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Standing out from the crowd is all about the company you keep. If your immediate neighbors are generic housing towers, attracting attention is easy in Hong Kong. But when you’re located between Central and Admiralty, with I.M. Pei’s twistingly triangulated Bank of China and Paul Rudolph’s “look-at-me!” Lippo Centre right next door, not to mention Foster + Partners’ fabled HSBC headquarters just opposite, the competition is far more daunting. This was the challenge facing developer Henderson Land, which in 2017 paid an eye-watering $3 billion for a 31,000-square-foot plot on Murray Road, next to Chater Garden, a public park. Seeking to wow the rental market, Henderson sought office-tower designs from a handful of globally acclaimed firms, choosing London-based Zaha Hadid Architects (ZHA) over names such as Foster and MAD.

Rising adjacent to the Bank of China tower (top of page), the Henderson cinches inward to shape a lobby (above). Photo © Virgile Simon Bertrand, click to enlarge.

“The client made it very clear they wanted to maximize the views,” says Sara Klomps, ZHA’s lead architect on the project. “Unless you’re on the waterfront, you don’t get panoramic vistas like this in Hong Kong. So it was a given that we had to design a tower in glass.” Henderson also wanted the 36-story, 650-foot-tall building to be “as clean as possible,” to exhibit “soft forms,” and to offer unencumbered floor plates, which meant pushing the elevator core to one side. “We also felt it was wrong for the tower to act as a barrier on meeting the ground,” continues Klomps, “which is why we lifted it up, to afford views through the greenery and allow Hong Kong’s aerial walkway system to connect up underneath.” The building also includes five levels of underground parking, which replace the garage that formerly stood on the site, and a glass-roofed lounge, known as Cloud 39, at its summit.

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The curves of the exterior (1) find their way into elements of the lobby (2) and common areas (3). Photos © Virgile Simon Bertrand

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Formally, says Klomps, the tower is “a very intuitive response to the Bank of China,” which rises to a rather staccato beat. At the Henderson, this translates into asymmetrical bulges in its glass facade, which are organized around two “pinch points,” as Klomps describes them, each located above one of the two giant trusses that compensate for the displacement of the elevator core. Though this aspect of the building’s structure is not expressed externally, its presence can be glimpsed through the air vents that ring the tower at these levels: the upper band corresponds to an outdoor refuge floor, as required by Hong Kong’s construction code, and the lower to a technical area (no machinery could go on the roof because of the lounge). Columns, which line the perimeter, are a composite of steel and concrete, while the floor beams are in steel with a composite deck.

From Cloud 39, the lounge, visitors have panoramic views of Kowloon. Photo © Virgile Simon Bertrand

“The Henderson was made at a moment when the technology was available to do it,” says Klomps of the digital bending ovens that shaped the many panes of curved glass used in the tower’s facade. But she is keen to point out that the building isn’t as extravagantly shaped as it might appear. “We went through a long rationalization phase to get the curvature to a reasonable amount. In the end, only 20 percent is double curved: there’s a fair amount of flat glass, and a fair number of single-curve panes. There’s nothing crazy.” What was probably novel, she concedes, was using so many curved pieces on a building of this scale, which posed a manufacturing challenge for the European firms that won the bid (locals proved too expensive), given the rapid construction timetable. While the majority of the facade comprises factory-preassembled units, which allow for quicker on-site construction, the “belly,” where the glass curls under at the base, was built the old-fashioned way, its components assembled in situ.

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Elevated catwalks weave through and beneath the tower’s reflective “belly” (4 - 6). Photos © Virgile Simon Bertrand

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All the Henderson’s glass is heat-strengthened and laminated, although, given the ferocity of South China Sea typhoons, Hong Kong code is conservative where laminate strengthening is concerned, allowing only 70 percent of the reinforcement effect to be taken into account. As a result, the glass is thicker than it would be in a European context, while the crown, where wind load is enormous, required seven layers of glass for each pane. Low-E coated to ensure optimum solar performance, the main envelope is also finished with a metal-oxide reflective finish, an aesthetic choice on ZHA’s part so that the city and Chater Garden appear to float in the facade. But this again is deceptive, since, unlike the Bank of China, which uses full-on ’80s mirror glass, most of the Henderson’s is only 20 percent reflective, the maximum now allowed under Hong Kong’s construction code due to problems with glare. As Andreas Komm, of German facade manufacturer Seele, explains, bending reflective glass is particularly challenging because the mirror finish can stretch too thin or crumple, depending on whether the curve is convex or concave. “If this happens, it’s immediately visible, like a dent. Our glass-making subsidiary, Sedak, undertook 3D quality controls on every single pane.”

“When we started out, we thought the facade would be the most challenging aspect, but, surprisingly, it wasn’t,” says Klomps. Covid, digging a basement over metro lines, and the logistics of building on such a constrained site proved far more taxing. “Getting the materials in to fit out the interior was the most difficult,” she says of the two ZHA-designed lobbies, whose soft forms are rendered in hard materials—stone and metal—that fare better in the intensely humid climate than wood or plasterboard. The Henderson includes publicly accessible spaces—lobbies, restaurants, Cloud 39—that have helped make it very popular, “not just because of its shape, even if that gets people excited, but because it’s open and inviting,” says Klomps. “It’s full of people, which really changes the dynamic of the neighborhood.”

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