Chapter 27.18 — R1 DISTRICTS

The R1 Single-Family Residence 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. The R1 districts are intended to protect the character and variety of neighborhoods, preserve privacy and prevent burdens on public facilities, while allowing reasonable housing opportunities for families.

The following uses are permitted:

(a) One-family detached dwellings, including manufactured homes on permanent foundations;

(b) Accessory dwelling units and junior accessory dwelling units subject to the provisions of Chapter 27.19;

(c) Accessory uses and structures;

(d) Detached accessory structures containing no more than two (2) plumbing fixtures or waste lines;

(e) Home occupations, subject to provisions of Section 27.16.040;

• (f) Community care facilities as follows:

(1) Unlicensed group homes subject to the objective development standards that apply to other residential uses of the same type in the same zone;

(2) Licensed residential care facilities including group homes with six (6) or fewer residents, in addition to the caregiver's family, subject to the objective development standards that

apply to other residential uses of the same type in the same zone. Certain licensed group homes shall be subject to separation requirements pursuant to Health and Safety Code Section 1267.9  , as amended from time to time; and

(3) Family day care for fourteen (14) or fewer occupants, in addition to the caregiver's family, when managed in the caregiver's residence and in accordance with State law.

(g) Temporary buildings for construction purposes for a period not to exceed the duration of such construction;

(h) Transitional housing and supportive housing subject to the objective development standards that apply to other residential uses of the same type in the same zone.

The following uses may also be allowed if a special use permit is approved:

(a) Detached accessory structures, other than accessory dwelling units, containing more than two (2) plumbing fixtures or waste lines;

(b) Swimming pools, hot tubs and spas located in required front yard or street side yard;

(c) Cemeteries, mausoleums, and columbaria, subject to the provisions of the Section 27.18.120;

(d) Churches, convents, parish houses, and monasteries, including as a permitted accessory use emergency shelters subject to the requirements in a residential zone;

(e) Community services including but not limited to libraries, parks, playgrounds, and community centers;

(f) Group homes that provide licensed services to seven (7) or more residents without disabilities, in addition to the caregiver's family, subject to the objective development standards that apply to other residential uses of the same type in the same zone. Certain licensed group homes shall be subject to separation requirements pursuant to Health and Safety Code Section 1267.9  ;

(g) Public and private educational facilities;

(h) Day care centers when located within a public or quasi-public structure such as a school, recreation center, church, temple or similar facility;

(i) Philanthropic and eleemosynary uses;

• (j) Public utility facilities; and

(k) Temporary real estate sales offices for a period not to exceed the duration of the construction and sale of homes within the subdivision wherein the sales office is to be located.

(Ord. No. 2025-03 § 18; Ord. No. 2003-12 § 11; Ord. No. 2000-13 § 2; Ord. No. 2000-11 § 2; Ord. No. 1994-2 § 5; Ord. No. 1992-16 § 10; Ord. No. 1992-15a § 5; Ord. No. 1992-15 § 12; Ord. No. 1989-18 § 13; Ord. No. 1987-33 § 3; Ord. No. 1985-17 § 25; Ord. No. 1983-16 § 2; Ord. No. 1982-22 § 23; Ord. No. 1981-27 § 26; Ord. 1979-1 §§ 3, 4; Ord. No. 1978-18 § 81; Ord. No. 1975-23 § 9; Ord. No. 1971-17 § 2; prior code § 146.02(B).)

Cross References

Section 27.18.080(d)

(a) A special use permit shall be required for the substantial removal of an existing residence, regardless of whether it is currently inhabited. "Substantial removal" shall mean the demolition of 50% or more of the structure's exterior walls (measured in lineal feet) and/or roof (measured in square feet). Existing exterior walls that are converted to interior walls shall be counted as walls to be demolished. Substantial removal for a roof shall not apply to permit applications for reroofing where roof pitch alterations do not exceed an increase in height of more than two (2) feet as measured at the highest point or where a Single Family Dwelling Design Review (SFDDR) planning application has been submitted as part of the proposed dwelling's improvements. Doors, including garage doors, entry doors, and sliding glass doors, shall not be included in the percentage calculation of an existing structure's exterior walls. This section shall not apply to an accessory building or to a residence that has been declared a public nuisance under this Code.

