In late December 2025, California's housing department told the City of Hermosa Beach that its own accessory dwelling unit ordinance broke state law. The city had thirty days to explain itself or fix it. It chose to fix it. Ordinance No. 26-1498 repealed and replaced the entire ADU chapter of the municipal code, adopted March 24, 2026 and effective April 23, 2026, a little more than four months before this writing. If you have been circling the idea of adding a rental unit, an in-law suite, or a long-term income property behind your Hermosa Beach home, the code you would build under today is genuinely new.
It is also not the part of the process that decides how long your project takes or what you will spend before a shovel touches dirt. That comes down to a line that predates the ordinance rewrite by decades: the edge of California's Coastal Zone, which runs through Hermosa Beach from the sand up to Ardmore Avenue. Land on the wrong side of that boundary and the state's own housing law, however permissive on paper, runs straight into a second permitting process that owners in some neighboring beach cities never have to think about at all.
The Rewrite Was Not Optional
The prior ordinance, No. 1484, had only been on the books since January 28, 2025 when California's Department of Housing and Community Development reviewed it and, in a findings letter dated December 29, 2025, ruled that it failed to comply with state ADU law. HCD gave the city until January 30, 2026 to respond with either a fix or a documented justification. Hermosa Beach's City Council introduced the replacement ordinance on March 10, 2026, adopted it on March 24, and it took effect a month later. The city's own notice of adoption describes the rewrite plainly: it exists to bring the local code back into alignment with current state law.
That is worth sitting with for a second. This was not a routine annual update. It was a state agency telling a coastal city that its housing ordinance did not hold up, and the city rebuilding it from scratch under a deadline.
What Actually Changed: Two Classes, Real Ceilings
The new chapter organizes every ADU project into one of two tracks, and knowing which one applies to you changes what you can build and how it gets reviewed.
- Class 1 ADUs are the state-protected pathway. They move forward on a building permit alone, with no separate local ADU permit, no design review, and no public hearing. For a new detached unit built under this pathway, the size caps out at 800 square feet.
- Class 2 ADUs fall under the city's own development standards. A studio or one-bedroom unit is capped at 850 square feet, a two-or-more-bedroom unit at 1,000 square feet, and an attached Class 2 unit cannot exceed half the floor area of the primary home.
Want more square footage than 800 feet on a new detached build? You are no longer in Class 1. You are in Class 2, with the fuller local design review that comes with it.
Most homeowners will land in one category or the other depending on whether they are converting existing space or building new detached square footage. The distinction matters because it determines whether your project gets a straightforward building-permit review or a fuller local design process.
The Permit the Rewrite Didn't Touch
Here is the part that generic ADU guides tend to skip, because it does not apply everywhere in California the same way. Hermosa Beach's Local Coastal Plan defines the Coastal Zone as extending inland from the beach to Ardmore Avenue, with limited exceptions. Inside that boundary, the city's local development standards keep applying regardless of Class 1 or Class 2 status, and a Coastal Development Permit runs concurrent with your building permit. Unlike Manhattan Beach, where many Class 1 projects can move forward on the state law pathway alone, Hermosa's coastal overlay means that bypass largely does not exist here.
The height rules carry their own version of the same gap. Hermosa's attached ADUs top out at 25 feet or the underlying zone's height limit, whichever is lower, and there is no path here to a freestanding two-story detached unit. The only way to reach two-story ADU height in Hermosa Beach is to attach the unit to an existing two-story primary home. Manhattan Beach's code includes an allowance for building above a detached garage up to 26 feet, a specific option Hermosa's ordinance does not carry.
