Book excerpt: As the reproduction cost of housing has increased, consumers have made intensive use of existing dwellings. Conversions of the housing stock have regained prominence as a source of supply. This book introduces the accessory apartment and assesses its potential as an emerging resource for meeting local and national housing needs. Although accessory apartments help meet some of the nation's housing needs, they are not entirely without problems. Some of these are environmental problems, such as physical alterations that are out of character with the design and appearance of surrounding structures, while other problems are cultural and ideological. The accessory apartment in a single-family house deviates from the image of housing, family, and neighborhood that prevails in American culture. It symbolizes a change in the way the single-family house is used and the kinds of people who live in it. These changes clash with the traditional meanings attached to the categories of residential zoning. Martin Gellen evaluates and answers the following questions throughout the text: How do we live with accessory apartments? Control their number? Ensure their soundness?--and maintain neighborhood standards? He focuses on the physical planning problems of conversions and examines the zoning issues they raise. This includes a realistic appraisal of the purposes of density and occupancy controls in exclusive single-family districts. The author provides new methods for regulation of density and occupancy which permit more flexible use of single-family housing to meet the housing needs of a more diverse population. Whether in an aging suburb or new tract, the accessory apartment is a current challenge. This book provides a clear headed approach toward a popular trend in the ever changing housing industry.