San Mateo | Zoning Districts
San Mateo, California Zoning Districts: R1, R2, R3, R4, R5, Downtown Districts, Overlays and Four New High Density Districts
A zoning district is an area of the city where one set of rules on uses, home counts and building size applies. San Mateo's districts are in Title 27 of the Municipal Code, which the City publishes in its own law library. This page covers the City of San Mateo only; San Mateo County has a separate code for land outside city limits. It sets out what each residential district allows, where homes are allowed in commercial and downtown districts, and how General Plan 2040 now overrides the older numbers. The San Mateo overview has the summary.
San Mateo zoning districts in six facts
- The San Mateo City Zoning Code sets the rules for residence districts in Chapters 27.18 to 27.26: R1 for houses, R2 for two-family homes, and R3, R4 and R5 for multiple-family homes. Source: Zoning Code 27.16.010
- A new R1 parcel needs 10,000 square feet in R1-A, 6,000 square feet in R1-B and 5,000 square feet in R1-C. Source: Zoning Code 27.18.040
- R3, R4 and R5 set the number of homes by parcel area per home: on a parcel of 15,000 square feet, 1,250 square feet per home in R3 and 870 in R4 and R5. Source: Zoning Code 27.22.040 and 27.24.040
- The three downtown residential districts, R4-D, R5-D and R6-D, each have a maximum floor area ratio of 3.0, and R6-D is limited to 50 units per acre. Source: Zoning Code Chapter 27.28
- Where the Zoning Code and General Plan 2040 conflict, the uses, densities, intensities and heights in Table LU-1 of the General Plan control. Source: Zoning Code 27.02.220
- An ordinance listed for adoption on September 22, 2026 creates four districts, R6, R7, MU3 and MU4, at up to 99 and 130 homes per acre, and it rezones no parcel. Source: City Council agenda report, September 8, 2026
How the Zoning Code Is Organized
Section 27.02.010 gives Title 27 its name: "San Mateo City Zoning Code." Section 27.16.010 says "Use and bulk regulations applying specifically to residence districts are set forth in Chapters 27.18 through 27.26." Each district chapter lists permitted uses, which need no use permit, and special uses, which need a special use permit decided after a hearing. A use on neither list is prohibited. Section 27.02.110 says "it shall be assumed that such uses are prohibited unless it is determined by action of the City Council that the use is similar to and not more objectionable than uses listed."
Each district also permits the uses of the districts before it. R2 permits "Any use permitted in the R1 districts," R3 permits any R1 or R2 use, and so on up to R5. The code describes density in words in Section 27.04.145: R1 is low, R2 medium-low, R3 medium and R4 high, and "Unit density shall be based on the minimum lot area standards as designated in the zoning code." The note under each section lists the ordinances that wrote and changed it. The R1 parcel size section cites Ordinance No. 1992-16, and the R3 parcel table cites ordinances of 1979, 1985 and 1991.
This guide read the copy of the code the City publishes for bulk download. Its index page prints "Current through" October 8, 2026 and names Ordinance No. 2026-09 as the last ordinance written into the code. Section links on this page go to the same sections in the City's online law library.
R1: The One-Family Districts
Section 27.18.010 says the R1 districts "are intended to create, preserve and enhance areas suitable for single-family dwellings with a substantial presence of open space and opportunities for outdoor living." Section 27.18.020 permits "One-family detached dwellings, including manufactured homes on permanent foundations," accessory dwelling units (ADUs, second homes on a lot) and junior ADUs under Chapter 27.19, home occupations, small licensed care homes, and transitional and supportive housing.
| District | Minimum parcel area | Minimum parcel width | Floor area ratio | Front yard |
|---|---|---|---|---|
| R1-A | 10,000 sq ft | 75 ft | 0.4 on the first 10,000 sq ft of parcel, plus 0.2 on the area above it | 25 ft |
| R1-B | 6,000 sq ft | 60 ft | 0.5 on the first 6,000 sq ft of parcel, plus 0.2 on the area above it | 15 ft, 20 ft for a garage |
| R1-C | 5,000 sq ft | 50 ft | 0.5 on the first 6,000 sq ft of parcel, plus 0.2 on the area above it | 15 ft, 20 ft for a garage |
Source: San Mateo Zoning Code, 27.18.040, 27.18.060 and 27.18.070. Parcel width is measured at the front setback line.
