Palo Alto — Overlay Districts

Last reviewed: July 2, 2026

Overview

This page explains the overlay and combining districts that modify base zoning in Palo Alto’s municipal zoning code (Title 18). It synthesizes specific Palo Alto overlays and combining districts—what they do, where they apply, and the most decision-relevant numeric standards and procedures—based only on the city ordinance text. For the city’s broader context, see the Palo Alto Zoning overview and the general Palo Alto — zoning & planning overview. § citations below point to the controlling code text; where the ordinance uses site‑specific agreements (Stanford Development Agreement) the code defers to that agreement. See also the city's Development Standards, parking, design review, ADUs, and the state California Building Standards Code for related requirements referenced by the ordinance.

• First mentions of related topics (internal links): Palo Alto Zoning, Palo Alto — zoning & planning overview, Development Standards, parking, Design Review, ADUs, California Building Standards Code.

How this page is grounded

All requirements and procedures below are taken from Title 18 of the Palo Alto Municipal Code (Zoning). Every ordinance citation is given as the controlling section (§ number) and is supported by the retrieved municipal code text. File previews supporting each § are cited inline.

Overlay / Combining Districts — District-by-District

Alternative Standards Overlay Districts (AS1, AS2, AS3) — Chapter 18.60

Purpose: Provide site‑specific, alternative development standards (optional for the affected property owner) to implement the 2005 Stanford Development Agreement; these are applied only to the identified Stanford sites and may replace the underlying zoning when elected by the landowner. See § 18.60.010 – § 18.60.040 for purpose, definitions and applicability.

• Where they apply:

  • AS1 — El Camino Site / Extended El Camino Site (2450, 2470, 2500 El Camino Real; optional extension including 505 California Ave) § 18.60.050.
  • AS2 — Upper California Site (1451, 1501, 1601 California Ave) § 18.60.060.
  • AS3 — Mayfield Site (2650, 2700, 2780 El Camino Real) § 18.60.070.

• Typical permitted uses:

  • AS1: multi‑family residential plus limited commercial (retail/service/eating), child care and live/work lofts; underlying zoning may be displaced if owner elects AS1 § 18.60.050.
  • AS2: single‑family, two‑family, and multi‑family residential uses; child care center; BMR provisions per Development Agreement § 18.60.060.
  • AS3: public recreation/soccer complex uses with site‑specific modified standards (lighting, fencing) § 18.60.070.

• Key dimensional / programmatic standards:

  • AS1 and AS2 allow the applicant (Stanford, on those sites) to elect development under the AS standards; if elected the underlying zoning “does not apply” for that site § 18.60.050.A (AS1), § 18.60.060.B (AS2).
  • AS2: 20 ft minimum California Avenue frontage setback is specified in the AS2 standards table § 18.60.060.
  • AS3: lighting up to 70 ft and ball-control fencing up to 14 ft are explicitly permitted as modified standards § 18.60.070.
  • Applicability and elect/ rescind process: Property owner must file notice at time of discretionary review and may rescind its election prior to building permit issuance § 18.60.040.

• Practical notes:

  • These are site- and owner‑specific overlays tied to the Stanford Development Agreement; they are optional and only identified parcels may use them § 18.60.030.
  • For AS1/AS2 some base zoning alternatives are offered as options (e.g., develop under an RM district at applicant’s option)—see § 18.60.050.B and § 18.60.060.B.

Single‑Story Height Combining District (Single‑Story (S) Combining) — § 18.12.100

Purpose: Preserve prevailing single‑story character by limiting structures to single story within mapped combining districts. § 18.12.100 describes applicability, standards and the neighborhood petition process.

• Where it applies: Only when combined with R‑1 or an R‑1 subdistrict (e.g., R‑1(650), R‑1(743)) as shown on the zoning map § 18.12.100(a).
• Permitted uses: Uses remain those of R‑1 (single‑family) but development standards change. § 18.12.100(b).
• Key standards:
  • Maximum height 17 ft to roof peak (special flood zones may allow up to 20 ft) § 18.12.100(b)(1).
  • Limit of one habitable floor (lofts/mezzanines counted as habitable) § 18.12.100(b)(2).
• Creation/removal process:
  • Owner‑initiated application to the Director; creation requires a district map and signatures from 70% of included properties (or 60% where deed restrictions exist) § 18.12.100(c)(2)(B)(C); processed per Chapter § 18.98 (map amendments) § 18.12.100(c)(3).

Pedestrian and Transit Oriented Development (PTOD) Combining District — § 18.34.030 – § 18.34.070

Purpose: Encourage mixed‑use and higher‑intensity housing near transit corridors while managing impacts through specified limits and design/performance standards. § 18.34.040 lists PTOD combining district regulations and development standards tables.

• Where it applies: PTOD boundaries are map‑based (e.g., PTOD — California Avenue, University Avenue placeholders) and properties must be rezoned/combined to PTOD to be subject to the standards § 18.34.060.
• Permitted uses (PTOD — California Avenue example):
  • Multiple‑family residential and restricted non‑residential (retail, personal services, limited offices), with certain ground‑floor limitations (see PTOD tables) § 18.34.030 & § 18.34.040.
  • Prohibited uses on California Ave PTOD: single‑family/two‑family, heavy manufacturing, and hazardous R&D above exempt quantities § 18.34.030(c).
• Key numeric standards (PTOD — California Ave Table):
  • Maximum residential intensity example: 40 DU/AC in the California Avenue PTOD table (see development standards table) § 18.34.040 Table 2.
• Review/rezoning process: Rezoning to PTOD follows Chapter § 18.80 (map amendments) and includes Planning & Transportation Commission and City Council review; upon approval projects go through Architectural Review Board major review § 18.34.060 & § 18.34.040(d).

