Rethinking Residential Zoning

Residential zoning districts encompass 70 percent of San Francisco’s private land. Across most residential districts, current zoning permits only one or two units per lot. As the housing crisis in San Francisco and the Bay Area becomes more acute, and as the City and the region continue to grapple with transportation and sustainability, the practice of exclusionary zoning – zoning which segregates people by income or economic class – is coming under increasing scrutiny. Recent changes to San Francisco and state law have opened up areas of low-density residential zoning to more housing and more diverse housing by legalizing accessory dwelling units. Even bigger changes could be on the way. SB 827, a bill by Senator Scott Wiener that would radically alter residential zoning controls in transit-rich areas of California, including most of San Francisco, will be debated in the state legislature this year.

Defenders of low-density residential zoning counter with appeals to defend the established character of neighborhoods, and concerns about the effects of increased density and more residents, particularly on parking and traffic.

Exclusionary zoning practices:

  • Segregate neighborhoods by income
  • Make housing less affordable
  • Limit housing choices for moderate and low-income households
  • Exclude new residents from transit-rich areas and abet sprawl development.
  • Privilege driving and parking over walking, cycling, and transit

One would expect San Francisco, with its progressive and environmental values, to be in the forefront of reforming exclusionary practices. But over half the city’s land area is subject to exclusionary zoning. There’s an increasingly clear way forward for San Francisco to reduce economic exclusion, diversify income-segregated neighborhoods, and expand housing opportunities, while preserving the character and livability of neighborhoods, preventing the loss and displacement of existing housing and residents, and improving access and expanding sustainable mobility in neighborhoods. San Francisco should be a leader, not a laggard, in reforming residential zoning.

Exclusionary zoning in San Francisco

Exclusionary zoning can be defined as “a legal practice that has been used for decades to keep lower-income people—disproportionately racial minorities—out of wealthy and middle-class neighborhoods across the country.” As legislative analyst Elliott Anne Rigsby explains:

“The Fair Housing Act prohibits discrimination based on race, color, national origin, religion, sex, ability, and familial status. Notably, however, it does not prohibit class-based discrimination. As a result, the Fair Housing Act provides a loophole for discrimination that confines low-income people to certain neighborhoods by systematically preventing them—through economic tactics such as minimum lot size and other expensive requirements—from moving into areas of with access to opportunity.”

San Francisco’s high housing prices mean that exclusionary zoning excludes not only low-income households, but increasingly middle-income households.

San Francisco exclusionary practices include strict density limits – limiting the number of dwelling units per lot to one or two units. It also includes minimum lot sizes, prohibitions on secondary buildings, parking requirements, and how dwelling units are defined. Exclusionary zoning prohibits many missing middle housing types – multi-unit or clustered housing types compatible in scale with single-family houses.

Residential zoning districts cover a majority of San Francisco’s private land. RH-1 zoning, which permits only only one house per lot, covers 27 percent of all San Francisco’s private land. RH-1-D, which permits only one house per lot and requires side yards between buildings, covers another 11 percent. RH-2 districts, which permit a maximum of two units per lot, cover 16%. RH-3 districts cover 5%, and RM districts, which permit a mix of houses and apartments, cover 9%. Transit-oriented residential districts like RTO, RED, which have no density limits or parking requirements, cover only 2% of the city. 37% of the city’s private land is zoned for only one unit per lot, and a majority of the city’s private land is zoned for a maximum of either one or two units.

Most of San Francisco was built prior to the imposition of zoning laws after World War  II, and many neighborhoods evolved for decades without zoning. This created the diversity of housing types and uses that one sees in most older San Francisco neighborhoods – single-family houses mixed with houses of stacked flats and apartment buildings, cottages and carriage houses tucked in the back of lots or along alleys, and storefronts at street corners or lining public transit routes. The imposition of zoning in San Francisco severely limited opportunities to add housing or diversify housing in neighborhoods. Strict density limits made the addition of new units, whether in new buildings or existing ones, illegal. The zoning of San Francisco also made over 50,000 existing units ‘nonconforming’ – denser than the new zoning allowed – and encouraged the removal of non-conforming units. Minimum parking requirements made housing more expensive to build, made it practically infeasible to add or divide units in many instances. Parking requirements also degraded neighborhood character by proliferating garage doors and driveways instead of front gardens and generous porches.

