A single-story overlay is a zoning layer placed on top of a neighborhood's base residential zone. It limits houses, and often every structure on the lot, to one story and a lower height. Sunnyvale, Cupertino and Palo Alto all use them, including on many Eichler tracts in Sunnyvale and Palo Alto, and in each of those cities the process starts with the owners on the street.
This guide covers how to tell whether your street has one, what the rules limit, how owners apply to add or remove an overlay, and where state ADU and housing laws come in. It draws on city and state records read in November 2026. Some of the city detail comes from 2017 and 2018 documents, and we say so where it does.
How to check whether your street has a single-story overlay
The overlay shows up as a suffix on the zoning designation, so start by looking up the parcel on your city's online zoning or parcel map. The labels differ by city:
Sunnyvale: "/S" after the base zone, as in R-0/S, R-1/S or R-2/S. The district is set out in Sunnyvale Municipal Code Section 19.26.200.
Cupertino: the letter "i" after the R1 zone and its lot-size number, written R1-Xi in the code, which says it may be combined with all R1 zones. The number is the minimum lot size in thousands of square feet.
Palo Alto: "(S)" in the zone name, as in R-1 (S), R-1 (7000)(S) or R-1 (8000)(S). The city's parcel data lists 17 feet as the maximum building height on these lots, except where a creek, a flag-lot shape or an easement keeps it from assessing one.
Then confirm with the planning division before you rely on a map. A two-story house on the block doesn't rule out an overlay, because Sunnyvale's 2017 report and Cupertino's 2017 FAQ both said legally built second stories become legal non-conforming once a district is added. Private CC&Rs are a separate layer and can limit homes to one story on their own. Palo Alto's 2018 Eichler guidelines note that the city's planning department doesn't enforce CC&Rs, but residents may. For local background, see our Sunnyvale mid-century homes page.
What a single-story overlay limits
The details differ by city. A September 2017 Sunnyvale Planning Commission report on one of its single-story rezonings listed what the district would do:
One habitable floor. Lofts, mezzanines and attics that meet habitable standards are prohibited.
The one-story limit applies to every structure on the property, including detached garages and accessory living units.
Maximum height of 17 feet, down from 30 feet.
Maximum floor area ratio of 45 percent. Additions beyond that need a Variance.
A basement isn't a story unless it extends more than two feet above the ground, and then it counts toward the floor area limit.
The current code, as posted in November 2026, sets the same core limits: 17 feet, one habitable floor (lofts and mezzanines count, basements don't) and a 45 percent floor area ratio.
Cupertino's municipal code, as posted in November 2026, limits homes in an R1-Xi district to one story, not to exceed 18 feet. A second story isn't ruled out entirely: a new two-story home or second-story addition needs a Conditional Use Permit. Under the 2017 ordinance that set up the process (No. 17-2162), the Planning Commission had to find that the project wouldn't cause privacy impacts, shadowing, intrusive noise, odor or other adverse impacts. The city's 2017 draft FAQ said such a project also needs the Two Story Permit that any second story in an R1 zone needs, and that lot coverage, floor area ratio and setbacks stay the same. Our Cupertino mid-century homes page covers the city's Eichler areas.
In Palo Alto, the city's adopted 2018 Eichler design guidelines (Resolution No. 9748) said the overlays then overlapped with eleven Eichler tracts. They put the overlay rules in Palo Alto Municipal Code 18.12.100. The 17-foot figure in the parcel data is the one limit we read directly, so ask the planning division for the rest.
An overlay doesn't force anyone to remove an existing second story. Sunnyvale's 2017 report said legally built homes over 45 percent floor area ratio, over 17 feet or with second stories become legal non-conforming. They can be maintained and repaired with permits as long as the non-conformity isn't increased. Cupertino's 2017 draft FAQ said the same about existing two-story homes.
How owners apply for an overlay
Owners start the process in each city we checked. In Sunnyvale and Cupertino, the City Council makes the final decision.
Sunnyvale (Municipal Code 19.26.200, as posted in November 2026):
The base zone must be R-0, R-1 or R-2.
At least 55 percent of the property owners in the proposed district must support it, shown with a written list of signatures.
The district must be clearly mapped and include at least 20 homes.
At least 75 percent of the homes must be one story.
To the extent feasible, the boundary should follow a recognizable feature such as a street, stream or tract boundary.
Meeting the minimums doesn't guarantee approval. The city's 2017 report said the Planning Commission holds a hearing and makes a recommendation, and the City Council may approve the rezoning if it finds the change is in the public interest.
Cupertino (Municipal Code 19.28.050(B), as posted in November 2026):
The boundary must take in one or more entire city blocks, one or more entire subdivision tracts, or street faces opposite one another within a block.
