a way that the two of mass timber can be a particular draw, stability to the panel. materials act as one. resulting in higher rents and longer-term There isn’t a prescriptive code path One example is the University of tenants. for the use of DLT under the current IBC, Massachusetts Design Building described The Radiator in Portland, Oregon—a and the NDS doesn’t provide published later in this course (see Schools), which five-story, Type IIIA project completed in design values or equations for calculating includes CLT/concrete composite floors. 2015—is part of a surge of mass timber offices capacities of wood dowel joints. To According to architect Tom Chung of Leers in the Pacific Northwest. Designed by PATH calculate capacities, the Timber Framers Weinzapfel Associates, the team relied Architecture for the Kaiser Group, gravity Guild provides some information. on the CLT panels for the building load loads for the 36,000-square-foot structure are However, because nothing is referenced requirements. However, the composite handled through a system of glulam beams in the code, the use of DLT would require action between the CLT and concrete and columns, while a mass timber deck with approval by the Authority Having provided extreme stiffness and minimal wood structural panels creates the structural Jurisdiction on a case-by-case basis. deflection which, along with an insulation floor diaphragm, and dimension lumber Among the advantages of DLT, acoustic layer between the materials, provided good walls sheathed with wood structural panels strips can be integrated directly into the acoustic separation between floors. provide shear capacity. Beams, columns, bottom surface of a panel. This can help a and the underside of the floor decking are designer achieve acoustic objectives, while WHEN IS MASS TIMBER APPROPRIATE? all left exposed, contributing to the interior’s keeping the wood exposed and allowing Because of its strength and dimensional contemporary industrial character. for a wide variety of surface finishes. stability, mass timber offers a low-carbon Further expanding the possibilities, the With growing interest in DLT, alternative to steel, concrete, and masonry seven-story, 220,000-square-foot T3 building continued product innovation is likely, for many applications. A complement in Minneapolis, Minnesota, includes a mix of along with increased availability to U.S. to other wood framing systems, it can glulam columns and beams, NLT floors, and building designers. be used on its own, in conjunction with a concrete core. Architect Michael Green, a other wood systems such as post-and- long-time advocate of using wood to reduce the Structural Composite Lumber (SCL) beam, or in hybrid structures with steel or carbon footprint of buildings, calls the Type SCL is a family of wood products created concrete. Mass timber is not necessarily IV project “a game changer for the commercial by layering dried and graded wood veneers, a good substitute for light wood-frame building industry and a milestone for mass strands, or flakes with moisture-resistant construction, only because dimension timber construction in the United States.” In adhesive into blocks of material, which lumber framing offers such a compelling addition to its carbon benefits, Green cites are subsequently re-sawn into specified combination of performance and cost the ability of modern wood products to bring sizes. Two SCL products—laminated where permitted by code. For this reason, warmth and beauty to the interior, while veneer lumber (LVL) and laminated building types where designers typically promoting a healthy indoor environment. strand lumber (LSL)—are relevant to default to forms of construction other Demonstrating some of the efficiencies the mass timber category, as they can be than light wood-frame—including offices, associated with mass timber, the wood manufactured as panels in sizes up to 8 public/institutional buildings, schools, and structure of T3 took an average of nine feet wide, with varying thicknesses and taller mixed-use occupancies—may offer days to erect per 30,000-square-foot floor. lengths, depending on the product and greater appeal for mass timber than low- More than 100 truckloads of glulam and manufacturer. Parallel strand lumber rise commercial or residential buildings, NLT panels arrived as they were needed (PSL) columns are also commonly used though examples of the latter do exist. at the project site, with steel connections in conjunction with other mass timber “We’re seeing a lot of interest in mass preinstalled, allowing the structural products. timber for midrise buildings such as hotels components to be assembled quickly. The EDUCATIONAL-ADVERTISEMENT MASS TIMBER IN NORTH AMERICA 5