Beyond exclusionary zoning

While all zoning excludes something, ending exclusionary zoning doesn’t mean doing away with zoning altogether. Zoning done right can contribute enormously to the livability of cities, and can do much more to preserve and foster inclusion and diversity than laissez-faire approaches. San Francisco’s current zoning is a complicated mix of practices which institutionalize exclusion and others which further inclusion. Progressive reform of San Francisco’s planning and zoning laws can reduce regulated exclusion and instead foster inclusion, affordability, and livability.

It makes sense to limit development in environmental hazard zones – areas subject to flooding or coastal erosion, and steep slopes subject to fire and landslides – and to protect historic buildings and unspoiled areas of wild habitat and scenic beauty. It also makes sense to separate housing from certain incompatible uses, like heavy industry. Zoning can limit the size of new buildings and building lot coverage to respect the established built character of neighborhoods, provide public and private open space, and preserve residents’ access to sunlight, greenery, views.

Sometimes, ‘preserving neighborhood character’ is code for a desire to exclude – not wanting to live near renters or lower-income people. But often neighborhood character means the things we love about our neighborhoods – distinctive and historic architecture, mature trees, gardens, and green open spaces, and established residents, businesses, and community institutions. We can reject exclusion while embracing character, and insisting that new development respect and enhance the character of neighborhoods.

San Francisco’s exclusionary zoning often serves to erode character. In most of the city, it’s easier to build an oversized monster home than to build a modestly-sized three-unit building, or add a rear cottage to a lot with a modestly-sized house. As many cities with overheated real estate markets are finding, zoning codes that permit only ever-larger single-family homes while excluding modestly-sized multi-unit housing are eroding both housing affordability and the built character of neighborhoods.

Many cities are turning to form-based codes to preserve and enhance neighborhood character while adding compatible new housing and commercial uses to neighborhoods. Unlike conventional zoning, also known as Euclidean Zoning, which often hard-wires exclusion, form-based codes can build-in housing diversity by accommodating diverse housing types in a given neighborhood, including those in the missing middle.

Creating housing diversity by embracing the missing middle

Missing middle housing types. Source: Opticos Design

The ‘missing middle’ includes a range of housing types compatible in scale with single-family houses, but which allow greater density and variety than currently permited by single family zoning in San Francisco and elsewhere. It includes familiar San Francisco housing types, like townhouses, stacked flats, and cottages, and types like courtyard apartments and bungalow courts seldom seen in San Francisco but common in older neighborhoods in other California cities. Legalizing the missing middle means relaxing current zoning limits on density and minimum parking requirements. For some types, allowing small residential buildings on both the front and rear of a lot, or providing open space in a central court rather than a rear yard, opens the possibilities.

Both San Francisco and California law now allow one accessory dwelling unit (ADU) on any residential lot. ADUs in San Francisco must be within an existing building, including detached cottages and garages, and cannot expand into an existing residential unit. ADUs can be built in parking spaces, and can be built without required off-street parking. Under current San Francisco law, ADUs can’t be built at the same time as the main dwelling; they can only be added to a main dwelling that’s at least three years old. Allowing ADUs to be built at the same time as the main dwelling would decrease the cost and disruption of adding ADUs, and encourage more of them to be built.

San Francisco also prohibits new housing at the rear of a lot, which mostly prohibits new cottages. Cottages are only permitted at the rear of a lot if the lot has street frontage at both ends (typically lots that run between a street and a rear alley) and if both adjacent lots already have residential buildings at the rear of the lot. However a garage is permitted at the rear of any lot. Changing the law to allow required rear yard space to be located between a front dwelling and a rear cottage instead of only at the back of a lot would permit many more cottages without eliminating mid-block open space. Vancouver legalized small cottages along residential alleys in 2010 (known locally as laneway houses) and the city now has over 2000 new laneway houses. San Francisco has fewer residential alleyways, but enough for laneway houses to make a contribution to housing diversity in the neighborhoods which do.

The Alfred E. Clarke Mansion, also known as the Caselli Mansion, on Caselli Avenue in the Castro. This Victorian mansion, built as a single house, was divided into 15 apartments of various sizes.

Another strategy that permits more housing and more affordable options in low-density neighborhoods is to remove the City’s minimum lot size requirements. San Francisco’s Planning Code requires a minimum lot size of 2500 to 4000 square feet. Permitting smaller lots would allow smaller and more affordable houses, including ‘pocket neighborhoods’ of row houses or cottages with individual or shared yards.

In the RH-1-D districts which require side yards, new detached multi-unit buildings could be permitted, or existing buildings divided into two or more units. Detached cottages can be built at the rear of lots. These strategies would conserve the established character – detached buildings set in yards and gardens – while adding new housing and diversifying housing opportunities.

