Wood in civic buildings

Dowel-laminated timber (DLT) panels have alternate 2x4 and 2x6 members creating a corrugated soffit. The 600-mm (24-in.) gap between panels accommodates lighting and is concealed with an acoustic panel. Photo © Dave Best
Dowel-laminated timber (DLT) panels have alternate 2×4 and 2×6 members creating a corrugated soffit. The 600-mm (24-in.) gap between panels accommodates lighting and is concealed with an acoustic panel.
Photo © Dave Best

The RFP required the project comply with the Wood First bylaw recently adopted by the village, and aspires to the creation of a “100-mile building,” (the Wood First Act was passed by the British Columbia government in October 2009 with the aim of generating demand for wood products, promoting climate-friendly construction, and stimulating economic activity in forest-dependent communities). Maximizing the use of locally harvested wood, processing capacity, manufacturing, and fabrication capabilities and craft skills would combine to provide the greatest possible social and economic benefits to valley communities.

Accordingly, UAA set up an integrated design process, in which various municipal departments, user groups, local industry representatives, and members of the broader community were invited to contribute their ideas and expertise to the conceptual development of the project. In bringing the community together, the meetings and open house events also helped build a broad consensus and strong commitment to the project.

By identifying the wealth of local materials, resources, and labour that could be incorporated into the project, the consultation process also ensured that, by reducing the effect of transportation, the embodied energy, carbon footprint, and life-cycle impacts of the building would be minimized. The result is a building incorporating approximately 288 m3 (10,171 cf) of wood products harvested mostly from forest licenses within 50 km (31 mi) of the site and processed at a local mill.

The building is organized and oriented to maximize the effectiveness of passive design strategies, with a long linear form on the east-west axis, permitting natural daylighting and cross ventilation. Strategically located roof overhangs control solar exposure. Window locations are carefully calibrated to capture  views of the mountains and connect to the park while maintaining less than 40 per cent window-to-wall ratio for energy efficiency.

The formal inspiration for the building came from the simple utilitarian sheds dotting the Columbia Valley. Unlike chalet-style roofs, low-pitched roofs allow snow to build up over the winter, with little danger from shedding snow or large icicles.

The building is clad in charred wood siding, a reference to the agricultural and ranching traditions of the valley. The charring machine, created by a local millwright took the form of a pizza oven fitted out with propane burners. The depth of char was controlled by varying the speed at which the material was run through the oven.

The interior spaces are defined by the variegated dowel-laminated timber (DLT) roof structure, and are layered with minimal wood detailing at key areas (DLT is a mass timber structural panel constructed of standard dimensional lumber, friction-fit together with hardwood dowels, not requiring the use of nails, screws, or adhesives. This combination results in a structural system with a high potential for demountability, adaptability, and reuse). The ramp down into the hall is lined with a wood screen, filtering views into the hall, and referencing the pine forests. Composite wood and acoustic panels provide sound attenuation at the stage.

Beyond its energy-efficient design and locally sourced materials, the building acts as the living room and social heart of the community. Co-locating the library and community hall provides cross-pollination and increases overall use. The community kitchen was designed with the local seniors’ group to ensure accessibility and ease of use.

The siting of the building creates a variety of exterior rooms within the public realm that can be occupied throughout the year. Indoor-outdoor connectivity promotes social well-being and expands year-round use of the adjacent park.

The building structure is relatively simple, with a post-and-beam frame supporting a shallow shed roof. With a tight budget, it was important to give the various product suppliers in the region equal opportunity to participate in the project. Accordingly, structural engineers Equilibrium Consulting, Inc., created a schematic design and performance specification that could accommodate either glue-laminated (glulam) timber or LVL columns and beams and CLT, nail-laminated timber (NLT), or DLT panels.

DLT panels of 1220-mm (48-in.) wide and lengths up to 6000 mm (236 in.) using 2×4 and 2×6 Douglas fir dimensional lumber were prefabricated. The panels were hand assembled using jigs to ensure accuracy and consistency, with the members fastened together using beech dowels. Adhesives were not employed to fabricate the panels. The tolerances achieved were in the order of 2 mm (79 mils), much finer than those for cast-in-place concrete foundations, and remarkable given that no computer numerically controlled (CNC) machinery was used. When completed, the DLT panels were transported to the site in a choreographed sequence to maximize efficiency.

Alternating the 2×4 and 2×6 timbers created a self-finished ceiling with a variegated texture. By spacing the panels 600 mm (24 in.) apart, the modular system was able to integrate lighting services in the gaps, which were later bridged by smaller removable panels finished with sound-absorbent material to enhance room acoustics.

Interior light wood framing was prefabricated onsite and installed in panels. The use of prefabrication for all elements of the structure reduced the overall construction time and helped the project stay on budget.

A high-performance building envelope, combined with passive design strategies and energy-efficient mechanical systems were used to minimize the building energy loads. A heat recovery ventilation system is augmented with large low-velocity fans and passive ventilation strategies to reduce cooling demand. Air source heat pumps and high efficiency boilers provide heating for the building, switching between systems to maximize efficiency.

A participatory design process has been shown to instill pride of ownership in a new building, encourage ongoing care and maintenance of the facility and improve its overall life-cycle performance.

The past decade has seen a number of important changes in the size and types of buildings permitted to be constructed in wood. It is important to remember the requirements for the specification of structural wood products and wood building systems are set out in the model National Building Code (NBC), which is concerned with health, safety, accessibility, and the protection of buildings from fire or structural damage.

In the 2015 edition of NBC, changes were made to increase the permitted height limit of wood construction for some buildings. These changes, which are the result of a rigorous scientific and engineering process by expert committees of the Canadian Commission on Building and Fire Codes, were incorporated into BCBC in 2018.

Whether built with light wood framing materials or engineered mass timber products, the added height and area of these buildings has given designers new options for an expanded range of occupancy types. These changes reflect the broad consensus that wood is a safe, economic, and more environmentally friendly alternative to concrete or steel construction. Additionally, the local availability of wood and wood products in most regions of the country means the majority of Canadian communities can benefit both economically and socially from the expanded opportunities offered by the new code provisions (the full case study, titled Wood in Civic Buildings, can be viewed at www.wood-works.ca/bc).

Jim Taggart, FRAIC, is a Vancouver-based journalist who has written on the subject of contemporary architecture in wood for over 20 years. His credits include more than 100 articles for national and international magazines, numerous technical case studies for wood industry organizations, and the books Toward a Culture of Wood Architecture (2011) as well as the recently released, Tall Wood Buildings: Design, Construction, and Performance (Second and Expanded Edition), written in collaboration with architect Michael Green. He can be reached at architext@telus.net.

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