Rohnert Park's ADU Ordinance: 10 Rules HCD Says Don't Comply

You're drawing up a backyard ADU in Rohnert Park. The city's ordinance hands you the rules: a 16-foot height cap on a detached unit, a design that has to be "architecturally compatible" with your house, and — if you want two detached units — a combined 800-square-foot ceiling. So you shrink the project to fit.

Here's the thing: HCD reviewed that ordinance and found ten of its provisions out of step with State ADU Law. That's HCD's read, not a court's ruling — but it's a map of exactly where Rohnert Park's ADU rules diverge from the state floor, and several of the barriers land right on the homeowner.

What HCD reviewed

On January 20, 2023, HCD sent written findings to Rohnert Park's Planning Division on the City's ADU Ordinance No. 950, adopted August 25, 2020. HCD reviewed it under State ADU Law (Gov. Code § 65852.2) and issued the findings pursuant to subdivision (h). Its bottom line, in HCD's own words:

HCD finds that the Ordinance does not comply with section 65852.2 in the manner noted below.

The letter then works through ten provisions, each keyed to a section of the ordinance. HCD gave the City 30 days — a written response due February 17, 2023 — to amend the ordinance or adopt findings defending it.

Verified against HCD's ADU Ordinance Findings letter to the City of Rohnert Park (Ordinance No. 950), dated January 20, 2023.

The 16-foot ceiling

The ordinance said a detached ADU "may not exceed 16 feet in height." HCD found that number below the current floor. State ADU Law, HCD wrote, had been "amended to increase the maximum height limitation that may be imposed" to 18 feet where the ADU sits within a half-mile of a major transit stop or a high-quality transit corridor, or is detached on a lot with an existing multifamily, multistory dwelling — and it allows up to 25 feet for an ADU attached to the primary dwelling. HCD's position: a flat 16-foot cap doesn't conform to current statute.

"Architecturally compatible" is a judgment call

The ordinance told applicants their ADU had to be "architecturally compatible" with the primary dwelling and, for a unit above a garage, designed to "minimize privacy impacts." HCD held that language against the rule that an ADU is approved ministerially — no discretionary review. Quoting the statutory definition, HCD described an objective standard as one that involves "no personal or subjective judgment by a public official." Its finding was direct: "Terms such as 'architecturally compatible' and 'minimize privacy impacts' are subjective and therefore discretionary, potentially violating state statute." In HCD's view, the City must remove the language.

More barriers on the list

• 800 vs. 850 square feet. The ordinance capped two detached ADUs at a combined 800 square feet. HCD found State ADU Law "permits two detached ADUs of up to 850 square feet each."
• One ADU and one JADU. HCD read the ordinance to allow either a detached or an attached unit — where § 65852.2, subdivision (e)(1)(A) "permits one ADU and one JADU per lot with a proposed or existing single-family dwelling."
• Four-foot setbacks. The ordinance's "sufficient for fire and safety" setback language, HCD found, could "preclude an ADU that meets the minimum four feet rear and side setbacks"; the most a city can require is four feet.
• The sink rule. The ordinance required a JADU efficiency kitchen to include a sink. HCD noted that requirement "was removed" from statute.
• Utility connections. HCD flagged that the ordinance could require a new utility connection for an ADU that § 65852.2, subdivision (f)(4) exempts.

What this means for your project

None of this is automatic. An HCD findings letter is the agency's interpretation, not settled law — courts are the final word. Rohnert Park had 30 days to amend the ordinance or adopt findings defending it, and State ADU Law has been amended more than once since this 2023 letter. So before you resize a project or push back on a plan-check comment, confirm the current ordinance text and the current statute with the City's Planning Division — and, on anything with real money or timeline riding on it, with your own counsel. The letter is leverage, not a ruling.

What CrossBeam does with it

When the letter lands on your desk, CrossBeam turns it around the same day: what each item is actually asking, the code or law behind it, and a written response you can hand to your team or your attorney — the back-and-forth that used to eat weeks, done in a couple of hours.