We like to think of buildings as being permanent, unchanging. They feel permanent; after all, it is part of a building’s basic purpose, reliably sheltering us from the elements. But the unfortunate truth is that most buildings do not last long. It might shock you to learn that a 2001 U.S. Census report found that the average age of a residential building was a mere thirty-two years. In neighboring Canada, the average age of all non-residential buildings falls just short of eighteen years.1 Nor is this perpetual youth—a symptom in part of wear and tear, constant development, and demolition—restricted to everyday buildings; it’s true of capital-A architecture as well. Many Modernist buildings, even those designed by important architects, are considered obsolete after only two or three decades. 

Fortunately, for some buildings, the large institutions behind Capital-A architecture and Capital-P preservation devote considerable time and resources to safeguarding the architectural legacies of Great Artists, or the buildings that once housed Great People or played spectator to Great Events. These are the fewer than 2,600 buildings deemed National Historic Landmarks, those structures which, according to the qualifying criteria: “have the strongest association with a significant event in our nation’s history, that best [tell] the story of an individual who played a significant role in the history of our nation, that are an exceptional representation of a particular building or engineering method, technique, or building type, and/or have the potential to yield new and innovative information about the past through archeology.”

In reality, even this loftiest of federal designations lacks the teeth to prevent significant alteration to historic buildings: property owners are free to make any changes (including demolition) unless doing so is prohibited or restricted by local law. And the more common designation, inclusion in the National Register of Historic Places, which covers over ninety thousand sites, still leaves many buildings vulnerable to demolition or significant modification—all the better to please the rentier class. In an article debunking “common myths” on the National Trust for Historic Preservation website, homeowners with listed properties are reassured about the supremacy of private ownership over history: “Some people may consider your house to be a national treasure, but it’s still your house. You can rent it out, lease it, transfer it, will it away, or dispose of it in any way that tickles your fancy.” 

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• 1. It’s difficult, of course, to find statistics on the actual lifespan of buildings, however it is easy to find policy that explains why the age of buildings skews so low. An average building age of thirty-two years conveniently coincides with an interesting date range in the US tax code, the “recovery period,” part of the IRS tax deduction for depreciation, which “allows you to recover the cost or other basis of certain property over the time you use the property. It is an allowance for the wear and tear, deterioration, or obsolescence of the property.” As Baltimore City preservationist Jackson Gilman-Forlini explained to me via email: “The IRS determines how much you can deduct based on the value of the property or the improvements (the ‘basis’) divided over the lifespan of the asset. This lifespan is called the ‘recovery period’ and is set at 27.5 years for residential rental property and thirty-nine years for non-residential property.” When a building reaches the end of this recovery period, it is no longer eligible for the tax deduction because it is considered valueless. This, in turn, encourages redevelopment at a rate of 27.5 or thirty-nine years