Building with CLT: New applications for wood structures in Ontario

by mdoyle | April 13, 2014 11:06 am

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By Kate Salmon, B.A.
Built in the 1970s, the Wayne Gretzky Sports Centre (WGSC) has been the hub of recreation and leisure activity in the Brantford community for over 35 years, offering visitors and residents year-round access to a wide range of programs and activities. In 2009, the southwestern Ontario city decided to expand and renovate the centre’s aging infrastructure to accommodate competitive training and increased community demands. Designed by CS&P Architects in association with MMMC Architects, the $58-million expansion was implemented under a construction management contract.

The first phase of the new centre, which opened in June 2011, provided:

• four-pad arena;
• change rooms;
• restaurant;
• café;
• multi-purpose rooms;
• gymnasium; and
• indoor running track.

The second phase, completed in September 2013, upgraded the existing facilities and added a 25-m (82-ft) lap pool, wellness centre, therapy pool, fitness centre, aerobics room, and a dry-land training centre. It also completed the site’s total redevelopment, with new pedestrian walkways and outdoor recreation spaces. A significant feature of the second phase was the use of a cross-laminated timber (CLT) roof deck system over the new pool—the first commercial use of CLT in Ontario.

From the outset, the use of wood was central to the design of the centre’s expansion. The original design concept featured a glued-laminated timber (glulam) and heavy timber roof deck system over the new pool. Glulam purlins would have spanned between the main glulam roof beams, with a 100-mm (3.9-in.) thick Douglas fir tongue and groove roof deck laid atop the glulam roof beam and purlin framing.

“Wood was such a predominant material in the original building, so it seemed logical to incorporate wood in a meaningful way in the design of the new facility,” says project architect Paul Marcoccia.

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When it came time to begin construction, however, the commercial-grade Douglas fir specified in the design proved difficult to source based on the specified dimensions. The design team carefully considered some other conventional material options with the construction manager and decided to investigate alternative solutions.

Enter CLT
The contractor proposed CLT as an alternative to the Douglas fir roof deck due to the material’s availability and speed of installation. Sourced from a manufacturer in Penticton, B.C., the province’s abundant supply of spruce pine fir (SPF) was converted into CLT panels at a production rate of 464 to 557 m² (5000 to 6000 sf) daily. The design team began evaluating the efficacy of the material in consultation with the client and the CLT supplier.

“Although the project team had never worked with CLT previously, it quickly became apparent this material was well-suited for the project. The original design intent would be maintained,” says Marcoccia.

After careful consideration, the selection of CLT for the centre’s roof deck system was accepted, and the Wayne Gretzky Sports Centre became a flagship project for the commercial use of CLT in Ontario. The required CLT panels, measuring 29.7 m² (320 sf) each, were manufactured over the course of two weeks and then delivered to the jobsite. The entire process took approximately three months.

Schedule implications
In addition to its design benefits, the CLT panel system significantly accelerated the roof deck construction. The simplified, crane-assisted installation required a reduced construction team of only six people, and the 1200 m² (12,916 sf) of CLT panels were installed within four days. All connections were screwed in place, and can easily be disassembled and re-used if any changes are proposed in the future.

The construction manager was able to shave two weeks off the schedule due to the speed of the CLT roof erection, saving approximately $40,000 in combined labour and energy consumption. The accelerated construction schedule also allowed subsequent finishing trades to begin work earlier than originally scheduled. In comparison to the metal roof deck used on the remainder of the facility, the CLT roof deck went up quicker, resulted in less waste, and reduced the labour requirement. Its ease of installation and opportunities for reuse make CLT an ideal construction material for institutional projects, where schedules and budgets are often constrained.

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Environmental benefits
CLT can provide tangible sustainable design benefits on many levels. As a renewable, locally produced building material, wood’s use can help environmentally conscious clients achieve Leadership in Energy and Environmental Design (LEED) certification.

“It’s a highly adaptable structural material, and helped to offset the embodied energy of other materials used in the building,” Marcoccia explains. For example, the 120 m³ (4237 cf) of CLT sequestered 40 metric tonnes of carbon dioxide (CO₂), avoiding 80 metric tonnes of greenhouse gas (GHG) emissions.

The use of wood has positive implications in multiple components of the LEED certification system, and can result in various credits for new construction in v.4, including:

• Location and Transportation (LT), Surrounding Density and Diverse Uses;
• Sustainable Sites (SS), Site Development–Protect or Restore Habitat;
• Energy and Atmosphere (EA), Optimize Energy Performance;
• Indoor Environmental Quality (EQ), Low-emitting Materials;
• EQ, Thermal Comfort;
• EQ, Interior Lighting; and
• EQ, Acoustic Performance.¹[4]

LEED points associated with CLT usage are well-earned because the product requires no maintenance when used indoors and has a lifespan comparable to heavy timber, outperforming other building materials, such as galvanized metal roof deck systems, with lower embodied energy. Even more important from an environmental standpoint, CLT production generates negligible waste as the panels are produced in a controlled environment and any off-cuts are burned onsite to supplement the heating of the production facility.

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Of central importance to the design and construction team was the opportunity to support Canadian manufacturing. The forest sector contributed $24 billion to the gross domestic product (GDP) in 2012, employing 593,200 people and supporting 192 communities.²[6]

Design implications
“Incorporating CLT into the project allowed us to utilize new materials and technology in a manner that we had not previously attempted,” says Marcoccia.

However, the use of wood in the new centre went far beyond the CLT panels installed above the pool. The existing glulam roof beams, originally located in the arena that Wayne Gretzky played in as a youth, were carefully salvaged and re-finished for reuse as part of the new pool roof structure. The combination of the re-finished glulam roof beams and the new CLT panel roof deck system makes for a warm roof structure visible to all using the pool, as well as visitors looking into the pool from the adjacent double-height public gallery space.