- Floor area ratio. Floor area ratio, or FAR, is building floor area divided by lot area. Whatever the ratio gives, "In no case shall more than 6,000 square feet of total floor area be permitted per parcel in residential use."
- Older small parcels. A house may be built on a parcel below the minimum "if the parcel was recorded under separate ownership from adjoining parcels prior to March 3, 1947," if its map was approved with exceptions, or if it has a certificate of compliance.
- Removing a house. Section 27.18.035 requires a special use permit for "the substantial removal of an existing residence," which it defines as demolition of 50 percent or more of the exterior walls or roof.
- More than one home. All R1-A, R1-B and R1-C land is also in the Two-Unit Development Residential Overlay District of Chapter 27.21, the City's version of state SB 9. An overlay district adds a second set of rules on top of the base district. This one allows "up to two detached or attached primary housing units on one parcel." The ADUs and SB 9 page covers it.
- San Mateo Park. Section 27.18.115 adds larger garage and side setbacks in the San Mateo Park planning area shown on a map in the section.
R2: Two-Family Homes
Chapter 27.20 permits "Two family dwellings" in R2. The definitions call a two-family dwelling "a building(s) designed or altered to provide attached (duplex) or detached dwelling units for occupancy by two families living independently of each other." The limit per lot is in Section 27.20.030: "Not more than two buildings designed or used as residences for not more than two families shall be erected, located, or maintained on any one zoning plot." A zoning plot is one or more lots that share an approved development.
A new two-family dwelling needs a parcel of 5,000 square feet. Parcels recorded before March 3, 1947 need 4,400 square feet, and a table note adds "Parcels must also be northeast of El Camino Real." The floor area ratio "shall not exceed 0.6." In two mapped areas, the Central Neighborhood and the North Central Neighborhood, the limit is "0.5 for parcels up to 7,500 square feet and 0.6 for parcels greater than 7,500 square feet." Yards follow the R1-B rules, and height and the daylight plane follow R1.
R3, R4 and R5: Multiple-Family Homes
The code defines a multiple-family dwelling as "a building or portion thereof, designed or altered for occupancy by three or more families living independently of each other." R3 is the first district that permits one. Chapter 27.22 also permits "One family row dwellings" and, since April 2025, supportive housing as a use by right. R4 adds "Single Room Occupancy Units," and R5 permits "Any use permitted in the R1, R2, R3 or R4 districts."
None of the three chapters states a number of homes per acre. Each has a table of minimum parcel area, minimum parcel width and minimum parcel area per dwelling unit, and a larger and wider parcel earns a smaller area per home.
| Parcel size and width | R3: sq ft of parcel per home | R4 and R5: sq ft per home | R4-D and R5-D: sq ft per home |
|---|---|---|---|
| 4,000 sq ft and 40 ft wide (parcels northeast of El Camino Real recorded before March 3, 1947) | 2,200 | 2,200 | 2,200 (parcel of 4,400 sq ft) |
| 5,000 sq ft and 50 ft wide | 2,500 | 2,500 | 2,500 |
| 8,000 sq ft and 65 ft wide | 2,000 | 2,000 | 2,000 |
| 10,000 sq ft and 80 ft wide | 1,500 | 1,000 | 1,000 |
| 12,000 sq ft and 100 ft wide | No row | No row | 900 (R4-D only) |
| 15,000 sq ft and 100 ft wide | 1,250 | 870 | 870 |
Source: San Mateo Zoning Code, 27.22.040, 27.24.040, 27.26.040, 27.28.016 and 27.28.046.
