Does anyone have any idea what the expected life of a modern sky-scraper (constructed in the last 10 years) is if it is properly maintained? If it is not maintained?

• ID# 42.2 (reply to #42.1) - 27 Jun 1998
  Several decades...? ;^)
  Perhaps the question can be divided into two parts: the lifespan of the frame and the lifespan of the cladding and interiors.
  If properly maintained and founded, the frame should last well into the 21st Century -- I see no reason why the steel frame should degrade even in a long timespan. Perhaps you structural enginers can elaborate / correct me...?
  The nature of the internal frame in the skyscrapers built in the 1960s and 1970s provides an interesting deviation, though. The economically designed frames have shown a severe tendency to sway in heavy winds. The Sears Tower and 200 Water Street are such examples -- in the latter case the frame had to be strengthened as the (originally office-) building was converted into apartments; the degree of swaying would have been unacceptable in an apartment tower.
  In contrast, the frames of the skyscrapers around the 1930s were in a sense "over-engineered", they were built as relatively rigid and sturdy structures, with more expense put on steel... Perhaps the more lavish expenditure on the older high-rises (as well as their style and decor, and the more fashionable "image") has led to the increased renovation and conversion of the Art Deco skyscrapers in the 1990s.
  Which leads us to the lifespan of cladding & interiors. These, obviously, require much more care and attention than the frame to keep them in good shape and preserve them in original condition. If left unattended in detrimental conditions (dampness, cold, pests) for a long time, the interiors will surely start to detoriorate. Similarly, the exterior will unavoidably gather grime, the cladding may start falling off or get damaged.
  If not maintained, the building can be usually brought "up-to-date", but the repairs will always cost a great amount of greenbacks, and at some point the repairs may not be cost-effective anymore. ED.
  • ID# 42.3 (reply to #42.2)
    From: Frank Gerlak ([email protected]) - 30 Jun 1998

    Unfortunately, the real life span of a skyscraper is the duration of its positive cash flow to the developer. As most of these buildings are depreciated, when the depreciation allowance ends (usually 7 years) their cash flow slows down and they are often sold. Unless the economy is booming and the buildings are fully rented, they are sold to another developer who can depreciate them again. If a building has deteriorated, it must then have a "mid-life" rehab. Depending on zoning regulations in effect when the building was constructed, the rehab may be quite extensive. Or, if the zoning regulations have improved (for the developer), and a developer can build a bigger buuilding, it may be demolished. Often stone and steel last much longer than money thus cash flow becomes the controlling factor in the life of a skyscraper.
    Remember, a skyscraper represents a great risk to a developer and is usually not completed for 3-4 years after a developer gets the idea to build because of a "hot" market. Think about the skyscrapers that were started in 1929 because the market was hot and then completed in 1931 in great haste. That is why we had the "Empty Space Building" instead of the Empire State Building. Most New York skyscrapers started in 1929 were not "solvent" until World War II and their "occupation" by the U.S. Government.

    • ID# 42.4 (reply to #42.3) - 30 Jun 1998
      At last we're getting some hard-boiled data to counter your site upkeeper's construction-centered, "idealistic architect" views... ;^)
      I agree on the cyclical nature of the lifespan of a high-rise, but I find it interesting that, after all, in the last decades, rather a few skyscrapers have in fact faced the wrecker's ball, even in NYC (even discounting the effect of the Landmarks Preservation Commission). Rather often the new scrapers have been built rather on the sites of older low-rise buildings, utilizing their air-rights and allowed the old buildings' owners to capitalize on the "frozen asset" of the "underdeveloped" site. Apart from improved zoning (=more allowed building volume on site than previously), what other decisive factors are there to favour the construction of a new building -- especially if the building has been built after, say, the 1950s, with somewhat decent provisions for internal cableways and ductwork?
      As far as I know, the Manhattan office scrapers have a rather healthy rate of vacancy even now, but apparently (Yes! Holland's Bergkamp (the god of Arsenal) just scored 1-0 in the match 'gainst Yugoslavia! Superb!) Ehum, yes, apparently, after the lean years of the early 1990s, the construction scene in NYC seems to have refreshed and obviously the developers expect to get all the new space rented (as optimistic as it seems to me, despite the new investments into the City...). E "Seedorf" D.