Hazardous Waste Facility Combining District (HW) — Chapter 18.62

Purpose: Restrict and condition siting of new or expanded hazardous waste facilities; facilities only allowed in a designated Hazardous Waste combining district and must meet county hazardous waste plan siting criteria § 18.62.010.

• Key rules:
  • New or expanded hazardous waste facilities prohibited unless located in an HW combining district § 18.62.010(b)–(c).
  • Chapter defines facility types, applicable siting criteria, and prohibits residuals repositories § 18.62.020 – § 18.62.060.

Other Combining/Overlay References Found in Title 18

• Retail (R) combining district, Automobile Dealership (AD) combining district, Landscape (L) combining, and others are referenced in chapter use tables and standards (see e.g., CC/CN/CS rules referencing R and AD overlays) § 18.16.060 and Chapters 18.28 / 18.30 references.

Quick Reference Table — Decision‑relevant standards and permitted uses

Checklist

An applicant seeking to rely on or establish an overlay/combining district in Palo Alto must (where applicable):

• Confirm the parcel is one of the sites listed for a site‑specific overlay (e.g., El Camino Site, Upper California Site, Mayfield Site) § 18.60.030 . Verify with the jurisdiction.
• For AS1/AS2: at time of discretionary review file the notice electing the AS district and track any rescission deadline (rescission permitted prior to building permit issuance) § 18.60.040 .
• For Single‑Story (S) district creation/removal: prepare district map, owner signature list meeting the 70% (or 60% if deed restrictions) support threshold, and the written statement required by the Director; submit as a zoning map amendment per Chapter 18.98 § 18.12.100(c) .
• For PTOD rezoning: follow Chapter § 18.80 amendments process; plan for Planning & Transportation Commission and City Council rezoning limits and ARB major review after rezoning § 18.34.060 and § 18.34.040(d) .
• For hazardous waste proposals: confirm the site is within a designated HW combining district; otherwise proposals are prohibited § 18.62.010(c) .
• Check related development standards (setbacks, FAR, site coverage) in Development Standards and specific district chapters; consult the city’s parking and Design Review rules early (link to those pages). Verify whether ADUs and other accessory uses are affected by the combining district § 18.09 / cross refs.

Risks & Ambiguities

Plain‑English Summary

Palo Alto’s overlays/combining districts are special, map‑based rules that can change what you can build on a parcel. Some are small‑scale neighborhood overlays (the Single‑Story (S) combining district that caps height at 17 ft) while others are site‑specific, optional standards for Stanford lands (AS1/AS2/AS3), and still others like PTOD or HW control uses and intensity near transit or for hazardous facilities. Always check the zoning map and the specific § of Title 18 that lists the overlay standards before you design—verify parcel inclusion and whether the overlay replaces or supplements the base zoning. See the city’s Development Standards, parking, Design Review, and ADUs pages for related requirements and the California Building Standards Code for building rules.

Source References

• § 18.60.010 – § 18.60.070 (Alternative Development Standards for Stanford lands — AS1/AS2/AS3): § 18.60.010, § 18.60.030, § 18.60.040, § 18.60.050, § 18.60.060, § 18.60.070.
• § 18.12.100 (Single‑Story (S) Combining District — applicability, standards, creation/removal procedures).
• § 18.34.030 – § 18.34.070 (PTOD combining district land uses, standards, review/rezoning procedures).
• Chapter 18.62 (Hazardous waste facility combining district — § 18.62.010 – § 18.62.060).
• Cross‑references and combining district mentions in other district chapters (e.g., CC/CN/CS mixed‑use rules; special purpose districts Chapter 18.28) § 18.16.060, § 18.28.050.

If you need the exact unabridged ordinance text or the official map layers for any of these overlays, verify with Palo Alto Planning & Development Services or check the City’s official municipal code and GIS zoning maps. Verify parcel‑specific application with the City.

Retrieved passages

• Palo Alto Zoning Code (Chapter 18.60) High relevance show source text
• Palo Alto Zoning Code (section shall) High relevance show source text
• Palo Alto Zoning Code (Chapter 18.64) High relevance show source text
• Palo Alto Zoning Code (Section 6.4.2) High relevance show source text
• Palo Alto Zoning Code (Chapter 18.98.) High relevance show source text
• Palo Alto Zoning Code (Chapter 18.12) High relevance show source text
• Palo Alto Zoning Code (Section 18.12.040) High relevance show source text
• Palo Alto Zoning Code (§ 2) High relevance show source text

Cited sections

• **§ 18.60.010 – § 18.60.070** (Alternative Development Standards for Stanford lands — AS1/AS2/AS3): **§ 18.60.010**, **§ 18.60.030**, **§ 18.60.040**, **§ 18.60.050**, **§ 18.60.060**, **§ 18.60.070**. (§ 18.60.010)
• **§ 18.12.100** (Single‑Story (S) Combining District — applicability, standards, creation/removal procedures). (§ 18.12.100)
• **§ 18.34.030 – § 18.34.070** (PTOD combining district land uses, standards, review/rezoning procedures). (§ 18.34.030)
• **Chapter 18.62** (Hazardous waste facility combining district — **§ 18.62.010 – § 18.62.060**). (Chapter 18.62)
• Cross‑references and combining district mentions in other district chapters (e.g., CC/CN/CS mixed‑use rules; special purpose districts Chapter 18.28) **§ 18.16.060**, **§ 18.28.050**. (Chapter 18.28)
• PaloAlto_ZoningCode.md

• Official Palo Alto code library