Housing Equity Glossary: Key Terms for the Bay Area
By Ryan Fukumori and Michelle Huang
This glossary is a foundational resource to the Housing Equity in the Bay Area: Numbers and Narratives series, defining key terms, concepts, and policies related to housing justice and equitable community development in the Bay Area. It is designed to help readers navigate the often complex language surrounding housing equity by offering clear and accessible explanations. By demystifying these concepts, the glossary empowers readers to engage more effectively with discussions and solutions shaping the region’s housing landscape.
Affirmatively Furthering Fair Housing (AFFH) Rule: This provision of the 1968 Fair Housing Act mandates that the US Department of Housing and Urban Development (HUD) and the organizations it funds take active measures to eliminate housing discrimination, address disparities in housing needs, and remove barriers to equal access in housing opportunities. The Biden administration is currently preparing updated guidelines for the AFFH rule, which will supersede the 2015 guidelines established during the Obama administration.
Association of Bay Area Governments (ABAG): This regional planning agency and advisory body represents local governments across the nine-county Bay Area. As the designated Council of Governments (COG) for the region, ABAG collaborates with the California Department of Housing and Community Development (HCD) to develop comprehensive housing strategies. It is responsible for producing the multiyear regional housing needs allocation (RHNA), which outlines the number of homes each city and county must build to address regional housing demands during each housing element cycle. The ABAG Executive Board also oversees the Bay Area Housing Finance Authority.
Accessory Dwelling Unit (ADU): An accessory dwelling unit (ADU) is a secondary or auxiliary housing unit situated on a single-family housing parcel. They are designed with a separate entrance and include dedicated kitchen and bathroom facilities. ADUs can be standalone structures (e.g., a backyard shed or cottage) or attached to the main dwelling (e.g., a converted garage or basement). As of 2021, California mandates that cities and counties develop plans to encourage the construction of ADUs as viable affordable housing options.
Affordable Housing: Affordable housing is defined by the US Department of Housing and Urban Development (HUD) as housing in which occupants pay no more than 30 percent of their household income on housing costs (e.g., rent, mortgage payments, property taxes, and utilities). By this definition, affordable housing does not create a housing burden for residents. The term also can serve as a proxy for subsidized housing, which includes below-market-rate rental units that are restricted to households with incomes below specific thresholds based on household size. Subsidized housing is supported through vouchers, tax credits, and other public subsidies that cover some or all of the residents’ housing costs. Both market-rate housing that does not burden middle-income households, and deed-restricted housing that serves low-income households, are critical components of affordable housing.
Bay Area Housing Finance Authority (BAHFA): Established by the state legislature in 2019, BAHFA is the first regional housing finance authority in California. Its mission is to elevate and coordinate regional strategies to address the Bay Area’s housing crisis. BAHFA has the authority to issue voter-approved bonds to finance the development of affordable housing within the region. The agency has considered adding a significant regional housing bond measure to a future general election. In 2024, BAHFA explored the possibility of proposing a $20 billion housing bond for the November ballot but ultimately decided to postpone these plans due to unfavorable electoral conditions.
California Department of Housing and Community Development (HCD): This state government agency is responsible for establishing housing policies and regulations while managing statewide housing finance and community development initiatives. HCD collaborates with the California Department of Finance and the Association of Bay Area Governments (ABAG) to define the aggregated, multi-year housing needs for the nine-county Bay Area, categorizing these needs by income level. ABAG then determines the regional housing needs allocation by distributing these aggregated housing needs among all counties, taking into account demographic and socioeconomic trends. HCD also collects and reports data from local governments regarding the actual number of housing units permitted and constructed at each income level.
California Housing Opportunity and More Efficiency (HOME) Act: Also known as Senate Bill (SB) 9, the HOME Act is a statewide upzoning law that permits homeowners to split a single-family parcel into two lots and to build at least two housing units on each lot. This legislation took effect on January 1, 2022, with the aim of overriding restrictive zoning practices in neighborhoods that limit development to single-family homes. Despite its intent to promote increased housing options, SB9 has faced opposition from local governments and civic groups advocating for the preservation of low-density development.
