May 16, 2017
By John Metras, Ralph Austin, and Karla Fraser
The Brock Commons Tallwood House at the University of British Columbia (UBC) is nearing completion. This 18-storey timber hybrid residence in Vancouver will be the tallest contemporary mass-wood building on the planet. It is the first mass-wood, concrete, and steel project taller than 14 storeys.
As part of UBC’s mandate to increase student housing on campus, Brock Commons will have living capacity for more than 400 upper-year and graduate students. Each unit contains a kitchen and bathroom, with floorplans ranging from single-bed studios to four-person accommodations. Study and social spaces will be located on the ground floor with a student lounge on the 18th floor, where the wood structure will be left exposed for demonstration and educational purposes.
Vancouver’s Acton Ostry Architects designed the building in collaboration with structural engineer Fast + Epp, along with tall wood advisor Architekten Hermann Kaufmann of Austria. UBC Properties Trust is managing the project.
The school’s building requirements showcase the university’s commitment to sustainability. Wood, a renewable material, was chosen in part to reflect this commitment. The building was also designed to meet Leadership in Energy and Environmental Design (LEED) Gold certification. The project will be a living laboratory in which UBC faculty and graduate students, as well as architecture, engineering, and forestry practitioners, can collaborate with the school’s operational staff and industry partners on the design, development, and construction of other tall wood buildings. It represents yet another impressive wood structure on the school’s Vancouver campus, added to a list that includes the AMS Student Nest, Engineering Student Centre, Centre for Interactive Research on Sustainability (CIRS), Bioenergy Research and Demonstration Facility, and Earth Sciences building. (Previous Construction Canada articles on these projects include “Building the Earth Sciences Building at the University of British Columbia” by Eric Karsh, M.Eng., P.Eng., Struct.Eng, MIStructE, Ing. and “Think Globally, Act Locally: Net-zero Impact Development” by Blair T. McCarry, P.Eng., PE, ASHRAE Fellow, LEED AP. Articles on wood buildings on UBC’s Okanagan campus include “Constructing an All-wood Building: The Wood Innovation and Design Centre” by Werner Hofstätter and “Overcoming the Learning Curve: Design and Construction of the UBCO Fitness and Wellness Centre” by Patrice R. Tardif, LEED AP. Visit www.constructioncanada.net to read.)
Building and structure
The Brock Commons building is a hybrid structure; it has a concrete podium and two concrete-stair cores, with 17 storeys of cross-laminated-timber (CLT) floors supported on glued-laminated (glulam) wood columns. (For more on CLT, see previous Construction Canada articles like “Seismic Design with Wood” by Jim Taggart, FRAIC, and “Building with CLT: New Applications for Wood Structures in Ontario” by Kate Salmon. For more on glulam, see Taggart’s “Trees in the Tower: Designing the Surrey Memorial Hospital Critical Care Tower.”) The podium level is wrapped with curtain wall glazing and glass spandrel panels. An extensive CLT canopy runs the length of the building.
The main structure was completed in less than 70 days. The prefabricated mass-wood components, supplied by a Penticton, B.C.-based company, were delivered to the site in a just-in-time process as the structure was assembled. (“The panels arrived in Vancouver ready to be assembled like puzzle pieces, allowing for swift construction. We loaded them on the truck in exactly the same way the installer was going to pull them off, so basically they pulled the panel off the trailer on the site, and put it in place,” explained Bill Downing, president of Structurlam Products, which supplied the CLT panels and glulam for the project.) This allowed for efficient material-handling and avoided onsite storage. Construction is currently being focused on interior elements, with completion expected around the time this magazine is published—four months faster than a typical project. The building is expected to open this summer.
The floor structure is composed of five-ply CLT panels supported on glulam columns on a 2.85 x 4-m (9.4 x 13-ft) grid. This results in the CLT panels acting as a two-way slab diaphragm, eliminating the need for load-carrying beams. To avoid a vertical load transfer through the CLT panels, a steel connector allows for a direct load transfer between the columns and also provides a bearing surface for the CLT panels. (For more, see the article, “Specifying Modern Timber Connections” by Maik Gehloff, Dipl.-Ing. (FH), M.A.Sc. Visit www.constructioncanada.net/specifying-modern-timber-connections.)