(b) No existing residence may be substantially removed unless either: (1) an application for a residence is submitted concurrently with the application for removal and is approved pursuant to the SFDDR procedures; or (2) plans for a permitted use other than a residence are submitted concurrently with the application for removal and, if the permitted use does not contain a principal structure, removal shall be conditioned upon subsequent SFDDR of a new principal structure; or (3) application for a special use permit is submitted concurrently with the application for removal and is approved; if the special use permit does not contain a principal structure, removal shall be conditioned upon subsequent SFDDR of a new principal structure.

(Ord. No. 2009-7 § 15; Ord. No. 2006-9 § 1; Ord. No. 2001-36 § 7; Ord. No. 2000-2 § 5.)

Cross References

Section 27.21.140(a)

(a) Newly created parcels. Dwellings developed after the effective date of this title shall be developed on recorded parcels which meet the following prescribed standards:

(b) Existing substandard parcels. Dwellings may be erected on parcels which do not meet the minimum standards of section (a) above if the parcel was recorded under separate ownership from adjoining parcels prior to March 3, 1947, if the subdivision map was approved with exceptions or if a recorded parcel has received a certificate of compliance.

(c) Width at street frontage. All parcels shall provide a minimum width of thirty (30) feet on a recorded public street frontage, or on a street as designated by resolution pursuant to Section 17.04.010. However, less width may be provided, if a permanent access easement to a public street was either recorded prior to this title's effective date, or is approved by the City.

(a) Maximum height. The maximum height of structures shall be 24 feet measured from existing grade to the building plate line and 32 feet measured from the existing grade to the highest point of the roof. Existing residences that exceed these limits may construct additions in accordance with their existing roof lines but shall not increase the non-conformance with these height limits.

(b) Daylight plane. No structure shall extend above or beyond a daylight plane having a height of twelve (12) feet at each side property line and extending into the parcel at an angle of forty-five (45) degrees, with the following encroachments allowed:

• (1) Television and radio antennas, chimneys, flues, eaves, or skylights;

(2) Dormers or similar architectural features, provided that the horizontal length of all such features shall not exceed a combined total of fifteen (15) feet on each side, measured along the intersection with the daylight plane;

(3) Gables or similar architectural features, provided that the horizontal length of all such features shall not exceed a combined total of eighteen (18) feet on each side, measured along the intersection with the daylight plane, and provided that the intersection of the gable with the daylight plane closest to the front property line is along the roof line;

(4) Where the finished first floor of an existing dwelling is more than three (3) feet above existing grade and is being extended by an addition, the initial height of the daylight plane shall be fourteen (14) feet;

(5) Where the slope of a parcel measured between the side property lines at the front setback is fifteen percent (15%) or steeper, the initial height of the daylight plane shall be fourteen (14) feet on the downhill side of the parcel; and

(6) Where the slope of a parcel measured between the front and rear most points of the structure is fifteen percent (15%) or steeper, the daylight plane shall be measured at the front setback line and each thirty (30) feet thereafter, and the height limits established at these points shall be extended horizontally to the next measurement point.

The floor area ratio of buildings and structures on a parcel shall not exceed the following limitations:

In no case shall more than 6,000 square feet of total floor area be permitted per parcel in residential use.

(a) A front yard setback not less than twenty-five (25) feet in an R1-A district and not less than fifteen (15) feet in an R1-B or R1-C district shall be provided.

(b) Garage setback. A front yard setback not less than twenty (20) feet in an R1-B or R1-C district shall be provided for a garage.

(c) Private roads. Buildings erected or enlarged on property fronting upon a private road or easement shall maintain a front setback of at least fifty (50) feet from the centerline of such

private road or easement.

(d) Limits on paving. This subsection regulates the amount and location of paving in order to: (1) maintain an aesthetic, landscaped appearance along the street frontages; and (2) maximize the amount of usable open space and landscape areas for single-family properties. The portion of the required front yard setback that is paved shall be limited to driveways or walkways. The paving (including pervious and non-pervious surfaces), shall be limited to:

(1) that required for necessary driveway, as follows:

(A) Single car garages: 17 feet maximum in width or 40% of the street frontage, whichever is less, beginning at the side property line adjacent to the driveway, and including any contiguous paving (i.e. pedestrian walkways) with the following exception:

(i) For those parcels with single car garages, carports, or open parking spaces setback more than 35 feet from the front property line, no paving in addition to the driveway shall be allowed in the front yard setback.

(B) Two-car garages or larger: 20 feet maximum in width.

(C) For properties located on a cul-de-sac, a driveway at least 10 feet in width shall be permitted when providing access to two or fewer garages, carports, or open parking spaces, and 12 feet in width when providing access to three or more garage, carport, or open parking spaces;

(2) Circular driveways subject to SPAR review; and

(3) Pedestrian walkways which are five (5) feet or less in width.