At least 75 percent of the homes must be single-story.
At least 66-2/3 percent of the owners must sign the petition, with one signature per developable lot.
The City Council decides whether to add the "i" suffix.
After the petition comes a mailed ballot (Section 19.12.090, added in 2017). The city mails ballots to the owners of record, one vote per developable lot, with a 45-day return date. The application goes to a public hearing only if at least 66-2/3 percent of the owners in the proposed or existing district support it. The city's 2017 FAQ described a Planning Commission recommendation followed by the City Council's decision.
Palo Alto (2018 guidelines): any property owner in a neighborhood may submit an application, and the guidelines said the code then required evidence that 70 percent of owners support it. Where CC&Rs already restrict development to one-story homes, 60 percent was enough. The guidelines place the rezoning process in Municipal Code 18.80.035.
If your house is in another city, ask its planning division whether it has a single-story zone and how it works. This guide covers only the three cities whose records we read.
Removing an overlay
Removal follows the same path in reverse. Sunnyvale's current code lets owners apply to repeal a district at any time, with the support of 55 percent of the owners in it. Districts created before October 1, 2005 expire seven years after they took effect unless owners apply to renew them. Cupertino's current code lists adding or removing the "i" suffix as a City Council decision, and its two-thirds petition and ballot rules cover an existing district as well as a proposed one. The city's 2017 draft guidelines said the 75 percent single-story rule doesn't apply to removal. In Palo Alto, ask the planning division how removal works under Municipal Code 18.80.035.
Where state ADU and housing laws fit in
ADUs. As of November 2026, HCD's ADU Handbook (March 2026) says a city can't set a height limit for a detached ADU below 16 feet. Within a half-mile walk of a major transit stop or high-quality transit corridor, the floor is 18 feet, with an allowance for a roof pitch that matches the main house (Gov. Code 66321(b)(4)). Our mid-century ADU guide covers HCD's point on two-story ADUs, plus design and permits.
SB 9 and new overlays. Cupertino's code says SB 9 units on a lot with an "i" suffix are also subject to the overlay standards. Separately, as of November 2026, the Housing Crisis Act of 2019 (Gov. Code 66300, added by SB 330 and last amended effective January 1, 2024) says an "affected" city or county, as determined by HCD, can't enact a standard that reduces the intensity of land use below what its zoning allowed on January 1, 2018, except as the statute provides. The statute says that includes reductions to height, density or floor area ratio, and HCD's 2024 SB 9 fact sheet says the limit applies in all zones, including single-family residential zones. HCD's determination of which cities are affected stays valid until January 1, 2030. Neither the statute nor HCD's fact sheets name single-story overlays, so ask your city whether it's accepting new overlay applications and how it applies the law. The latest single-story rezoning we found in Sunnyvale's online legislative records was a 79-lot district (Ordinance No. 3130-18) on the City Council's February 6, 2018 consent calendar.
This is general information as of November 2026, not legal advice. Zoning codes and state housing law change, so confirm the rules for your lot with your city's planning division before you buy, design or sign a petition. For a question about how a code applies to your property, ask a land use attorney.
Frequently asked questions
Can I build a second story in a single-story overlay?
It depends on the city. Sunnyvale's code allows one habitable floor, and its 2017 report said the limit covers every structure on the lot. Cupertino's current code allows a second story only with a Conditional Use Permit, and its 2017 FAQ said a Two Story Permit is needed too.
Does a single-story overlay stop me from building an ADU?
Not necessarily. HCD says a city can't deny a detached two-story ADU that fits the state height allowances and the building code just because zoning limits the main house to one story. Check your city's current ADU ordinance for the details.
How many owners have to agree?
Sunnyvale's code needs 55 percent of owners. Cupertino's code needs a two-thirds petition and then two-thirds support in a mailed ballot, one vote per lot. Palo Alto's 2018 guidelines put the figure at 70 percent, or 60 percent where CC&Rs already limit homes to one story.
Related reading
Royal Manor Eichler History: Reading Palo Alto's 1957–58 Tract
Los Arboles Eichler, Palo Alto: The Tract, Overlay and Addition No. 2
SB 9 Lot Split on an Eichler Lot: State Rules and City Overlays
Tree Removal Permit in Palo Alto and Nearby Cities Before a Remodel
Do You Need a Permit for a Shed in California? Bay Area Rules
More guides on this topic: Owning & Renovating a Mid-Century Modern Home
Wondering whether a house you own or want to buy sits in a single-story overlay? Call or text the Boyenga Team at Compass at (408) 373-1660 or (650) 383-8606, or contact the Boyenga Team to talk through the zoning before you plan a remodel or make an offer.
