Title 8 — ZONING & DEVELOPMENT CODE›Article 1 — ZONING DISTRICTS, OVERLAY, AND COMBINING DISTRICTS›Chapter 8.110 — RH, RESIDENTIAL HILLSIDE DISTRICT
San Mateo County Zoning Code § 8.100 Rh, Residential Hillside District
San Mateo County Zoning Code · 2026-06 edition · updated 2026-09-23 · San Mateo County
Cite as: San Mateo County Zoning Code § 8.100 · Text as of 2026-09-23
8.100.040 - Minimum Building Site.¶
The minimum building site shall be determined in accordance with the following definitions and tables:
(a) “Contour Interval” shall mean the difference in elevation between adjacent contour lines on a topographical or planimetric map.
(b) “Average Percent of Slope” shall mean the percent of slope as computed by the following formula:
S = 100 IL
A
Where S = average percent of slope; I = contour interval in feet; L = summation of length of all contour lines in feet; A = area in square feet of parcel being considered. In calculating the average percent of slope, any part of the parcel will be excluded from the calculation if the owner so elects; however, if the owner makes this selection then in determining land use densities applicable to the parcel only the land used in the slope calculation shall be used in calculating allowable density. If the owner chooses this option, then land excluded from the calculation of density must remain undeveloped and a deed restriction recorded.
| MINIMUM BUILDING SITE | |
|---|---|
| Average Slope of Parcel (percent) |
Minimum Area (square feet) |
| 0 - 17 | 12,000 |
| 18 | 13,000 |
| 19 | 14,000 |
| 20 | 15,000 |
| 21 | 16,000 |
| 22 | 17,000 |
| 23 | 18,000 |
| 24 | 19,000 |
| 25 | 20,000 |
| 26 | 22,000 |
| 27 | 24,000 |
| 28 | 26,000 |
| 29 | 28,000 |
| 30 | 30,000 |
| 31 | 33,000 |
| 32 | 36,000 |
| 33 | 39,000 |
| 34 | 42,000 |
| 35 | 45,000 |
| 36 | 48,000 |
| 37 | 51,000 |
| 38 | 54,000 |
| 39 | 57,000 |
| 40 | 60,000 |
| 41 | 63,000 |
| 42 | 66,000 |
| 43 | 69,000 |
| 44 | 72,000 |
| 45 | 75,000 |
| 46 | 78,000 |
| 47 | 81,000 |
| 48 | 84,000 |
| 49 | 87,000 |
| 50 and over | 90,000 |
When new divisions of land are proposed, the minimum size of each new parcel shall be based on the average slope of the land within each new parcel proposed in the land division. Areas devoted to public or private roads, rights-of-way, or access easements shall not be included in parcel size calculations.
After land division, if the maximum number of new parcels permitted by average slope measurement is created, a separate document shall be recorded that specifies that newly created parcels cannot be further divided into smaller parcels. If the maximum number is not created, leaving potential for future land division, the applicant must specify in a separate recorded document which parcels will eventually be divided.
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