Accomodating diverse households

San Francisco households are increasingly diverse, and planning and zoning for residential neighborhoods should accomodate that diversity by permitting both a greater variety of households, and by permitting households to adapt buildings to meet changing needs.

A dwelling unit is defined in the Planning Code as “a room or suite of two or more rooms that is designed for, or is occupied by, one family doing its own cooking therein and having only one kitchen.” Family has a somewhat convoluted definition, which include single people, and unlimited number people related by blood, marriage or adoption along with ‘necessary domestic servants’ and three or fewer roomers or boarders, or five or fewer unrelated persons. Many of the rules in the Planning Code, including the limitation to one kitchen and restrictions on full bathrooms in ‘rooms down‘, are aimed at disallowing the creation of additional units. However these restrictions can make housing less suitable to different sorts of households – households with three generations living under the same roof, seniors who wish to live independently but close to a family member or caregiver, or intentional communities. Since both San Francisco and the state now permit at least one accessory dwelling unit in any residential building, planners’ imperative to control the details of dwellings’ interior layout makes little sense. It still makes sense to limit the loss of existing dwelling units, but there’s no good reason to ban second kitchens, or a ground floor bedroom with a full bath.

Many of the strategies discussed so far allow for smaller houses and smaller units. The City should also consider strategies which preserve or create units suitable to larger households. When the City created transit-oriented residential districts a decade ago, some of the Supervisors were concerned that removing density limits would result only in studios and one-bedroom units, and limit housing opportunties for larger households, especially households with children. In response, the transit-oriented districts included controls which require at least 40% of units in multi-unit buildings to have at least two bedrooms. The controls also require that at least one large unit be retained when existing large units divided into two or more units.

Current law permits the creation of accessory units in garage spaces, but in most residential districts it’s still illegal to expand living space for existing dwelling units into garage spaces. Households should be able to expand living space into car-storage space if their household gets bigger.

Neighborhood architecture: continuity and transformation

Most San Francisco neighborhoods were originally laid out with a pattern of gridded streets, and small narrow lots with individual houses, or sometimes multiple flats. With the exception of a few set-piece neighborhoods encumbered with restrictive covenants,  most San Francisco neighborhoods diversified over time – some houses were divided into apartments, some smaller buildings replaced with larger apartment buildings, and corner stores were added here and there, including raising up wood-framed residential to add storefronts on the ground floor. These transformations were documented in Anne Vernez Moudon’s Built for Change: Neighborhood Architecture in San Francisco. The apartment buildings built in the first half of the 20th century were generally larger than neighboring houses, and increased residential density. They mostly proved to be architecturally compatible, even when they were in built in contrasting styles like Art Deco or Mediterranean Revival. Their designers articulated buildings into a base, middle, and top, used similar rhythms and proportions for features like window bays and entries, and used ornament to provide visual interest and human scale.

Designers of buildings built after World War 2 mostly rejected the architectural patterns which would have connected them to existing neighborhood architecture. Some of the biggest changes came at street level. Instead of a residential building base and generous front entries, buildings built from the mid-20th century on devoted building ground floors to parking. It was partially in response to increased auto ownership, but also in response to changing zoning codes. In 1955 San Francisco imposed minimum parking requirements citywide. Multi-unit buildings typically dedicated the entire ground floor to parking to meet requirements, and garage doors and open carports came to dominate  ground-floor building fronts, especially on narrow lots. Another factor was the imposition of a 40′ height limit across most of the city. Builders couldn’t lift the ground floor units a few feet above the sidewalk for livability and privacy, as older buildings do, without sacrificing an upper floor, so they typically defaulted to parking on the ground floor, with residences only on the second floor and above.

The new planning requirements imposed between 1955 and 1960 – strict density limits, strict height limits, minimum parking requirements, and the prohibition of non-residential uses in residential districts – mostly outlawed the sort of incremental development that previously diversified neighborhoods. Builders could only add new one- or two-unit buildings. These buildings were typically boxy and larger than neighborhood buildings, and were pejoratively labeled “Richmond Specials” after the San Francisco’s Richmond District where they were common. Neighbors’ objections to ill-fitting new buildings – apartment buildings in the neighborhoods where they were still permitted, and Richmond Specials elsewhere – boiled over in the 1970s. As Anne Vernez Moudon observed, “Such widespread discontent make it clear that the problem was not only overdevelopment, but also the ‘fit’ (or lack thereof) between new structures and the existing context;  issue was as much the character as the scale of new development”. In 1978 Planning Department responded by lowering allowable density even further in some neighborhoods, and crafting residential zoning controls and design guidelines that limited the size of new buildings and building additions to conform more closely to adjacent buildings. The 1970s zoning reforms maintained core elements of the 1960 zoning framework like use restrictions, density limits, and minimum parking requirements.