Photo courtesy of StructureCraft CONTINUING EDUCATION CONTINUING

Designed by MGA, the seven-story T3 building in Minneapolis, Minnesota, includes glulam columns and beams, and NLT floors. project team estimates that it is 30 percent of its kind, suggesting new opportunities MASS TIMBER: lighter than a comparable steel design and 60 for open-layout buildings made from AN EFFICIENT SOLUTION percent lighter than post-tension concrete. CLT. The planned long-term use of the In addition to the structural, aesthetic, building as a commercial vendor and and environmental advantages, mass Public and Institutional public assembly space is a significant and timber can be an efficient and practical Reasons to use mass timber in public and sustainable departure from the typical Arsenal,solution an to Army design base challenges. near Huntsville, Ala- institutional buildings are similar to those for design exhibition model of temporary bama.With Developed prefabricated and designed panels, by mass Lendlease, timber offices and schools, including carbon footprint, installations. theconstruction hotel is part is of fast—approximately the Privatization of Army 25 and wood’s biophilic effects. The aesthetic With a growing body of research Lodgingpercent (PAL) faster program, than concrete, created according to provide possibilities are also exciting to many designers. supporting the positive impacts of wood on qualityto Bernhard private-sector Gafner lodgingof Fast +for Epp, soldiers and In the United States, examples include occupant well-being, there is also a trend theirbased guests. on his Compared firm’s experience. to typical PAL Gafner hotel Chicago Horizon, a Type IV public toward the use of mass timber in healing ofsays 54,891 it also square results feet, inLendlease 90 percent says less the new pavilion designed by Ultramoderne environments. 62,688-square-footconstruction traffic CLT and hotel 75 waspercent erected fewer in for the Chicago Architecture Biennial. 37workers percent onless the time, active with deck, a 44 percentmaking reducit - Elegantly crafted, this award-winning Schools tionwell-suited in structural to urban person infill hours. sites. In terms of structure includes a CLT roof supported Mass timber has a number of structuralBecause performance, mass timber the is lighterhotel’s thanlocation stee onl and concrete, it can be a good solution for on 13 glulam columns distributed in a characteristics that make it attractive for a military base meant it also had to meet Anti- sites where poor soil is an issue. radial pattern to address lateral loads and schools and universities—from the ability Terrorism and Force Protection standards. There is also a trend toward the uplift. The pavilion represents the first to construct an entire project over the integrationAnother project of services at the into preconstruction prefabricated use of exposed CLT in the city of Chicago, summer while students are off campus, stageelements, is a 70,000-square-foot such as panels and hotel/condo trusses. The- providing local precedent for the approval to the potential efficiencies of replicable miniumfact that complex the labor in isAustin, done off-siteTexas. Knownmeans and use of mass timber for government modular designs, a lighter carbon asgreater a leader quality in sustainable control and design, a less architecture hectic and public assembly applications. In footprint, and the positive impacts of firmjob Lake|Flatosite. was interested in whether addition, the two-way slab roof is the first exposed wood on student well-being. mass timber could meet both structural and 6 MASS TIMBER IN NORTH AMERICA EDUCATIONAL-ADVERTISEMENT

Image courtesy of Michael Green Architecture

T3 Location: Minneapolis, Minnesota Design Architect: Michael Green Architecture Architect of Record: DLR Group Structural Consultant: MKA Design Assist + Build: StructureCraft CONTINUING EDUCATION CONTINUING

