On December 29, 2025, the California Department of Housing and Community Development sent Hermosa Beach a letter saying the city's own accessory dwelling unit ordinance was illegal. The letter covered the ordinance the city had adopted less than a year earlier, on January 28, 2025, the one homeowners had been using to plan backyard units, size their projects, and budget their permits. HCD gave the city 30 days to respond.

The city responded with a full replacement. On March 24, 2026, the Hermosa Beach City Council repealed the entire ADU chapter of its municipal code and replaced it, effective April 23, 2026. That version is the one governing every project in the city today. It is five months old.

If you are weighing an ADU in Hermosa Beach right now, for rental income, for a parent or adult child, or as part of a renovation plan before a sale, the rulebook you find on a builder's website or in a conversation from a year ago may already be the wrong one. This is the third time the city has rewritten this chapter since 2023.

What the state actually flagged

HCD's findings letter was specific about where the January 2025 ordinance fell short. One problem sat in how the city wrote its size-floor exception, the rule that says a handful of restrictions (setback limits, lot coverage, open space) can never shrink a compliant ADU below 800 square feet. State law lists several categories that trigger this floor. The city's version left two of them out, floor area ratio and minimum lot size, which meant a homeowner on a small or heavily built-out lot could have been told their unit had to be smaller than state law actually allows. A second problem involved the city's architectural matching requirements, written broadly enough that HCD found they could functionally block projects the state statute protects.

State ADU law changes almost every legislative session, and HCD reviews local ordinances against the current statute. The March 2026 rewrite replaced the whole chapter instead of amending it again.

The rulebook now in effect

The new chapter divides every ADU project into one of two tracks, and which one applies changes your process more than almost anything else in the code.

Class 1 is the fast lane. If your project fits inside its scenarios, mainly a conversion of existing space plus a junior ADU, or a new detached unit at 800 square feet or under, the city cannot require design review or a hearing. You pull a building permit and build.

Class 2 buys you more square footage in exchange for more process. A two-bedroom detached unit at 1,000 square feet clears the local ADU permit process, but it also has to match your house's roofline and siding, sit at least 4 feet from the side and rear property lines, and stay within whatever lot coverage standard applies to your zone.

One detail affects how many units a lot can hold. The municipal code text describes a single-family lot as allowing one ADU plus one JADU. State law allows up to three units on that same lot in the right configuration: a conversion ADU, a JADU, and a new detached ADU under 800 square feet. Where the two differ, state law controls by statute, so the number of units a lot can hold depends on reading both documents together.

The fork that matters more than the square footage

For a homeowner deciding how to use a backyard, the real choice isn't between 800 square feet and 1,000. It's between certainty and scale. Class 1 removes the city from the equation almost entirely, no hearing, no design review, a predictable permit timeline. Class 2 gets you a larger unit, room for a real second bedroom, but it puts your project in front of the same review process that governs any other addition, with the timeline uncertainty that comes with it.

For someone renovating with resale in mind, that distinction changes the math on when to start. A Class 1 unit can move from decision to permit quickly enough to fit inside a normal pre-listing renovation window. A Class 2 unit, with design review in the mix, is a longer runway, and worth starting well before you're thinking about putting a home on the market.

The owner-occupancy myth

One assumption that circulates long after it stops being true: that you have to live in the house to build an ADU. Under the current Hermosa Beach ordinance, owner-occupancy is not required for a standard ADU on a single-family or multi-family property. That reflects a statewide change, not just a local one. The rule that still applies is narrower and specific to junior ADUs, the smaller units carved out of existing living space. New 2026 state law tightened owner-occupancy specifically for JADUs, and Hermosa Beach's rewritten chapter already builds that distinction in. Full ADU, no occupancy requirement. JADU, owner-occupancy still applies.

What doesn't change no matter which track you're on

A few rules sit outside the Class 1 versus Class 2 split entirely. The City of Hermosa Beach says an ADU in Hermosa Beach cannot be rented for stays under 30 days, regardless of size or permit path, which forecloses the short-term rental route some buyers assume is available. The City of Hermosa Beach says that if the unit sits within 600 feet of a property listed on the California Register of Historic Resources, it has to be sited so it doesn't compromise that resource, a detail that matters more than it sounds like it should in a city with as many older beach cottages as Hermosa has.

And on the financial side, property taxes are worth considering when adding an ADU.

Why the paper trail matters at the closing table

None of this is abstract once a property changes hands. A buyer touring a Hermosa Beach home with a backyard unit is going to ask when it was permitted and under which version of the chapter. A seller who added an ADU under the 2023 or January 2025 version of the code has a permit history to account for. But the permit history becomes part of the story any competent buyer's agent will dig into, and a seller who can produce clean documentation showing which class the unit was built under saves everyone time during inspection and disclosure.

That is the quieter cost of an ordinance that has been rewritten three times in three years. It isn't just that the rules changed. It's that every property with an ADU now carries a small piece of regulatory history that has to be read correctly to understand what's actually there.

FAQ

Can I sell my ADU separately from my house in Hermosa Beach? No. The city has not opted into the state program that allows separate sale of ADUs as condominiums, so an ADU here stays tied to the primary lot and transfers only as part of the whole property.

Do I need a public hearing to build a small backyard unit? Not if it qualifies as Class 1. A conversion within your existing home, or a new detached unit at 800 square feet or under, moves through building permit review only, with no design review and no hearing required.

How many units can I legally put on one lot? The municipal code text describes one ADU plus one JADU on a single-family lot, and state law, which controls where it differs, allows a third unit in the right configuration: a conversion ADU, a JADU, and a new detached ADU under 800 square feet.

If you're weighing an ADU as part of getting a Hermosa Beach property ready to sell, or sizing up what one adds to a home you're considering buying, Liz Bird Fine Homes can walk through what the current rules mean for your specific lot and timeline. Let's Connect.

This article is general information, not legal, tax or financial advice. Consult a qualified professional about your situation.