VanPlex arithmetic shows what the tables mean. An acre is 43,560 square feet, so 1,250 square feet per home equals 34.8 homes per acre and 870 square feet per home equals 50.07. An R3 parcel of 8,000 square feet yields four homes (8,000 divided by 2,000). An R4 parcel of 10,000 square feet yields ten homes (10,000 divided by 1,000). Where the division leaves a fraction, the tables do not say how to round; ask the Planning Division.
| District | Homes allowed | Floor area ratio and coverage | Chapter |
|---|---|---|---|
| R2 | Two-family dwellings and any R1 use; no more than two residential buildings for two families on a zoning plot | 0.6; 0.5 on parcels up to 7,500 sq ft in the Central and North Central neighborhoods | Chapter 27.20 |
| R3 | Multiple-family dwellings, one family row dwellings and any R1 or R2 use | 0.85; up to 1.0 with Zoning Administrator permission | Chapter 27.22 |
| R4 | R3 uses plus Single Room Occupancy units | 1.5; up to 2.0 with Zoning Administrator permission | Chapter 27.24 |
| R5 | Any use permitted in R1 to R4 | 2.0; up to 3.0 for residential high-rise buildings by special use permit | Chapter 27.26 |
| R4-D | Uses permitted in R1 to R4 | 3.0; parcel coverage up to 45 percent | Chapter 27.28, Article I |
| R5-D | Uses permitted in R1 to R5 and R4-D | 3.0; no maximum parcel coverage | Chapter 27.28, Article II |
| R6-D | Uses permitted in R1 to R5, R4-D and R5-D; no more than 50 units per acre | 3.0; parcel coverage up to 55 percent | Chapter 27.28, Article III |
Source: San Mateo Zoning Code, Chapters 27.20, 27.22, 27.24, 27.26 and 27.28.
On height the three chapters say the same thing: "Building height shall not exceed the standards set forth on the Building Height Plan of the General Plan." The Measure T and height limits page explains what that plan is today.
The Downtown Residential Districts
Chapter 27.28 has three districts for the Downtown Specific Plan area. R4-D and R5-D use the parcel-area tables above. R6-D has one line in place of a table: "Residential development on properties zoned R6-D shall not exceed 50 units per acre regardless of parcel size." All three set a maximum floor area ratio of 3.0. R4-D limits parcel coverage, the share of the lot under buildings and enclosed parking, to 45 percent, and R6-D limits it to 55 percent. R5-D says "There is no maximum coverage of parcels in this district."
Each downtown home needs usable open space: 100 square feet of private space per home in R4-D and 80 in R5-D and R6-D, or common space equal to 150 percent of that figure. In the Gateway area of the Downtown Specific Plan, setbacks and heights are set street by street. On Gateway streets other than Third Avenue, buildings sit 15 to 20 feet back from the street property line for at least 60 percent of the building frontage, and new buildings must meet the Gateway Design Guidelines.
Homes in Commercial, Office and Overlay Districts
- C1, Neighborhood Commercial. Section 27.30.010 permits "Residential units above the ground floor, subject to R3 district" minimum development standards and the City's affordable housing requirements.
- C2 and C3. C2 permits "Residential units, subject to R4 district" minimum development standards, and C3 permits the C1 and C2 uses with homes under the R4 standards.
- C4, Service Commercial. C4 permits the uses of C1, C2 and C3 "except that residential uses" and three other listed uses "are prohibited."
- CBD, Central Business District. Chapter 27.38 permits "Multiple-family dwellings, when part of a mixed use development," and "Residential development on properties zoned CBD shall not exceed 50 units per acre regardless of parcel size."
- E1 and E2, the office districts. E1 permits "Residential units, subject to R3 district" minimum development standards, and E2 permits the E1 uses.
