Built an Unpermitted ADU Before 2020? Your City May Have the Wrong Date

You finally want to make the backyard cottage legal. It has been there for years — maybe it came with the house, maybe a previous owner built it without pulling a permit. Now you want it on the books: legal, insurable, rentable. So you open your city's ADU code to find the legalization path, and the first thing you hit is a date. Built before 2018? You're in. Built after? The city says you're out of luck.

Here's the thing: the cutoff in state law isn't 2018. It's January 1, 2020 — and it covers junior ADUs, too.

What state law actually says

Government Code § 66311.7 is the legalization path for older unpermitted units. It bars a local agency from denying a permit for an unpermitted ADU — or JADU — built before January 1, 2020, just because the unit violates building standards or doesn't match the local ADU ordinance. The date landed at 2020 through AB 2533 (Chapter 834, Statutes of 2024).

There is one way out for the city, and it's narrow. A permit can be denied only on a finding tied to one specific standard — Health and Safety Code § 17920.3, the list of conditions that make a building legally substandard. Not a general "we're worried about health and safety." A finding tied to that one section.

And there is no expiration. The statute sets no sunset — no deadline by which you have to apply.

Three ways cities quietly shrink the path

HCD reviews city ADU ordinances and issues written findings when they fall short of state law. In 2026 it flagged this same legalization provision in city after city — each shaving the path a different way.

The wrong date. The City of Colusa's ordinance (Ordinance No. 568) kept the old cutoff: no permit denied for a unit "constructed before January 1, 2018." HCD's finding was blunt:

"Because the Ordinance uses the incorrect date, omits JADUs, and applies a different denial standard, the Ordinance is more restrictive than State ADU Law."

The City of Paramount carried the same stale date in Ordinance No. 1191. HCD pointed to the fix:

"AB 2533 (Chapter 834, Statutes of 2024) amended the corresponding section in State ADU Law, to apply to ADUs created prior to January 1, 2020."

An invented deadline. The City of San Carlos wrote a sunset into its code — applications had to come in "Prior to January 1, 2030." HCD said the statute has no such thing:

"Government Code section 66311.7 provides a pathway to compliance for unpermitted ADUs constructed before January 1, 2020, and does not include a sunset provision."

A looser denial test. San Carlos's pathway let an owner apply to delay fixing building-code violations, and set its own bar for granting that request: the Building Official would approve only if enforcing the standard was "not necessary to protect health and safety" — a broad, subjective call. HCD's position is that the finding has to be made on compliance "with the standards specified in section 17920.3 of the Health and Safety Code" — the same narrow standard Colusa missed.

Verified against HCD's ADU Ordinance Findings Letter to the City of Colusa (July 24, 2026), with the same provision flagged in HCD's Ordinance Findings Letters to Paramount (July 1, 2026) and San Carlos (May 6, 2026).

Why this one matters

Each of these looks like a technicality — a year here, a deadline there, a word swapped in a denial test. Stacked up, they decide whether your unit is legal or not. A 2018 cutoff erases two years of units. A 2030 sunset turns a standing right into a use-it-or-lose-it deadline. A vague "health and safety" test hands a plan checker a reason to say no that the statute never gave them.

Here is the part that matters for a homeowner: these are HCD's enforcement positions, not a court ruling, and HCD letters interpret the law — they don't replace it. But the statute underneath is plain, and HCD is applying it the same way across the state. If your city's ADU code sets a 2018 date, adds a sunset, or blocks your permit on a general health-and-safety concern, that's worth a second look before you take "no" for an answer. Check the current text of § 66311.7, and verify with your building department or counsel before you rely on any of it. This isn't legal advice.

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.