Steel vs concrete parking garage cost cycle

Material competition. A parking garage can be dated to within a decade by which material was cost-competitive at construction.

Concrete and steel compete for buildings. If you go around the country and look at parking garages — that's the example I like to give — you can look at parking garages and see if they're made out of steel or out of concrete. And if you know anything about the relative cost at different points in time of reinforced concrete versus steel frame structures, you can almost pinpoint within about a one-decade period when that parking garage was built, just on straight economics of which one was more competitive at the time.