May 4, 2015 Housing Action Coalition

The History and Future of Granny Flats in San Francisco

For decades, accessory dwelling units (ADUs) were hotly contested in San Francisco. Concerns over parking and added density raised issue with residents, and local opposition stifled any proposals that encouraged the construction of these low-impact, naturally affordable homes. But in the past two years, several new pieces of legislation have been adopted or are underway that will allow for the creation of new ADUs and legalize existing ones. Last week, at a forum we co-hosted with SPUR and AIA San Francisco, an all-star panel dug into the history and future of these homes.


  • Kearstin Dischinger | SF Planning Department
  • Mark Hogan | OpenScope Studio
  • Scott Wiener | District 8 Supervisor
  • Kevin Casey | New Avenue Homes

ADUs housed many of the City’s workforce during World War II. But as Kearstin Dischinger’s timeline shows, suburban development patterns favored more parking while density limits restricted their construction from the 1950s-80s. Three efforts to incentivize building new ADUs during the 1990’s failed. Today, a changing political climate that recognizes the need for more housing sees these homes as a smart way to add to the city’s housing stock in a flexible and inexpensive way.

Supervisor Wiener, a champion for passing legislation last year that legalizes building new ADUs in the Castro, acknowledged that trying to pass city-wide legislation in the past was a mistake. It’s best to focus on this effort neighborhood by neighborhood. His most recent legislation expands building ADUs in Noe Valley, Diamond Heights and Twin Peaks. Supervisor Christensen is working on bringing this neighborhood approach to District 3.

To help provide examples and expand the thinking around how new ADUs can be added to existing properties, OpenScope Studio, created a Handbook that provides different prototypes and financial models. Building a new ADU can cost as little as $200,000, compared to $500,000 for a unit in a new multi-family building. Different prototypes include converting a freestanding garage, converting existing space in the bottom floor or building an entirely separate unit in the back of a property, amongst others.

On the panel, Kevin Casey discussed how other cities and countries have used ADUs as a housing choice long before San Francisco even started considering them. Eighteen years ago, he was working in Bali, Indonesia, where he lived with unrelated individuals on one lot that contained three homes and a guest room (pictured below). Inspired by his experience, Kevin formed New Avenue Homes, an online platform where all of the necessary parties can connect and work together to build the home.


Whether you call them in-laws, granny flats, or our personal favorite – Fonzie Flats – we should continue to incentivize the construction of new ADUs in San Francisco. They’re cheaper to build, work for a variety of households and have minimal impact on the physical character of our neighborhoods.

View Kearstin Dischinger’s Presentation

View Mark Hogan’s Presentation

Check Out the ADU Handbook

Top image: Zillow
Bottom image: New Avenue Homes

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Housing Action Coalition

The Housing Action Coalition is a member-supported non-profit that advocates for the creation of well designed, well-located housing at all levels of affordability. We believe more housing means more choices and better solutions.

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