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Stepping on thin air


May 9, 2008
By Chris Skalkos

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Tourists visiting the Calgary Tower in Calgary, Alberta, will be able
to virtually step on thin air when standing on the new glass floor of
the tower’s observation deck.

Tourists visiting the Calgary Tower in Calgary, Alberta, will be able to virtually step on thin air when standing on the new glass floor of the tower’s observation deck. The famous tower, built in 1967, is a striking visual landmark that graces the cityscape and offers a breathtaking view of the beautiful Rocky Mountains in western Canada.

3a
Looking down through the new glass floor of the Calgary Tower’s observation deck in Calgary, Alberta. Photos Courtesy Of Brent Harder, Ferguson Corporation.

Perched 525 feet (160 metres) above street level, the new glass floor in the observation deck opens up the view for visitors to look straight down and directly out in front to see the downtown core and most of the city.

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The glass supplied by Oldcastle Glass Calgary was installed by Ferguson Corporation, a company known for glazing high profile projects in the province. The total area of glass consists of 310 square feet of one inch sealed units in the vertical wall and 115 square feet for the floor. A total of six 71 by 42 inch sealed units were installed for the floor glass using 21⁄4 inch super clear glass. The composition of the floor glass included a 1⁄4 inch glass wear lite on top, a one inch laminated tempered glass top lite, 1⁄2 inch air space and a 1⁄2 inch laminated tempered glass bottom lite.

The wear lite on top is intended to be the wear layer that can be easily unscrewed to be replaced if it becomes scratched or scuffed. The glass floor is 36 feet long and more than four feet wide.

Margaret Townsend, sales manager, from Oldcastle Glass Calgary says the tempered glass was a PPG product called Starphire Ultra-Clear Glass which is described as a high-purity, low-iron product with exceptional clarity and five percent higher light transmission compared to ordinary clear glass.

3b
Designers
blended in the observation deck for a seamless transition following the
existing glazing angles and glass design elements of the tower.

“There are five pieces of glass, the sacrificial 1/4 inch glass on top, two pieces of 1/2 inch laminated together and two lites of six millimeter for the bottom,” she says, adding that this product was chosen for its clarity. “The designers wanted as much visible light as possible. They went with this glass for its aesthetic qualities.”

Pat Arts from Ferguson Corporation says installing the heavy glass, with each unit weighing approximately 525 pounds, was a challenge as glaziers were working over open cavities at great heights. “To ensure safety, the openings on either side were closed in with glass or covered with plywood, and all workmen were tethered at all times. It’s interesting and a little scary working that high up over an open area,” says Arts. “The floor incorporates a replaceable, ‘sacrificial’ glass lite that sits flush with the stainless steel pressure plates above the glass floor which sits on steel hollow structural sections.”

Vince Dods MAAA, MRAIC, LEED AP, the project architect with Gibbs Gage Architects in Calgary, says that the use of glass allowed designers to fulfill the architectural and structural requirements without it becoming a conspicuous addition to the structure that looks out of place.

3c
Glaziers
from Ferguson Corporation use a Wood’s Powr-Grip lifter to install one
of the six 71 by 42 inch sealed units on the glass floor which totals
115 square feet.

“The biggest challenge was how to design something that wouldn’t look like a pimple sticking out of the side of the tower. We used exterior glass to match the existing glass for a seamless transition. From the outside it looks good because the symmetry of the tower was followed and the glazing angles and glass matched existing design elements of the tower,” says Dods.

“We had to extend the floor beyond the existing parameter to see out and down. We picked the north side for this because the angles of the walls allowed us to include vertical elements to keep in alignment with the same angle of the tower itself,” he says, adding that the goal was to maximize the glazing and to minimize the structure and supporting elements. The glass specified for this project played an important role in that because designers did not want any glass intrusion.

“We needed clear glass without any reflective coating. The intent was to create the experience from within so that visitors get the sensation that they are stepping out onto nothing… like stepping on thin air.” -end-

Project Profile

Project name:
Calgary Tower Observation Deck, Calgary, Alberta.

Web site: www.calgarytower.com/Observation_Deck.html

3d
An
inside view of the observation deck. Oldcastle Glass Calgary supplied
the PPG Starphire Ultra-Clear Glass that was fabricated to consist of a
1⁄4 inch glass wear lite on top, a one inch laminated tempered glass
top lite, with a 1⁄2 inch air space and a 1⁄2 inch laminated tempered
glass bottom lite.

Architect:
Gibbs Gage Architects, Calgary, Alberta.

General contractor: PCL Construction Management Incorporated.

Structural consultant: Read Jones Christoffersen Limited, Consulting Structural Engineers, Calgary, Alberta.

Glazing contractor: Ferguson Corporation, Calgary, Alberta.
Web site: www.ferguson.ca

Dates:
Started March 2005.
Completed June 2005.

Glass supplier: Oldcastle Glass.

Total area of vision glass:
Vertical wall = 310 square feet.
Floor = 115 square feet.

Glass size:
Vertical wall = 70 by 48 inches typical, 12 units.
Floor = 71 by 42 inches typical, six units.

Glass type:
PPG Starphire Ultra-Clear
Vertical wall = one inch sealed units.
Floor = 21⁄4 inch sealed units.
Total glass thickness:
21⁄4 inch super clear glass.

Composition: 1⁄4 inch glass wear lite. One inch laminated tempered glass top lite. 1⁄2 inch air space. 1⁄2 inch laminated tempered glass bottom lite.

Size: Approximately 71 by 42 inches.

Material supplier: Engineered Aluminum Products (EAP) Incorporated.

Vertical wall: EAP 400 Series.

Sealant supplier: Dow Corning.

Steel contractor: Three Star Steel (Calgary) Limited. -end-


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