Portola Valley — Zoning

Last reviewed: July 2, 2026

Overview

Portola Valley's zoning rules are codified in the town zoning ordinance (codified as chapters in Title 18 of the municipal code) and are implemented by the official zoning map adopted by the town. The ordinance establishes base use districts (for example R-E, R-1, R-MF, M-R, C-C, A-P, M-U, O-A, P-C), combining/overlay districts (for parcel-size, slope, floodplain, historic resources, design review), development standards, and special setback lines that are mapped and enforced locally. The zoning map is adopted by reference and boundary interpretation rules are explicit; plan-level processes such as planned unit developments and design review are integrated into district rules. See the town's Portola Valley zoning & planning overview for context. Key controlling citations below use the town code § numbers (for example § 18.06.010) and are grounded in the retrieved ordinance text.

How Portola Valley organizes zoning (quick primer)

• The ordinance establishes base districts in § 18.06.010 and combining districts in § 18.06.020.
• The official zoning map is adopted by reference in § 18.08.010 and boundary interpretation rules are in § 18.08.020.
• Special setback lines (Scenic/setback S) — including strict setbacks along Skyline Boulevard, Alpine Road, and Portola Road — are in § 18.58.020 (examples: 200 ft skyline setback; 75 ft Alpine Road; Portola Road rules varying by parcel size).

District-by-district breakdown

Below are the principal districts established by the ordinance. Each subsection gives the district purpose, typical permitted uses (where the code lists them), the controlling development/approval references, and what numeric standards are explicitly present in the retrieved materials. Where the ordinance defers to tables not contained in the retrieved snippets (for example Tables 1/2 of § 18.48.010), I note “Not found in retrieved materials” — verify with the town for parcel-specific numbers.

Notes:

• The ordinance frequently refers to general use lists in § 18.36.010 and development standards in district-specific subsections (e.g., § 18.15.050 for R-MF). Where the district chapter references other sections, those sections are cited.

R-E (Residential estate) — purpose & uses

• Purpose: accommodate large-lot, estate residential development consistent with the General Plan and minimize disturbance to terrain. (See § 18.06.010.)
• Typical permitted uses: estate single-family dwellings and accessory uses; the chapter cross-references the general use provisions applied elsewhere (see district chapters). Not all use lists appear in the retrieved material for R‑E specifically. Not found in retrieved materials for a complete use table.
• Key controls to check: combining districts (parcel-size combining like 1A, 2A, 5A in § 18.06.020) and special setbacks in § 18.58.020 that often affect R‑E parcels.

R-1 (Single‑family residential) — purpose & uses

• Purpose: to control density and provide rural/single-family opportunities consistent with the General Plan. § 18.10.010 lists district purposes applied across residential districts.
• Typical permitted uses: the code explicitly lists in § 18.14.020 that single-family dwellings, group homes without licensable services, residential care facilities (≤6 persons), supportive/transitional housing, and public schools (if GP‑consistent) are permitted. Conditional uses (e.g., larger care facilities, residential PUDs) are in § 18.14.030.
• Dimensional standards / setbacks / bulk: R‑1 relies on the general yard rules (yields in Tables 1 and 2 of § 18.48.010) and Chapters 18.52–18.56 (yards, bulk, landscaping). Specific numeric setbacks for Portola/Alpine/Skyline special setback lines are in § 18.58.020 (see 75 ft, 200 ft, etc.). Verify parcel-specific yard numbers in the town’s development standards tables.

R‑MF (Multi‑family residential) — purpose & uses

• Purpose: promote multi‑family housing variety, fire‑resilient design, privacy and visual amenity. See § 18.15.010.
• Typical permitted uses: expressly includes single‑family dwellings, duplexes, multi‑family dwellings, emergency shelters, supportive housing, transitional housing, and resident care facilities (see § 18.15.020). There is an explicit “by‑right” provision for qualifying affordable developments per housing element law in § 18.15.025.
• Dimensional & design controls: the chapter points applicants to § 18.15.050 (development standards), § 18.15.060 (design standards), and Chapters 18.52–18.60 for yards, bulk, parking, and landscaping. The actual numeric tables for R‑MF development standards are referenced but not fully included in the retrieved excerpts. Verify the numeric standards with the town.

M‑R (Mountainous residential)

• Purpose & application: intended for residential development in steeper/mountainous terrain; the chapter exists (see § 18.06.010 listing) and the ordinance provides slope‑sensitive controls (slope density combining districts in § 18.06.020 and planned unit development rules in § 18.50.050).
• Uses and standards: the code allows the planning commission flexibility to reduce lot area in R‑E and M‑R when it results in less environmental disturbance; see § 18.50.050(B)(1). Specific numeric lot‑area versus slope tables are in the planned unit development / slope density sections (Table 3 referenced in § 18.50.050).