For a 14,000-square-foot addition to Regarding the impact of wood on Tom Chung of Leers Weinzapfel Associates Common Ground High School in New Haven, students and teachers, he adds, “It’s well- said, “Generally, mass timber doesn’t have Connecticut, for example, Gray Organschi known that, as a hygroscopic material to radically change the design concepts Architecture and engineering partner (cellular plant structure), wood surfaces we already use; we can accomplish what Bensonwood chose a combination of CLT serve as moisture buffers, moderating we are already familiar with in steel and and glulam. CLT panels provide the tension swings in interior humidity and thereby concrete. Steel post-and-beam can be surface (and final ceiling finish) in a system of improving air quality. It’s worth done as glulam post-and-beam. Concrete/ prefabricated stressed skin assemblies that span mentioning that during the first few masonry shafts can be done in CLT. Steel/ the upper classrooms and circulation spaces. weeks the new building was being used, a concrete floors can be CLT/concrete Vertical CLT panels form bearing and shear teacher commented to me that people were floors. A steel deck roof can be a CLT roof. walls throughout the building, while glulam remarking on the freshness of the air in Steel braces can be glulam braces. For the rafters and heavy timber trusses span a large the classrooms. Anecdotal, I know, but it UMass project, we went step by step, asked ground-floor multipurpose space. A treated squares with the scientific predictions of ourselves what the precedents were and glulam bridge deck on laminated timber piers health benefits of using wood (especially how we could go about maximizing the use provides access from the upper campus. unfinished wood) in building interiors.” of timber. Discussing some of the advantages of mass Common Ground High School is Type “If the project started out in wood and timber, Design Principal Alan Organschi says, VB Construction, fully sprinklered, and the primary objective was to design the “CLT and glulam can serve as both primary was designed under the 2005 Connecticut most efficient mass timber building, then structure and finished interior surface at State Building Code. the shape and massing may have been the same time. This creates efficiencies in Another example, the Design Building more along the lines of a conventional deploying trades and sequencing construction, at the University of Massachusetts – ‘box,’ which is the shape of most of the which has very real monetary implications. Amherst (UMass), features an exposed mass timber structures built so far. But As the construction industry, accustomed glulam post-and-beam structure, CLT since there were other important design to building institutional buildings like decking and shear walls, CLT/concrete objectives, the UMass building has unique schools using conventional wall, roof, and floors (rigidly connected by glued-in angles and cantilevers that required steel floor assemblies, gains more experience with steel fasteners), and a ‘zipper truss’ roof in addition to wood. Our goal was to use these versatile new timber products, greater spanning a two-story-high common space. the most appropriate materials to meet the production economies will accrue and more of One challenging aspect of this project was structural objectives at hand.” timber’s potential benefits—light weight, high that it started as a steel design. Keen to make Chung also said that educating code strength, workability, etc.—will be captured.” the building a showcase for sustainability, the officials is an important part of the process. Organschi also stressed construction speed. university made the decision to use wood part The UMass project team was in constant Assisted only by a mobile crane, a five-person way through the design process. communication with a Massachusetts state assembly crew installed the entire primary Noting that he may have made different building inspector and, because the building structure and enclosure in just four weeks. choices had he started with wood, architect represented a new type of construction, also EDUCATIONAL-ADVERTISEMENT MASS TIMBER IN NORTH AMERICA 7

Photo courtesy of David Sundberg went before the Massachusetts state board of appeals for official approval. The project Common Ground High School was approved after the team was able to Location: New Haven, demonstrate its performance capabilities Connecticut as well as the long history of mass timber Architect: Gray Organschi structures in Europe and Canada. Architecture Scheduled for completion in 2017, the Timber Engineer: Bensonwood UMass project is a combination of Type IV and IIB Construction.

Multifamily and Hospitality In the United States, a recent example of a multi-story mass timber building is a CONTINUING EDUCATION CONTINUING four-story CLT hotel, Candlewood Suites at Redstone Arsenal, an Army base near Huntsville, Alabama. Developed and designed by Lendlease, the hotel is part of the Privatization of Army Lodging (PAL) program, created to provide quality private-sector lodging for soldiers and their guests. Compared to typical PAL hotel of 54,891 square feet, Lendlease says the new 62,688-square-foot CLT hotel was erected in 37 percent less time, with a 44 percent reduction in structural person hours. In terms of structural performance, the hotel’s location on a military base meant it also had to meet Anti-Terrorism and Force Protection standards. Another project at the preconstruction stage is a 70,000-square-foot hotel/ condominium complex in Austin, Texas. Known as a leader in sustainable design, architecture firm Lake|Flato was interested in whether mass timber could meet both structural and environmental objectives for a multistory building. The project includes five buildings, three of which use mass timber construction, with a combination of NLT, glulam, and prefabricated wood-frame walls.

