The Portland Cement Association, market development and public affairs, completed a survey of sixty-six firms comprising about 30 percent of office building contractors. The importance of construction time and front-end investment in construction material, exacerbated by interest rates, make the results of this study particularly important.
Construction times for buildings actually built were queried as well as an estimate of time needed for the alternative material designed. From the sample of 179 buildings actually built, it was found that concrete had an average time advantage of two months. This advantage was most evident in buildings from 5 to 29 stories high. For buildings over 29 stories, however, the small sampling of nine concrete and nine steel framed structures showed steel to have a three-month advantage. Overall, it appears that concrete frame buildings are more often built when superstructure times for concrete are close to or even slightly more than the time for the steel alternative. This may be due to the uncertainties in steel delivery. Only 6.6 percent of the concrete frame buildings surveyed encountered material delays, while 19.2 percent of the steel frame structures were delayed by material supply problems.
Since construction time can be considered as part of first cost, and was ranked ahead of first cost in survey results, the Portland Cement Association concluded that it is one of the most important elements of first cost and is a major determinant of framing type.