Existing purlins from the original arena were also re-finished and re-purposed as exterior bench seats located throughout the project site. Reusing the existing glulam beams and purlins was a critical strategy for connecting the new building with the original facility’s history on the site, and resulted in less material consumption for the project as a whole.

To conceptually connect all interior and exterior spaces in the new centre, the ceiling plane at the feature bulkhead in the main public gallery was enriched with clear-stained solid maple slats, which extend horizontally and also wrap vertically at the end wall of the bulkhead to continue as a wall finish. Wood is also featured in the restaurant, the Lookout Lounge, where wood wall finishes complement the wooden hockey stick shafts used as accents behind the bar.

“CS&P Architects created a world-class facility with their creative use of wood features,” says Sandy Jackson, director of recreation at the City of Brantford. “The inclusion of wood has provided a warmth that contrasts the concrete structures typically used for pools and arenas, creating a comfortable, calm setting for families and athletes to enjoy.”

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CLT use on a smaller scale
CS&P Architects also investigated alternate applications of CLT in the design of three unique picnic shelters for Chinguacousy Park, in Brampton, Ont. From the outset of the design process, CLT was considered an appropriate structural system to satisfy the design intent. The material provided long two directional spans, eliminating the requirement for a secondary structure and creating a simplified, smooth surface which is easily maintained and aesthetically pleasing.

“It was important for the structures to fit within the surrounding context of Chinguacousy Park,” says project architect Nolan Bentley. “The CLT roof deck provides a flat simple element which relates to the horizon of the park.”

Rather than use a wood mill-deck or conventional wood deck and steel secondary system, the design team wanted to support the new CLT technology. The CLT panels were manufactured in Chibougamau, Que., and installed in a few days, which proved advantageous to the project’s compressed construction schedule. The process required only three staff, including a crane operator, and resulted in no onsite waste. By using locally sourced CLT, the embodied energy involved in import and transportation was minimized, and the client was pleased with the use of Canadian resources to support sustainable design.

When used outdoors, CLT retains its colour most effectively when stained every year; however, the material is much easier to maintain than a conventional wood roof deck due to its single, flat surface. The 297 m² (3200 sf) of custom-made CLT panels cost $201.82/m² ($18.75/sf), which is slightly elevated in comparison to alternate roof deck options, but Bentley envisions the inception of standardized panels as a means of reducing the product’s cost.

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“As demand increases, manufacturers may start to offer standard-sized panels that are cheaper and produce less waste. These standard sizes will be considered in the design process, although the customizability of CLT will still prove advantageous in many cases,” says Bentley.

Future use of CLT
With so many potential benefits to offer a project’s budget, schedule, and sustainable design goals, CLT is proposed for several CS&P projects currently in the design stage. The early concept stages of a new project provide the best opportunities for testing the possibilities of various structural systems in terms of their fit with the project goals. Project considerations such as intense time frames, challenging budgets, and the overall implications of climate change have often pointed toward greater use of the CLT system.

“It’s an industry close to home and is relatively easy to get locally, which is a key element to a sustainable culture,” notes Craig Goodman, a senior design principal at the firm. The design team is focused on the full impact of each early concept decision, with careful consideration given to the long-term practicality of various building systems and their impact on the environment.

Currently, CS&P is examining the benefits of CLT for numerous projects and a mix of building types. The most common application of CLT is mid-rise infill residential projects—a building type whose use of CLT has been well-tested in Europe and the lessons of adaptability are clear, with emphasis on short spans, multiple shear panels, and a cellular spatial organization.

For example, CLT has been proposed for a Toronto neighbourhood church, featuring a single auditorium volume sitting as a second floor over an undercroft of multiple smaller spaces. The upper auditorium has the character of a small recital hall with the goal of maximizing the opportunities for exposed wood finishes. The metaphor of the auditorium as a communal musical instrument with an exposed interior wood lining has interesting implications for the benefits of the CLT system.

In the education sector, CLT is currently being considered for a classroom addition to a boys’ independent school in Toronto. The school has adapted an older single-storey public school as the initial home for classes, but is now proceeding through a series of phased additions and alterations to meet increased program demands.

The original 60-year-old building features a post-and-beam wood frame system with tongue and groove Douglas fir wood planking for the roof deck. The adaptive reuse of this building is focused in part on exposing these previously hidden structural systems and celebrating the use of wood, which offers a warm and acoustically soft interior. For the new addition, CLT was proposed as a modern interpretation of the original building shell which would benefit the project’s tight schedule and allow the school to remain occupied during construction.

Conclusion
The examples outlined indicate how a rigorous design methodology can lead to innovative CLT solutions for nearly any building type. The alignment of a project’s site, function, schedule, and desired environmental impact is leading architects at CS&P to design innovative solutions with the most relevant of available new technologies.

Notes
¹ Visit www.usgbc.org/credits/new-construction/v4[9] for more information about LEED v4. (back to top[10])
² For more information, visit www.fpac.ca/index.php/en/page/industry-by-the-numbers[11]. (back to top[12])

[13]Kate Salmon is a marketing co-ordinator at CS&P Architects, a Toronto firm which offers a range of architectural, planning, interior, and urban design services to institutional, recreational, commercial, and residential clients in both the private and public sectors. Her writing consolidates the expertise of several CS&P staff and benefits from the firm’s 51 years of experience in the construction industry. She can be reached at ksalmon@csparch.com[14].

Source URL: https://www.constructioncanada.net/building-with-clt-new-applications-for-wood-structures-in-ontario/

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