Tall Wood While most of this course focuses on structures that can be built under current U.S. building codes, a discussion of mass timber is incomplete without reference Completed in 2014, it is made from an In the United States, a number of tall to wood high-rises. Many examples exist innovative combination of glulam post- wood buildings are in design, including worldwide, illustrating the potential of mass and-beam construction and built-up CLT the winners of the U.S. Tall Wood Building timber to bring environmental and other floor panels. It includes six stories, plus a Prize Competition. Established by the advantages to higher-density projects. A penthouse and mezzanine. U.S. Department of Agriculture (USDA), recent reThink Wood infographic (www. An 18-story student residence—one Softwood Lumber Board (SLB), and rethinkwood.com) highlights 17 tall of the tallest mass timber buildings in the Binational Softwood Lumber Council wood buildings built in the past five years, world—is also under construction at the (BSLC), the competition was the first including: University of British Columbia (UBC). The step in a process to showcase the safe • Treet – Norway – 14 stories, 2014 structure, Brock Commons, is a hybrid application, practicality, and sustainability • Trafalgar Place – United Kingdom – 10 system comprised of CLT floor slabs, of tall wood structures (minimum 80 feet stories, 2015 glulam columns, steel connectors, and in height) using mass timber, composite • Forté – Australia – 10 stories, 2012 concrete cores. Scheduled for completion in wood technologies, and innovative building • Banyan Wharf – United Kingdom – 10 2017, it has been designed to achieve LEED techniques. It was created to provide stories, 2015 Gold certification. scientific and technical support for the Closer to home, architect Michael Green UBC is a strong proponent of utilizing design and construction of tall wood foreshadowed his work on the T3 project wood for its carbon benefits, and Brock buildings, and the winners received a with the 96-foot-tall Wood Innovation and Commons is just the latest of several mass combined $3 million in funding to further Design Centre in British Columbia, Canada. timber buildings on its campuses. develop their projects. 8 MASS TIMBER IN NORTH AMERICA EDUCATIONAL-ADVERTISEMENT

Photo courtesy of naturally:wood

Brock Commons Location: University of British Columbia, Vancouver, Canada Architect: Acton Ostry Architects Structural Engineer: Fast + Epp CONTINUING EDUCATION CONTINUING

In the Pacific Northwest, the developer/ STRUCTURAL PERFORMANCE a standard fire that reached over 1,800 architect team responsible for The Radiator AND LIFE SAFETY degrees Fahrenheit in the first 90 minutes has also designed an eight-story (85-foot- There are a number of factors propelling of exposure. While only seeking a 2-hour high) residential building known as the increased use of mass timber by North rating as required by building code Carbon 12. The building includes a heavy American building designers, most notably provisions, the test specimen lasted 3 hours timber gravity frame, CLT floors, and CLT the precedent of mass timber structures 6 minutes. This test, along with a series core walls. The building is expected to elsewhere in the world, and the abundance of CLT wall and floor tests conducted by break ground in late 2016. of research demonstrating its safety and FPInnovations, was used to substantiate Given that wood buildings over six structural performance. the performance of CLT, leading to its stories are not currently within the Because glulam and SCL have a long recognition in the 2015 IBC. prescriptive height limits of the IBC, history in the market, a great deal of Until a few years ago, CLT research designers of taller projects must follow an research and design data is available for centered largely on European-made alternative means process in consultation these products. As such, this section focuses products and design requirements of the with the Authority Having Jurisdiction on recent research related to CLT and the European market, which is where most over appeal of the building project. viability of tall wood buildings. of the projects were being built. However, However, the ICC Board of Directors In 2012, for example, the American there has been a proliferation of recent recently approved the formation of a Tall Wood Council sponsored an ASTM E119 studies and data specific to North America. Wood Ad Hoc Committee. Comprised fire endurance test on CLT. A 5-ply CLT Research is being supported by a variety of 7 of stakeholders, code officials, and other specimen (6 ⁄8 inches thick) was covered organizations, including the SLB, BSLC, 5 interested parties, the committee will on each side with a single layer of ⁄8- USDA Wood Innovation Grant program, study tall wood construction, and their inch Type X gypsum wallboard loaded Natural Resources Canada, FPInnovations, findings may contribute to code changes to the maximum load attainable by the and the Canadian NEWBuildS Network, as for the 2021 IBC. test equipment. It was then exposed to well as designers such as Arup. EDUCATIONAL-ADVERTISEMENT MASS TIMBER IN NORTH AMERICA 9

