Chapter 18.12
HILLSIDE (H) OVERLAY DISTRICT Revised 1/24

Sections:

18.12.010    Purpose. Revised 1/24

18.12.020    Applicability. Revised 1/24

18.12.030    Hillside subdivision standards. Revised 1/24

18.12.040    Excavations and grading. Revised 1/24

18.12.050    Development standards. Revised 1/24

18.12.060    Building design standards. Revised 1/24

18.12.070    Landscaping. Revised 1/24

18.12.010 Purpose. Revised 1/24

The Hillside (H) Overlay District is intended to protect the health, safety, and welfare of residents of the City by establishing regulations for managing the development of hillside areas. The specific purposes of the H Overlay District are to:

A.    Protect public health and safety by minimizing hazards, including soil erosion and fire danger associated with development on hillsides;

B.    Preserve and enhance San Carlos’ scenic character, including its natural hillsides;

C.    Conserve the City’s open spaces and significant natural features;

D.    Require hillside development to be designed and constructed in a manner that respects and minimizes the disturbance of existing terrain, native vegetation, and significant natural landforms and features. (Ord. 1603 § 3 (Exh. A), 2023; Ord. 1480 (Exh. B (part)), 2015: Ord. 1438 § 4 (Exh. A (part)), 2011)

18.12.020 Applicability. Revised 1/24

A.    The provisions of this chapter apply to all lots and sites that have an average slope of twenty percent (20%) or greater. The average slope shall be determined using the formula set forth in Section 18.03.070, Determining average slope. Depending on the scope of the project, the Director may require a survey and slope analysis to determine whether the provisions of this chapter apply to a specific property or development.

B.    These regulations may be combined with any district. In the event of a conflict between the provisions of this chapter and any underlying base district, the most restrictive provisions shall apply. (Ord. 1603 § 3 (Exh. A), 2023; Ord. 1480 (Exh. B (part)), 2015: Ord. 1438 § 4 (Exh. A (part)), 2011)

18.12.030 Hillside subdivision standards. Revised 1/24

A.    Further Reduction in Number of Allowed Lots. The review authority may reduce further than required by this section the maximum number of lots in a new subdivision based upon site-specific problems or constraints identified through the environmental review of the proposed subdivision.

B.    Building Site Requirements. Each proposed lot shall be designed and located to provide at least one (1) building site where all proposed structures can comply with all other applicable requirements of this title.

C.    Roads. Each new road shall follow natural terrain contours to minimize grading. Deviation from this standard shall be allowed based on site-specific conditions identified through the preliminary grading plan. Proposed driveways shall comply with the requirements of Section 18.12.050, Development standards. (Ord. 1603 § 3 (Exh. A), 2023; Ord. 1443 § 4 (Exh. A (part)), 2012; Ord. 1438 § 4 (Exh. A (part)), 2011)

18.12.040 Excavations and grading. Revised 1/24

The following requirements shall be in addition to all other requirements which may from time to time be adopted by the City in various building and engineering regulations, and specifically Chapter 12.08 (Grading and Excavations), unless such regulations specifically repeal or state they supersede the standards of this section.

A.    Grading and excavations shall result in the minimal disturbance feasible to the terrain and natural land features. A plan shall be provided identifying ridgelines, hilltops, drainage courses, and rock outcrops, and indicating how those features will be retained on the grading plan.

B.    Existing trees and native vegetation shall be retained to stabilize hillsides, reduce erosion and to preserve the natural state site conditions. Deviation from this standard may be allowed based on site-specific conditions identified through the preliminary grading plan.

C.    Grading plans shall balance cut and fill materials on site so that the import and export of materials for development is achieved. Where balance cannot be achieved, a plan shall be provided indicating a schedule for import/export activities, the volume of import/export materials anticipated, and haul routes for trucks transporting materials.

D.    All areas of the site not planned to be under structures that have a finished average slope greater than fifteen percent (15%) shall not be covered by any impervious surface.

E.    Final contours and slopes shall generally reflect existing landforms and transition to existing grades on adjoining property unless retaining walls are used consistent with the provisions of this chapter.