- The residential overlays /R, /R4 and /R5. Chapter 27.29 says these "may be superimposed only on those lands classified E or C (except C4)." In /R5, "residential development shall not exceed 50 units per acre, regardless of parcel size." In /R outside downtown, a parcel of 20,000 square feet may have one home per 582 square feet, with a note that "Densities above 50 units per acre are permitted only where specific criteria are met as stated in the General Plan Land Use Element."
- The Housing Opportunities Overlay, H. Ordinance No. 2024-4 added the H overlay "on the 39 properties listed in Exhibit A." A project with at least 20 percent lower income homes there is approved by right at "a minimum density of at least 30 dwelling units per acre." See the three or more homes page.
Plan Districts Near the Train Stations
In three districts the code says a plan document sets the rules. In the TOD district, Chapter 27.90 applies "to the two geographic zones delineated on the Rail Corridor Plan as the Hillsdale Station TOD zone and the Hayward Park Station TOD zone," and "in the event of a conflict" the Rail Corridor Plan governs. Chapter 27.88 does the same for the Bay Meadows Specific Plan district, and Chapter 27.92 for the Hillsdale Station Area Plan. This guide did not read those three plans, so their densities, heights and parking numbers are left out. Of the 39 H overlay sites, 19 are zoned TOD.
General Plan 2040 Now Controls Density and Height
The City Council adopted General Plan 2040 on March 18, 2024, and voters approved its Land Use Element as Measure T on November 5, 2024. In April 2025 the Council added Section 27.02.220: "In case of conflict or inconsistency between Title 27 of the Municipal Code (Zoning Code) and the General Plan 2040, the uses, densities, intensities and heights specified in Table LU-1 (Land Use Designations) in the Land Use Element and associated with the Land Use Map shall control."
Table LU-1 gives each land use designation, the category the General Plan map gives a parcel, a density range and a height in stories: for example Residential Low II at 20 to 35 homes per acre and 2 to 4 stories, and Residential High at 100 to 130 homes per acre and 5 to 8 stories. A lot zoned R3 with a General Plan designation that allows more homes than the R3 table follows the General Plan number. A note under the table says the range "does not set a minimum required density."
Mixed-use projects are the exception on minimums. Section 27.02.230, added in July 2025, requires a mixed-use project with five or more homes within a half mile of a Caltrain station to reach 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.
Four New Districts: R6, R7, MU3 and MU4
The staff report of September 8, 2026 says "the current Zoning Code does not allow for the higher-density residential and mixed-use development envisioned by the General Plan." The Council introduced an ordinance that day to add four districts, and the agenda of September 22, 2026 listed it for adoption on the consent calendar, the list of routine items the Council passes with one motion. The report for that meeting says "If adopted, the Ordinance will become effective 30 days after adoption."
| District | General Plan designation | Maximum density | Height | Floor area ratio |
|---|---|---|---|---|
| R6, High Density Multiple Family Residential | Residential Medium II | 99 homes per acre | 6 stories and 75 ft | None in the ordinance text |
| R7, High Density Multiple Family Residential | Residential High | 130 homes per acre | 8 stories and 100 ft | None in the ordinance text |
| MU3, Medium Density Mixed-Use | Mixed-Use Medium II | 99 homes per acre | 6 stories and 75 ft with homes; 4 stories and 50 ft without | 4.0, on nonresidential floor area only |
| MU4, High Density Mixed-Use | Mixed-Use High | 130 homes per acre | 8 stories and 100 ft with homes; 5 stories and 65 ft without | 4.5, on nonresidential floor area only |
Source: City of San Mateo, draft ordinance in the September 22, 2026 Council packet, proposed Chapters 27.50 to 27.53, and the agenda report of September 8, 2026.
- No house lots. The staff report says of R6, "detached single-family dwellings will not be permitted in this district," and says the same of R7.
- Yards. Each district asks for a 5-foot rear yard and, next to an R1 or R2 district, a buffer of 10 feet at the side and 15 feet at the rear.
- Open space. 50 square feet of private usable open space per home, or 75 square feet of common space, or a mix with at least 30 square feet of private space.