The following sections on fire performance and structural/seismic performance are RESEARCH LIBRARY WWW.RETHINKWOOD.COM excerpted from the paper “CLT Research: For current mass timber research in the United States and worldwide, including Available and Accessible to North American CLT and tall wood buildings, the reThink Wood website includes a library of stud- 3 Building Designers” published in Wood ies, categorized by topic area and updated regularly. Design Focus magazine. For a complete list of research references, download the paper at: www.woodworks.org/wp-content/uploads/ thickness needed to accommodate fire- CLT-Research_Podesto_Breneman.pdf. on the design examples in the fire chapter resistive requirements. When structural of the U.S. CLT Handbook by allowing for strength and fire resistance are so Fire Testing laminations of varying thicknesses. Further intertwined, a prescriptive method for Fire performance, and specifically exposed study and additional full-scale panel determining fire resistance cannot offer fire resistance, may be one of the most asked tests continue to be done, not necessarily material efficiency. CONTINUING EDUCATION CONTINUING about areas in terms of additional research to prove legitimacy of the CLT char A comparison of the ASTM E 119 information—but, in reality, suffers more from methodology, but to support expansion fire-tested CLT performance and the misperception than lack of research data. of its applicability. Areas of expansion predicted performance using the calculated The predictability of wood’s char rate include new assembly configurations (in method demonstrates the reliability of char has been well-established for decades and pursuit at the Advanced Composite Lab calculations for CLT. Such a comparison can has also been recognized for years in U.S. and the University of Maine), exploring be done by independent designers but is also building codes and standards. However, performance under nonstandard fires and shown in graphical form with tests done prior the use of existing code provisions has not developing performance prediction tools. to 2013 in the fire chapter of the U.S. CLT been commonplace in modern commercial It is commonly asked why there are Handbook (Karacabeyli and Douglas 2013). construction; therefore, jurisdictional not Underwriters Laboratories (UL) or The impressive ability of CLT to meet comfortability with an expanded use of equivalent tested assemblies available for two and three hours of fire resistance with those provisions for the purpose of CLT CLT, and this area is often suggested for and without gypsum protection seems design has presented a challenge. research. The truth is that the calculated to be overshadowed by concerns about The 2015 NDS includes a char method offers more flexibility to designers its combustibility. The increase of wood calculation procedure to provide calculated than a series of UL assemblies and provides volume raises necessary questions about fire resistance of up to two hours. It expands more precision with regard to the panel the additional potential for structural

Design Building, University of Massachusetts (UMass) Location: Amherst, Massachusetts Architect: Leers Weinzapfel Associates Structural Engineer: Equilibrium Consulting

Photo courtesy of Alexander Schreyer, UMass 10 MASS TIMBER IN NORTH AMERICA EDUCATIONAL-ADVERTISEMENT