F.    Slopes created by grading of the site shall not exceed thirty percent (30%).

G.    The outside corners or edges of all cut and fill slopes, except at the tops of slopes, shall be rounded to eliminate the sharp corners and shall have a minimum curvature radius of at least five (5) feet.

H.    Exceptions to the standards of this section may be approved by the Planning and Transportation Commission through the design review process pursuant to Chapter 18.29 if the following findings are made:

1.    The project design alternative substantially meets the purposes of the H Overlay District; and

2.    The project incorporates alternative design solutions that minimize grading, retain more of the project site in its natural state, minimize visual impacts, protect mature trees, and/or protect natural resources and result in a demonstrably superior project designed with greater sensitivity to the natural setting and compatibility with nearby structures. (Ord. 1603 § 3 (Exh. A), 2023; Ord. 1438 § 4 (Exh. A (part)), 2011)

18.12.050 Development standards. Revised 1/24

A.    General Site Planning Standards. Each structure shall be located in the most accessible, least visually prominent, most geologically stable portion or portions of the site, and at the lowest feasible elevation based on unique site conditions, including geology, presence of drainage features, and presence of mature trees and native vegetation. Structures shall also be designed and located to align with the natural contours of the site prior to any planned grading, and to be screened by existing vegetation, depressions in topography, or other natural features.

B.    Parking Front Setback Adjustment. To reduce grading, required parking (including a private garage) may be located as close as five (5) feet to the street property line; provided, that portions of the dwelling and accessory structures other than the garage shall comply with the setback requirements of the base zoning district.

C.    Natural State. Any area of the lot that is not part of a building pad, underneath any allowed cantilever building section, disturbed to install required utilities, used as an uncovered parking area, a paved patio area or deck adjacent to a structure, or a swimming pool/spa shall remain in a natural state consisting of ungraded terrain and indigenous vegetation, with no improvements whatsoever. That which is not considered natural state is considered disturbed area. The minimum required percentage of a lot to remain in its natural state and undisturbed is thirty-five percent (35%) notwithstanding the exceptions below. Exceptions include:

1.    Any area used as an uncovered surface parking area shall not be larger in area than eight hundred (800) square feet.

2.    The combined area of any paved patio area, swimming pool/spa, accessory structure, and/or deck shall not exceed five hundred (500) square feet.

3.    A terraced area or areas not exceeding a combined total of one thousand (1,000) square feet may be used for the planting of decorative, nonnative landscaping, including trees.

4.    Connecting pathways consisting of pervious surfaces may be constructed to connect the primary unit and/or accessory dwelling units (ADUs) to other improved areas on the lot.

5.    A Statewide exemption accessory dwelling unit (ADU) as defined in Section 18.23.210 is not subject to natural state requirements, and its area is not counted as disturbed, for the purposes of demonstrating natural state compliance.

This standard may be reduced for lots zoned PD or developed with clustered development, subject to approval by the review authority. Statewide exemption accessory dwelling units (ADUs) are exempt from natural state calculations.

D.    Site Access, Driveways. Each driveway shall follow natural terrain contours to minimize grading. Deviation from this standard shall be allowed based on site-specific conditions identified through the preliminary grading plan. The following additional standards shall apply:

1.    Maximum Grade. The finished grade of a driveway shall conform to the finished grade of the lot, but in no case shall exceed an average grade of eighteen percent (18%).

2.    Agency Review. The location and design of any driveway shall be referred to the Fire Department for review and comment as to on- and off-street safety of vehicles, vehicle passengers and pedestrians, and access for emergency vehicles consistent with standards established by the Fire Department.

E.    Retaining Walls. Large retaining walls in a uniform vertical or horizontal plane shall not be permitted. Retaining walls higher than eight (8) feet shall be divided into terraces and include landscaping on the terraces to screen the walls and stabilize the soils. The horizontal run of any retaining wall shall not extend greater than thirty (30) feet without a recessed offset feature measuring at least three (3) feet in depth to break up the length of the wall. No retaining wall located in the front or rear yard area shall be higher than six (6) feet. (Ord. 1604 § 4 (Exh. B), 2023; Ord. 1603 § 3 (Exh. A), 2023; Ord. 1480 (Exh. B (part)), 2015; Ord. 1438 § 4 (Exh. A (part)), 2011)

18.12.060 Building design standards. Revised 1/24

A.    Height Limits. A proposed structure shall comply with the setback requirements of the base zoning district and the following:

1.    Overall Height Limit. The maximum overall height of a structure shall not exceed a height of thirty-five (35) feet, measured from the lowest finished grade to the highest point of the roof.

