From the publication Innovative Applications of Engineered Wood, originally published by the Canadian Wood Council.
Engineered Wood Products (EWPs)
Engineered Wood Products (EWPs) are high-tech, highperformance products that offer consistency of structural performance, dimensional stability and freedom from defects, making it possible to integrate them successfully with other construction materials on large and complex projects. Environmentally, the benefits of EWPs are significant. All engineered wood products utilize small dimension lumber, veneers, or wood fibers that help to maximize the potential of the world’s only truly renewable construction material.
Glue Laminated Timber (Glulam)
Glulam was first introduced in the 1950s and, along with plywood, remains one of the most familiar EWPs. Glulam technology continues to advance, and the material still plays a significant role, structurally and aesthetically. Glulam traditionally uses 2x laminations glued together under pressure to form simple beams or arches. Nowadays, glulam may also be curved in two directions or have laminations stepped to correspond to the bending moment diagram, resulting in greater efficiency and increased expressive possibilities.
Parallel Strand Lumber (PSL)
PSL uses high-grade veneers peeled from small dimension trees and bonded together with water-resistant, thermosetting glue. PSL is comprised of shreds of veneer that are mixed with glue and extruded into billets up to 80 feet in length. The material is then cut to a range of standard sizes for use as lintels, beams, posts, and truss members.
Laminated Strand Lumber (LSL)
The manufacture of LSL converts up to 75 percent of a log into useable lumber. The process utilizes small-diameter, plentiful trees that are not suitable for use as conventional sawn lumber. The wood is cut into thin strands and then glued together using a steam injection process. The result is a large billet that can be milled into a range of sizes for use as rim boards, headers, beams, columns, studs, sill plates, and stair stringers.
Wood I-Joists (TJIs)
Wood I-joists are made up of 2x3 or 2x4 solid sawn lumber, laminated veneer lumber, or machine stress rated (MSR) lumber flanges and an oriented strand board or plywood web. They are manufactured in long lengths and provide a roof and floor framing system that can run continuously over a number of supports. Holes can be drilled in the web to accommodate ductwork and other services, making wood I-joists a viable alternative to open-web steel or composite joists. Various profiles of wood I-Joists are available.
Laminated Veneer Lumber (LVL)
LVL is essentially thick plywood, but with the grain in each layer of veneer laid in the same direction. From the resulting billet, generally 1-3/4 inches thick, a range of standard beam sizes can be cut, the grain of the veneers running along the length of the beam. LVL is generally used for lintels and headers but also to support point loads in a range of building types. Wider beams can be fabricated onsite by nailing several LVL members together, making handling easier and eliminating the need for a crane.
Carlo Fidani Peel Regional Cancer Centre, Mississauga, ON
Farrow Partnership Architects are at the forefront of a new humanist movement in architecture, a movement that believes buildings should be designed with human interests and dignity in mind. In the field of health care in particular, research is beginning to provide empirical proof that patients heal more quickly and staff morale and performance increases in a non-institutional setting where natural materials, such as wood, and natural light figure prominently. This knowledge was uppermost in the architects’ minds when they approached the design of a lobby/ atrium space that would connect the new Regional Cancer Centre with renovated existing space at the Credit Valley Hospital in Mississauga, ON. Conceived as a village gathering space, the 40-foot high atrium features a forest of nine tree columns whose glulam branches curve and intertwine. The organic forms enhance the emotive quality of the space, which is bathed in natural light from clerestory windows.
The intertwined glulam trees constitute a single structural system interconnected by embedded steel plates. The intricate form and the complexity of fabrication meant that collaboration between architect, structural engineer, and glulam manufacturer was essential from the outset. The roof system is supported at five points, four of them steel beams at the second floor level. Within the structure, 35 potential load paths needed to be analyzed to ensure that the net maximum connection forces were realized. The glulam supplier was instrumental in resolving the many complex connections and addressing the challenges of fabrication and assembly ahead of time. Most of the steel plate connections are concealed, maintaining the integrity of the overall concept. The complexity of the structure also posed problems with respect to fire protection. Analysis showed that conventional sprinklers could not reach all the exposed surfaces of the structure, presenting an unacceptable fire risk. The solution was to import and test a high-pressure misting system that would protect the structure by coating it with a thin film of water droplets. Released from misting heads mounted five feet off the ground, water vapor would be carried upward with the increasing air temperature, enveloping all surfaces of the structure. The water vapor prevents oxygen in the air from coming in contact with the wood and thus starves the fire. With its humanist approach, complex forms, and innovative technology, this project represents a new benchmark in the use of engineered wood.