contribution to combustion and what notable addition of testing procedures for follow the Federal Emergency Management it means for fire safety. Full-scale fire evaluating the in-plane strength of CLT Agency (FEMA) P-695 process, which is tests completed by FPInnovations and panels. Having acceptance criteria for CLT currently underway, to rigorously quantify funded by Natural Resources Canada panels allows manufacturers to pursue seismic performance factors (R, Ωo, and and others are intended to help address directed testing culminating in an ICC-ES Cd) for a type of CLT shear wall system for this issue. In association with a 13-story evaluation report. Evaluation reports are use following seismic design procedures mass timber demonstration project (12 helpful in gaining jurisdictional approval of ASCE 7. This comprehensive study was stories of CLT over one story of concrete) for new materials, further assisting preceded by a site- and building-specific in Quebec, the provincial government designers. Current North American CLT FEMA P-695-like study to estimate whether there funded full-scale CLT fire tests to manufacturers are promising evaluation a seismic response modification factor of R prove CLT’s equivalence to 2-hour-rated reports in the near future. = 4.5 met the performance objectives of the noncombustible construction. Research into connection technology for candidate design (Pei 2013). One series of full-scale compartment North American CLT has included static To date, CLT shear wall systems for CONTINUING EDUCATION CONTINUING tests compared the performance of light- and cyclical testing of self-tapping screws seismic resistance have been designed using gauge steel, light-frame wood, and CLT. for CLT-to-CLT and CLT-to-wood beams conservative seismic performance factors or Tests included a three-story encapsulated performed at the University of British using advanced performance-based seismic CLT apartment simulation that ran for Columbia in Vancouver, Canada (Hossain design procedures. The completion of this three hours. Results of the apartment 2015 and Ashtari 2014). In addition to research will be a significant step toward simulation show the effectiveness of connection behavior, Ashtari et al. looked easier design of CLT shear wall systems for encapsulation in significantly delaying at the behavior of a horizontal CLT floor seismic resistance and eventual inclusion CLT’s potential contribution to fire system as a diaphragm of a lateral force- of CLT in the seismic structural design growth and proved that the structure can resisting system. standards used throughout the United States. withstand complete burnout. Using CLT components in lateral Another research project evaluating CLT Another test focused on a 25½-foot CLT (wind or seismic) force-resisting systems walls for seismic resistance is a Network stair/elevator shaft (exposed on the inside is an area of considerable ongoing for Earthquake Engineering Simulation face with two layers of gypsum protection research. A much-anticipated project is (NEES)/National Science Foundation (NSF) on the fire side) and studied the smoke the Development of Seismic Performance project investigating seismic-resistant tall propagation and leakage as well as its Factors for Cross Laminated Timber with wood buildings for the Pacific Northwest structural stability as a fire exit. The test ran principal investigator John van de Lindt of (Pei 2014a). This multi-university project for 2 hours and showed no sign of smoke or Colorado State University. This project will is executing an inclusive process to develop heat penetration into the shaft. Research recently completed by FPInnovations and funded by Natural Resources Canada/The Canadian Forest DESIGN GUIDANCE AND RESOURCES Service evaluated the ability of selected fire There are many resources available to architects and engineers designing mass stops and sealing joints in CLT assemblies, timber projects. both for panel joints and around through- penetrations to prevent the passage of • For general information, the reThink Wood website (www.rethinkwood.com) hot gasses and limit heat transfer. Results offers an expanding library of materials on mass timber products, research, showed that products commercially building examples, and developments related to tall wood buildings. available for use in light-frame and concrete construction are also feasible for CLT • The National Design Specification (NDS) for Wood Construction (www.awc. applications (Dagenais 2014). org) is the IBC-referenced design standard for lumber, glulam, SCL, and CLT, including fire design, fasteners and connections, etc. A mass timber building in Structural and Seismic Testing the United States cannot be designed without the NDS. There has been a proliferation of industry and academic research initiatives to • The U.S. CLT Handbook (www.rethinkwood.com) includes detailed technical build out the body of knowledge on information on the use of CLT. It should be used in conjunction with information CLT structural performance in U.S. provided by manufacturers since most CLT currently available in North America applications. Some have pertained to is propriety (i.e., lay-ups aren’t standard across suppliers). standards and testing methods suitable to North America, such as the investigation • APA Product Reports (www.apawood.org/product-reports) signify a product’s of testing protocols for evaluation of compliance with relevant provisions of the model building codes. The L-Series in-plane shear strength of CLT panels covers products manufactured from lumber, veneer, or other wood base, such as (Gagnon et al. 2014). These and other glulam and structural composite lumber (SCL). efforts have led to the new “Acceptance Criteria For Cross-Laminated Timber For one-on-one support (at no cost), technical experts at WoodWorks are available Panels for Use as Components in Floor to provide free project assistance related to nonresidential and multifamily and Roof Decks” (AC455) from the buildings in the United States, including those using mass timber. Designers have ICC Evaluation Service. This product the option of contacting an expert in their region (www.woodworks.org/project- evaluation standard is generally assistance) or emailing [email protected]. compatible with the ANSI/APA PRG 320 qualification requirements with a EDUCATIONAL-ADVERTISEMENT MASS TIMBER IN NORTH AMERICA 11

