An SB 9 lot split lets the owner of a qualifying lot in a "single-family residential zone" divide it into two parcels, and a companion section allows up to two primary homes on a lot, both with ministerial, staff-level approval. On an Eichler lot, that state law meets city rules written for the tract: Palo Alto's Eichler design standards, single-story overlays, and Cupertino's R1-e district.
This guide covers the state rules as of November 2026 and how Palo Alto, Cupertino and Sunnyvale apply them. It draws on the current Government Code, California Department of Housing and Community Development (HCD) guidance and city documents read on November 6, 2026.
SB 9 in brief, as of November 2026
SB 9 (Chapter 162, Statutes of 2021) is in Government Code Sections 65852.21 (two units) and 66411.7 (the urban lot split). HCD's SB 9 fact sheet (September 2024) says a city must approve up to two primary units, a split into two parcels, or both, which can mean up to four units on one original lot. Cities may apply objective standards, such as heights, roof pitch and materials, unless they would physically preclude up to two units or units of at least 800 square feet. Side and rear setbacks can't exceed four feet, and an existing structure, or one rebuilt in the same footprint, needs none (Sections 65852.21(b)(2) and 66411.7(c)).
Later bills:
SB 450 (Chapter 286, Statutes of 2024), effective January 1, 2025, requires a decision within 60 days of a complete application, with the project deemed approved if the city misses it. It also bars standards that don't apply uniformly in the underlying zone (Section 65852.21(b)(3)).
AB 1061 (Chapter 505, Statutes of 2025), effective January 1, 2026, amended both sections.
SB 1426 (Chapter 56, Statutes of 2026) amended both again, effective June 30, 2026, so read the current text.
Is your lot eligible?
Start with the zoning: the lot split section applies only in a single-family residential zone (Section 66411.7(a)(3)(A)). Palo Alto's interim ordinance listed R-1 (and its subdistricts) and R-E; Cupertino's 2022 guide lists R-1, RHS, P(R1) and planned development zones that allow only one-unit homes; and the ordinance Sunnyvale introduced in October 2026 lists R-0, R-1, R-1.5, R-1.7/PD, R-2 and some downtown blocks. Then check the exclusions:
Hazards. HCD and the city documents list farmland, wetlands, very high or high fire hazard zones (unless mitigation measures apply), earthquake fault zones, flood hazard areas (with exceptions), habitat for protected species and listed hazardous waste sites.
Tenants. No demolition or alteration of rent-restricted or rent-controlled housing, or housing occupied by a tenant in the last three years (Sections 65852.21(a)(3) and 66411.7(a)(3)(D)). Sunnyvale's ordinance and Palo Alto's interim ordinance also exclude parcels where an owner withdrew units from rent or lease within the past 15 years.
Historic status. As of November 2026, a lot split isn't allowed on a historical landmark property on the State Historic Resources Inventory or on a city or county landmark site (Section 66411.7(a)(3)(E)). In a California Register or local historic district, a split is barred only if it would require demolishing or altering a contributing structure or an existing exterior structural wall (66411.7(a)(3)(F)). The two-unit section still excludes a contributing structure in a historic district on the State Historic Resources Inventory or under a city or county ordinance, a parcel individually listed on that inventory, and a city or county landmark (65852.21(a)(5)).
In Palo Alto, the Greenmeadow and Green Gables tracts were listed on the National Register as historic districts in 2005, and both also carry single-story overlays. National Register listings are part of the State Historic Resources Inventory and the California Register (Public Resources Code Sections 5020.1(p) and 5024.1(d)(1)), so both historic rules above can come into play there. If you own in either tract, ask the planning division how they apply to your parcel. Our Mills Act and historic designation guide covers what listing means for an owner.
Lot split rules in the cities we checked
Section 66411.7 sets the core terms: two parcels of roughly equal size, neither under 40 percent of the original lot and each at least 1,200 square feet unless the city allows smaller; no split of a parcel created by an earlier split, or where the owner, or someone acting in concert, already split an adjacent lot; rentals only for terms over 30 days; and no duty for a city to allow more than two units per new lot, counting ADUs. The owner signs an affidavit of intent to live in one unit as a principal residence for at least three years from approval of the lot split (66411.7(g)(1)). Palo Alto's interim ordinance counted the three years from recording of the parcel map.
Palo Alto. Its Objective Lot Design Standards for an Urban Lot Split, on the City's SB 9 forms page, allow side-by-side lots, flag lots with a pole at least 10 feet wide, or, on lots under 50 feet wide, a 10-foot access easement. Splits can't be more uneven than 60/40, side-by-side lots need 25 feet of frontage, lots deeper than 200 feet must use the flag layout, and the lots share one driveway unless that would mean demolition.
Cupertino. Its lot split application guide (revised November 2022) sets lots at 40 to 60 percent of the original and turns interior lots with less than 60 feet of frontage into a flag lot. The guide predates SB 450, so confirm current terms.
