Survey on actual service lives for North American buildings

This paper presents results of a demolition survey in a major North American city that captured building age, building type, structural material and reason for demolition for 227 buildings. The findings challenge many common assumptions about building longevity, and, in particular, the relationship between structural material and service life. Although it is often believed that “durable” structural materials such as steel and concrete will provide the longest service lives for their buildings, our results suggest there is no significant relationship between the structural system and the actual useful life of the building. Reasons for demolition were instead related to changing land values, lack of suitability of the building for current needs, and lack of maintenance of various non-structural components. Only eight buildings identified a specific structural failure. Indeed, the service lives of most buildings are probably far shorter than their theoretical maximum lives; the majority of demolished steel and concrete buildings in our study were less than 50 years old. In the context of sustainable construction, this raises some interesting questions and shifts the spotlight away from durability of materials and on to 1) flexibility of design to allow future changes; 2) deconstructability; and 3) the use of more accurate life span predictions in life cycle assessment calculations on whole buildings. Introduction It is generally understood that, within a fairly short time frame, a building will become functionally obsolete, or neighborhood characteristics and land values will change such that the building is no longer delivering the highest value for the land. Nonetheless, many practitioners in the building industry believe that buildings last a long time, and that longevity is related to structural material (1,2), as shown in Figure 1, with wood buildings believed to have the shortest lives. Accordingly, there is an increasing tendency to make assumptions or claims about the relative durability of competing structural materials, particularly for the purpose of highlighting presumed environmental characteristics of those materials. The assumption that wood can’t offer the same durability as steel and concrete excludes it from building applications where longevity is important. In addition, the environmental profile of wood is hurt by this durability image. A short service life has a negative effect on life-cycle environmental analysis results, as the impact of a replacement building will be included in the calculation. The hypothesis behind this survey was that no relationship exists between structural material and service life of a building, and that buildings are most likely demolished far before the end of the useful life of the structural systems. Building industry beliefs that some structural materials last longer than others are most likely confusing how long a building could last with how long it is actually kept in service. In fact, a few previous studies indicate that service lives of most