As San Francisco and most other cities were imposing citywide minimum parking requirements, segregation of uses, and strict limitations on density, urbanists were critiquing the negative effects that postwar planning conventions, also called Euclidean zoning, had on cities. Jane Jacobs’ The Death and Life of Great American Cities remains one of the most popular and durable critiques. Jacobs argued that city neighborhoods can be both dense and livable, that a mix of uses benefits city neighborhoods, that sidewalks were essential neighborhood public spaces, and cities should be walkable rather than dominated by the automobile. As Jay Wickersham observed:

Jacobs shows us that Euclidean zoning has been hard where it should be soft and soft where it should be hard. Zoning has been hard, or overly rigid, in dividing our cities and towns into uniform, low-density districts, each dedicated to a single primary use. And zoning has been soft, or overly permissive, in its failure to set design standards for streets, and for how buildings front upon those streets, that would reinforce the fundamental character of streets as public spaces.

Form-based codes, as described above, integrate the insights of Jacobs and others into plans and regulations intended to create urbane and walkable neighborhoods, including looking to older livable and lovable buildings and neighbohroods for patterns. Form-based codes typically pay more attention than Euclidean codes do to how buildings meet the street and how they shape and engage the public spaces around them – streets and sidewalks, and rear yards – and to architectural standards. Form-based codes for urban neighborhoods also relax the strict segregation of uses, as well as strict density limits and minimum parking requirements. San Francisco’s current code remains largely Euclidean, with form-based elements grafted on. A form-based code for San Francisco’s residential neighborhoods could allow more and more diverse housing options in neighborhroods, while conserving and enhancing the desirable built qualities of neighborhoods, and even allowing some of the damage done in recent decades to be repaired as buildings are renovated or replaced.

Preserving and expanding affordability in residential districts

Most of the strategies discussed so far are ‘affordable-by-design’ strategies, aimed at incremementally adding housing in neighborhoods, and providing more flexibility in accommodating both large and small households. However if we want truly diverse neighborhoods in an expensive city, we’ll need to strategies for preserving affordable rental housing in neighborhoods, and creating more permanently affordable units in all neighborhoods.

Preserving existing rent-controlled units in neighborhoods is key to preventing displacement of existing households. The city has limited condominium conversion in existing rental buildings, but residents are still being displaced by Ellis Act evictions and owner move-in evictions. For many households, a no-fault eviction means they can no longer afford to live in the neighoborhood, or even in San Francisco.

Units are also being lost to mergers. Mergers tend to increase as neighborhoods become more affluent, and unit mergers reduce the supply and diversity of housing and make what remains more expensive. Until 2014, the Planning Code encouraged the merger of units which exceeded current density limits. This policy resulted in the loss of many rent-controlled and affordable units in San Francisco. Livable City worked with the Board of Supervisors to amend the Planning Code to discourage mergers, regardless of whether they exceed current density limits. The new controls have saved many units that would formerly have been lost, but includes a loophole allowing ‘unaffordable’ units to be merged. Because of San Francisco’s surging housing costs, the unaffordable threshold is now over $1.6 million, but in San Francisco’s most expensive neighborhoods, most housing exceeds the threshold. This loophole may allow the merger of seven large apartments on Presidio Avenue into two units, with one exceeding 11,000 square feet. Mergers like this are making already unaffordable neighborhoods less diverse, and even less affordable.

Affordable housing developers tend to avoid building in low-density neighoborhoods, mostly because what they can build is so limited that it makes more sense to build where greater density is permitted. The City’s recently adopted HOME-SF program, which allows more density and larger buildings for projects which are 100% affordable or which include more affordable units, explicity exempts land in RH-1 and RH-2 districts, which will further limit affordable housing opportunities in residential districts. One opportunity to create more affordable housing in residential neighborhoods is to expand the City’s Small Sites Acquisition Program, which provides grants to nonprofit housing providers to purchase existing rental housing and keep it permanently affordable.

Sustainable mobility and ten-minute neighborhoods

Anxiety about transportation, particularly traffic and parking, is one of the most common justifications for limiting housing opportunities in residential districts, and one of the most commonly raised objections to new housing in neighborhoods.