seismic performance goals, as well as a variety to North American products and building of potential high-performance/low-damage codes, many are predicting a dramatic seismic force-resisting systems. Since the increase in mass timber construction, 2014 publication on this project, the research similar to the increase seen in Europe over team has progressed to running a series of the past 10 years. experimental tests of CLT rocking walls at “Mass timber structures have been Washington State University. Additional built in North America for more than 100 research is being performed on the design of years,” says Epp, citing the nine-story Butler CLT rocking walls at Clemson (Gu et al 2014) Building in Minneapolis, Minnesota, built and the University of Alabama. in 1908 and still in use. “They’ve proven The first full-scale application of CLT to be inherently durable, and research rocking walls is expected to be on the is providing the information on fire Framework building in Portland, Oregon, protection, acoustics, etc., that will make CONTINUING EDUCATION CONTINUING which will use the 12-story-high rocking it easier to design mass timber buildings walls as a self-centering seismic lateral in the United States using next-generation force-resisting system. Full-scale testing products. With the advantages offered by is currently underway at Oregon State these materials—performance, construction University and Portland State University. speed, carbon footprint, opportunity for For more information on CLT innovation, beauty—the interest we’re research, another good source is the seeing within the design community can paper “An Overview of CLT Research only increase, especially as uptake from and Implementation in North America”4 developers continues to lend credence to the developed for the 2016 World Conference on cost competitiveness of these structures.” Timber Engineering. END NOTES The Research Behind Tall Wood 1“Wood as a Restorative Material in While some of the CLT research noted above Healthcare Environments.” FPInnovations. has implications for tall wood buildings, 2015. https://fpinnovations.ca/media/ numerous studies have also focused specifically publications/Documents/health-report.pdf on the feasibility of wood high-rises. 2“Wood and Human Health.” FPInnovations. One recent example, “Mass Timber High- 2012. https://fpinnovations.ca/media/ Rise Design Research: Museum Tower in publications/Pages/default.aspx Los Angeles Reimagined in Mass Timber,”5 3Podesto, Lisa and Scott Breneman. “CLT demonstrates the design of a code-compliant, Research: Available and Accessible to North high-rise mass timber apartment tower in American Building Designers.” Wood Design Los Angeles. Using the existing reinforced Focus. V.26, N.1. www.woodworks.org/wp- concrete Museum Tower Apartment building content/uploads/CLT-Research_Podesto_ as a basis, the study demonstrates architectural, Breneman.pdf structural, and fire performance improvements 4Shilling, Pei and D. Rammer, M. Popovski, and trade-offs of the mass timber design T. Williamson, P. Line, J. van de Lindt. compared to a reinforced concrete design. “An Overview of CLT Research and Another report, the “Survey of Implementation in North America.” 2016 International Tall Wood Buildings,”6 offers a World Conference on Timber Engineering. look at ten international tall wood buildings, 5Timmers, Matthew and Andrew Tsay Jacobs, and presents common lessons learned from Bevan Jones, James O’Neill. “Mass Timber the experiences of key stakeholders, including High-Rise Design Research: Museum Tower the developer/owner, design team, Authorities in Los Angeles Reimagined in Mass Timber.” Having Jurisdiction, and construction team. 2015 Structural Engineers Association of To stay abreast of research related to mass California Convention Proceedings. http:// timber, including CLT and tall wood buildings, www.woodworks.org/wp-content/uploads/ the reThink Wood website (www.rethinkwood. Mass-Timber-Highrise-Design-Research.pdf com) includes a library of studies, categorized 6“Summary Report: Survey of Tall Wood by topic area and updated regularly. Buildings.” Forestry Innovation Investment. Binational Softwood Lumber Council. 2014. CONCLUSION http://www.rethinkwood.com/webform/ Over the next decade, as researchers get-summary-report continue to provide information specific

reThink Wood represents North America’s softwood lumber industry. We share a passion for wood and the forests it comes from. Our goal is to generate awareness and understanding of wood’s advantages in the built environment. Join the reThink Wood community to make a difference for the future. Get the latest research, news, and updates on innovative wood use. Visit reThinkWood.com/CEU to learn more and join.