Editing Skyscraper (section)

===The elevator conundrum===
The invention of the [[elevator]] was a precondition for the invention of skyscrapers, given that most people would not (or could not) climb more than a few flights of stairs at a time. The elevators in a skyscraper are not simply a necessary utility, like running water and electricity, but are in fact closely related to the design of the whole structure: a taller building requires more elevators to service the additional floors, but the elevator shafts consume valuable floor space. If the service core, which contains the elevator shafts, becomes too big, it can reduce the profitability of the building. Architects must therefore balance the value gained by adding height against the value lost to the expanding service core.<ref name="HSW3">{{cite web|url=http://science.howstuffworks.com/skyscraper3.htm|title=How Skyscrapers Work: Making it Functional|date=3 April 2001|publisher=HowStuffWorks|access-date=30 October 2008}}</ref>
[[File:HK Wan Chai North 中環廣場 Central Plaza 26th floor sky lift lobby October 2018 SSG 01.jpg|thumb|Sky lobby at [[Central Plaza (Hong Kong)|Central Plaza]] in [[Hong Kong]] which has clear signage of the floors served by the different elevators.]]
Many tall buildings use elevators in a non-standard configuration to reduce their footprint. Buildings such as the former [[World Trade Center (1973–2001)|World Trade Center Towers]] and Chicago's [[John Hancock Center]] use [[sky lobby|sky lobbies]], where express elevators take passengers to upper floors which serve as the base for local elevators. This allows architects and engineers to place elevator shafts on top of each other, saving space. Sky lobbies and express elevators take up a significant amount of space, however, and add to the amount of time spent commuting between floors.

Other buildings, such as the [[Petronas Towers]], use [[double-deck elevator]]s, allowing more people to fit in a single elevator, and reaching two floors at every stop. It is possible to use even more than two levels on an elevator, although this has never been done. The main problem with double-deck elevators is that they cause everyone in the elevator to stop when only person on one level needs to get off at a given floor.

Buildings with sky lobbies include the [[World Trade Center (2001–present)|World Trade Center]], [[Petronas Twin Towers]], [[Willis Tower]] and [[Taipei 101]]. The 44th-floor sky lobby of the John Hancock Center also featured the first [[high-rise]] indoor [[swimming pool]], which remains the highest in the United States.<ref name=Emporis>{{cite web|url=http://www.emporis.com/en/wm/bu/?id=116876|archive-url=https://web.archive.org/web/20040415075239/http://www.emporis.com/en/wm/bu/?id=116876|url-status=usurped|archive-date=15 April 2004|title=John Hancock Center|author=Emporis GmbH}}</ref>