Building an ADU in Cerritos. Rules, costs, timeline.

Can I build an ADU in Cerritos?

Five things to know before you start

If you read nothing else here, read these. They are the five points that change the most projects in this city.

How many units your lot can take

Everything in this section is grounded in Gov. Code §§ 66310–66342, which is the whole rulebook here, with the 2006 local text at Cerritos Municipal Code § 22.40.210(3) named wherever it says something different. We won’t re-cite the local subsection on every line.

On a single-family lot, state law requires the City to allow a conversion ADU created from existing space of the house or an accessory structure, plus a junior ADU, plus one new detached ADU of up to 800 square feet (Gov. Code § 66323(a)(1)–(2)). That is up to two ADUs and a junior unit on one lot. The worked example in the HCD ADU Handbook (March 2026), p. 17 is the reference point if anyone tells you the ceiling is one unit.

Apartment properties work differently. On a lot with an existing multifamily building you may convert space that is not livable — storage rooms, boiler rooms, passageways, attics, basements, garages — into at least one ADU and up to 25% of the existing unit count (Gov. Code § 66323(a)(3)(B)). Detached units are allowed up to eight, never exceeding the number of existing units (Gov. Code § 66323(a)(4)(A)(ii)). With a proposed multifamily building the detached limit is two. Junior ADUs are a single-family product only.

Owner-occupancy

You do not have to live on the property to build or rent an ADU here. Gov. Code § 66315 bars an owner-occupancy requirement for an accessory dwelling unit statewide, and with no compliant local ordinance that rule reaches a Cerritos lot without argument.

Junior ADUs are the one place owner-occupancy still appears in state law, and the local code has nothing to say about them — § 22.40.210(3) contains no junior-ADU provisions at all, because it predates them. So Gov. Code § 66333 governs with no local overlay, which is unusually clean.

What about an unpermitted unit already on the lot?

A unit built before January 1, 2020 gets a streamlined path to legal status. The City may not refuse a permit to legalize it on the ground that it violates building standards, or that it does not comply with ADU law. The narrow exception is a finding that correcting the violation is necessary to protect health and safety (Gov. Code § 66311.7, added by AB 2533 and renumbered by SB 543 effective January 1, 2026).

What an ADU costs in Cerritos (2026)

Our Signature plans are fixed-price — architectural design and full permit processing included, the same number whether the lot is in Cerritos, Lakewood or the Westside. Construction is separate: once your plans are permitted, you build it yourself, bring your own licensed contractor, or build with one of our vetted construction partners. The figures below are the estimated cost to build each model with an independent licensed general contractor.

The two-story models are shown for reference. On a Cerritos lot the detached envelope is single story, so the Lincoln at 1,000 sqft is the largest plan that permits as drawn — and it lands exactly on the size floor a city must allow for a unit with two or more bedrooms. Custom work is priced per project, $9,990–$19,990 for design and permit processing.

City fees and pass-throughs

Those figures come from the City of Cerritos Master Fee Schedule, adopted by Council Resolution 2017-4 and revised July 13, 2026. Add Construction and Demolition Debris Diversion and State Green Building charges, and a utility connection or capacity charge where a separate connection is required. An ADU converted from existing space usually needs no new connection at all.

What it returns: renting your ADU

Long-term rental only, at 31 days or more. For a rent benchmark, the government figure is HUD’s Fair Market Rent for the Los Angeles–Long Beach–Glendale HUD Metro FMR Area, which covers Cerritos. For FY 2026, as revised effective May 21, 2026: $2,079 for a studio, $2,328 for a one-bedroom, $2,903 for a two-bedroom, and $3,681 for a three-bedroom. Those are metro-wide figures spanning the full range of housing stock and unit ages, so treat them as a floor rather than a forecast — a newly built detached ADU generally rents above FMR. A local property manager can price your specific street.

A newly constructed ADU first occupied after February 1, 1995 is generally outside California’s local rent-ceiling controls under the Costa-Hawkins Rental Housing Act (Civ. Code § 1954.50 et seq.). The statewide rent-cap framework under AB 1482 (Civ. Code § 1947.12) may still apply depending on the ADU’s structure and ownership. Confirm both with a landlord-tenant attorney before you write the lease.

HUD FMR figures: FY 2026 Fair Market Rents, Los Angeles–Long Beach–Glendale HUD Metro FMR Area, as revised effective May 21, 2026 (91 FR 21301). Your ADU’s actual performance depends on finish level, lot, access, parking and the rental market at the time you lease it. For payback math keyed to your lot, use the ADU ROI calculator or the ADU calculator.