(e) Landscaping. Other than the paving for driveway and walkway that are permitted in subsection (d) above, the remaining portion of the required front yard setback is intended to: (1) be improved with landscaping and elements for outdoor living, and (2) provide space for the preservation of heritage trees. Parking is prohibited in outdoor living areas and in areas delineated in Section 27.64.023 of the San Mateo Municipal Code.

(a) Interior side yards. Interior side yard setback not less than seven (7) feet in an R1-A district and not less than five (5) feet in an R1-B or R1-C district shall be provided.

(b) Street side yards. For corner parcels, a side yard adjacent to the street is a street side yard and a setback is required as follows:

(1) For ground floors: Fifteen percent (15%) of the lot width as measured at building location, not less than 7.5 feet and not to exceed 25 feet in the R1-A district and 15 feet in the R1B and C districts.

(2) For construction above the first story: Minimum of ten (10) feet.

(3) For garages: Minimum of twenty (20) feet.

(4) Limits on paving. This subsection regulates the amount and location of paving in order to: (1) maintain an aesthetic, landscaped appearance along the street frontages; and (2) maximize the amount of usable open space and landscape areas for single-family properties. The portion of the required street side yard setback that is paved shall be limited to driveways or walkways. The paving (including pervious and non-pervious surfaces), shall be limited to:

(A) that required for necessary driveways, as follows:

(i) Single car garages: 17 feet maximum in width or 40% of the street frontage whichever is less, beginning at the side property line adjacent to the driveway, and including any contiguous paving (i.e. pedestrian walkways) with the following exception:

(I) For those parcels with single car garages, carports, or open parking spaces setback 35 feet or more from the street property line, no paving in addition to the driveway shall be allowed in the side setback.

(ii) Two-car garages or larger: 20 feet maximum in width.

(B) Pedestrian walkways which are five (5) feet or less in width.

(5) Landscaping. Other than the paving for driveway and walkway that are permitted in subsection (4) above, the remaining portion of the required street side yard setback is intended to: (1) be improved with landscaping and elements for outdoor living, and (2) provide space for

the preservation of heritage trees. Parking is prohibited in outdoor living areas and in areas delineated in Section 27.64.023 of the San Mateo Municipal Code.

(c) Extensions of walls having non-conforming side yards. When an existing interior side yard of a legally constructed single-family dwelling is less than that required by this Section, a single story, horizontal addition may be constructed maintaining the existing non-conforming setback line, provided that:

(1) The existing side yard setback to be extended is at least three (3) feet from the side property line;

(2) The maximum height of the extended wall is twelve (12) feet to the plateline;

(3) The total length of the extension along a single side wall shall not exceed twenty (20) feet; and

(4) The proposed extension is the subject of Site Plan and Architectural Review (SPAR) conducted by the Zoning Administrator pursuant to the provisions of Section 27.08.030.

(d) Non-residential uses. Newly constructed or expanded structures for non-residential uses allowed under Section 27.18.030 shall provide minimum side yards, both interior and street, of fifteen (15) feet or one-half the building height, whichever is greater.

A rear yard of not less than fifteen (15) feet shall be provided; a rear yard not less than twenty-five (25) feet shall be provided for new construction above a single story.

27.18.100 STRUCTURES AND BUILDING PROJECTIONS IN REQUIRED YARDS.

• (a) The following structures, building projections and features shall be permitted in all yards:

(1) Arbors and trellises, having a maximum height of eight (8) feet, except in no case shall any such structure be used to cover driveways located in required setbacks in the front 2/3 of the property;

(2) Awnings, canopies and covered patios, having a maximum height of eight (8) feet;

• (3) Basements completely below grade;

(4) Eaves, projecting a maximum of three (3) feet of fifty percent (50%) of the required yard width, whichever is less;

(5) Chimneys, solariums, greenhouse windows and oriel bay windows projecting two (2) feet or less into the yard, provided that the outside face of the projections shall be at least three (3) feet from the property line;

(6) Balconies and decks projecting two (2) feet or less into the yard, excluding projections into interior side yards above the first floor, and provided that the outside face of the projection shall be at least three (3) feet from the property line;

(7) Flag poles, garden ornaments and play equipment;

(8) Steps which are necessary to provide access to the first floor of a permitted building, or to a parcel from a street or alley;

(9) Uncovered decks, subject to the following standards:

(A) Uncovered decks that are eighteen (18) inches in height, or shorter, are allowed in all required yards; and

(B) Uncovered decks that are taller than eighteen (18) inches and no taller than thirty (30) inches in height are allowed in some portions of required yards provided that they are not located within five (5) feet of property lines.