Community Land Trust (CLT): A community land trust (CLT) is a nonprofit, place-based organization that owns land and facilitates the development and long-term maintenance of affordable housing, community sites, parks, and commercial spaces. CLTs serve as a strategy to ensure the availability of permanently affordable housing in mixed-income neighborhoods where people live, work, and play. Some CLTs encourage local residents to actively participate in the governance of the trust and the stewardship of specific development projects.
Community Opportunity to Purchase Act (COPA): This city-level policy grants nonprofit organizations within a city the right of first offer and/or first refusal to purchase specific housing developments or land parcels. For example, San Francisco’s COPA law mandates that sellers of buildings containing three or more housing units, or land that could be developed into at least three homes, must first present the property for sale to a group of qualified nonprofit agencies before listing it on the open market. COPA ordinances support community organizations in their efforts to prevent the displacement of low-income residents and to preserve rent-controlled housing from market-rate redevelopment.
Duplex: A duplex is a single housing parcel that contains two housing units, which are typically attached. Duplexes differ from townhomes, which are single-family homes that share walls but occupy separate land parcels. Other examples of smaller multifamily properties include triplexes and fourplexes, which consist of three and four units on a single parcel, respectively.
Housing Burden: This term refers to the condition in which a household allocates more than 30 percent of its income to housing expenses, including rent or mortgage payments and utilities. Households that spend more than 50 percent of their income on housing costs are classified as severely burdened. This issue is also referred to as cost burden. See also: rent burden.
Housing Element: This legally required component of the general plan for each city and county in California outlines the fundamental strategies that local governments will employ to meet the identified housing needs within their communities. In the Bay Area, housing elements specify the number of homes to be developed at various income levels over an eight-year period, as determined by the Association of Bay Area Governments (ABAG) through the regional housing needs allocation. Each eight-year timeframe is referred to as a housing element cycle, with the current cycle addressing regional housing needs from 2023 to 2031.
Housing Unit: A housing unit refers to a house, apartment, collection of rooms, or single room that has been designated as a distinct living space for a single household.
Just Cause Eviction: Just cause eviction policies restrict landlords’ ability to terminate rental leases and evict tenants. Legal evictions fall into two categories: “at fault,” which occurs when a tenant fails to pay rent or violates lease terms, and “no fault,” which occurs when the rental property is removed from the market, such as when the owner occupies the unit or the building is demolished. These laws protect tenants from arbitrary displacement and landlord malpractice, such as attempts to raise rents by evicting current residents to re-lease the unit at a higher price. California’s Tenant Protection Act has been in effect since 2020, and several cities, including San Jose and Oakland, have their own supplementary just cause eviction ordinances.
Landlord Registry: This type of database, which requires property owners to register their rental properties before leasing them, is maintained by city or county governments. Also known as rent registries, these databases help local governments collect data on rent levels and eviction trends, ensuring landlords are held accountable for maintenance and livability standards. For example, Marin County established a landlord registry in 2019 for its unincorporated areas to ensure compliance with the state’s just cause eviction laws.
Multifamily/Multi-unit Building: These housing structures or complexes are located on a single parcel that contains multiple housing units. Common examples of multifamily housing include apartments and condominiums.
Overcrowded Household: An overcrowded household is defined as one with more than one occupant per room, excluding kitchens and bathrooms. For example, a couple living in a one-bedroom apartment is not considered overcrowded, as they have two people in two rooms. However, the addition of a child would make the unit overcrowded. Overcrowding is more prevalent among renters, particularly in low-income households and communities of color, and can have negative effects on residents’ physical and emotional well-being.
Rent Burden: Rent burden refers to the situation in which a renter-occupied household spends more than 30 percent of its income on rent and utilities. Households that allocate more than 50 percent of their income to these expenses are classified as severely rent-burdened. See also: housing burden.
Rent Control: Rent control encompasses policies and ordinances that limit the amounts landlords can charge for rent. The most common form of rent control allows landlords to set initial rental prices freely for units on the market but restricts year-to-year rent increases for existing tenants in qualified housing units. California’s Tenant Protection Act, enacted in 2020, establishes statewide caps on annual rent increases. Additionally, 13 cities in the Bay Area have localized rent control ordinances that supplement the statewide policy.
