Changing Skyline: An umbrella for pedestrians

An elegant, functional sidewalk shed has won a prize for a Penn architecture student.

Urban Umbrella design by Young Hwan Choi, with Andrés Cortés, AIA, and Sarrah Khan, PE, of Agencie Group. Design team members also include Will Robinette, Todd Montgomery and Zachary Colbert. (Courtesy of urbanSHED)

Young-Hwan Choi arrived in Philadelphia from his native South Korea in August. By October, the University of Pennsylvania architecture student had devised an elegant new design for the sidewalk sheds that protect pedestrians during construction. And he was barely into his second semester when New York announced it was adopting his innovative system as its official prototype.

As immigrant success stories go, that surely must rank as a record turnaround.

On Jan. 21, Choi, 28, found himself in Lower Manhattan at his first American news conference, being introduced to the audience by a beaming Mayor Michael Bloomberg. Choi's concept for improving the humble sidewalk shed had just won a city-sponsored design competition, beating out 163 entries from around the world, most of them by accomplished architects. Even better than the $10,000 prize is New York's commitment to construct a full-size mock-up this summer, the first step to putting the design into production.

There is a certain irony in having a Philadelphian - albeit a newly minted one - chosen to improve the latticework sidewalk shed, a crude-looking assemblage that is traditionally bolted together with steel pipes and wooden boards.

In New York, where contractors are legally required to keep the sidewalks safe and clear for pedestrians, the covered sheds are a ubiquitous part of the urban landscape. But Philadelphia builders have vociferously resisted the safety feature, citing limited sidewalk space on the city's narrow, colonial-era streets.

To be fair, the sheds have become more visible here since City Councilman James Kenney persuaded the Department of Licenses and Inspections to toughen its rules in 2008. Most sheds you see around town these days have been erected for long-running facade-repair projects, such as the one now taking place at Centre Square.

But exemptions are all too common, and pedestrians still find themselves wading unprotected into traffic at construction sites. Currently, neither the National Museum of Jewish American History nor Drexel University's new gym provides pedestrians with the safe passage of a sidewalk shed, even though both high-profile projects face Market Street, among Philadelphia's widest streets. They don't even bother to carve out a path in the street with concrete Jersey barriers.

I suspect that most people in Philadelphia would be thrilled just to have New York-style sidewalk sheds mandated for every construction site, even if the pipes and boards do have all the architectural finesse of a child's tree house. But for New York, that rustic look just wouldn't do anymore.

New York sees good design as integral to its image as a modern city on the move. A few years ago, it hired Jan Gehl, the visionary Danish urban-design consultant, to suggest some low-cost, easily implemented improvements.

Gehl couldn't help noticing that an awful lot of New York sidewalks were in shadow. At any given moment, sheds cover about a million linear feet of ground. Often the clunky structures are left in place for years, casting a dark pall over their environs and making it hard for ground-floor retailers to stay in business.

New York decided the best way to develop a better shed was to tap the brains of designers through an open competition, organized with the help of the local chapter of the American Institute of Architects. "Design is all about rethinking what we already know," New York Planning Commissioner Amanda Burden said in explaining the approach.

Penn's Choi had never actually seen a New York sidewalk shed when he decided to enter the competition. They don't exist at home in Seoul, either, he told me. He took a trip to New York one weekend shortly after arriving in Philadelphia so he could examine the structures close-up. It was immediately evident that there was room for improvement.

"I tried to think, 'What is wrong with this scaffolding?' It's complicated. I thought the structure should be simplified."

The brilliance of Choi's solution, which he refined into a real design with the help of Andres Cortes and Sarrah Khan at the New York-based Agencie Group, is its striking merger of beauty and function. He calls the design the "Urban Umbrella," because the steel columns open up like the bones of an umbrella to support the shed roof.

Those curved struts appear to weave together, forming an arched canopy that calls to mind the ribs of vaulted medieval ceilings, such as the one at England's Exeter Cathedral. While we admire such soaring vaults for their looks, they were developed because of their inherent strength. The streamlined Urban Umbrella can support as much weight as the bulky cross braces now in use, yet it promises a clear, airy path for pedestrians.

You can't very well enclose such an elegant arcade with a roof made from wooden boards, so the design team instead calls for translucent fiberglass panels that allow sunlight to penetrate and illuminate the footpath. The scheme includes an artful array of LEDs to guide pedestrians at night. It's such an improvement over the existing dim tunnels that you can imagine (as the image renderer Todd Montgomery did) the structure doing double duty as a canopy for an outdoor restaurant

Although the mock-up won't be ready until summer, the design team has clearly thought out many small details. To make the design more appealing to scaffolding contractors, who already have warehouses full of steel pipes, they adopted the same material for the Urban Umbrella. Contractors also can use their own pipes for the Umbrella's main column, though not for the struts.

Still, it's likely to take some persuasion to get installers to spend money to acquire the new system. New York isn't offering any price breaks. The hope is that building owners, and especially retailers, will pressure contractors to adopt the more attractive system.

It may not be possible to mandate good design at urban construction sites, even in New York. But safety? That's a different matter entirely.


Contact architecture critic Inga Saffron at 215-854-2213 or