When an ADU isn’t the right move

Not every Cerritos property is a good ADU candidate, and it is cheaper to learn that now than after you have paid for plans. Four situations where we would tell you to wait, pick a different unit type, or not build:

• Your numbers depend on short-term rental income. They will not work. Gov. Code § 66323(e) requires a rental term longer than 30 days on the units it reaches, and the local code sets no shorter floor because it sets none at all. Run the math on a 31-day-plus tenancy or reconsider.
• You want a separate-sale exit. Cerritos has not adopted an AB 1033 condominium ordinance, so the ADU cannot be sold apart from the house. If a condominium-style exit is the plan, this is the wrong jurisdiction for it.
• You need two stories of detached space exactly as our stock plans draw it. The detached envelope is 16 feet, or 18 near qualifying transit. The honest routes are a single-story plan, a modified two-story plan, or a custom design — not a variance, which takes the project out of ministerial review entirely.
• You want certainty about the local rulebook more than you want the unit. Building against state law in a city with no ADU ordinance is legally solid, but it means the counter conversation is occasionally an argument about which text governs. If that prospect makes you uncomfortable, a garage conversion or an interior conversion is the lower-friction way in.

The rules that make Cerritos different

Why there is no local ADU ordinance

Most LA County cities adopted an ADU ordinance to mirror state law, and sometimes to add local detail on top of it. Cerritos did not. Its only second-home provision sits inside Cerritos Municipal Code § 22.40.210, a section titled “Pets and accessory residential uses” that also covers pigeons, chickens and collapsible patio canopies. Subsection (3), “Second Dwelling Units or Second Units,” carries a history line ending at Ordinance 911 in 2006, with earlier amendments in 2003, 1996, 1992 and 1972. It has not been touched since — the municipal code is current through Ordinance 1062, passed April 13, 2026, and none of the intervening ordinances reached it.

It reads like a different era. It allows one “second unit,” and only on a lot of at least ten thousand square feet. It caps the unit at 750 square feet, one bedroom, one bathroom and two occupants. A detached unit is held to one story and must sit at least ten feet from the house. The unit must be attached if the lot abuts an arterial street. An extra parking space is required. Garage conversions are banned outright. And the whole thing runs through a discretionary “second unit permit” decided by the director of community development, on grounds that include roof type and paint color.

None of that governs an accessory dwelling unit today, and the legal route to that conclusion is short. If you treat the 2006 text as Cerritos’s ADU ordinance, it is null and void because it does not comply with state law, and the City must apply the statutory standards instead (Gov. Code § 66316; § 66326(d)). If you treat it as what it plainly is — a pre-ADU-law relic, with no ADU ordinance ever adopted — then the City must approve ADU applications ministerially against those same statutory standards (Gov. Code § 66314). The two readings arrive at the same place, which is why this is a settled question rather than an argument.

What the 2006 text still says, and what replaces it

The rental floor, where the local code is silent

Subsection (3) says nothing at all about how long a second unit may be rented for. That silence does not create freedom — it leaves the statute as the only floor, and the statute is strict.

Separate sale: two statutes, and only one of them is open

Cerritos Municipal Code § 22.40.210(3)(f) allows a second unit to be rented but bars selling, transferring or assigning it separately from the primary residence, and requires a recorded deed restriction saying so. State law reaches the same result by a different route, with one narrow exception the local text does not mention. Two different statutes are involved and they are not the same rule.

• Gov. Code § 66342 is the condominium route people usually mean by “AB 1033.” A city may adopt a local ordinance permitting the house and the ADU to be conveyed separately as condominiums. Cerritos has not adopted one, so that exit is closed here. Among LA-area cities only a handful have — Santa Monica (SMMC § 9.31.026) and Culver City (CCMC § 17.400.096) among them.
• Gov. Code § 66341 is a separate statewide pathway, and it is mandatory — no local opt-in is needed and no local deed restriction can foreclose it. It is also narrow: it reaches units built or developed by a qualified nonprofit corporation and sold to a qualified low- or moderate-income buyer under a recorded tenancy-in-common agreement. It is a below-market-housing tool, not a route for an ordinary homeowner.

For practical purposes: build in Cerritos for rental income, family housing, or long-term value in the primary asset.

Pre-approved ADU plans

Under AB 1332 (Gov. Code § 65852.27) every California city was required to run a pre-approved ADU plan program. Cerritos states on its residential permitting page that it is currently accepting accessory dwelling unit plans for pre-approval, and directs interested designers to the Department of Community Development. As of this review the City does not publish a catalog of accepted plans, so treat the program as live but thin, and ask what is on the list before you rely on it.

The reason to ask is a shorter clock rather than a shorter queue. Gov. Code § 65852.27(b) gives some detached-ADU applications a 30-day decision instead of 60. To qualify, the application has to use a plan the agency pre-approved within the current triennial California Building Standards Code cycle, or a plan identical to one it already approved in that cycle. That is half the ordinary ADU clock, and it is a right most applicants never invoke.