Regional Housing Needs Allocation (RHNA): This housing development plan outlines multi-year housing needs for all jurisdictions within a metropolitan region, broken down by income level. The Association of Bay Area Governments determines the RHNA for all jurisdictions in the Bay Area, and the RHNA figures are incorporated into updates for each city and county’s housing element plans.
Single-family Home: A single-family home is a housing unit that occupies its own parcel of land. These units can be either standalone structures or attached, such as townhomes, which share walls with other single-family units while maintaining separate land parcels.
Social Housing: This term refers to publicly financed, mixed-income housing that is integrated into neighborhoods, providing residents with access to local schools, jobs, transit, and opportunities for connection. Some definitions of social housing focus solely on publicly owned and operated developments, while others include nonprofit and cooperative housing supported by public resources. Unlike previous generations of US public housing projects, which often economically segregated low-income residents in under-resourced communities, social housing emphasizes economic equity and integration through a community-level approach. Recent state housing policies, such as the Stable Affordable Housing Act of 2023, reflect a similar commitment to long-term housing affordability by emphasizing alternatives to privately owned, for-profit housing.
Stable Affordable Housing Act: Signed into law in 2023, this legislation mandates the California Department of Housing and Community Development (HCD) to conduct a study aimed at generating long-term housing affordability for under-resourced communities across the state. Also known as SB555, the bill directs HCD to investigate a combination of state-sponsored strategies, including publicly owned housing, cooperative housing models, and nonprofit housing production and acquisition. Social housing advocates played a crucial role in the bill’s passage, highlighting its significance in fostering broader support for the public financing of equitable and ecologically sustainable housing development.
Tenant Anti-Harassment Ordinance (TAHO): This policy prohibits landlords from engaging in intimidating, retaliatory, and/or disruptive behaviors toward tenants. This includes actions such as withholding legally required maintenance or verbally abusing or threatening renters. TAHO laws are essential complements to rent control and just cause eviction ordinances, as they help prevent landlords from coercing tenants into leaving voluntarily to facilitate rent increases for new renters or retaliating against tenants who hold them accountable to housing laws. Cities in the Bay Area that have enacted rent control laws, such as San Francisco, Oakland, and Concord, often include TAHO provisions within those regulations.
Tenure: Tenure refers to the ownership status of an occupied household. Households can be categorized as either owner-occupied or renter-occupied.
Tenant Opportunity to Purchase Act (TOPA): This policy requires rental property owners to first offer their tenants the right to purchase the property if they decide to sell it. Similar to the Community Opportunity to Purchase Act (COPA), TOPA policies aim to preserve affordable housing and help residents maintain their long-term homes. These laws can also provide renters with a pathway to homeownership and promote individual ownership over corporate ownership. While no cities in the Bay Area have enacted TOPA laws, city council members in Berkeley and Oakland have previously introduced proposals for their implementation.
Upzoning: Upzoning refers to changes in a community or municipality’s land use codes that allow for increased density and/or greater development. For example, the California HOME Act permits the construction of multifamily buildings in neighborhoods that have historically been zoned exclusively for single-family homes. Upzoning is one strategy among many that housing justice advocates and policymakers have leveraged to address California’s housing crisis.
Vacancy: Vacancy describes the state of a housing unit when it is unoccupied. This includes housing units that are currently on the market (for sale or rent), units that are leased but not occupied, and homes intended for seasonal use (e.g., secondary vacation homes). In some cases, landlords and developers may intentionally keep housing units vacant to limit supply and drive up rents for available units.
Vacancy Tax: This municipal policy imposes taxes on property owners whose housing units remain vacant for an extended period. For instance, San Francisco’s Empty Homes Tax levies taxes on housing units in buildings with three or more units that sit empty for more than 182 days each year. Vacancy taxes are designed to prevent the intentional withholding of housing from the market, ensuring that more units are available for potential residents.
