Built-In Flexibility Helped a Project Team Erect the Tallest Building in Africa
BY JEN THOMAS
55 stories above Johannesburg, South Africa’s financial district, the Leonardo is a rugged yet gleaming mixed-use skyscraper. But it wouldn’t be the tallest building in Africa unless the project team had anticipated a surprise growth spurt.
The journey from a proposed 33-story edifice to a record-breaking, 233-meter (764-foot) behemoth has been long—with at least two major scope changes over the project’s six-year construction phase. Five years into the US$209 million project, the sponsors agreed to fund the additional floors so the building could house a luxury hotel in the future.
Much like the building’s namesake Renaissance inventor, the project team—led by developer Legacy Group and designer Co-Arc International Architects Inc.—was brimming with forward-thinking ingenuity and creative problem-solving.
“It was never our intention to build the tallest building in Africa,” says Jamie Hendry, director, Legacy Group, Johannesburg, South Africa.
—Jamie Hendry, Legacy Group, Johannesburg, South Africa
A FLEXIBLE FOUNDATION
The Leonardo was built on a site that had been excavated by an earlier developer who abandoned the project after laying the concrete footings and grid. To save time and money, the Leonardo team decided to leave the existing concrete in position and make the necessary modifications to work around the previous build—with modifications for quality control.
Pouring new footings to avoid most of the existing ones was intended as a risk-mitigation move, says Catharine Atkins, director, Co-Arc International Architects Inc., Johannesburg: “We didn’t want to trust this previous mass concrete intended for another building and that had been poured without our knowledge."
When it came to laying the foundation for the Leonardo, the team opted for a structure that could support a 55-story skyscraper—despite the project being budgeted at just 33 stories. The foundation choice didn’t add cost, but it gave the team greater flexibility, Ms. Atkins says. That early, enterprising decision proved integral as it gave the client and design teams the elasticity they later needed when the project scope ballooned.
At the sponsor’s urging, the project team fashioned adjustable plans so that, if the economy lifted during the project’s execution phase, the building’s scope could be changed as well.
When the project sponsor signaled that the skyscraper’s height might change, Ms. Atkins ran the broad change request through careful analysis, aware of the risks it introduced for structural integrity and design—not to mention budget and schedule. “The approval to proceed can take a bit of time, but then the trick is to keep ahead of the main contractor and avoid any abortive work or rework on-site,” she says.
With the approved change request in hand, the team reached out to every subcontractor and consultant—including structural, mechanical, facades, plumbing and electrical teams—to initiate the design amendment. “It’s a bit like cruising on the highway when all of a sudden you need to gear down for that quick burst of speed and power so you can reach your revised destination further away within the same amount of time,” she says. In the end, the design team was able to execute the expanded scope without missing the project’s original deadline.
—Catharine Atkins, Co-Arc International Architects Inc., Johannesburg, South Africa
Reaching New Heights
2013: The project is launched by Legacy Group.
2015: Construction begins after the budget and scope are finalized for a 33-story building.
2017: The project sponsor increases the building to 42 stories.
2018: The height increases to 55 stories.
Late 2019: The building is slated to open for occupancy.
Rendering of the top floor of the Leonardo. Below, the building under construction
When the Leonardo opens later this year, it will house street-level retail, a large conference venue, a main restaurant with supporting coffee shops and bars, five levels of offices, 26 levels of apartments, seven levels of hotel space to be developed in the future, four floors of penthouses and a three-floor, approximately 3,000-square-meter (32,000-square-foot) “Leonardo Suite” with an asking price of approximately US$17.5 million.
To meet the sponsor’s requirements of indoor and outdoor living, Ms. Atkins says the design incorporated balconies—built with depth in mind to help provide shading from the African sun and conserve energy.
A MATERIAL SHIFT
When the scope increased to 42 stories and then ultimately to 55 stories, the team had to carefully manage a change in materials to reduce the structure’s overall carry. For instance, the building design used lighter coffer slabs rather than traditional, weightier concrete slabs. And developers opted for aerated concreted blocks instead of bricks for the inside of the building.
“Initially the building was to be built in brick, which is true for the majority of construction projects in South Africa,” says Mr. Hendry. “But once we completed the podium, we then moved over to lightweight concrete blocks. And on the internal walls we used all drywall instead of plaster.”
Getting materials to the project site proved challenging, too. Storage spaces and big-rig parking aren’t plentiful in the bustling Sandton district. Placing and storing bulk materials on-site simply wasn’t an option. So Mr. Hendry leaned hard on project planning, coordinating deliveries to within days of when a material would be used on-site.
“The team places bulk orders on steel, for example, but they only call in the delivery for what they require when they require it,” he says. “Delivering materials has been of huge interest to the team and something that was always a topic of discussion.”
The team was determined to ensure the Leonardo, the first skyscraper to be built in South Africa since 1973, remained a purely South African affair so all benefits remained within the country.
“We’re very proud of the fact that we don’t have any international consultants of any form,” says Ms. Atkins. “We’re all proudly South African.”
The design-build project delivered a boon for the South African economy, which has been struggling in the wake of a 2018 recession, including a jobless rate that topped 25 percent this year and last.
“At the peak of the project’s execution phase, we had 2,000 laborers on-site,” says Mr. Hendry. “We’re really proud of that.”
It’s a feeling that the project team hopes will extend long into the future, when the Leonardo continues to tower over the city’s skyline. “We see the Leonardo as a real beacon of hope in the country,” he says. PM
director, Co-Arc International Architects Inc., Johannesburg, South Africa
Experience: 22 years
What was the biggest project challenge?
I’ve never managed a team this large before. As the changes were made, I had to coordinate with all of the consultants and contractors and make sure that everything was in hand and adjustments were made.
How do you blow off steam after-hours?
One of my main forms of de-stressing is mountain biking. This project has taken a bit of my private time away, but I’ll get back on my mountain bike soon.
What career lesson did you learn on this project?
How to convey changes to people while keeping the motivation and enthusiasm high.
What famous person would have been useful on the team?
It’s probably quite trite, but Leonardo da Vinci with his insight through design and visionary qualities could have come in handy.