Earlier editions: 2026-09
Portola Valley Municipal Code Ch. 18.48 Parcel Area, Open Space and Bulk—basic Requirements
Portola Valley Municipal Code · 2026-10 edition · updated 2026-10-04 · Portola Valley
Cite as: Portola Valley Municipal Code Chapter 18.48 · Text as of 2026-10-04
18.48.010 - Basic requirements.¶
The following tables, Table 1 and Table 2, set forth the basic parcel area, open space and bulk regulations which apply to all districts. These basic regulations are further defined and supplemented by additional requirements and exceptions in subsequent chapters. For convenience, the numbers of these chapters are set forth in column headings in the tables.
TABLE NO. 1 BASIC AREA, OPEN SPACE, BULK AND DENSITY REGULATIONS FOR RESIDENTIAL DENSITY COMBINING DISTRICTS
| Column 1 | Column 2 | Column 3 | Column 3 | Column 3 | Column 4 | Column 5 | Column 6 | Column 7 |
|---|---|---|---|---|---|---|---|---|
| Ch. 18.50 | Ch. 18.52 | Ch. 18.52 | Ch. 18.52 | Ch. 18.54 | Ch. 18.56 | |||
| Combining District | Parcel Area Square Feet | Required Yards, Feet least Depth or Width | Required Yards, Feet least Depth or Width | Required Yards, Feet least Depth or Width | Height Limit Feet | Maximum Ht. Limit Feet | Maximum Floor Area Square Feet | Maximum Impervious Surface Square Feet |
| Combining District | Parcel Area Square Feet | Front | Rear | Side | Height Limit Feet | Maximum Ht. Limit Feet | Maximum Floor Area Square Feet | Maximum Impervious Surface Square Feet |
| (7.5 M) | 7,500 | 20 | 20 | 5 | 15-28* | 34 | 3,019 | 2,231 |
| (15 M) | 15,000 | 20 | 20 | 10 | 15-28* | 34 | 3,623 | 3,877 |
| (20 M) | 20,000 | 20 | 20 | 10 | 15-28* | 34 | 3,910 | 5,090 |
| (1 A) | 43,560 | 50 | 20 | 20 | 28 | 34 | 5,260 | 7,808 |
| (2 A) | 87,120 | 50 | 20 | 20 | 28 | 34 | 7,013 | 11,358 |
| (2.5 A) | 108,900 | 50 | 20 | 20 | 28 | 34 | 7,514 | 13,177 |
| (3.5 A) | 152,460 | 50 | 25 | 25 | 28 | 34 | 8,065 | 15,566 |
| (5 A) | 217,800 | 50 | 25 | 25 | 28 | 34 | 8,766 | 17,370 |
| (7.5 A) | 326,700 | 50 | 25 | 25 | 28 | 34 | 9,581 | 19,822 |
* See Section 18.54.020 (B) a) To determine the maximum amount of floor area or impervious surface permitted on a parcel, the figures from Table 1 must be inserted in Tables 1A and 1B to determine the Adjusted Maximum Floor Area and Adjusted Maximum Impervious surface. The Adjusted Maximum Floor Area and Adjusted Maximum Impervious Surface figures then supersede the Maximum Floor Area and Maximum Impervious Surface figures from Table 1. b) For parcels over 7-1/2 acres and up to 10 acres, the floor area can be increased at the rate of 216 square feet per acre to a maximum of 10,121 square feet, and the impervious surface can be increased at the rate of 794 square feet per acre to a maximum of 21,807 square feet. For parcels 10 acres and larger, floor areas and impervious surfaces may exceed these limitations when a conditional use permit is granted therefor as provided in Chapter 18.72. The resultant floor area and impervious surface figures are to be inserted in Tables 1A and 1B to determine the Adjusted Maximum Floor Area and Adjusted Maximum Impervious Surface.
