If you own in a Palo Alto Eichler tract, your zoning just got more complicated

What a Single-Story Overlay Is

A single-story overlay (SSO) is a zoning combining district layered on top of a base residential zone. It does one thing: it replaces the standard height and story rules with tighter ones, so that new construction and vertical additions on covered parcels must stay within a single habitable floor.

In Palo Alto, the overlay is called the Single-Story (S) Combining District. Its purpose is to modify the site development regulations of the R-1 single-family residence district, to preserve and maintain single-family living areas of predominantly single-story character. That description fits Eichler tracts exactly: flat or low-pitched roofs, floor-to-ceiling glass facing private patios, and a horizontal massing that a second story would puncture from above.

The Eichler floor plan makes the overlay's rationale concrete. The most important aspect of Eichler neighborhood design is backyard privacy. A two-story addition on any lot in a tract of single-story glass-walled homes puts neighbors' open living areas and patios in direct view from above.

Where Overlays Exist in Eichler Tracts

Palo Alto is the city that has adopted this tool most extensively for Eichler neighborhoods. The City of Palo Alto currently has Single Story Overlay Combining Districts that overlap with eleven Eichler tracts. Named tracts that have gone through the process include Greenmeadow, Van Auken Circle, Los Arboles, Greer Park North, and Faircourt, among others, with some tracts obtaining overlays at different times. Van Auken Circle and adjacent Eichler homes were granted Single Story Overlay zoning in 2002. The City Council adopted the SSO as a standard zone district in 1992 and later took related action in 2015 on the overlay process.

San José has Eichler tracts but has taken a different route. The City of San José, working with consultant Page & Turnbull, created Eichler Neighborhood Objective Design Standards (ODS) for proposed exterior changes to Eichler houses listed on the San José Historic Resources Inventory; currently those ODS apply only to properties within the Fairglen Additions historic district. San José's tool governs design character, not story height — it does not create an SSO-style height cap across the tract.

Sunnyvale has Eichler Design Guidelines listed among its planning documents, though no SSO ordinance for Eichler tracts appeared in official sources reviewed for this article. Owners in Sunnyvale Eichler tracts should verify the current zoning map and applicable design guidelines with the city's planning division directly.

If your Eichler sits in a city other than Palo Alto, the building department for that city — not the county — writes the rules. No countywide SSO for Eichler tracts exists.

How Palo Alto's SSO Works in Practice

For sites within the single-story height combining district, the maximum height is 17 feet, as measured to the peak of the roof; in a special flood hazard area the maximum height is increased by one-half of the increase in elevation required to reach base flood elevation, up to a maximum building height of 20 feet. New homes within an SSO district are restricted to a maximum building height of 17 feet and one habitable floor.

New construction and remodels are restricted to one story, and an existing second story may not be expanded. However, existing two-story houses become "legal non-complying facilities" and owners are not required to alter them.

Creating an SSO is not automatic. It is a rezoning, initiated by property owners, not the city. PAMC Section 18.12.100 requires, for creating a single-story overlay district, a list of signatures evidencing support by (i) 70% of included properties, or (ii) 60% of included properties where all included properties are subject to recorded deed restrictions intended to limit building height to a single story, whether or not such restrictions have been enforced. A neighborhood must also demonstrate that it is well-defined and predominantly single-story, with a minimum of 80% of homes being one story.

Any property owner or owners within a neighborhood may submit an SSO rezoning application; applicability and site development regulations are summarized in PAMC Section 18.12.100, and the rezoning process is in Section 18.80.035.

Removal follows a parallel process. The SSO does not expire on its own — a future group of owners would need to petition to take it off, just as a prior group petitioned to put it on.

What State Housing Law Now Adds

Two bodies of state law create real friction with local SSOs, and owners should know both.

SB 9 (2021). Senate Bill 9 (Chapter 162, Statutes of 2021) requires ministerial approval of a housing development with no more than two primary units in a single-family zone, the subdivision of a parcel in a single-family zone into two parcels, or both. A local agency may impose objective zoning, subdivision, and design standards, unless those standards would have the effect of physically precluding the construction of up to two units or physically precluding either of the two units from being at least 800 square feet in floor area.

Palo Alto has acknowledged this directly. The city's SB 9 Objective Design Standards state that all SB 9 projects must meet all requirements of the zoning code, including development standards and special requirements for flood zones and single-story overlays. In other words, Palo Alto is currently treating the SSO as applicable to SB 9 projects — but if a standard would physically preclude two units of 800 square feet, state law requires the city to relax it. What that line is in any specific case is a determination made by the building department, not by the owner or a neighbor.

State ADU law. Local ADU ordinances must be carried out consistently with Government Code section 66310 and must not unduly restrict the creation of ADUs; local governments should carefully weigh zoning, development standards, and other provisions for their impacts on ADU development. State ADU law sets height allowances for detached ADUs that function independently of local single-story overlays. There is no limit on the number of stories in state ADU law; a local agency must allow at least two stories, and an attached ADU may be built to the height of the zoning for the primary dwelling or up to 25 feet, whichever is lower. Whether and how that interacts with a specific SSO parcel is a question for the city's planning department.

What This Means for Owners

If you own in a Palo Alto Eichler tract: confirm whether your parcel carries the (S) combining designation before planning any vertical work. The zoning map and parcel lookup on the city's planning portal will show it. If you live in a tract without an SSO and your neighbors are discussing pursuing one, the process runs through PAMC §18.12.100 and requires a formal rezoning petition.

If you own in a San José or Sunnyvale Eichler tract: the applicable controls are design standards and base zoning, not an SSO. Check with that city's planning department for current rules before designing any addition.

For any project touching height, story count, or ADUs in an SSO area, a licensed architect familiar with the applicable municipal code and current state housing law is the right starting point — not this article.

Where to Check

• Palo Alto Municipal Code §18.12.100 — Single Story Overlay regulations and rezoning criteria
• Palo Alto Eichler Tracts and Single Story Overlays Map
• Palo Alto Eichler Neighborhood Design Guidelines (final) — explains SSO context and the individual review process
• San José Eichler Neighborhood Objective Design Standards — covers the Fairglen Additions historic district
• Sunnyvale Design Guidelines and Standards — Eichler Design Guidelines
• California HCD — State ADU Law handbook — current ADU standards and height rules
• SB 9 — California Legislative Information — full bill text
• California HCD SB 9 Fact Sheet — how SB 9 interacts with local zoning standards

Tim McMullen · CA DRE #02016832
tim@mcmullen.properties · (415) 691-9272