Sunnyvale. Under the ordinance introduced in October 2026, every split needs a tentative parcel map and a parcel map, and each new parcel must adjoin the street or have access at least 10 feet wide, and measure at least 40 feet in width or depth.
How Eichler and overlay rules carry over
Palo Alto. Interim Ordinance 5645 (passed January 13, 2025) made two-unit projects in R-1 follow Chapter 18.12 and the City's two-story objective design standards, relaxed only as needed for an 800-square-foot unit. It says it expires December 31, 2025 unless extended or replaced. As of November 6, 2026, the City's SB 9 forms page still lists it and we found no extension, so ask the planning division which SB 9 rules apply. In mapped Eichler tracts, Section E of the Two-Story Objective Design Standards (effective February 14, 2025), also on that page, sets a 22-foot maximum roof height with a flood-zone allowance, roof pitches of 3:12 or less in gable, shed, butterfly or flat forms, vertical board or similar siding, and no projecting entry porch. On substandard lots, a second floor is allowed only in an SB 9 project and only as needed for an 800-square-foot unit. The City's 2024 SB 9 standards said SB 9 projects must meet single-story overlay requirements.
Cupertino. The municipal code says SB 9 units on property with an "i" or "e" suffix after the R1 designation "are also subject to the respective overlay standards." An "i" district limits homes to one story, not over 18 feet; our single-story overlay guide covers how those districts work. The R1-e Eichler district's design requirements include a 3:12 maximum roof slope and entries integrated with the roofline, and the code adds that they aren't meant to preclude "a harmonious two-story home." Our Fairgrove guide covers the full R1-e list.
Sunnyvale. As of November 6, 2026, Sunnyvale's council had introduced Ordinance 3262-26 (October 27) and scheduled it for adoption on November 10, with the ordinance taking effect 30 days after adoption, so check the city's adopted code before you plan. As introduced, it re-adopts Chapters 18.26 and 19.78 to follow SB 450, drops the floor area ratio limit and some SB 9-only design standards, sets height and stories by the zoning district, and applies the Lower Density Residential Objective Design Standards (approved July 2026) to two-unit projects. As posted in the council packet, those standards don't apply to homes subject to the Eichler Design Guidelines. How that fits the uniform-standards rule is a question for the planning division.
Process, timing and a checklist
Review is ministerial, without discretionary review or a hearing (Sections 65852.21(a) and 66411.7(b)). A city has 60 days from a complete application to approve or deny it, or the application is deemed approved (65852.21(h) and 66411.7(b)). Sunnyvale's staff report says its new ordinance requires no public notice and allows no appeal. Before you apply or buy, gather:
The full zoning designation, including any "S," "i" or "e" suffix.
Fire hazard, flood and earthquake fault zone status for the parcel.
Rental history for the last three years, and any withdrawal of units from rent.
Historic status: National Register, state inventory, or city landmark or district.
Lot width, depth and frontage, and where existing walls sit.
Whether the lot, or an adjacent lot under the same owner, was already split.
Utility service: Sunnyvale's ordinance, as introduced, requires a separate utility connection and electrical panel for each SB 9 unit.
Our ADU guide covers the other way to add a unit. This is general information as of November 2026, not legal advice. SB 9 rules changed again in 2026, so confirm the rules for your parcel with your city's planning division and ask a land use attorney how they apply.
Frequently asked questions
Can I split my Eichler lot under SB 9?
Possibly, if it's in an eligible zone, each new lot would be at least 1,200 square feet and 40 percent of the original, and no exclusion applies, such as a hazard zone, recent tenants or historic status. City design and overlay standards still apply to what you build.
Does a single-story overlay apply to SB 9 homes?
In Cupertino, the code says SB 9 units on "i" and "e" lots follow the overlay standards. Palo Alto's 2024 SB 9 standards said projects must meet single-story overlay requirements, and Sunnyvale's ordinance, as introduced in October 2026, sets stories by the zoning district. Confirm with the city for your parcel.
Do I have to live in the house?
For a lot split, yes: the owner signs an affidavit of intent to occupy one unit for at least three years, with exceptions for community land trusts and qualified nonprofits (Section 66411.7(g)). HCD's March 2025 letter to Riverside says there's no owner-occupancy requirement for a two-unit project without a split.
Related reading
Single-Story Overlay Districts: Check Your Street, Know the Rules
Mills Act in California: Historic Designation and Mid-Century Homes
Fairgrove Eichler, Cupertino: The R1-e Tract and Its Two-Story Rules
Lot Line Adjustment in California: Maps, Surveys and City Steps
More guides on this topic: Buying & Selling a Mid-Century Modern Home
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Weighing an Eichler lot's SB 9 options before you buy or sell? 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 lot and the timing.
