The CN Tower In Toronto

Ms. Sudeshna Mukherjee
Assistant Editor, Civil Engineering and Construction Review

CN Tower is the most relied upon directional marker, serving as the best way to orient, when temporarily lost. But while the upper features of the tower, most notably its two pods, have become ingrained in our consciousness, it was quite a different story during construction.

Construction on the CN Tower began on February 6, 1973. And while an ingenious construction method using poured concrete meant that the lower half of the tower shot up rather quickly, it wasn’t until June 26, 1976 that it officially opened.

Between these two historic dates, people who lived in Toronto were treated to one of the most remarkable construction projects ever undertaken. The world’s tallest structure (at the time) steadily rose above the city, and nothing’s been the same since.

Defining the Toronto skyline at 553.33m (1,815ft5in), the CN Tower is Canada’s most recognizable and celebrated icon. The CN Tower is an internationally renowned architectural triumph, an engineering Wonder of the Modern World, world-class entertainment and dining destination and a must see for anyone visiting Toronto. Each year, over 1.5 million people visit Canada’s National Tower to take in the breathtaking views and enjoy all the CN Tower has to offer.

After 40 months of construction, the CN Tower was well on its way to becoming the country’s most celebrated landmark. It is the centre of telecommunications for Toronto serving over 16 Canadian television and FM radio stations, the workplace of over 500 people throughout the year, and an internationally renowned tourism destination.

Although the CN Tower inspires a sense of pride and inspiration for Canadians and a sense of awe for foreign tourists, its origins are rooted in practicality. The 1960s ushered in an unprecedented construction boom in Toronto transforming a skyline characterized by relatively low buildings into one dotted with skyscrapers. These buildings caused serious communications problems for existing transmission towers, which were simply not high enough to broadcast over the new buildings. Signals bounced off the buildings creating poor television and radio reception for residents. With its microwave receptors at 338m and at the 553.33m antenna, the CN Tower swiftly solved the communications problems with room to spare and as a result, people living in the Toronto area now enjoy some of the clearest reception in North America.

The CN Tower was built in 1976 by Canadian National who wanted to demonstrate the strength of Canadian industry by building a tower taller than any other in the world. Building the CN Tower was a vast and ambitious project that involved 1,537 workers who worked five days a week for 40 months to completion.

Tower construction crews moved in on February 6, 1973, and started to remove over 56 metric tonnes of earth and shale for the foundation. Once the foundation was ready, work began on the CN Tower’s 335 m concrete shaft, a hexagonal core with three curved support arms. This involved pouring concrete into a massive mould or ‘slip-form’. As the concrete hardened, the slip form, supported by a ring of climbing jacks powered by hydraulic pressure, moved upwards, gradually decreasing in size to produce the CN Tower’s gracefully tapered contour.

Eight months later, the CN Tower’s concrete shaft was the tallest structure in Toronto and by February 1974, it was the tallest in Canada. In August 1974, work began on the seven-story tower sphere that would eventually house the observation decks and revolving restaurant. The CN Tower approached completion in March 1975, when Olga, the giant Sikorsky helicopter flew into the city to lift the 44 pieces of the antenna into place. The CN Tower was finished on April 2, 1975, and opened to the public June 26, 1976.

When the 44th and final piece of the CN Tower’s antenna was bolted into place April 2, 1975, the CN Tower joined the ranks of 17 other great structures that had previously held the title of World’s Tallest Free-Standing Structure, a record the Tower would hold for an incredible 34+ years.

In 1995, the CN Tower was classified as one of the Seven Wonders of the Modern World by the American Society of Civil Engineers. Canada’s Wonder of the World shares this designation with the Empire State Building, the Chunnel under the English Channel, the Golden Gate Bridge in San Francisco, Itaipu Dam on the Brazil/Paraguay border, the Panama Canal, and the North Sea Protection Works off the European coast.

Since the CN Tower opened, Canadians and tourists from around the world have made the trip to Toronto to celebrate this marvel of engineering. Besides serving as a telecommunications hub, the CN Tower provides a wide range of unique attractions, exhibits and food and beverage venues.

Over the years, millions of dollars have been invested in expanding and revitalizing the CN Tower to continue to provide visitors with a world class experience:

– In 1998 a base expansion project added 75,000 square feet of attractions and shopping at the Base of the Tower including a theatre and gift shop.

