Title 8 — ZONING & DEVELOPMENT CODE

Chapter 8.244 — S110 DISTRICT (COMBINING DISTRICT, LADERA)

San Mateo County Zoning Code · 2026-06 edition · ingested 2026-07-06 · San Mateo County

8.244.010 - Regulations For “S-110” Combining District (Ladera).

The following regulations shall apply in any single-family residential district with which the “S-110” District is combined.

8.244.020 - Purposes

  1. Control house mass and bulk to preserve privacy and sunlight, and to prevent significant change to the community’s overall character.

  2. Encourage houses that harmonize with the neighborhood’s existing scale of development, rather than dominate or loom above adjacent structures.

  3. Balance a property owner’s need for larger living space with minimizing impacts on neighbors.

  4. Encourage houses that respect and conform to natural landscape features, including topography.

8.244.030 - Definitions

  1. Basement

    • a. Whole Basement. A whole basement is:

      • (1) A floor level where the undersides of the floor joists of the floor immediately above are not more than three (3) feet above the adjoining exterior natural or finished grade, whichever is lower, at any point along the perimeter of that floor level, or

      • (2) A floor level that in part meets the criterion described in (1) above, and for the portions of the floor level perimeter that do not meet this criterion, at least one of the following apply:

        • (a) Window wells and/or exterior stairwells are provided to the extent that: (1) they are required by the building code for minimum light, ventilation, and/or egress, and (2) individual wells do not exceed the minimum size required by the building code.

        • (b) A perimeter wall is entirely blocked from external view by other portions of the building.

    • b. Partial Basement. When a floor level partially meets 1.a above, the basement portion shall be determined as follows:

      • (1) Measure the outside perimeter of the floor level and designate it “A.”

      • (2) Measure the outside perimeter of the floor level that meets the criteria of 1.a above and designate it “B.”

      • (3) Multiply the area of the floor level by B/A. This constitutes basement. The remaining area of the floor level does not constitute basement.

  2. Building Setbacks. The minimum horizontal distance that must be maintained between a building and the specified parcel line.

  3. Daylight Plane. A series of planes defining a three-dimensional volume of space in which a building must be constructed.

  4. Finished Grade. The grade level that exists upon completion of all grading and construction.

  5. Maximum Building Floor Area. The maximum allowed amount of floor area of all buildings and accessory buildings on a parcel.

  6. Maximum Building Height. The maximum allowed vertical dimension of any building on a parcel.

  7. Maximum Parcel Coverage. The maximum amount of a parcel that may be covered, expressed as a percentage of parcel area.

  8. Natural Grade. The grade level that exists prior to any new grading or construction.

  9. Uninhabitable Attic. The area(s) located between the ceiling joists of the topmost floor level and the roof immediately above that meets all of the following criteria: (1) there is no wall or ceiling drywall covering, (2) the floor joists are only covered with an unfinished floor surface, (3) access to the area is only from the inside of the building by a trap door or pull-down ladder, (4) electricity to the area is limited to two lighting fixtures and one receptacle outlet, (5) no heating is provided to the area, and (6) no rough or finished plumbing is provided to the area.

(Prior code § 6300.19-20.1.a Amd. Ord 4003:11/14/00)

8.244.040 - Parcel Width.

The minimum parcel width shall be an average of 100 feet.

8.244.050 - Lot Slope Regulations.

The following regulations for determining lot area requirements and lots per gross acre shall apply in the S-11 District:

LOT AREA REQUIREMENTS LOT AREA REQUIREMENTS
Slope
Category In
Percent
Gross Area
Acres Per
Dwelling Unit
Required
Minimum Lot
Area in Acres
Slope
Category In
Percent
Gross Area
Acres Per
Dwelling Unit
Required
Minimum Lot
Area in Acres
(1) (2) (1) (2)
1 & under 1.14 1.00 26 1.91 1.52
2 1.16 1.00 27 1.97 1.61
3 1.18 1.00 28 2.02 1.69
4 1.20 1.00 29 2.08 1.77
5 1.22 1.00 30 2.14 1.86
6 1.24 1.00 31 2.21 1.94
7 1.26 1.00 32 2.28 2.03
8 1.29 1.00 33 2.36 2.12
9 1.31 1.00 34 2.44 2.19
10 1.33 1.00 35 2.53 2.27
11 1.36 1.00 36 2.62 2.36
12 1.39 1.00 37 2.72 2.45
13 1.42 1.00 38 2.83 2.55
14 1.44 1.00 39 2.95 2.66
15 1.47 1.00 40 3.07 2.78
16 1.51 1.00 41 3.21 2.91
17 1.54 1.00 42 3.37 3.05
18 1.57 1.00 43 3.54 3.20
19 1.61 1.00 44 3.72 3.38
20 1.65 1.00 45 3.93 3.57
LOT AREA REQUIREMENTS LOT AREA REQUIREMENTS
--- --- --- --- --- ---
Slope
Category In
Percent
Gross Area
Acres Per
Dwelling Unit
Required
Minimum Lot
Area in Acres
Slope
Category In
Percent
Gross Area
Acres Per
Dwelling Unit
Required
Minimum Lot
Area in Acres
(1) (2) (1) (2)
21 1.68 1.09 46 4.16 3.79
22 1.73 1.18 47 4.42 4.03
23 1.77 1.26 48 4.71 4.31
24 1.81 1.34 49 5.05 4.63
25 1.86 1.43 50 & over 5.43 5.00

Slope category is determined by the average ground slope which is calculated by the following formula:

.00229 IL S = A

  • Where I = interval of measured contours S = average ground slope of parcel L = combined length of contours in feet (i.e., map measurement of contours in inches X scale)

  • A = area of parcel in acres

Where a parcel being subdivided contains lands in excess of 50% slope, such lands may be treated separately from the rest of the parcel and the number of dwelling units permissible on the 50% and over lands may be added to the number permissible on the balance of the parcel to obtain the total permissible on the entire parcel.

For the purpose of providing flexibility of design in subdivisions, individual lots may be as much as fifteen percent (15%) smaller than indicated in Column Two, provided that the total number of lots within the parcel being subdivided does not exceed the number determined from Column One and provided further that no lot contains less than one (1) acre.

8.244.060 - Building Setbacks.

The minimum building setbacks shall be:

Front Rear Side
50 feet 20 feet 20 feet

8.244.070 - Parcel Coverage.

The maximum parcel coverage shall be .15 (15 percent) and shall include all: (1) buildings, (2) accessory buildings, and/or (3) structures, including decks, balconies, and porches, that are eighteen (18) inches or more above finished grade. Maximum parcel coverage excludes fences and walls.

8.244.080 - Building Floor Area.

The maximum building floor area shall be established according to the following table:

Parcel Area
(in square feet)
Maximum Building Floor Area
(in square feet)
<8,000 2,800
8,000 - 16,000 .1 (parcel area - 8,000) + 2,800
16,001 - 40,000 .06 (parcel area - 16,000) + 3,600
>40,000 .04 (parcel area - 40,000) + 5,040

Building floor area includes: (1) the area of all stories of all buildings (including interior stairs) and accessory buildings requiring a building permit, as measured from the outside face of all exterior perimeter walls; and (2) the area of all garages and carports that exceeds 400 sq. ft. Building floor area excludes basements and uninhabitable attics.

8.244.090 – Building Height.

The maximum building height shall be established according to the following table:

Slope of Building Site* Maximum Building Height
<15 percent 28 feet
>15 percent 30 feet
*Measured as the average slope of area covered by the main residence.

Building height shall be measured from any point on the natural or finished grade, whichever is lower, to the topmost point of the building immediately above, except where a floor of the building is lower than the adjoining exterior natural or finished grade, whichever is lower.

Building height above any portion of a floor of a building that is lower than the adjoining exterior natural or finished grade, whichever is lower, shall be measured from such lower grade.

Slope of building site is calculated by (1) subtracting the lowest point of natural grade immediately adjacent to the house from the highest point of natural grade immediately adjacent to the house, and then (2) dividing the resulting number by the horizontal distance between those two points.

Chimneys, pipes, mechanical equipment, antennae and other common facilities may extend beyond maximum building height to a maximum of 36 feet as required for safety or efficient operation.

8.244.100 DAYLIGHT PLANE .

The daylight plane shall be established by measuring along all setback lines a vertical distance of 15 or 20 feet (depending on slope, see table below) from natural or finished grade, whichever is lower, and then inward at an angle of 45 degrees until the maximum building height is reached.

