News · June 9, 2026 · Menlo Park's updated ADU ordinance, adopted June 9, took effect July 10, 2026; the state housing department had no comments. [1]
If you drew ADU plans in Menlo Park before July 10, check them against the new rules. The city repealed its old ADU chapter and replaced it with a new one, Ordinance 1129 [2]. The state found it substantially compliant in June, "as of this writing" [3], and two new state laws take effect January 1, 2027 [4][5][6].
How many ADUs does Menlo Park allow, and how big?
Menlo Park's chapter sets out two paths [2].
The state path ("66323 Units"): up to three units
A single-family lot can have up to three. One is an ADU inside the house or an existing accessory building. One is a junior ADU, a unit of up to 500 square feet inside the house. One is a new detached ADU of up to 800 square feet, with 4-foot side and rear setbacks, 16 feet tall, or 18 within a half-mile walk of a major transit stop or high-quality transit corridor [2].
The city path ("66314 Units"): one ADU per lot
The city's own rules allow one per lot, such as an attached ADU. An attached or detached one can be up to 850 square feet with one bedroom or less, or 1,000 with more, but an attached one also can't exceed half the size of the existing house [2]. Any city-path ADU gets 100 more square feet if it meets the building code's accessibility rules. Floor area, coverage, open space and parking rules can't block one of at least 800 square feet with 4-foot side and rear setbacks, except for the attached-ADU cap [2].
Menlo Park ADU parking and permit deadlines
No parking spaces are required for a city-path ADU or a junior ADU, and garage or carport spaces lost to a city-path ADU don't have to be replaced. The city has 15 business days to say whether your application is complete, or it's deemed complete. On a lot with an existing home, it then has 60 days to approve or deny, or the application is deemed approved [2].
What did the state say about Menlo Park's ADU rules?
In December 2025, HCD, the state housing department, wrote that the newest Menlo Park ADU ordinance it had on file was from 2020 and "may be outdated and out of compliance." It reminded the city that an ordinance failing state ADU law is "null and void," and state standards apply until a compliant one is adopted [7][8]. On June 15, 2026, HCD found the new chapter "substantially compliant" and closed the matter "as of this writing," adding that "as State ADU Law is updated, the City's ordinance will need to continue to be updated as well" [3].
What changes for Menlo Park ADUs on January 1, 2027?
On the state path, the chapter allows one new detached ADU per single-family lot [2], but AB 956, signed September 29, 2026, requires cities to approve two, within state limits, from January 1, 2027 [4][6].
SB 1117, signed the same day, changes fees from the same date. For up to two ADUs on a lot, one over 750 square feet of interior living space pays impact fees only on the area above 750, still prorated to the house's size [5][6]. It doesn't cut sewer connection or capacity charges, which state law keeps out of "impact fee" [5]. West Bay Sanitary District, Menlo Park's main sewer provider, charges a new detached ADU a capacity fee based on its drainage fixture units, and bills each ADU, but not a junior ADU, its own yearly sewer charge: $1,512 at the standard residential rate for July 2026 to June 2027 [9][10].
Before you design for a second cottage, ask the city in writing which rules it will apply to your application.
Amiari Construction builds ADUs and additions on the Peninsula.
How we checked this: In October 2026, Amiari Construction read the city's June 29 announcement, its Ordinance No. 1129 and Chapter 16.79 on the city's official code site, HCD's December 2025 and June 2026 letters to the city, AB 956, SB 1117 and Government Code §66316 in the legislature's own data, the state constitution, West Bay Sanitary District's regulations, and the city's sanitary sewer page.