(10) Open parking spaces within a rear yard.

(b) The following structures, building projections and features shall be permitted in front yards:

Covered porches projecting two (2) feet or less into required front yards, and only when the required yard meets current yard setback requirements. The projection into the required yard may not be enclosed with walls or other material. The projection shall not exceed 50% of the width of the house as measured at the front property line,

(c) Location of detached accessory buildings. A detached accessory building located within the rear one-third of a parcel is exempt from the requirements for interior side and rear yards, provided that such structure:

(1) Shall be separated from the principal building by a distance not less than four (4) feet in width that is open to the sky, and

(2) Shall not exceed a height of nine (9) feet to the plate line and sixteen (16) feet to the roof peak, and

(3) Shall not extend above or beyond a daylight plane having a height of nine (9) feet at each side and rear property line and extending into the parcel at an angle of forty-five (45) degrees, excepting eaves and flues, and

(4) Shall be limited to one habitable floor on the ground level. Habitable floor for the

purposes of this subsection shall mean that served by permanent access and containing windows and/or plumbing fixtures, but shall exclude basements.

(d) Maximum coverage of required rear yards. Accessory buildings shall not occupy more than fifty (50) percent of a required rear yard.

(Ord. No. 2021-9 § 4; Ord. No. 2009-7 § 17; Ord. No. 2006-9 § 1; Ord. No. 1992-16 § 10.)

Cross References

Section 27.70.020(a)

(a) Off-street parking facilities shall be required for all permitted and special uses in accord with Chapter 27.64.

(b) Minimum parking requirements for single family uses permitted in the R1 Districts shall be as follows:

(c) Location in required yards. Required parking may not be located within a required front yard or side yard.

(d) Garage doors. For garages located within fifty (50) feet of a street frontage, no more than fifty (50) percent of the ground floor building facade facing the street shall be composed of garage doors or open covered parking facilities.

Notwithstanding other provisions of this chapter, the following shall be applicable to the San Mateo Park planning area as is designated on the map shown below:

(a) For both new residences and additions to existing residences:

(1) Garages shall provide a front yard setback of at least 50 feet when garage doors face the street, or 25 feet if garage doors do not face the street, except in cases where an existing or previously existing garage faced the street with less than a 50 foot front setback and in those cases the new garage may face the street with a front yard setback equal to or greater than that which previously existed and with no increase in the number of garage spaces that face the street.

(2) Sideyard setbacks shall be a minimum of 10 feet for interior lots of widths equal to or greater than 75 feet and 7 feet for interior lots of widths less than 75 feet.

(b) For additions to existing residences:

(1) Street sideyard setbacks shall be equal to 15% of the lot width as measured at the building location but not less than 10 feet nor more than 25 feet.

(c) For new residences constructed on corner lots of widths equal to or greater than 75 feet:

(1) Both street frontages shall be treated as front yards with a minimum setback of 25 feet.

Cemeteries, mausoleums, and columbaria shall be subject to the following use conditions:

(a) Cemeteries, mausoleums, and columbaria shall be closed from sunset to 7:00 a.m., and all gates shall be locked during the hours of closure. Signs indicating hours shall be prominently displayed at all entry/exit gates at all times.

(b) The minimum setback for cemeteries existing on November 16, 1992, shall be established by resolution of the City Council or shall be as shown on a previously issued special use permit. Minimum setbacks for new cemeteries shall not be less than the setbacks established for R1-A districts and shall be established as part of the special use permit process. No burials may be located within setbacks excepting those burials that have occurred on or before November 16, 1992.

(c) A special use permit shall be required for construction or placement of mausoleums, columbaria, monuments, or other above ground structures that exceed a height of four (4) feet above grade. However, no mausoleum, columbarium, or monument exceeding a height of seven (7) feet above grade shall be permitted.

(d) Applicants for a special use permit for a cemetery use shall be required to submit a landscape plan for setback areas as part of the application.

(e) Cemeteries shall be required to upgrade parking facilities in compliance with the standards of Chapter 27.64 as part of the special use permit process.

(Ord. No. 1992-15a § 6; Ord. No. 1992-15 § 13.)

Cross References

Section 27.18.030(c)