C‑C (Community commercial) and A‑P (Administrative‑professional)

• Purpose: provide for small‑scale village/commercial uses (C‑C) and office/professional campus uses (A‑P). Both are established by § 18.06.010.
• Typical permitted/conditional uses: code cross‑references the general use lists (see district chapters); commercial PUDs are allowed with specific requirements in Chapter 18.44. Not all line‑by‑line permitted uses appear in the retrieved snippets. Not found in retrieved materials for a full use table.
• Key numerical standards called out: landscaping minima in non‑residential districts are explicit: C‑C parcels must maintain 30% natural vegetative or landscaped cover and A‑P parcels 40%, per § 18.56.020. Floor area/coverage percentages for some commercial districts are set in other tables (see Chapter references).

M‑U (Mixed‑use district)

• Purpose: provide for mixed residential and non‑residential development in targeted areas; see § 18.23.050 for the detailed development standards table.
• Key numeric standards (explicit in Table 18.23.050):
  • Density: Min. 3 du/ac; Max. 6 du/ac.
  • FAR residential: Max. 0.28 (with exceptions noted for supportive housing overlay).
  • FAR non‑residential: Max. 0.22.
  • Lot area min.: 1.0 acre (note footnotes for site‑specific exceptions).
  • Max building height (principal): 34 ft, with a vertical measurement cap (28 ft vertical in certain illustrations).
  • Front setbacks: 75 ft along Alpine Road (special setback line), 30 ft on other ROWs; interior side 15 ft, rear 25 ft (footnotes and site exceptions apply).
  • Coverage Area Ratio (CAR): Max. 0.22 (with overlay exceptions).
    See § 18.23.050 for the full table and footnotes.

O‑A (Open area) and P‑C (Planned community)

• Purpose: preserve open lands, parks and planned community development; both are listed in § 18.06.010. Development in P‑C districts is governed by approved general development plans and must follow the P‑C chapter requirements in Chapter 18.28 and planned unit development rules in Chapter 18.44.

Combining/Overlay districts (examples)

• The ordinance establishes combining districts including residential density bands (7.5M, 15M, 1A, 2A, etc.), D‑R (design review combining district), F‑P (floodplain), and S‑D (slope density) in § 18.06.020. These combining districts modify base district rules (parcel area, yard, density).
• Historic resource combining district H‑R exists and is applied where identified in the General Plan; design review and special treatment for such parcels is required (see references to historic resources in § 18.64.010 and § 18.31).

Key local rules that often affect every project

• The zoning permit is required before change of use or erection of structures; application procedures are in § 18.62.020 (site plan, ASCC referral where applicable).
• Architectural and site plan review (design review) applies broadly (e.g., building permits for additions ≥ 400 sq ft or two stories, all commercial buildings, structures on arterial roads, and other categories) in § 18.64.010. Consult the town Portola Valley Design Review page for process steps.
• Special setback lines — scenic/special setbacks — govern placement of structures along key corridors: Skyline Boulevard (200 ft), Alpine Road (75 ft), and Portola Road (rules vary by district/parcel size). See § 18.58.020.
• Off‑street parking requirements are set separately (see chapters 18.60 and consult the town Portola Valley Parking resource). The ASCC reviews uncovered parking as noted in § 18.64.010.
• Floodplain (F‑P) areas and associated development permit requirements are incorporated by reference and mapped as part of the zoning map; see § 18.32.030 and the FEMA map incorporation.

Representative decision‑relevant table (selected districts & highlights)

Practical guidance / interpretation notes

• Always confirm the parcel’s mapped district and any combining overlays on the official zoning map adopted in § 18.08.010; boundary interpretation rules in § 18.08.020 control where lines are ambiguous. For boundary disputes, the planning commission can make an official determination.
• If a proposed project sits within 100 ft of Skyline Blvd, Alpine Rd frontage, or Portola Rd, special setbacks or allowed reductions by the ASCC apply; see § 18.58.020 for the scenic setback structure and the ASCC’s authority to permit reductions.
• Many district chapters refer applicants to general tables for yards, lot coverage, and FAR (e.g., § 18.48.010, Chapters 18.52–18.56). If you don’t see numeric values in the district chapter, the town uses those cross‑referenced tables — request those tables or the parcel‑specific development standards from planning staff. Not found in retrieved materials: full text of Tables 1 & 2 in § 18.48.010.
• Architectural and site plan review (design review) is a common trigger; additions ≥ 400 sq ft or 2 stories, and all commercial work, require ASCC review in § 18.64.010 — factor time and submittal detail accordingly. See the town Portola Valley Design Review page for how design review tends to be scheduled and assessed.

Links for related application items you will commonly need:

• For what counts as permitted land uses see Portola Valley Land Use.
• For numeric setback, coverage and bulk rules consult Portola Valley Development Standards.
• Parking minimums & review triggers: Portola Valley Parking.
• If your parcel is in an overlay, check Portola Valley Overlay Districts.
• Nonconforming use rules are in Portola Valley Nonconforming Uses.
• For accessory dwelling units, see Portola Valley ADUs in addition to California ADU law guidance at California ADU law.
• If your work implicates building code compliance, the state code is at California Building Standards Code.

