Canadian Architect

Feature

Cutting Edge

CNC technology changes the face of wood design in four distinct projects.

May 1, 2005
by Jim Taggart

Five years ago, I wrote on the subject of design in wood (CA, November 1999) and made some unflattering comparisons between the high-precision timber structures common in Europe and our own rough and ready approach. The difference I acknowledged was largely due to a technology gap–the Europeans had access to digitally instructed cutting machines, and we did not. Now, I am pleased to report that the gap is closing fast and North American wood architecture is taking a new direction.

In 1999, there were only ten small computer-numerically-controlled (CNC) machines in North America; now there are too many to count. In addition, we have four large machines that are capable of precision-milling components of almost any size. The one Canadian machine by Structurelam is located in Penticton, BC, which makes the interior region of the province an unlikely hotbed of architectural innovation.

CNC technology also opens the door for the use of high-efficiency proprietary connection systems that make possible lighter, more elegant structures. The BVD system, designed in Germany, is now imported into Canada and has been used in a number of recent projects– notably the Sk’elep School in Kamloops.

Sk’elep School of Excellence

The Sk’elep School of Excellence, designed by Ib G. Hansen Architects and engineered by Equilibrium Consultants, is located in the arid interior region of BC on a prominent site overlooking the North Thompson River and the City of Kamloops. The school adopts the language of bright colours and bold geometric forms typical of architecture in desert regions. The effect is to make the building both part of the landscape and distinct from it. The program is arranged to take advantage of the stunning views and to ensure that daylight penetrates deep into the occupied spaces.

The classrooms are articulated as a series of pods within the overall composition, and feature an innovative timber roof structure that takes the form of a two-way lattice or grid. These lattices consist of intersecting pairs of 114mm* 114mm Hem-Fir sawn timber elements, stitched at each end with high tension BVD connectors, tight-fit pins and blocking to form beam elements, each 356mm deep. 38mm* 140mm diagonal tongue-and-groove decking triangulates the system, providing an effective diaphragm without the use of additional plywood sheathing. The grids effectively form the wood version of a concrete waffle slab, creating a rich and textured roof structure. The seven identical 5.6m* 6.5m grid panels were fabricated on the ground, then raised and set in place with a crane.

The gymnasium also features an innovative roof structure. The trusses consist of an elegant hybrid between glue-laminated beams and a king post truss. A pair of glulam beams, symmetrical about the centreline, are sculpted to create a dynamic form and are connected together into a king post truss with double-steel rod bottom chords.

Maurer House

Also in the interior of BC, architect Florian Maurer’s own glulam-framed house at Naramata combines the precision of CNC technology with the simple, pragmatic forms characteristic of his architecture. Structural engineers for the project were Fast and Epp Partners of Vancouver.

Set in a subdivision of large lots overlooking Lake Okanagan, the chosen site was distinguished by a bedrock ledge and a stand of mature Ponderosa Pines. Under the existing zoning it would have been impossible to integrate the house with these natural features, so Maurer applied to the regional District for relaxations that would permit him to construct not one large centrally placed structure, but a series of four smaller pavilions clustered around a courtyard. Not only does the house expose the limitations of existing zoning bylaws in supporting environmentally responsible design, but it also breaks with the plan book approach that dictates the form of so much suburban development today.

The complex is entered from the street through a portico formed by the studio and garage pavilions that lead to a treed courtyard. Beyond the trees to the west and perched on the bedrock ledge is the main pavilion with living and dining areas, kitchen and guest bedroom, all with views to the lake. The pavilions share a consistent vocabulary of simple forms and durable materials. Shallow shed roofs with large overhangs sit atop rectangular volumes clad in high-performance glass and galvalume. Internally, the post and beam frame is exposed and its elements are joined by elegant bolt and pipe connections that are an important decorative device in an otherwise simple composition.

The seven-foot structural module derives from the most economical sizes of the exterior glazing units, and consequently the tongue-and-groove timber roof decking has been specially milled to a greater than normal thickness, enabling it to bridge this span without intermediate supports. Glazing is direct to the glulam frame and the exposed sills and headers are detailed to finish flush with the floor and ceiling plane to enhance the visual connection between interior and exterior spaces.

False Creek Community Centre

In the unique urban context of Vancouver’s Granville Island, the new extension to the False Creek Community Centre designed by Henriquez Partners and engineered by Fast and Epp showcases a unique application of CNC technology to engineered wood panels.

The existing community centre 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 centre inserted 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 piled foundations that are commonly used in this area. The heavy timber frame is unfilled with wood stud walls and the shear resistance is provided by a layer of plywood sheathing. The plywood was upgraded to “Good One Side” and was fixed to the inside face of the studs eliminating 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 counter-intuitive application of Timberstrand 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 Timberstrand board, and the truss completed with a steel cable extending along the bottom edge as a tension chord. As a nice touch, the “waste” material from the manufacture of the trusses has been assembled to form benches in the newly expanded lobby.

Big Ten Burrito Restaurant

To date in North America, the aesthetic possibilities of CNC technology have been best exploited south of the border. In Ann Arbor, Michigan, PLY Architecture recently completed the interior of the Big Ten Burrito Restaurant using plywood panelling decorated with organic patterns incised by CNC cutting machines.

One of the attractions of the technology has been its ability to deliver complex shapes without the consequent problem of wastage when starting from rectangular board products. Rather than find a use for the waste product as at the False Creek Community Centre, PLY explored the potential of the technology to express formal and spatial comple
xity without compromising the integrity of the rectilinear plywood sheets.

The character of the small restaurant interior is created by the interplay of decorative plywood panels against a backdrop of walls, floor and ceiling–all painted a rich monolithic red. The plywood panels define two distinct areas, the table seating area and the takeout counter.

The design objective was to create an intimate space that would be economical to build, yet have a tactile and sensual quality. PLY’s response was to take a prosaic material–plywood–and “dematerialize” it, so as to alter the viewer’s perception and experience. To this end, the treatment of the joint and surface of the rectangular panels were of particular interest as a means to alternately disguise or emphasize the modularity.

This has been achieved by varying the depth of cut by the hemispherical blade, which in turn alters the width of cut and the exposure of individual laminations, and allows the scrolling patterns to flow uninterrupted from one panel to another regardless of the joint between them. Within the patterning, a vocabulary is developed with lines converging to define the zone for lighting fixtures, and diverging and penetrating the entire sheet depth to create locations for HVAC diffusers. By contrast, the furniture surfaces are composed of smaller plywood tiles with a varied pattern achieved by rotating, translating or book-matching adjacent tiles. The overall effect is remarkable for its richness of texture and detail.

While the hand-built tradition of North American wood construction will continue to have its place long into the future, there is also the sense that we are at the dawn of a new era–one in which CNC technology will support greater economy and efficiency in the use of wood, while opening the door to new applications and architectural expression.

For more information on recent architectural projects in wood design, please refer to the recent The Wood Design Awards 2004 (Halifax: Tuns Press, 2004), edited by Don Griffith. The Wood Design Awards is the only award program in North America specifically devoted to wood architecture. The annual program is open to new and renovated projects from Canada and the United States. For 2004, twelve projects were selected, including three interior projects, an historic building renovation and a modular home. The jury for the 2004 awards comprised Vincent James, Patricia Patkau and Mark Simon. The Big Ten Burrito Restaurant by PLY Architecture received an Honor Award. Two projects from Canada received Citation Awards: the Garden Pavilion in Toronto, Ontario by Paul Raff Studio and the Minton Hill Residence in North Hatley, Quebec by Affleck + de la Riva Architects.




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