San Mateo | Three or More Homes

San Mateo, California Three or More Homes: Who Approves Apartments, Objective Design Standards, Below Market Rate Homes, By-Right Sites, the Density Bonus and SB 79

San Mateo's code calls a building for three or more families a multiple-family dwelling. This page covers what such a project must pass in San Mateo: the site plan and architectural review, the objective design standards, the Below Market Rate program that starts at five homes, the 39 sites approved by right, the density bonus, the 2025 state transit law SB 79, and the duties owed to tenants when existing homes are demolished. The districts that allow these buildings are on the zoning districts page, and the San Mateo overview has the summary.

Site Plan and Architectural Review

Section 27.08.030 requires site plan and architectural review, which the City shortens to SPAR, for "any building, new parking lot, fence over seven (7) feet in height, or an extension, alteration, or addition of or to an existing building or parking lot." Houses and accessory buildings that meet the R1 standards are exempt. Every apartment building therefore files a planning application for SPAR. The approval body must find five things, among them that "The structures, site plan, and landscaping are in scale and harmonious with the character of the neighborhood."

Who decides depends on the number of homes and on whether the design meets the City's objective design standards. Objective standards are written rules that can be measured, such as a setback in feet, so that two reviewers reach the same answer.

Sources: San Mateo Zoning Code, 27.06.020, 27.06.040, 27.06.050 and 27.94.020; City of San Mateo, Planning Application Guide, April 3, 2026.

• How the staff threshold grew. Ordinance No. 2023-12, adopted December 4, 2023, gave the Zoning Administrator projects of "Up to twenty-five (25) residential dwelling units that meet objective design standards." Ordinance No. 2025-03, adopted April 7, 2025, raised the number to ninety-nine. Its recitals record that the Planning Commission had "recommended a threshold of 150 units, or, in the alternative, no threshold at all."
• Referral. The Zoning Administrator "may refer the application to the Planning Commission for hearing and action when it is unclear whether the necessary findings for project approval can be made."
• Environmental review. Staff approval applies "provided that the projects do not result in any significant impacts pursuant to the California Environmental Quality Act (CEQA)." A project with an environmental impact report goes to the Commission.
• Where to read the standards. The City's Planning Resource Documents page posts the Multi-Family and Residential Mixed-Use Objective Design Standards and a checklist. This guide did not read the standards document, so no design rule from it is stated here.
• Consulting architect. The fee schedule lists a $5,000.00 initial deposit for design review by a consulting architect, which it requires for "projects with 6+ units, 10,000+ SF non-residential" and other projects named by City resolution.

The R3 Building Standards

Chapter 27.22 sets the base standards for a multiple-family building, and R4, R5 and the commercial districts borrow most of them. The home count comes from parcel area per home, covered on the zoning districts page.

• Floor area ratio. 0.85 in R3. The Zoning Administrator may allow up to 1.0 where the extra floor area covers parking that would otherwise be open and gives "more usable yard area." R4 starts at 1.5 and R5 at 2.0.
• Open space. "Not less than two hundred (200) square feet per bedroom of open parcel area" for the first bedroom in each home and "at least one hundred (100) square feet per bedroom" for each one after it. Parking areas and driveways are left out of the count. A balcony or roof deck counts for an upper-floor home if it has at least 100 square feet and is at least 6 feet in each direction.
• Minimum home sizes. Section 27.22.110 sets 350 square feet for a studio, 540 for a one-bedroom home with a kitchen, 750 for a two-bedroom home with a kitchen and 960 for a three-bedroom home, measured "from the center of the walls enclosing each dwelling unit."
• Yards and height. A 15-foot front and rear yard, 6-foot side yards for one and two story buildings, and larger yards as the building rises or sits next to R1 or R2 land. See the parking, setbacks and height page.
• Parking. 1.5 to 2.2 spaces per home by bedroom count outside downtown, in Section 27.64.160.
• Steep sites. In multiple-family and commercial districts, "Only those areas of a site have existing slopes of less than twenty-five (25%) percent shall be considered in the calculation of allowable floor area and density limits."

The Below Market Rate Program

Section 27.16.050 says the requirements of the Below Market Rate (BMR) Program "are regulated by resolution adopted by the City Council." The guidelines in force are marked "Rev. Reso. No. 72 (June 16, 2025)"; this guide read the copy attached to the City Council agenda of October 5, 2026. They apply to "all development projects that include five (5) or more residential units or parcels," including new rental and ownership homes, subdivisions for houses or duplexes, condominium conversions and the conversion of nonresidential space to homes. The guidelines define affordable rental housing as affordable to households at or below 80 percent of the area median income, and affordable ownership housing at or below 120 percent.

