HUGE SKYSCRAPERS.

Ashburton Guardian, Volume 50, Issue 137, 22 March 1930, Page 2

HUGE SKYSCRAPERS.

ISO STOREYS HIGH. Sky-scrapers with about 150. floors, almost two-fifths of a mile high, or nearly four times the height of Washington Monument, now can be built with safety, says a writer in the San Francisco “Chronicle.”

But their “economic height,” for the best rental profits, js around 75 storeys. This economic top is limited at present in Chicago, Detroit, New York, and possibly a few other American cities where land values are extremely high. These statements summarise a report issued htt the American Institute of Steel Construction. It is based on two years research to learn the skyscraper limit, and the “economic considerations” which “will be the determining factor in this as in other fields of human progress.” The skyscrapers forecast are of the present setback or tower architecture, in their probable spread is seen a modi- , lied type of a big city, in which co-op-erative endeavour provides increased) facilities for health and comfort. Each building is likely to occupy a fidl city block, he says. Costs and profits will dictate this. Each structure may house an almost complete small city. Street congestion may be decreased by substituting more “vertical' traffic” for horizontal, and by constructing arcaded sidewalks and three-decked or four-decked streets. A way out of the poor light and ventilation of city canyons is seen. “I think,” says an expert, “that there will be artificial atmospheric control in a few years that will astound us. A few engineers already predict artificial lighting more satisfactory than that which is brought in windows.”

The institute report says “buildings of 75 storeys are not only economical, but under certain conditions will return more on the investment than a building of 50 or 30 storeys.” The 75storey estimate is based on land values of more than 200 dollars (£4O) a square foot. The height of 75 storeys is calculated to range from 880 to nearly 1000 feet.

The report estimates the profits on eight imaginary skyscrapers, ranging from 10 to 75 floors. It finds the highest net profit, 10.24 per cent, in a 63storev building, the next best, 10.06 in 75-storeys, 8.5 per cent, for a 34, and 4.22 for a 10-storey building. The physical 150-storey limit of twofifths of a mile is not due to lack of structural steel strength above that height. Too much weight would be required in elevator cables, says the report, and the average human ear would not withstand the vibration in an elevator travelling at the speed required for service. This speed is estimated in excess of 1500 feet a minute. Present elevator speeds are 750 to 800 feet.