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12.05.2007
Hoist Me Up
Aaron Seward finds out what it takes to maintain today's adventurous facades

At the Engineering Transparency conference at Columbia University in September, Laurie Hawkinson, of Smith-Miller+Hawkinson Architects, quipped that with all the glass we are using these days, how will we ever clean it? Her discussion of window washing began and ended there, but the comment revealed an issue that is a growing concern for architects around the world. As buildings use more glazing and become more complex in form, the systems for accessing their facades—not just for cleaning, but also for repair—have had to keep pace. Not that there have been any major revolutions in access technologies, but architects, one hopes, are taking facade access into consideration much earlier in the design process: If you can build that bravely curved or drastically angled envelope, you had better know how to get up there to keep it looking handsome (in an economically feasible way) throughout the life of the building.

Facade access technology has remained basically the same for the past 40 or 50 years. As was done in the time of the Seagram Building, you still hang a basket over the edge of the parapet, drop it down on ropes, and haul it back up. But two things have changed. For one, never-before-seen building profiles and rooftops crowded with mechanical systems have challenged facade access engineers to fit their machines within tighter spaces while pushing them to attain spans of over 100 feet and drops in excess of 1,000 feet. And secondly, this pushing of the envelope (along with code changes) has brought about a convergence of the systems used in the United States and those employed in other countries.

As with many aspects of the building industry, facade access technology developed along different lines in the United States than it did in Europe. This divergence in approach centered on one essential point: Where to put the hoist that raises and lowers the basket? In Europe they favored mounting the hoist on the roof of the building and powering descent and lift from there, whereas here, with our love of individualism and need to be in control, we decided to put the hoist right in the basket.

Both methods have their virtues, of course, and are suitable for a variety of applications. The machinery for self-powered baskets, for example, is quite a bit cheaper than its roof-mounted counterpart. But roof-mounted systems have become more sophisticated and versatile—employing cranes with telescoping booms and articulating heads—capable of reaching 100 percent of a building’s envelope no matter how curvaceous it may be. This factor alone has made these systems a necessity for much of today’s architecture. A quick glance around the recently completed high-profile buildings in New York, including the Hearst Tower, InterActive Corp’s headquarters, and The New York Times Building, will reveal a spate of these European devices. The roof-mounted systems are also more suitable for tall buildings since they store all excess rope, wire, or other necessary tools on the roof. Federal Occupational Safety and Health Administration (OSHA) code states that rope cannot dangle beneath the window cleaning platform, meaning that self-powered systems must hold all excess rope on the basket. And when an elevation is very high, the amount of rope it will take to reach all the way down can begin to outweigh the lifting capacity of standard hoists.

Someone very recently noticed this problem and, despite the grumblings of the penny-pinching American building market, decided to do something about it. The American Society of Mechanical Engineers (ASME) A120.1-2006 Revised Standard demands that buildings in excess of 490 feet use a system where the hoist is anchored on the rooftop. Of course, the vast majority of buildings going up across the country are well under 490 feet, and the codes that govern facade access, like most codes in the building industry, are self-enforcing and loosely policed. Furthermore, where there is one code that demands you do the utmost, there is another that allows you to put forth the least amount of effort, not to mention upfront capital cost. The International Window Cleaning Association (IWCA) I-14 Safety Standard allows buildings under 300 feet tall to employ boatswain’s, or bosun’s, chairs—basically a plank dangling from a rope on which a window washer sits.

In fairness, the IWCA standard was targeted at building owners who were not equipping their roofs with any system, an all too common phenomenon that led to workers tying off to vent pipes and then falling to their deaths. Liability concerns aside, facade access consultants, as a rule, do not recommend bosun’s chairs. “Facade access isn’t just about window washing, but about building maintenance,” said Keenan Potter of Lerch Bates, one of the country’s largest facade access consulting firms. “In bosun’s chairs you can’t replace glass, just wash windows.” His point is an important one for those who think about the life cycle of buildings. While expensive, the price of sophisticated facade access systems is nominal when compared to overall building costs. And they get even cheaper when you consider that in 15 to 20 years, when your mullions begin to leak, you won’t have to cover your building in scaffolding just to patch it up.

Aaron Seward