Even Los Angeles, often blamed for spawning the culture of sprawl, is evaluating a measure that would limit the size of single-family infill housing—some 300,000 properties.
Although there is no single set of nationwide data on such ordinances, the National Trust for Historic Preservation tracks the issue through its anti-teardown initiative. In a May 2006 study it found that more than 300 communities in 33 states have taken steps to combat teardowns and overbuilding by imposing demolition delays, limits on square footage, and creating conservation districts. "We're finding that it's as much about what goes up afterward as what comes down," says Adrian Fine, director of the Trust's Northeast field office in Philadelphia.
Among the more innovative attempts to curb McMansion building, Boulder County, Colorado, is hashing out the details of a quasi cap-and-trade scheme. The county's median house size ballooned from 3,881 square feet, in 1990, to 6,290 square feet in 2006—more than twice the national averages for both size and growth rate during that period. "We have seen a dramatic increase in the number of extraordinarily large additions, more than doubling the original home size, and in scrape offs and rebuilds of much larger homes," says Michelle Krezek, Boulder's manager of special projects, adding that these trends are expected to continue. A proposed "transferable development rights" (TDR) plan would require homeowners and developers seeking to exceed 6,500 square feet in the flatlands, or 4,500 square feet in the mountains, to purchase credits either from the owners of properties that are under those caps, or from a county clearinghouse. Exact details of the credit system, including pricing and the mechanics of the transactions, are being fine-tuned; the county's planning commission is expected to take up the matter in early 2008.
Proponents contend that although Boulder's plan avoids setting an upper limit on the total amount of permissible development countywide, it nevertheless creates a financial disincentive to build big. It could also help increase the stock of affordable housing. Sellers whose properties carry deed restrictions will most likely get a one-time payment as opposed to tax breaks, Krezek explains, and subsequent owners will be unable to increase square footage.
This untested market system has its skeptics. "As house prices go up, people who sell their credits might regret it," says planner Lane Kendig, a principal of the Kendig Keast Collaborative in Sturgeon Bay, Wisconsin, and author of an American Planning Association (APA) report on regulating homebuilding. "The house won't be expandable. If I sell, I've boxed my house in. What if I have another kid and need the space?"