Pest by design: Street art from San Francisco.
Credit: Cassidy Curtis Pest by design: Street art from San Francisco.

Regarding those things that crawl, bite, and go bump in the night—or undermine foundations and building structures: What if it were possible to prevent them from getting inside and underneath in the first place? The city of San Francisco has just published a set of guidelines to do exactly that. The city is pitching "Pest Prevention by Design" as the new standard for architects, engineers, and builders interested in making buildings inhospitable to pests.

Some background: In 2005, the city’s Integrated Pest Management (IPM) staff took stock of the city's pest problem. Despite having achieved an 80 percent decline in the usage of pesticides in the first eight years of the program, staff realized that the city hadn't made any further progress in reducing pesticide use on its properties. San Francisco had reached a limit. When the IPM managers consulted with their field staff, they learned that remaining pest problems were likely attributable to design problems—in both buildings and landscapes.

The city was particularly concerned about pests in its low-income housing projects, and ultimately received a grant from the U.S. Centers for Disease Control and Prevention (CDC) to work on the issue of asthma in low-income housing. The grant included a specific provision to address the root causes of rampant pest problems.

According to Chris Geiger, manager for green purchasing and IPM programs with San Francisco’s Department of the Environment, a study of seven U.S. inner-city housing projects published in Environmental Health Perspectives included a number of astonishing findings that prompted San Francisco's next steps. Among those findings: Toddlers exposed to pesticides were twice as likely to develop asthma; 73 percent of the dwellings studied had cockroaches; and 49 percent of those dwellings had mice. In turn, most of the adults and children had developed cockroach dust allergies, and many to mice urine.

Part of the CDC grant enabled the city to work with architects, engineers, pest control professionals and researchers, IPM experts, and public agencies to develop guidelines for building pest control into structures—to stop pests at the source, reduce pesticide use, and curb pest-related health problems.

The resulting guidelines are geared toward common North American pests. They focus on common-sense solutions for designing away rodents, termites, cockroaches, beetles, flies, mosquitos, opossums, raccoons, and birds such as starlings and pigeons. Others, too.

“What [the guidelines] lack in glamour, they make up for with their potential to improve people’s health,” Geiger says.

The guidelines are recommendations, rather than formal codes, since many pest-control issues are site-specific. The guides offer a series of general principles for architects and engineers to consider, such as using pest-resistant materials or designing for a recommended level of pest tolerance. For example, an industrial food production facility will likely have a much more stringent “tolerance” level than a suburban home. Other recommendations include sealing off openings and minimizing moisture: more common-sense stuff. But there are much more specific guidelines, too, regarding the construction of foundations and slabs, building exteriors, roofs, and landscaping near structures.

The green building movement is the next frontier for legitimate pest prevention through design. “It’s a topic that often isn't addressed at all, though it would make sense to include it," Geiger says. "We've already seen examples of big pest problems in some certified green buildings. False ceilings can serve as rat condos, a nice little home for someone.”

Designing buildings to stop pests before they become a problem is “just not in people’s universe yet,” Geiger says. Though these guidelines are tailored to architects and engineers, San Francisco is producing another set of similar guide materials geared toward small-property managers and residents, Geiger says. Ultimately, he hopes to see the guidelines incorporated into sustainability standards such as LEED, the International Green Construction Code, and others.

“My hope is that architects will have this thing ['Pest Prevention by Design'] on their shelves and think about these factors," Geiger says. "It really is part of having healthy buildings with good indoor air quality and reduces costs in the long term.”