Sources: City of San Mateo, Below Market Rate Program guidelines, Section III; Development Fees summary, revised July 1, 2026. The fee summary also lists projects of 7 and 9 homes.

• Rounding. "In determining the number of BMR units required, any decimal fraction .5 or above shall be rounded up to the nearest whole number." A fraction below .5 is paid as a fee. By VanPlex arithmetic, 15 percent of 12 homes is 1.8, which rounds to two affordable homes, and 15 percent of 14 homes is 2.1, which is two homes and a fee for 0.1 of a home.
• No general fee option. "Fees in-lieu of constructing required BMR units shall not be allowed except for the provisions for fractional units."
• How long. Rental restrictions "shall be in force for the life of the building." Resale restrictions on ownership homes last 45 years and are recorded again at each resale.
• Rents and prices. A BMR rent may not exceed 30 percent of the gross monthly income of households "earning between 50-70 percent or less of area median income," and "In no event shall the annual rent increase exceed 4% from the prior year." The City Council adopts the rent and price tables each year.
• Size and placement. BMR homes are spread through the project, have the same share of bedrooms as the market-rate homes, and may be up to 10 percent smaller if they meet minimum sizes that start at 450 square feet for a studio.
• Other ways to comply. Off-site homes or an applicant's own proposal need City Council findings. The Council agenda of October 5, 2026 listed one such plan, for a "441-unit housing development project located at 1700 S. El Camino Real."
• The link to the density bonus. The guidelines print the bonus that the required homes earn under state law: 27.5 percent for a rental project with 15 percent lower income homes and 10 percent for an ownership project with 15 percent moderate income homes, each with one incentive.

One City page disagrees with the guidelines. The Developer Resources page says the program "applies to rental or for-sale developments of 6 or more units," and in the next sentence that "A fractional fee is charged for projects consisting of 5-10 units." The adopted guidelines and the fee schedule both start at five homes, and the guidelines are the adopted text.

By-Right Sites and Minimum Densities

State housing law requires by-right zoning on certain sites that a city's housing plan has listed before. By right means the City approves the use without a discretionary decision. Ordinance No. 2024-4, adopted July 15, 2024, created the Housing Opportunities Overlay District for that purpose and applied it to 39 properties. In Chapter 27.94, a project "in which at least 20 percent of the units proposed are affordable to lower income households" qualifies. "The Zoning Administrator shall not exercise any discretion in the review process for such projects and their decision shall be final," and the chapter says the review is not a project under the state environmental law. The project keeps the development standards of its district and the objective design standards. A project on one of these sites that does not include the affordable homes follows the normal process.

Since July 2025 the code also sets minimum densities for mixed-use projects of five or more homes. Section 27.02.230 requires 30 homes per acre in the Mixed-Use Low and Mixed-Use Medium I designations and 50 in Mixed-Use Medium II and Mixed-Use High "Within a 1/2 mile radius of a Caltrain Station." Farther from a station the minimums are 10, 15, 30 and 50. The City Council may lower a minimum for a project with more affordable homes than the BMR program requires or with public community benefits.

The Density Bonus

The state density bonus law, Government Code 65915, gives extra homes and relief from standards to projects that include affordable homes. Chapter 27.15 applies it "to the construction of five or more housing units" that meet one of four tests, such as "At least five percent of the total units are designated for very low income households." The request is filed with the planning application, and the body that decides the project decides the bonus.

• Incentives the City accepts. The chapter lists five that "are deemed not to have the adverse impact" that would justify a denial, among them "Reduced setbacks or buffers," "Increased maximum lot coverage" and "Increased maximum Floor Area Ratio," each "so long as the project remains consistent with the City's General Plan and any applicable design guidelines."
• What the City will not give. "The City will not, however, provide any direct financial assistance, waive fees or dedication requirements, or provide publicly owned land."
• All-affordable projects near transit. Section 27.15.080 lets a project that is 100 percent affordable and within a half mile of a major transit stop ask for "waivers or reductions from up to six applicable development standards" beyond the state incentives.
• Agreement. Before a building permit, "the developer must enter into an Affordable Housing Agreement" that is recorded and binds later owners.

Sections 27.15.010 to 27.15.070 cite ordinances of 2002, 2009 and 2018, and the statute was last amended effective January 1, 2026. The BMR guidelines still cite the density bonus ordinance as "Section 27.16.060 of the Municipal Code," its former number. Where the chapter and the statute differ, the statute controls.