TABLE 1A COMPUTATION OF ADJUSTED MAXIMUM FLOOR AREA
| 1. | Enter parcel area. ( _____ acres) | sf |
|---|---|---|
| 2. | Enter 0.5% of parcel area for each 1% of average slope or parcel. (__________% slope) (Slope shall be measured as specified in Section 18.50.041.) | less sf |
| 3. | Enter 50% of any area on a parcel classified as Pmw, Ms, Pd, Pdf, Psc or Pf on the Town's Ground Movement Potential Map. (Total area classified as Pmw, Ms, Pd, Pdf, Md, Psc or Pf: _____ sf.) | less sf |
| 4. | Enter 50% of any parcel area classified as floodplain area on the Flood Insurance Rate Map referenced in Section 18.32.030. (Total area in floodplain __________sf [Exclude any area (__________sf) identified in item 3. above.] a | less sf |
| 5. | Sum limes 1—4 to obtain Adjusted Parcel Area (APA) (__________ acres) | APA sf |
| 6. | Calculate Adjusted Maximum Floor Area (AMFA) as follows: | Calculate Adjusted Maximum Floor Area (AMFA) as follows: |
| a. | If APA is the same as or less than the minimum parcel area for which the combining district in which the parcel is located, determine AMFA directly or by interpolation from Table No. 1. | If APA is the same as or less than the minimum parcel area for which the combining district in which the parcel is located, determine AMFA directly or by interpolation from Table No. 1. | AMFA sf | |
|---|---|---|---|---|
| b. | If APA is greater than the minimum parcel area for the combining district in which the parcel is located, determine AMFA as follows: | If APA is greater than the minimum parcel area for the combining district in which the parcel is located, determine AMFA as follows: | ||
| (1) | Determine maximum floor area by interpolation from Table No. 1 using APA from line 5. | sf | ||
| (2) | Enter maximum floor area for combining district in which parcel is located. | sf | ||
| (3) | Subtract line (2) from line (1). | sf | ||
| (4) | To obtain AMFA add line (2). and 50% of line (3). | AMFA sf | ||
| c. | Enter 5% of line 6a. or 6b.(4) as appropriate, and add to total shown for 6a. or 6b.(4) to determine AMFA if building will not exceed 1 story (18 feet) in height and 24 feet from lowest point of contact with the ground to the highest point on the building. | Enter 5% of line 6a. or 6b.(4) as appropriate, and add to total shown for 6a. or 6b.(4) to determine AMFA if building will not exceed 1 story (18 feet) in height and 24 feet from lowest point of contact with the ground to the highest point on the building. | AMFA sf | |
| 7. | Calculate Maximum permitted area for any single building as 85% of line 6a., 6b.(4), or 6c.).;sup\sup; | Calculate Maximum permitted area for any single building as 85% of line 6a., 6b.(4), or 6c.).;sup\sup; | Calculate Maximum permitted area for any single building as 85% of line 6a., 6b.(4), or 6c.).;sup\sup; | sf |
(Ord. 2010-387 § 5, 2010; Ord. 2001-338 § 5 (part), 2001)
a When the town engineer finds that a flood hazard map appears inaccurate, the engineer may modify said map for the purposes of the administration of Table 1A and Table 1B of the zoning ordinance and such modification shall be used in calculating the area utilized in line 4.
;sup\sup;In all combining districts, the 85% limitation shall also include any detached garage or carport required by Title 18 "Zoning" of this Code. See Sections 18.48.020 for exceptions to the 85% limitation.
TABLE 1B COMPUTATION OF ADJUSTED MAXIMUM IMPERVIOUS SURFACE
| 1. | Enter parcel area. ( _____ acres) | Enter parcel area. ( _____ acres) | Enter parcel area. ( _____ acres) | sf |
|---|---|---|---|---|
| 2. | Enter 0.5% of parcel area for each 1% of average slope or parcel. (__________% slope) (Slope shall be measured as specified in Section 18.50.041.) | Enter 0.5% of parcel area for each 1% of average slope or parcel. (__________% slope) (Slope shall be measured as specified in Section 18.50.041.) | Enter 0.5% of parcel area for each 1% of average slope or parcel. (__________% slope) (Slope shall be measured as specified in Section 18.50.041.) | less sf |
| 3. | Enter 50% of any area on a parcel classified as Pmw, Ms, Pd, Pdf, Psc or Pf on the Town's Ground Movement Potential Map. (Total area classified as Pmw, Ms, Pd, Pdf, Md, Psc or Pf: _______ sf.) | Enter 50% of any area on a parcel classified as Pmw, Ms, Pd, Pdf, Psc or Pf on the Town's Ground Movement Potential Map. (Total area classified as Pmw, Ms, Pd, Pdf, Md, Psc or Pf: _______ sf.) | Enter 50% of any area on a parcel classified as Pmw, Ms, Pd, Pdf, Psc or Pf on the Town's Ground Movement Potential Map. (Total area classified as Pmw, Ms, Pd, Pdf, Md, Psc or Pf: _______ sf.) | less sf |
| 4. | Enter 50% of any parcel area classified as floodplain area on the Flood Insurance Rate Map referenced in Section 18.32.030. (Total area in floodplain __________ sf) [Exclude any area (__________sf) identified in item 3. above.] a | Enter 50% of any parcel area classified as floodplain area on the Flood Insurance Rate Map referenced in Section 18.32.030. (Total area in floodplain __________ sf) [Exclude any area (__________sf) identified in item 3. above.] a | Enter 50% of any parcel area classified as floodplain area on the Flood Insurance Rate Map referenced in Section 18.32.030. (Total area in floodplain __________ sf) [Exclude any area (__________sf) identified in item 3. above.] a | less sf |
| 5. | Sum limes 1—4 to obtain Adjusted Parcel Area. (__________ acres) | Sum limes 1—4 to obtain Adjusted Parcel Area. (__________ acres) | Sum limes 1—4 to obtain Adjusted Parcel Area. (__________ acres) | APA sf |
| 6. | Calculate Adjusted Maximum Impervious Surface (AMIS) as follows: | Calculate Adjusted Maximum Impervious Surface (AMIS) as follows: | Calculate Adjusted Maximum Impervious Surface (AMIS) as follows: | |
| a. | If APA is the same as or less than the minimum parcel area for which the combining district in which the parcel is located, determine AMIS directly or by interpolation from Table No. 1. | If APA is the same as or less than the minimum parcel area for which the combining district in which the parcel is located, determine AMIS directly or by interpolation from Table No. 1. | AMIS sf | |
| b. | If APA is greater than the minimum parcel area for the combining district in which the parcel is located, determine AMIS as follows: | If APA is greater than the minimum parcel area for the combining district in which the parcel is located, determine AMIS as follows: | ||
| (1) | Determine maximum impervious surface by interpolation from Table No. 1 using APA from line 5. | sf | ||
| (2) | Enter maximum impervious surface for combining district in which parcel is located. | sf | ||
| (3) | Subtract line (2) from line (1). | sf | ||
| (4) | To obtain AMIS add line (2). and 50% of line (3). | AMIS sf |
a When the town engineer finds that a flood hazard map appears inaccurate, the engineer may modify said map for the purposes of the administration of Table 1A and Table 1B of the zoning ordinance and such modification shall be used in calculating the area utilized in line 4.