The roof is made of prefabricated sections of steel beams and metal decking, with the roofing membrane pre-applied to achieve quick watertightness during construction. The building envelope is a prefabricated panel system clad with wood-fibre high-pressure laminate (HPL).
Using this combination of mass timber, concrete, and steel provides a cost-effective and sustainable solution to construction challenges, as well as options to improve building performance and design. There are several benefits associated with using mass timber-concrete-steel hybrid systems, including:
In this particular project, there was another benefit—exemplifying the wood products’ use in a high-rise building to inspire other design teams working in this burgeoning field.
“A key achievement for the Brock Commons Phase 1 project is the design of an innovative mass-timber structural system that is genuinely economically viable, repeatable, and adaptable to other building typologies and uses,” explained Russell Acton, a principal at Acton Ostry Architects. “This project will positively impact the wood, development, and building industries in British Columbia.”
This was echoed by Michael Giroux, president of the Canadian Wood Council.
“Above and beyond further establishing the safety, economic, and environmental credentials of massive timber products used in buildings, UBC’s Brock Commons will inspire current and future generations of architects and engineers to consider its use—ultimately creating another and most welcomed construction choice for builders and new markets for wood product producers,” he said.
Speed and ease of construction
The construction of Brock Commons has raised awareness about the opportunities afforded by prefabrication and manufacturing techniques using engineered wood products. Two of the most notable benefits are speed and ease of construction.
Once the concrete foundations and podium level were complete, the concrete elevator/stair cores were formed and placed from Level 2 to the roof using a unique climbing formwork system that made it possible to pour two cores, two floors per week. At this point, the steel angles that support the CLT panels at the cores were installed.
Once that work was completed, installation of the wood elements began. The first of these, the glulam columns, began on June 6, 2016. The first CLT floor (i.e. Level 3 ) was completed by June 10, while the last (i.e. Level 18) was completed by August 9—it took less than 10 weeks to complete 18 levels.
The assembly crew of 10 people would complete an entire floor plate installation on a three-day work cycle. The site worked six days a week, except statutory holidays, which resulted in two complete floor levels, each about 910 m2 (9800 sf), achieved every week.
On Day 1 of the cycle, the CLT floor plate would be installed. The three delivery trucks were scheduled to be received onsite as elements were required. This was necessitated by the site’s space constraints, which would not permit any overnight storage of wood elements.
Deck installation typically took 5.5 hours. Once this was finished, the splines connecting the panels and the drag straps connecting wood elements to concrete elevator shafts would be installed. At the same time, work began on installing the concrete acoustic topping three levels below the CLT installation. The setup of the concrete pumper and off-load of the five concrete trucks required was easily completed within the same timeframe as the CLT installation.
The second day of the installation cycle would see handrails installed, followed by placement and erection of the glulam columns on the CLT deck. At the same time, on the previous floor below, the curtain wall panels would be installed. A total of 22 envelope panels could be installed in approximately eight hours. This installation was critical in order to meet the encapsulation requirements for the permit.
On the final day of the cycle, the team installing the wood structure was able to complete installation of the column alignment braces, as well as installation of the L-angle bracket along the building perimeter. This enabled installation of the curtain wall panels. As well, flashing installation between the panels could be completed.
At the same time, and five levels below, the underside of the CLT panels had non-paper-faced Type X gypsum wallboard installed. This additional drywall encapsulation was necessary to meet the permitting requirements of the building.
Reduced waste and noise
Accurate timing and co-ordination of all deliveries was critical. Precise hourly scheduling ensured the site never became overly congested. One notable difference for this project was the consistent speed of installation. Wood assembly is not only considerably faster than concrete, but using it significantly reduces the amount of truck traffic through the residential neighbourhood. The lack of concrete, formwork, reinforcing, shoring, and reshoring greatly reduced onsite waste generation and subsequent waste-handling.
Additionally, the prefabricated wood and envelope components produced nearly zero site waste upon delivery. Since both elements are completed in a separate manufacturing facility, any waste generated can be managed—either for reuse, recycling, or consolidation—without ever coming to the site.
One of the side benefits was the significant reduction in noise generated from onsite assembly and construction processes. This was attributable to the accuracy of the machining of the wood components, which ensured a precision fit to allow fast, easy, and quiet assembly.