Laminated Strand Lumber
False Creek Community Center Vancouver, BC
In the unique urban context of Vancouver’s Granville Island, the extension to the False Creek Community Center, designed by Henriquez Partners and engineered by Fast and Epp, showcases a unique application of CNC technology to engineered wood panels. The existing community center occupied several converted warehouse structures of heavy timber and steel construction that were connected by circulation routes converging from three access points. A semi-derelict boat shed bordered the main access from the north, and this became the site of the new gymnasium, with a new fitness center added above the existing administrative offices. With a prominent site and a tight budget, the objective was to design a striking structure that would achieve economy through innovative design. By adopting a lightweight timber structure, it was possible to float the building on a waffle raft and avoid the expense of the piled foundations commonly used in this area.
The spaces between the vertical posts of the heavy timber frame are infilled with non-load-bearing, wood-stud walls, and the required lateral resistance is provided by a layer of plywood fastened to the inner face of the wall. The plywood was upgraded to good one side so that it could be exposed internally and eliminate the need for a separate interior finish for the gymnasium wall. The plywood is fixed with a carefully orchestrated arrangement of exposed screws and washers that addresses both structural and aesthetic considerations.
The gymnasium roof trusses were seen as having the greatest potential in determining the character of the interior space. Inspired in part by the wings of Granville Island’s ever-present seagulls, the trusses are a counterintuitive application of LSL panels made possible by CNC technology. Rather than build up trusses from a series of discrete positive elements in the usual manner, the negative shapes have been milled out of a single slab of laminated strand lumber board and the truss completed with a steel cable extending along the bottom edge as a tension chord. The leftover material from the manufacture of the trusses has been assembled to form benches in the newly expanded lobby.
Mountain Equipment Co-op, Ottawa, ON
The Mountain Equipment Co-op store in Ottawa was the first retail building to comply with Canada’s C-2000 green building standard. The two-story structure incorporates many materials and components salvaged from the singlestory grocery store that previously occupied the site.
Rebuilding from salvaged material posed some problems, as the original structure of steel columns, beams, and open-web joists had been sized for Ottawa snow loads but not for a retail floor load. Concrete and steel options were considered for the ground floor but did not score highly when rated for environmental performance.
Large Douglas fir timbers salvaged from old submerged log booms on the St. Lawrence and Ottawa rivers were also available, and a timber frame fashioned from these logs offered an interesting alternative. Ultimately, this option was chosen for its aesthetics, low embodied energy, and recycled or salvaged content.
To make the timber frame as light as possible, beams of 12x12 span between columns on a 22-foot grid were used. The lower face of the beam is reinforced at mid-span by lag bolting on a 3x10. This is engaged at each end by a 6x10 knee brace that transfers compression loads to the column. With structural loads carried by this post-and-beam frame system, the enclosing walls of the building became non-load-bearing.
Four options were compared for the building envelope:
• Concrete block with four inches of insulation in the cavity
• 2x6 salvaged studs with rock wool insulation
• A Durisol wall system—concretefilled forms made from wood waste and cement with cavity insulation
• A wood I-joist stud system filled with cellulose insulation.
• Wall systems needed to have a minimum insulation of R-20
The design team used the Green Building Assessment Tool—a chart that compares the attributes of the wall types according to the categories of re-usability, recycled content, embodied energy, longevity, structural efficiency, cost, thermal value, and ease of construction. The team gave a score between 1 and 4 for each wall system in each category. The 2x10 wood I-joist systems scored the highest based on the criteria and had a high thermal value R-value of 35. The walls extend the full two stories in a balloon-frame fashion. Bolted steel brackets at the floor line secure the I-joist studs to the timber floor beams. The stud walls are insulated and sheathed with oriented strand board and self-adhesive elastomeric air barrier strips taped at the joints. Cladding was applied as a rain screen with a 3/4-inch backup air space. The joists themselves offer the same advantages as when used as a flooring system, enabling services to be run through holes drilled in the center third of the member—an innovative solution readily transferable to a variety of other situations.