– For over three decades, the CN Tower continues to remain a critical telecommunications link adapting over the years to the incredible advances of the last decades by providing a cell site for wireless voice and data transmissions as well as for radio and television broadcasts.

– 360 The Restaurant at the CN Tower following extensive renovations and remodelling, re-opened to critical acclaim in 1995 with a newly appointed Chef’s team who would ensure the quality of the cuisine was every bit as spectacular as the view. Over the years, ongoing upgrades to the restaurant included the addition in 1997 of a state of the art 9,000 bottlewine cellar. Located at 351m, the Cellar was designated the World’s Highest Wine Cellar by Guinness in 2006 and continues to provide guests with one of the most extensive selections in the Toronto area.

– To meet the demands of growing numbers of visitors to the Tower, in 1996 two additional elevators were installed at the CN Tower for a total six glass fronted elevators taking visitors to the top along one of the longest elevator-hoist-ways on the planet.

– In 2002 the CN Tower underwent a dramatic upgrade when the Radome was replaced (white, donut shaped, Teflon-coated fiberglass fabric protecting the Tower’s microwave equipment at the base of the main pod).

– The CN Tower is always upgrading its security through investments in new equipment and training. In 2002, the CN Tower initiated an award-winning new training program as well as introducing a state-of-the-art, non-contact security archway at the entrance. The CN Tower has been a technological leader since it was first built in 1976 and technology advancements and security advancements are important to ensuring the safety and security of visitors and staff.

– In 2006 the CN Tower added new meeting and event space at the base to meet the growing demand for at this unique Toronto event venue, presenting 1,100 sq. ft. of flexible space adjacent to the CN Tower’s 140-seat Maple Leaf Cinema. The new meeting rooms, Aspen, Birch and Cedar are fully equipped for audiovisual presentations and a variety of room layouts can accommodate up to 90 people for meetings, breakout sessions, working lunches, and more.

– On June 28, 2007 With the installation of innovative programmable LED exterior lighting, the CN Tower now literally lights up the Toronto skyline each night vividly illuminating the structure elegantly in red and white. This new technology features 1,330 LED fixtures that are both energy efficient and cost effective to maintain- using 60% less energy that the conventionally lit Tower earlier. The system’s full capabilities are demonstrated during a spectacular light show at the top of every hour each night.

– Lifting off April 9, 2008, the CN Tower introduced North America’s first and the world’s highest glass floor panelled elevator. One of the Tower’s six glass-fronted elevators was recently enhanced to present a thrilling new perspective on the view 346m (1,136 feet) straight down. A portion of the elevator floor now features two glass panels, which when combined represent almost 0.6m2 (6 ft2) of floor space. Traveling at a speed of 22km/15mph, the Tower’s six glass-fronted elevators rocket guests to the top of its glass-fronted elevator shaft - 346m/1136ft in 58 seconds, earning the distinction as the World’s #1 elevator ride.

– 2010- A state-of-the-art high definition 3D theatre is the newest addition to the line-up of thrilling experiences at the CN Tower. The upgraded Maple Leaf Cinema is now one of the most technically advanced venues in the country for public and private screenings or presentations. This state-of-the-art theatre is fully equipped with leading edge high definition digital cinema technology projection and sound systems including the latest in high definition 3D.

– 2011 – The first of its kind in North America, Edge Walk is the world’s highest full circle hands-free walk on a 5 ft (1.5 m) wide ledge encircling the top of the CN Tower’s main pod, 356m, (1168 ft, 116 stories) above the ground. This adrenalin-fuelled experience allows thrill seekers to walk the edge of one of the world’s greatest man-made wonders. Adventure lovers walk ‘hands-free’ in groups of six, while attached to an overhead safety rail via a trolley and harness system. Trained Edge Walk guides encourage visitors to push their personal limits, allowing those who dare to lean back over Toronto, with nothing but air beneath them. Everyone who meets the stipulated requirements will be welcome to experience these breath-taking open-air views of Toronto and Lake Ontario. Every aspect of Edge Walk, from design, to build, to attraction logistics and operation has been developed with the utmost safety and security in mind. The entire experience will run 1.5 hours, with the walk itself lasting approximately 30 minutes.