2.    Downhill Facing, Street-Facing Building Elevation. Where the building elevation at the adjacent street is facing downhill and facing the street, the downhill facing, street-facing building elevation shall have a maximum height of twenty (20) feet from finished grade.

i.    Required Stepback. The building face of the next highest story shall step back a minimum of five (5) feet from the downhill facing building elevation. The intent of the rule is to create sufficient articulation, shadow lines, and minimized visual height and bulk viewed from the street.

An accessory dwelling unit attached to the main building at the downhill building elevation, and classified as a Statewide exemption accessory dwelling unit, may be constructed with a maximum height of twenty-five (25) feet from finished grade.

FIGURE 18.12.060-A: HILLSIDE OVERLAY DISTRICT HEIGHT LIMITS

B.    Articulation. The exterior wall surfaces visible from off the site shall utilize at least one (1) of the following single-story elements: bays, recesses, stepbacks, overhangs, landscaping, and/or other means of horizontal and vertical articulation. The intent of this regulation is to create changing shadow lines and to break up massive forms.

C.    Foundation Design. The use of multi-level foundations (floor levels separated by a minimum of four (4) feet) shall be the standard design for residential structures unless an alternative design involving less grading is approved through the design review process as appropriate for the site based on topography, soils or geologic conditions, protection of on-site natural resources and landforms, and/or presences of mature trees.

D.    Underfloors. Areas between the lowest floor and approved finished grade shall not exceed six (6) feet in height and shall be completely enclosed with fire-retardant materials to prevent exposure to wildfire hazard.

FIGURE 18.12.060-D: MAXIMUM UNDERFLOOR HEIGHT

E.    Decks. No portion of the walking surface of a deck with visible support structures shall exceed a height of six (6) feet above finished grade. Decks shall be integrated into the architecture of the building(s) through, at minimum, use of similar building materials, direct connection to the adjacent building floor at the same level, and alignment of the deck edge with the floor below (no cantilever), and shall not appear as an add-on to the primary building mass.

F.    Colors and Materials. Colors and materials shall be used to guard against wildland fire hazards and provide for structures to mimic the natural colors of the hillside vegetation and other natural features.

1.    Earth-tone colors shall be used for building walls and roofs. For the purpose of this requirement, earth-tone shall mean colors found in nature that have a variety of hues with brown undertones, including rust, marigold, burnt sienna brown, terracotta, sage, and turmeric. For the purposes of this definition, brown shall mean a hue with a hexadecimal RGB code of 964B00.

2.    In areas of potential high fire hazard, exterior building materials shall be fire-retardant and consistent with applicable requirements of the Fire Department. (Ord. 1604 § 4 (Exh. B), 2023; Ord. 1603 § 3 (Exh. A), 2023; Ord. 1480 (Exh. B (part)), 2015; Ord. 1438 § 4 (Exh. A (part)), 2011)

18.12.070 Landscaping. Revised 1/24

A.    Required Landscaping. Landscaping shall provide for the following:

1.    Screening of retaining walls over four (4) feet in height, accessory structures, and buildings visible from a downslope;

2.    Screening of parking areas in multiple residential or nonresidential developments; and

3.    Slope stabilization for all cut, fill, and natural slopes of three (3) feet or more in vertical height with deep-rooted plants.

B.    Fire Hazards. Within designated high-fire-hazard zones, landscaping shall comply with the requirements of the San Carlos/Redwood City Fire Department.

C.    Installation and Maintenance. Landscaping shall be installed and maintained consistent with the regulations of Chapter 18.18, Landscaping. (Ord. 1603 § 3 (Exh. A), 2023; Ord. 1438 § 4 (Exh. A (part)), 2011)