Skyscraper façades were arguably simpler and easier to clean when their windows opened. Indeed, façade cleaning prior to 1950 primarily meant window washing, which was carried out by a dedicated crew of workers who would strap themselves into leather harnesses and hook themselves to the sides of skyscraper windows. Though the window ledges they stood on were tiny, they felt relatively safe: if one hook failed, they would be left dangling from the other. But with the advent of the glass curtain wall building in the 1950s, windows effectively became the building façade. And because this façade was fixed—i.e., it didn’t open—window washing required access from the outside, and thus became infinitely more complex. To facilitate outside access for window cleaners, buildings had to be built with flat roofs to accommodate fixed or mobile window-washing equipment. A variety of mechanisms were developed to allow window-washing platforms to be suspended from rails or tracks atop a building roof, and to move up or down at the discretion of the operator.
As window-washing technology became more sophisticated, glass curtain wall buildings were able to break away from the mandatory flat-roofed silhouette. Slopes and multiple recesses, which had been prominent in designs during the first three decades of the 1900s (e.g., the Chrysler Building or the Empire State Building), began to reappear in skyscraper designs toward the end of the century. New forms of façade-access equipment were developed to serve these buildings, including arms that could act as supports for both window washing and hoisting. Today window washing remains at the heart of a building’s periodic maintenance routine. Most windows will be washed twice a year, with the exception of groundlevel retail and lobby entrances, which are done much more frequently. Nearly all of this work continues to be done by hand, although new experiments with automated cleaning robots—which rely on vacuum-powered suckers rather than guiderails to attach themselves to buildings—are under way in Europe and the Middle East.
Access to the sides of a skyscraper is important not just for window washing but also for metal cleaning, inspection of curtain wall conditions, and the hoisting of replacement panels. In buildings with straight sides, this access is generally provided by a rig mechanism that is anchored on the roof and has the ability to move up or down fairly easily.
However, an increasing number of skyscrapers—particularly in Asia—do not have straight sides and distinguish themselves by twisting curtain walls or by multiple setbacks. As a result, the building designers must—at an early stage in design—select a façade access technology that will work with the building’s unusual geometry.
The Petronas Towers in Malaysia (pictured at the top of this story) offer a good example of this complexity. Because of the towers’ multiple setbacks, traditional window-washing systems would be of little use. Instead, telescoping booms articulate out from hidden panels near the top of the structure, extending as far as needed to allow the cleaning rig to reach the protruding levels below.
This story was adapted from Kate Ascher's new book, The Heights: Anatomy of a Skyscraper, now available from The Penguin Press.