Students and faculty at the College of Environmental Design have long designed creative approaches to increasing density in residential neighborhoods. But California’s implementation of SB 375, the Sustainable Communities and Climate Protection Act of 2008, is putting new pressure on communities to support infill development. So the timing could not be more perfect for the Institute of Urban and Regional Development’s Center for Community Innovation to study small-scale infill, specifically, the potential impact of an accessory dwelling unit strategy in the East Bay.
In-law units, or accessory dwelling units (ADUs), are self-contained, smaller living units on the lot of a single-family home. They can be either attached to the primary house, such as an above-the-garage unit or a basement unit, or, as is more typical in Berkeley, an independent cottage or carriage-house. They are an easy way to provide homeowners with flexible space for a home office or an on-site caregiver, additional rental income, or a space for elderly family members to remain in a family environment. In short, they offer the kind of flexibility that has become imperative in today’s world to accommodate fluctuating work schedules and alternative family arrangements.
The concept, often termed “invisible density” or “distributed housing,” is hardly a new idea — indeed, the practice of building a supplementary unit behind a main house has been prevalent in Berkeley and throughout the East Bay for over a century. But ADUs particularly fit the context of Berkeley’s flatlands, with their historically “blue-collar urban form.” These “minimal-bungalow” districts are characterized by neat regularity, uniform land use, and little change — making them ideal for ADU development. Developers in the 1910s and 1920s widened the lots from 25 feet to 40 feet, created uniform setbacks, and supplied single backyard garages in order to maintain lower densities in the neighborhood. CED Professor Paul Groth argues that this uniformity was meant to create more predictable land values and erase the visual evidence of class struggle seen in more mixed-use, informal districts by imposing middle-class values. But today, the wide lots and historic garages provide an opportunity for infill.
ADUs provide benefits for both society and individuals. As infill development, they make efficient and “green” use of existing infrastructure and help increase densities to levels at which transit becomes viable — yet with lower costs and quicker permitting processes than for larger, multi-family building types. Because ADUs tend to be relatively small and their amenities modest, they provide more affordable housing options (at less than one-third of the cost of comparable units in multi-family buildings). Oftentimes, these units are the only rental housing available in older, predominantly single-family neighborhoods, making it possible for people from all walks of life to live in the area. Yet, they also significantly improve the value of the property, in essence constituting an asset-building strategy for homeowners.