TABLE NO. 2 BASIC AREA, OPEN SPACE, BULK AND DENSITY REGULATIONS FOR SPECIAL AND COMMERCIAL DISTRICTS
| Column 1 | Column 2 | Column 3 | Column 3 | Column 3 | Column 4 | Column 5 | Column 6 | Column 7 |
|---|---|---|---|---|---|---|---|---|
| Ch. 18.50 | Ch. 18.52 | Ch. 18.52 | Ch. 18.52 | Ch. 18.54 | Ch. 18.54 | Ch. 18.56 | ||
| District | Minimum Parcel Area Required | Required Yards, Feet Least Depth or Width | Required Yards, Feet Least Depth or Width | Required Yards, Feet Least Depth or Width | Height Limit Feet | Coverage Limit % | Floor Area Ratio Limit | Impervious Surface Limit % |
| District | Minimum Parcel Area Required | Front | Rear | Side | Height Limit Feet | Coverage Limit % | Floor Area Ratio Limit | Impervious Surface Limit % |
| C-C | 1 acre | 50 | 20 | 20 | 28 | 20 | 0.18 | — |
| A-P | 1 acre | 50 | 20 | 20 | 28 | 15 | 0.13 | — |
| O-A | 3 acres | 50 | 25 | 25 | 20 | 5 | — | 5 |
(Ord. 2010-387 § 6, 2010; Ord. 1998-312 § 2, 1998; Ord. 1995-285 § 1 Exh. A (part), 1995; Ord. 1989-244 § 1 (Exh. A) (part), 1989; Ord. 1988-242 § 2 (Exh. A) (part), 1988: Ord. 1981-181 § 3, 1981; Ord. 1979-166 § 8, 1979: Ord. 1969-99 § 1 (part), 1969: Ord. 1969-95 § 1, 1969: Ord. 1968-86 § 3, 1968: Ord. 1967-80 § 1 (6200), 1967)
18.48.020 - Maximum adjusted floor area.¶
The architectural and site control commission may allow the eighty-five percent figure stipulated in Line 7 of Table 1A to be increased up to a maximum of one hundred percent when it can make all of the findings set forth below:
A. Any one of the following:
The larger building will result in a superior design for the property in terms of grading, tree removal and use of the property than would be possible without the requested increase.
The larger building is appropriate because steep slopes, areas of unstable geology or areas subject to flooding so limit development of the property that in order to develop a reasonable plan for the property it is necessary to concentrate more than eighty-five percent of the floor area in a single building.
The larger building is appropriate because the reduction in permitted floor area caused by steep slopes, unstable geology and/or areas subject to flooding so reduces the floor area permitted for any single building that in order to develop a reasonable plan for the property it is necessary to concentrate more than eighty-five percent of the floor area in a single building.
B. The building will not impact significant views enjoyed by neighboring properties to any greater extent than would a design for the project without the increased floor area.
C. The building will not in any substantial way negatively affect neighboring properties to any greater extent than would a design for the project without the increased floor area.
D. The building will be in keeping with the character and quality of the neighborhood.
(Ord. 1998-312 § 3, 1998; Ord. 1995-285 § 1 Exh. A (part), 1995)
18.48.030 - One-time increase.¶
Any single-family residential building or related accessory building existing on October 25, 1995, may be increased one time up to a total of five percent of the existing floor area or one hundred fifty square feet, whichever is smaller, regardless of whether such increase exceeds the floor area limit that applies to the property. This provision shall not be applied to accessory dwelling unit maximums as described in subsections (i.) and (ii.) of Section 18.36.040.A.4.b.
(Ord. 2019-431, § 2, 2019; Ord. 1998-312 § 4, 1998: Ord. 1995-285 § 1 (Exh. A (part)), 1995)
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