SB 79 Near the Caltrain Stations

SB 79 is the 2025 state law that allows apartment buildings near major transit stops. HCD, the state housing department, says in its advisory of March 20, 2026 that the law "will take effect on July 1, 2026, in Alameda, Los Angeles, Sacramento, San Francisco, San Mateo, Santa Clara, and San Diego Counties." The City's SB 79 FAQs, prepared August 31, 2026, apply it to San Mateo: "this includes the City's three Caltrain stations (Downtown, Hayward Park and Hillsdale) and portions of the Burlingame Caltrain Station area that extend into the City. These areas are designated as Tier 1 Transit-Oriented Development (TOD) Areas under State law."

Source: City of San Mateo, SB 79 FAQs, table "Development Standards for SB 79 Projects." Gov. Code 65912.157 words these as limits a city may not go below and adds the first row as an increase of 20 feet, 40 homes per acre and 1 of floor area ratio for a site next to the stop.

• Which projects. The FAQs list the tests: within one-half mile of a qualifying stop on a site designated for residential, mixed-use or commercial development; "Includes five or more housing units"; "a minimum density of 30 dwelling units per acre"; and an average home of no more than "1,750 net habitable square feet." Mixed-use projects must also meet the minimum densities of Section 27.02.230.
• Affordable homes. A project must meet the statute's affordability rules "and the City's Below Market Rate (BMR) Ordinance."
• House lots. "Some single-family residential properties in San Mateo are located within SB 79 qualifying areas."
• No local version. "The City is not implementing SB 79 in the Zoning Code at this time. For projects that utilize SB 79, the State law's development standards apply and supersede any conflicting local zoning regulations."
• No alternative plan. The statute lets a city adopt its own transit plan that moves capacity between sites. The FAQs say that because of Measure T this "is not feasible for the City without voter approval."
• Review. An applicant may choose the ministerial process in Government Code 65912.159, a staff check against written standards with no hearing, or the City's normal review. Notices go to owners and tenants "within 500 to 1,000 feet."

This guide did not open the regional map that shows the stops and their half-mile zones, so it does not say which lots qualify. The State Legislation Information and Resources page links the City's buffer map.

When Existing Homes Are Demolished

• Relocation help tied to the planning application. Section 27.02.180 applies "In the event of demolition of existing residential dwelling units and/or conversion causing relocation." The applicant gives the Planning Division a list of the households, and each one receives "A list of available comparable housing within San Mateo County," "A relocation allowance in cash or check equivalent to three times the current monthly United States Department of Housing and Urban Development (HUD) Fair Market Rent for a dwelling unit of comparable size and type," and "A payment not to exceed one thousand dollars ($1,000.00) for actual moving costs."
• Just cause. Chapter 10.100, the Residential Tenant Protection Program, was adopted on December 1, 2025. "After a tenant has continuously and lawfully occupied a residential real property for 11 months, the owner of the residential real property shall not terminate a tenancy without just cause." State law sets that point at 12 months.
• Payment for a no-fault eviction. Demolition and substantial remodeling are no-fault causes under state law. For those the City requires relocation assistance "equal to one month of the tenant's rent," with half paid "within 15 calendar days of service of the notice of termination."
• After a remodel. When a tenancy ends for demolition or substantial remodel, "once the renovation of the property is complete and available for leasing, the landlord shall immediately issue a notice of availability of the property to the tenant(s) who were evicted."
• End date. "This Chapter shall remain in effect only until January 1, 2030, and as of that date is automatically repealed."
• Rent limits. The titles of the Municipal Code read for this guide contain no rent control or rent stabilization chapter. Chapter 10.100 points tenants to the statewide rent cap in Civil Code 1947.12; see the California rent and tenant rules page.
• Old buildings. The City's historic project review page says a Historic Resources Evaluation "is required when a planning application for substantial demolition (50% or more of exterior walls) is submitted for a property that is more than 50 years old and has not been surveyed previously." Chapter 27.66, rewritten in May 2026, requires a planning application to demolish a listed or eligible historic resource.

Limits of This Page

The code was read from the City's bulk copy, whose index page prints "Current through" October 8, 2026. The objective design standards document, the Housing Element, the regional SB 79 map, the Downtown Specific Plan and the Rail Corridor Plan were not read. The BMR guidelines were read from a Council packet attachment; the annual rent and price resolution was not read. City Council agendas were read for September 8, September 22 and October 5, 2026 only, and the ordinance on the new R6, R7, MU3 and MU4 districts is covered on the zoning districts page. Ask the Planning Division whether a newer ordinance or resolution is in force.

Where to Go Next

Related on VanPlex: the San Mateo overview, the California SB 79 page and the California impact fees page.

Frequently Asked Questions

Official sources (checked October 2026)