27.18.080 Side Yards
(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 R1-B 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.