Two primary homes on one lot: an SB 9 reading the city reversed

Where

Walnut, single-family lot in an R1 zone.

The project

Keep the existing house, legalize an existing detached dwelling as an ADU, and replace the garage with a second primary dwelling under SB 9, plus a new two-car garage, all without splitting the lot.

What the city said

In July 2025, planning staff wrote that because the owner was not pursuing an urban lot split, the property was “only eligible for ADUs/JADUs” and “the opportunity for two primary dwellings is not permissible.” Staff said the issue had been discussed with the City Attorney.

What we did

We responded that SB 9 has two separate parts: a two-unit housing development under Government Code section 65852.21(a), and the urban lot split. The first does not depend on the second, and a primary dwelling under that section is not an ADU. We supplied the statute language, HCD’s SB 9 fact sheet on primary units on a lot that has not been split, and an explanation of how it applied to the mix of existing and new buildings. We did not ask for a waiver or an exception, only that the city evaluate the proposal under the route the statute describes.

Outcome

Later in July, after internal discussion and further guidance from the City Attorney, the planner wrote that the owner could proceed under SB 9, noting it was the first project of its kind in the city.

Then

The owners chose the simpler route and converted the existing dwelling to an ADU. Planning approved that 709-square-foot legalization in December 2025, and building review approved it in 2026.

Status as of October 2026

SB 9 eligibility confirmed in writing; the ADU legalization approved.

What it shows

A written refusal during project discussion is not the end of the question. When the statute says something different from the city’s reading, the fastest path is to put the section in front of the planner and ask for the City Attorney’s review. See the SB 9 service page → · See duplexes, triplexes and fourplexes →

← All case studies

Next case: A changed Eaton Fire rebuild, carried through the County to issued permits →