A new, 30-storey condominium project broke ground in Seattle, WA., in the spring of 2007. The Escala was designed to be the very pinnacle of condominium design for a target market of former suburbanites downsizing their lives, but not willing to downsize some of the things that suburban living had afforded — hence the huge balconies, suitable for the entertaining that the owners had become accustomed to on their back decks. Setting off the whole aesthetic for the almost 280-unit structure is a very intricate set of precast concrete panels on its lower two levels that proved a not insurmountable handful for precaster APS Architectural Precast Structures Ltd.
Apart from a fireplace constructed high above the street on a communal terrace, precast was only used in the lower two floors as a means of decoration on these levels where commercial activity is centred. “I designed some really interesting historical designs in a contemporary manner,” explains Paul Thoryk, President of Thoryk Architecture, who designed the building in co-operation with MulvannyG2 Architecture, “so they were all designed to give that mid-town look, and it really blended into that area. The precast kind of creates a base for the building, and then, as the building rises up, that look becomes less and less, until it ends up looking like this huge, tubular, glass jewel is growing out of it.”
That doesn’t begin to tell the story, however, of the challenge that this decorative face presented to precaster APS, who had to come up with a method of creating forms that would work for casting a myriad of non-repetitive features, including recesses and projections.
The solution was to conceive and fabricate an adjustable bed. “Many of the pieces are curves, and they have different radii,” says Mehrdad Ahmadi, Chief Engineer for APS, “so the hard part was to fabricate an adjustable bed to make the form. We ended up making two forming beds, so that we were able to make two of these curved pieces of precast per day adjusting for the five different radii we were fabricating.”
Customized for this project only, the adjustable bed was designed with strong-backs crossing underneath the bed every 16 inches (400 mm), and a set of knobs and bolts connected and welded to APS’s original beds. “Playing with those bolts and adjusting them to the right height enabled us to get the curve that we were looking for,” says Ahmadi, “and to do that, we made a wooden template for each panel to match that curve.”
The system APS devised went beyond that however, because where architectural features on panel faces are common, they’re usually pretty uniform and consistent. The Escala was different and far more challenging to fabricate in that the depths and heights of every part of these recesses and projections differed. “We ended up using rubber, so different thicknesses of rubber were attached with glue to the curved bed to create those features. That system also was a one-time use design.”
Beyond the challenge of fabricating the differing specs of the panels, the spandrels had a soffit at the bottom to accommodate the corner column covers. “We had to cast them in two stages,” notes Ahmadi, “doing one side of the corner panels where the soffit of the corner spandrel was, and then putting it on the form again, flipping it 90 degrees, and then casting the second stage.”
One could imagine then, that the APS team was relieved that the specs for the colour of the precast ended up being about as straightforward as it gets. Architect Thoryk explains, “It was a light aggregate that we used to give it a light stone look. We wanted to make the building look light because most of the buildings in Seattle have a darker grey look that doesn’t have a lot of light, so we thought that this would give some liveliness to the look of the building.” That look was achieved using aggregate and white cement only. Ahmadi adds that it was also poured solid, as opposed to pouring the facing mix and the backing mix separately.
It was a distinct advantage for the APS team to be able to avoid dealing with a complicated mix or colouring, since determining how to cast for all of this detail, and then executing the resulting plan took a lot of extra time — Ahmadi estimates it took roughly 50 per cent longer than typical — meaning the team was working to a very tight deadline (which it was ultimately able to meet).
It’s possible, however, that APS might have been bogged right down to the point of jeopardizing that deadline, were it not for a key visual aid. “Because it was so complicated,” Ahmadi adds, “it wasn’t easy for our production crew to imagine all of those curvatures, projections and recesses, so we ended up making a one-tenth scale model of the façade for them to work from; we actually ended up with a small building in our production area. It was a good thing that the precast was only required for the main and mezzanine floors!”
Owner: 4th + Virginia
Architect: Mulvanney G2
Engineer: CKC Structural Eng
Contractor: JE Dunn
Precaster: APS – Architectural Precast Structures