- No lot is rezoned. "The creation of these districts will not result in the automatic rezoning of any existing parcels." Rezoning comes later, through a project application or the citywide code update that staff expects "will be completed by mid-2027."
The minutes of September 22, 2026 were not posted when this guide was written, so this page does not state that the Council adopted the ordinance. The City's Policy and Zoning Code Update Efforts page lists the second reading on that date. The code copy read for this guide does not contain Chapters 27.50 to 27.53.
Where the Code Disagrees With Itself
- Zoning tables and the General Plan. The R3 to R5 tables stop at one home per 870 square feet, which is 50 homes per acre. Table LU-1 allows up to 130. Section 27.02.220 says the General Plan controls.
- A missing chapter. Sections 27.28.044 and 27.28.074 send downtown parking design to "Chapter 27.25" and "Section 27.25.030." Title 27 has no Chapter 27.25; the R4-D parking design rules are in Section 27.28.014.
- Two section numbers that do not exist. The Gateway rules in Sections 27.28.023 and 27.28.053 point to "27.22.028" and "27.22.058." The R3 chapter has no sections with those numbers.
- A misprint in the overlay chapter. Section 27.21.050 names the land in the two-unit overlay as "R1-A, R1-B, and R-C." Section 27.21.130 prints R1-C.
- The density words. Section 27.04.145 calls R4 "High" and lists no R5, and the chapter titles call R4 and R5 both high density.
The general rule for conflicts inside Title 27 is in Section 27.02.040: "the provisions which are more restrictive (or which impose higher standards or requirements) shall govern." Section 27.02.220 is the later and more specific rule for densities and heights. Ask the Planning Division how it reads the two together on your lot.
Limits of This Page
The code was read from the City's bulk copy, whose index page prints "Current through" October 8, 2026. This guide read the City Council agendas of September 8, September 22 and October 5, 2026 only. The zoning map, the General Plan land use map, the Downtown Specific Plan, the Rail Corridor Plan, the Bay Meadows Specific Plan and the Hillsdale Station Area Plan were not read. No statement here says which district or designation covers a given lot. The S, SC, Q, agricultural and open space districts are left out because they add no general route to more homes.
Best For
- ✓ R3 parcels of 8,000 square feet and 65 feet of width, which yield four homes at 2,000 square feet of parcel per home.
- ✓ R4 and R5 parcels of 10,000 square feet or more, at 1,000 or 870 square feet of parcel per home.
- ✓ Commercial lots in C1, C2 and C3, where homes are a permitted use under R3 or R4 standards.
Usually Fails When
- ✕ A third home is planned as a zoning use on an R2 lot, where no more than two families are allowed on a zoning plot.
- ✕ A home count is taken from the R3 table without checking the General Plan designation, which may allow more.
- ✕ A site is priced as R6 or R7 before the City rezones it.
What To Verify Before Spending Money
- → The district, any overlay and the General Plan designation of the lot, with the Planning Division at (650) 522-7212.
- → Whether the ordinance creating R6, R7, MU3 and MU4 was adopted on September 22, 2026 and when it takes effect.
- → How the City rounds a fraction when parcel area is divided by the area required per home.
Where to Go Next
Related on VanPlex: the San Mateo overview, the parking, setbacks and height page and the California SB 9 page.
Frequently Asked Questions
What are the residential zoning districts in San Mateo, California?
What is the difference between R1-A, R1-B and R1-C in San Mateo?
Can I build a duplex on an R2 lot in San Mateo?
How many apartments can I build on an R3 lot in San Mateo?
What does the San Mateo zoning code count as a multiple-family dwelling?
Are homes allowed in the commercial districts of San Mateo?
What is the Housing Opportunities Overlay District in San Mateo?
Does the General Plan or the zoning code control density in San Mateo?
What are the new R6 and R7 zoning districts in San Mateo?
How do I find the zoning of a property in San Mateo?
Official sources (checked October 2026)
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