The practical effect: the CDP typically adds two to four months to your overall timeline and somewhere between $5,000 and $15,000 in soft costs, covering Coastal Commission processing, additional plan-set work, and any view-corridor or drainage analysis your project triggers. How much of that range you hit depends heavily on where in the city you are building.
| Project type and location | Scope of coastal review | Added timeline | Added cost |
|---|---|---|---|
| Attached ADU on a walk street south of the Pier | Largely documentation: site plan, elevations, drainage, view-corridor check | Toward the shorter end of two to four months | Lower end of $5,000 to $15,000 |
| Detached ADU on a sloped or view-eligible lot east of Hermosa Avenue | Materially more involved: slope stability and view-corridor analysis layered on top | Toward the longer end of two to four months | Higher end of $5,000 to $15,000 |
Senate Bill 1077 required the California Coastal Commission to publish coordinated guidance for streamlining coastal ADU review statewide by July 1, 2026, a deadline that has now passed. Whether that guidance meaningfully shortens Hermosa's CDP timeline in practice is not yet clear, and it is worth asking the city's Planning Division directly at the pre-submittal stage rather than assuming the new ordinance already accounts for it.
Two Details the City's Own Page Hasn't Caught Up To
If you go looking for answers on Hermosa Beach's official ADU page, you will find a line stating that owner-occupancy has been required in single-family zones starting January 1, 2025. That was accurate when it was written. State law has since moved past it. AB 976 permanently eliminates owner-occupancy mandates for ADUs permitted after January 1, 2026, though junior ADUs are still treated differently under that same law. A city page that has not caught up to a newer state statute cannot override it, but it can absolutely mislead a homeowner who takes it at face value. Confirm directly with planning staff before you assume you need to live on site.
The second detail concerns AB 1033, which lets some California cities allow homeowners to sell an ADU as a separate condominium from the main house. San Jose, Santa Monica, and San Diego have adopted local ordinances opting into that framework. Hermosa Beach has not. If part of your long-term plan involves eventually selling the ADU as its own unit rather than holding it as a rental, that exit does not currently exist here.
Running the Math With the Real Clock
Across the South Bay, a one-bedroom ADU typically rents for $2,500 to $3,500 a month, with beach proximity driving demand and smaller coastal lots pushing many owners toward garage conversions rather than new detached construction. At those rents, a typical detached ADU pays back its construction cost in twelve to eighteen years through rental income alone, before any property appreciation.
That payback clock does not start the day you sign a construction contract in Hermosa Beach. It starts after the Coastal Development Permit clears, which for many projects here is two to four months later than a comparable build in a city without the same overlay, and with $5,000 to $15,000 in permitting costs added to the front of the ledger before the first tenant moves in. None of that changes whether an ADU is a sound long-term addition to a Hermosa Beach property. It does mean the honest version of the math includes a permitting layer that a generic statewide ADU calculator will never show you.
Frequently Asked Questions
Do I need a Coastal Development Permit for every ADU in Hermosa Beach? If your property sits inside the Coastal Zone, which runs from the beach to Ardmore Avenue with limited exceptions, a CDP is reviewed concurrent with your building permit regardless of whether your unit is Class 1 or Class 2 under the new ordinance.
Does Hermosa Beach still require owner-occupancy for a new ADU? The city's own page cites an owner-occupancy requirement dating to January 1, 2025. State law under AB 976 removed that requirement for ADUs permitted after January 1, 2026. If you are permitting now, treat the newer state statute as controlling and confirm directly with the Planning Division.
Can I sell my Hermosa Beach ADU separately from the main house? Not currently. AB 1033 allows individual cities to opt into a condominium-sale framework for ADUs, and cities including San Jose, Santa Monica, and San Diego have done so. Hermosa Beach has not adopted that ordinance, so an ADU here stays tied to the sale of the primary residence.
Whether you are weighing an ADU as a rental income strategy, a way to house family close by, or one piece of a longer hold-rent-or-sell decision on a South Bay property, the ordinance is only half the picture. The other half is where your lot sits relative to a boundary that has nothing to do with the code the city just rewrote. If you are trying to model out what that actually means for a specific address, Merritt & Sanderson can walk through the site-specific numbers with you. Work With Merritt & Sanderson.