Most of San Francisco’s residential neighborhoods were developed as streetcar neighborhoods, and retain their walkable patterns – small residential lots, pedestrian-scaled streets and blocks, neighborhood-serving commercial districts along the main transit corridors, and corner stores. Only a few post-World War 2 neighborhoods were built on an automobile-dependent pattern. According to Walk Score, San Francisco has an average walk score of 86 (“very walkable”).

Most of San Francisco’s residential neighbohroods are served by transit. According to SFMTA, 95 percent of the City’s addresses are within two blocks of a MUNI stop.

As we wrote in our posts on retail and the livable city, the city has a strong foundation for ten-minute neighborhoods – neighborhoods where most of the requirements of daily life, including grocery stores, shops, services, schools, a library, and frequent public transit, are with ten minutes walk. San Francisco can now boast that every San Franciscan lives within ten minutes walk of a City park. Ten-minute neighborhoods should be a foundational City policy in the our general plan and neighborhoood plans. As one measure, San Francisco should aim to achieve a walk score of 90 (“pedestrian paradise”) for every San Francisco neighborhood. Fostering ten-minute neighborhoods will expand access and opportunity and improve livability for existing residents, and allow neighborhoods to add housing and new residents without increasing traffic congestion. Increasing the density of residents is a key strategy for fostering neighborhood-serving shops and services. Transportation surveys of San Francisco’s neighborhood commercial districts found that the overwhelming majority of shoppers walked, bicycled, or took transit.

Most residential districts need better management of off-street parking. On most residential streets, street parking isn’t managed at all. Anyone may park as many cars as they like on the street, at no cost, for as long as they like, moving them only on street-sweeping days where those exist. Since driveways eliminate curb spaces, requiring off-street parking also decreases the number of on-street spaces, with no guarantee that the off-street spaces will actually be used to store a car. Where there’s competition for off-street parking, requiring off-street parking isn’t likely to create free and abundant off-street parking; only managing street parking better will improve parking availability.

San Francisco can continue to expand shared and sustainable transportation options in neighborhoods – car-share within convenient walking distance of residents, and shared bicycles and scooters, including electric bikes and scooters for hilly neighborhoods and older residents.

An Action Plan for reforming residential zoning

Beyond exclusionary zoning

  • Eliminate strict lot-area density limits, and instead limit density by height limits and lot coverage limits, residential open space requirements, dwelling unit exposure requirements, and required dwelling unit mix.
  • Eliminate minimum parking requirements.
  • Eliminate minimum lot-size requirements.

Embrace the missing middle

  • Permit small cottages at the rear of lots with a yard in between buildings.
  • Allow more flexibility with yard and setback requirements to permit apartment courts and cottage courts.

Accomodating diverse households

  • Relax limitations on second kitchens and ‘rooms down’.
  • Allow living space to expand into garage spaces.
  • Require at least 40% of units in multi-unit buildings to be three or more bedrooms.
  • Limit the division of large units to preserve at least one multi-bedroom unit.

Neighborhood architecture

  • Expand requirements and incentives to preserve existing character-defining buildings.
  • Integrate planning code requirements and residential design guidelines into an cohesive set of standards.
  • Limit the width and location of garage entrances.
  • Strengthen greening and permeability requirements for front and rear yards.

Preserving and expanding affordability

  • Strengthen protections against speculative evictions and the conversion, demolition, or merger of rent-stabilized housing.
  • Provide technical, design, and financial assistance to homeowners who wish to add an accessory dwelling unit, or legalize an existing unpermitted unit, if they agree to keep it as a rental for a certain number of years.
  • Eliminate the ‘unaffordable’ loophole in merger restrictions.
  • Expand funding for the Small Sites Acquisition program to preserve affordable rental housing in neighborhoods as permanently affordable.

Walkable neighborhoods and sustainable mobility 

  • Improve Muni service in neighborhoods, including faster service between neighborhoods and downtown, and timed transfers between neighborhood bus routes and rail lines.
  • Make every neighborhood a ‘ten-minute neighborhood’ by zoning for neighborhood-serving commercial districts within walking distance of each neighborhood, permitting corner stores, strengthening City initiatives that support neighborhood retail businesses, and locating community facilities like libraries, elementary schools, parks, playgrounds, and recreation centers within convenient walking distance of all neighborhoods.
  • Invest in pedestrian and bicycle safety (Vision Zero) and neighborhood-scale traffic calming, including safe routes to schools and safe routes to transit.
  • Expand shared mobility services in neighborhoods – car-share, bike-share, and scooter-share.