The vertical dimension of the 536daylight plane at the setback lines shall be established according to the following table:

Slope of
Building Site*
Vertical Dimension of
Daylight Plane
<15 percent 15 feet
>15 percent 20 feet
*Measured as the average slope of area covered by the main residence.

Slope of building site is calculated by (1) subtracting the lowest point of natural grade immediately adjacent to the house from the highest point of natural grade immediately adjacent to the house, and then (2) dividing the resulting number by the horizontal distance between those two points.

Any portion of the building, including dormers, gables, or other architectural features, may protrude into the 45-degree portion of the daylight plane provided that: (1) the combined width of all protrusions into the daylight plane along any setback line does not exceed 15 feet, and (2) no protrusion measures more than a vertical distance of 24 feet from natural or finished grade, whichever is lower.

Cornices, canopies, eaves, chimneys, other architectural features, fire escapes, stairways, landing places, and uncovered porches may protrude into the daylight plane at any required yard, according to the provisions of Chapter 8.340.

Chimneys, pipes, mechanical equipment, antennae and other common facilities may protrude into the daylight plane to a maximum of 36 feet as required for safety or efficient operation.

8.244.110 - Basement Extent.

No basement, or portion thereof, shall be permitted to extend beyond the outside perimeter of the building above, except where necessary to meet the minimum requirements of the building code for light, ventilation, and egress.

(Prior code § 6300.19-6300.19.100. Ord. 3975: 07/11/00)

8.244.120 – District Changes

  • A. Each zoning district which is combined with a “B” District on the effective date of this section shall be combined with an “S” District as herein specified.

    1. B-1 Districts shall become S-7 Districts.

    2. B-2 Districts shall become S-8 Districts.

    3. B-3 Districts shall become S-9 Districts.

    4. B-4 Districts shall become S-10 Districts.

    5. B-5 Districts shall become S-11 Districts.

    6. B-6 Districts shall become S-S Districts in which the regulations shall be the same as those presently set forth for the B-6 District.

    7. B-D Districts shall become S-S Districts in which the regulations shall be the same as those presently set forth for the S-S District.

  • B. Each zoning district not combined with a “B” District on the effective date of this section shall be combined with an “S” District as specified in the following table:

    1. Each R-E District shall be combined with an S-7 District.

    2. Each R-1 District shall be combined with an S-7 District.

    3. Each R-2 District shall be combined with an S-5 District.

    4. Each R-3 District shall be combined with an S-1 District.

    5. Each F-1 District shall be combined with an S-13 District.

    6. Each A-1 District shall be combined with an S-11 District.

    7. Each A-2 District shall be combined with an S-11 District.

    8. Each A-3 District shall be combined with an S-11 District.

  1. Each H-1 District shall be combined with an S-3 District.

  2. Each C-1 District shall be combined with an S-1 District.

  3. Each C-2 District shall be combined with an S-1 District.

  4. Each U-1 District shall be combined with an S-11 District.

8.244.140 – Parcels With Insufficient Right of Way.

When any parcel which meets the minimum lot size for the zoning district in which it is located fronts upon a street having insufficient right of way for the construction of County standard street improvements, said parcel shall continue to be a legal building site after the dedication or acquisition of the necessary additional right of way, provided that the area reduction does not exceed 15% of the original parcel area, and further provided that any building placed upon said parcel subsequent to said dedication shall maintain the front, side and rear yard setbacks required in said zoning district.

(Prior code § 6303 Ord. 1542: 10/16/62)

(Prior code § 6303 Amd. Ord. 2833: 06/14/83)

(Prior code § 6303 Amd. Ord. 3158*: 09/13/88)

(Prior code § 6303) Amd Ord 3171* by State Coastal Commission; 01/24/89)

(Prior code § 6303 Rep. Ord 3596; 09/20/94)

(Prior code § 6304 Ord. 2240: 04/09/10/74)

(Prior code § 6305, 6306 Ord. 2868: 12/20/83)

(Prior code § 6305, 3506 Rep. Ord 3470; 02/02/93)

  • Ordinance No. 3158 not enacted by State Coastal Commission. Replaced by Ordinance No. 3171, enacted by State Coastal Commission - March 8, 1989, effective 30 days thereafter.