The 1960s marked a construction boom in Toronto as the city rapidly expanded. The CN Tower was built to resolve telecommunication issues caused by the city’s growing skyline of concrete and steel. As taller buildings obstructed radio waves, communication and signal reception were interrupted. To address this challenge, the Canadian National Railway Corporation initiated the construction of the CN Tower. Read more on toronto-future.com.
Radio waves, which previously transmitted freely across lower levels of the city, began to be disrupted by new concrete and steel buildings. The ability to communicate and receive signals was significantly hindered. To address this problem, the Canadian National Railway Corporation (Canadian National) initiated the construction of the CN Tower.
To build the CN Tower, Canadian National hired approximately 1,000 workers. The project took 40 months to complete. When construction finished, the CN Tower became the tallest freestanding structure in the world at 553.3 metres, capable of transmitting television signals even to the most remote areas of Toronto. Learn more about its construction and fascinating facts below.
Project Highlights
The construction plan for the CN Tower included the development of several floors starting at 1,100 feet, collectively called the Upper Accommodation. The lowest of these floors was designed as an open platform for microwave antennas, with additional protection against inclement weather.
The next level was designated as an observation area, followed by a closed observation deck that housed a restaurant. Other levels were planned to accommodate television transmitters, power transformers with cooling fans, and other telecommunications equipment.
Approximately 50 feet above the roof level, large water tanks were installed as part of the tower’s fire protection system.
Building the Tower
The Canadian National Railway Corporation first sought an appropriate site for construction, eventually selecting a plot between Front Street and Lake Ontario, previously owned by CN Railway. Architect Ned Baldwin and engineer Melaki Grant were brought on board for the project, with construction employing slipform techniques for the concrete structure.
In February 1973, construction crews began their work. Over 56 tonnes of soil and shale were excavated to lay the foundation. Once the base was complete, the 335-metre concrete shaft of the tower began to take shape.
To achieve the CN Tower’s distinctive tapered design, builders used a massive slipform mold. As the concrete set, the slipform—supported by a hydraulic jacking system—was gradually raised, reducing in diameter as it ascended to create the conical contour of the tower.
The tower boasts a unique feature: two “tuned mass dampers,” installed on the upper third of its steel mast. These 10-tonne rings are suspended from the mast and controlled by hydraulic cylinders to counteract swaying caused by wind. Additionally, a pendulum sensor continuously transmits tilt angle data to a computer for monitoring.
By the summer of 1974, construction crews began work on the seven-story pod, which would eventually house observation decks and a one-of-a-kind revolving restaurant offering a 360-degree view of the city.
Fascinating Facts
- Completion and Final Touches: On April 2, 1975, construction was completed when a large Sikorsky helicopter named “Olga” arrived to install 44 antenna segments atop the tower. With the final segment in place, the CN Tower became the tallest freestanding structure in the world.
- Opening: The CN Tower officially opened to the public on June 26, 1976.
- First Broadcasts: The first TV broadcasts from the CN Tower occurred on May 1, 1976, through CBC-TV and CFTO-TV, followed later that month by FM radio stations.
- Cost: The Canadian National Railway invested $63 million in the tower’s construction.
- Legacy: Today, the CN Tower serves as a crucial telecommunications hub and a popular tourist attraction, drawing visitors from across Canada and around the globe.
The CN Tower remains a testament to engineering ingenuity and innovation, continuing to inspire residents and visitors alike. From its practical purpose in telecommunication to its iconic status as a modern architectural marvel, the CN Tower is truly one of Toronto’s most remarkable landmarks.