(Each internal link above is the town-specific menu resource you will use for process and checklists.)

Checklist (what an applicant must satisfy before a zoning permit/building submittal)

• Confirm the parcel’s base district and all combining/overlay districts on the official zoning map (adopted § 18.08.010).
• Verify whether the proposed use is permitted, conditional, or prohibited in the base district (see district chapters such as § 18.14.020 for R‑1, § 18.15.020 for R‑MF).
• Check combining/overlay requirements (parcel minimums, slope density, floodplain). § 18.06.020 lists combining districts.
• Determine required setbacks/special setback lines per § 18.58.020 and yard/bulk tables (Chapters 18.52–18.56 and tables in § 18.48.010).
• Confirm whether the ASCC (design review) is required under § 18.64.010; prepare materials accordingly.
• Provide a site plan, landscape plan, parking plan (see Portola Valley Parking and Portola Valley Landscaping and Screening) and comply with applicable landscaping percentages (e.g., C‑C 30% / A‑P 40% per § 18.56.020).
• Pay applicable fees and complete the zoning permit application per § 18.62.020–030.

Risks & Ambiguities

Plain‑English Summary

Portola Valley’s zoning is a mapped, chaptered ordinance (Title 18) that assigns each parcel to a base district (like R‑1, R‑MF, C‑C, M‑U) and to combining overlays that change density, setbacks, and review. Permitted uses and key numeric controls are set both in district chapters and in cross‑referenced tables; important special setback rules (e.g., 200 ft along Skyline, 75 ft along Alpine) and routine design review (e.g., for additions ≥ 400 sq ft) are local hallmarks — always check the official zoning map and the exact district tables with town planners.

Source References

• Districts established: § 18.06.010 (district list) and combining districts § 18.06.020.
• Zoning map adoption and boundary interpretation: § 18.08.010 and § 18.08.020.
• R‑1 permitted uses (single‑family district): § 18.14.020; conditional uses § 18.14.030.
• R‑MF district purpose and permitted uses: § 18.15.010–020, by‑right affordable housing provision § 18.15.025.
• Mixed‑use development standards (Table 18.23.050 / § 18.23.050) — density, FAR, setbacks, heights.
• Yards and measurement rules: § 18.52.010 and cross‑references to § 18.48.010 tables.
• Special setback lines (Skyline/Alpine/Portola): § 18.58.020.
• Planned unit developments and slope density rules: Chapter 18.44 and § 18.50.050–060.
• Zoning permit application and requirements: § 18.62.020–060.
• Architectural & site plan (ASCC) review triggers: § 18.64.010.
• Landscaping percentages and non‑residential landscaping rules: § 18.56.020.
• Floodplain regulated areas adoption: § 18.32.030 (FEMA maps incorporated).

Retrieved passages

• Portola Valley Zoning Code (§ 19) High relevance show source text
• Portola Valley Zoning Code (§ 7) High relevance show source text
• Portola Valley Zoning Code (Section 18.62.080) High relevance show source text
• Portola Valley Zoning Code (§ 1) High relevance show source text
• Portola Valley Zoning Code (Section 18.08.010.) High relevance show source text
• Portola Valley Zoning Code (§ 1) High relevance show source text
• Portola Valley Zoning Code (section of) High relevance show source text
• Portola Valley Zoning Code (§ 1) High relevance show source text

Cited sections

• Districts established: **§ 18.06.010** (district list) and combining districts **§ 18.06.020**. (§ 18.06.010)
• Zoning map adoption and boundary interpretation: **§ 18.08.010** and **§ 18.08.020**. (§ 18.08.010)
• R‑1 permitted uses (single‑family district): **§ 18.14.020**; conditional uses **§ 18.14.030**. (§ 18.14.020)
• R‑MF district purpose and permitted uses: **§ 18.15.010–020**, by‑right affordable housing provision **§ 18.15.025**. (§ 18.15.010)
• Mixed‑use development standards (Table 18.23.050 / **§ 18.23.050**) — density, FAR, setbacks, heights. (§ 18.23.050)
• Yards and measurement rules: **§ 18.52.010** and cross‑references to **§ 18.48.010** tables. (§ 18.52.010)
• Special setback lines (Skyline/Alpine/Portola): **§ 18.58.020**. (§ 18.58.020)
• Planned unit developments and slope density rules: **Chapter 18.44** and **§ 18.50.050–060**. (Chapter 18.44)
• Zoning permit application and requirements: **§ 18.62.020–060**. (§ 18.62.020)
• Architectural & site plan (ASCC) review triggers: **§ 18.64.010**. (§ 18.64.010)
• Landscaping percentages and non‑residential landscaping rules: **§ 18.56.020**. (§ 18.56.020)
• Floodplain regulated areas adoption: **§ 18.32.030** (FEMA maps incorporated). (§ 18.32.030)
• PortolaValley_ZoningCode.md

• Official Portola Valley code library