We’ll look at 3 different buildings - the Empire State Building (completed in 1931), the World Trade Center (completed in the early 1970s), and a 4-story steel building AISC uses as a university case study (completed in 2003). But we can look at individual buildings built at different times, for which we have enough information to make some productivity calculations. Ideally, we would have a broad sample of the labor requirements for steel erection, but (as far as I know) such a dataset doesn’t exist. (This is somewhat less true of design requirements for lateral forces, which have often increased as we gain a better understanding of wind and earthquakes, but it's still broadly true.) Loading requirements for the 2020 New York State Building Code. The Empire State Building has had many renovations over the years that replaced older building systems with more modern, better performing ones, but it still has its original structural steel frame.Ībove: Loading requirements from the 1917 New York Building Code. A modern structural steel frame is doing the same job, and will be designed for similar loading, as a building built 100 years ago. Unlike other aspects of construction, the output of this task (a structural steel frame) doesn’t change substantially over time. In steel buildings, the steel acts as the structural skeleton supporting the weight of the building. One good task for this is structural steel erection. If people are spending slightly more hours to build a much better product, has productivity really stagnated? One way to overcome this problem would be to look at a productivity metric that doesn’t have the issue of quality increase obfuscating the data.
So part of the lack of apparent productivity increase is due to an increase in quality. A modern single family home has more insulation, a nicer kitchen, more bathrooms, etc., than a single family home built in the 1960s. The primary one is that the content of a single family home has changed over time. While I think this is a useful metric of construction productivity, it has some drawbacks. We previously looked at single family home construction, and noted that the number of hours required to construct 100 square feet of single family home has slightly increased over the past 50 years. This week we’re continuing our investigation of productivity trends in US construction.
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