Location: Montreal, Canada
Research area: Digital fabrication
Authors: Sima Chavooshi, Cesanne Mirkhani, CharlesWong, Jean-Roch Marion & Martin Chow
The project consisted on the design and fabrication of a balustrade for the terrace of McGill’s Redpath library. In form of teams of six, students worked on applying new techniques to design and manufacture a 1:1 scale prototype of the balustrade (1m length max). Students were also required to explore laser cutting and/or CNC-milling as forms of design output, pursuing an opportunity to work directly with advanced design technologies.
Our balustrade design was conceived based on a handful of guiding principles. The form should be as expressive as possible, of its structural and programmatic function. We desired to achieve this within an elegant, understated sculpture complimentary to the traditional architecture that it will be an addition to.
It must also minimize obstruction of views to the field from the terrace and library interior, while maintaining a seating orientation primarily towards the field. At the start of the design process, it was determined that this will be achieved with a massing that is cantilevered at a level lower than the terrace path. To eliminate the presence of an intrusive horizontal structural element, the vertical members must be cantilevered from below. The structure, while thickest at foot level, should fade to a minimum as it reaches the eye level of a seated person. A single, pure language must be shared by the floor, seating and railing components; at the same time it needed to be responsive to morphing requirements for structure and transparency. From this, the language of merging members is derived.
The regular, linear geometry of the existing terrace – with its democratic, non-hierarchical space lends itself to the use of repeating design elements along its entire length, expressing an inherent economy of scale. Each wing sparsely-spaced structural members in favor of thin, individually-weak pieces was consistent with the “responsive texture” desired as well as opens numerous possibilities in terms of material choice. An language of interlocking “L” and “Z” shaped structural members enable their dense arrangement on panels to be lasercut, minimizing waste to only 5% of the material surface.
The skeletal, fine-grain aesthetic that resulted – reminiscent of Gothic tracery, with the flex of a string instrument – was thus, a fitting, intellectual image within its architectural and academic context.
In order to compliment the simplicity and the elegance of the proposed balustrade, its connection to Redpath and McLennan terraces needed to be detailed in an equally simple way. The profile of the balustrade was designed to sit and to connect to the edge of the terrace and to straddle the right angle corner between the horizontal and vertical surfaces. This design decision was generated by the need to provide a stiff connection without having to rely on a complicated moment connection that would have generated a complex anchoring solution. Similar to brackets that are used to suspend flower boxes on a railing, the profile only required a cotter pin type connection to resist shear in order to counter the rotation forces created by the dead and live loads of the balustrade.
Once the main concept of the connection was decided, fabrication and installation procedures as well as waterproofing were considered. The desire to create a continuous surface between the finished surface of the terrace and of the profile of the balustrade was generated by the design requirements to integrate the guard rail into the elevation of the two libraries in a seamless way, eliminating an edge that could be damaged by snow shovels. Four feet sections are to be prefabricated and pined down on a preinstalled anchoring plate bolted on new concrete. The threaded rods that connect the profiles together need to be staggered as the sections are added linearly all along the terrace. The spacing of the profile members is wide enough to accommodate the tools needed for their installation.
For the Redpath Terrace section, waterproofing of the anchoring detail was crucial to avoid water infiltration between the granite cladding and the exterior wall of the terrace. The new concrete added to provide the horizontal surface required to bolt down the anchoring plate was slopped away from the terrace to avoid water accumulation under the granite pavers. A stainless steel flashing was added to protect the new concrete and the new membrane as well as providing a waterproof seal to all the joining materials of the wall section. The connection detail of the balustrade on the McLennan terrace section revealed to have no complicated waterproofing strategies, as all existing elements remain mostly untouched.