The manufacturing process of CLT is completed using a computer numerical control (CNC) machine, which enables very tight tolerances on the completed panels. For Brock Commons, all the penetrations for the mechanical, electrical, and plumbing (MEP)infrastructure were precisely cut at the fabrication facility. This ensured the installation in the finishing stages was exactly where it was designed to be.
The planning process for Brock Commons involved the virtual design company CadMakers, which produced a comprehensive 3D model of the project using input from the consultants, general contractor, trade contractors, and suppliers. Using this comprehensive 3D modelling approach, which was employed by the entire design and construction team, the general contractor significantly reduced the amount of RFIs and change orders because conflicts were discovered and resolved in the design stage.
In addition to the 3D model, the virtual design company was able to create animations showing work sequences. This was especially helpful for the formwork contractor, wood installation contractor, and envelope panel contractor for planning their crew size, work sequences, and safety plans.
As mentioned, UBC views its campus as a living laboratory where collaboration and creativity are encouraged. Certainly, its construction has already proved that to be the case. The collaboration between owner, consultants, general contractor, trade contractors, and suppliers was gathered and assembled by the virtual design company, then distributed to each of the participants.
The use of CLT and glulam as primary structural elements for Brock Commons was a perfect fit for this collaborative construction approach. The information contained in the comprehensive 3D model was easily shared with the engineered wood supplier and fabricator. This allowed those elements and steel connections to be digitally fabricated to a high degree of accuracy, the mechanical and electrical penetrations were completed, and the centre of gravity was determined so the panels would fly flat when lifted into place by the tower crane. The 3D animations helped determine the correct installation sequencing and, consequently, truck loading. As a result, when the wood installations began on June 6, there were no stumbling blocks.
The speed and simplicity of construction of Brock Commons was eye-opening for UBC as a building owner. Development of new student housing to meet increasing demand is a priority for the university. The project has demonstrated safe and sustainable residence facilities can be constructed with engineered wood products on a shorter timeline than traditional reinforced concrete structures. This experience has allowed UBC to confidently deliver much-needed student residence beds to tight schedules with must-have, start-of-term deadlines. Future engineered wood projects are also expected to benefit from a reduction in the construction period and associated interest costs as a result of the shorter overall project delivery time.
The significant reduction in noise and truck traffic associated with prefabricated wood construction is a bonus, as it allows for easier development of new facilities on campus with less disruption to teaching, research activities, and the lives of neighbouring residents. This is important at UBC, where most new building projects are in-fill developments in close proximity to academic facilities, student residences, and market housing neighbourhoods. This benefit clearly translates to any dense urban environment.
Finally, the project has helped the university achieve its ‘living laboratory’ goals, providing interdisciplinary learning and research opportunities for UBC faculty, students, and staff. This involves not just the study of the innovative engineered wood structure, but also analysis of the integrated design and construction process, which placed an emphasis on design for constructability. Hopefully, the lessons learned from creating Brock Commons can help inform and transform the way buildings are designed and constructed in Canada and around the world. (For more information on Brock Commons Tallwood House, visit naturallywood.com or contact Wood WORKS! BC through www.wood-works.ca/bc.)
John Metras is managing director of infrastructure development at the University of British Columbia (UBC). He and his team are responsible for planning and development of institutional facilities at the school, collaborating with campus stakeholders to create spaces for learning, research, and campus life. Metras has more than 20 years of experience in facilities development and operations, including his previous position as director of plant operations. He can be contacted via e-mail at firstname.lastname@example.org.
Ralph Austin is a principal at timber installer Seagate Structures Ltd. With an extensive background as a labourer, forming carpenter, framer, foreman, superintendent, estimator, project manager, and general contractor, he has a range of construction experience in residential, multi-unit residential, and high-rise building construction projects. Austin started Seagate in 2002 with prefabrication as the hallmark of its construction projects. He can be reached at email@example.com.
Karla Fraser is a senior project manager with Urban One Builders. Trained in civil engineering technology, she worked in construction for more than 20 years in building construction, including infrastructure, commercial, and tower projects. She can be contacted via e-mail at firstname.lastname@example.org.
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