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

Yes. Nothing about the current situation stops you, and it is worth being clear about that up front because the situation sounds alarming when you first read it. California ADU law applies in Calabasas the same way it applies everywhere else, and it is what the city has to work from. What is unsettled is the city's own ADU chapter, CMC § 17.12.170. The State has formally found that it does not comply with current law. That affects which local add-ons the city can enforce against you. It does not affect your underlying right to build.

The city's ADU chapter dates from 2020 and the law has moved a long way since. The city's own planning staff put the number in a June 2026 report: "over the past six years, forty-five new laws pertaining to ADUs and/or JADUs have been adopted by the State of California." On December 5, 2025 the California Department of Housing and Community Development wrote to the city saying the 2020 ordinance on file appeared out of date. The Planning Commission recommended a replacement in March 2026. Then, on May 4, 2026, HCD issued formal written findings under Gov. Code § 66326(a). That is a more serious instrument than the December letter, and it said plainly that "the Ordinance fails to comply with State ADU Laws." It stopped the replacement before it reached the City Council. The ordinance was rewritten a second time and taken back to the Planning Commission on June 18, 2026. As of this writing the City Council has not adopted a replacement.

State law, directly. Gov. Code § 66316 provides that where a local ADU ordinance fails state law, the ordinance is null and void. The city must then apply the state standards until it adopts a compliant one. HCD said so in the December 2025 letter, adding that it "recommends that a local jurisdiction with a noncompliant ADU ordinance repeal the ordinance to provide clarity for ADU applicants who may otherwise rely on the outdated ordinance." In practice that means you should design to the state standards, and if a local requirement comes back at you in plan check that HCD has already flagged, that is the moment to put the findings letter in front of the city in writing.

The city's published guidance says up to 1,200 square feet for an ADU and 500 square feet for a junior ADU. Underneath that sits a floor the city cannot go below whatever happens to its ordinance. Gov. Code § 66321(b)(3) bars any limit on lot coverage, floor area ratio, open space, front setbacks or minimum lot size that would not permit an ADU of "at least 800 square feet of interior livable space and with four-foot side and rear yard setbacks to be constructed in compliance with all other local development standards." That closing clause matters: the 800 square feet is protected against size rules, not against the building code or fire standards. That is the provision HCD used against the city's 30 percent rear-yard coverage rule. Its words: "the City's standard is unlawful as it does not apply if it does not permit an ADU of up to 800 square feet of livable space." Separately, § 66321(b)(2) bars a maximum-size rule below 850 square feet of interior livable space, or 1,000 where the unit has more than one bedroom. Note the unit of measurement throughout: interior livable space, measured inside the walls, not gross floor area.

The local table says detached units get "one story, 16 ft. maximum," and that if the ADU sits above a garage the zoning district's height standards apply instead. HCD found that limit non-compliant — not because 16 feet is itself too low for a plain detached unit, since 16 feet is the state floor, but because the ordinance does not allow the other floors state law requires. Under Gov. Code § 66321(b)(4) the city must allow 18 feet for a detached ADU within a half-mile walking distance of a major transit stop or high-quality transit corridor, plus two more feet to match your main house's roof pitch; 18 feet on a lot with a multifamily multistory dwelling; and 25 feet, or your zone limit if lower, for an ADU attached to the house. Until the ordinance is fixed, expect to have to point at the statute for anything above one story.

More than the local ordinance says. CMC § 17.12.170 allows "a single accessory dwelling unit, or junior accessory dwelling unit" on a legal lot, and HCD found that this "does not fully describe what is allowed by State ADU Law." On a single-family lot, Gov. Code § 66323(a)(1) and (2) let you create one junior ADU, one conversion ADU inside existing space, and one detached new-construction ADU — in combination, not as alternatives. HCD adds that those may be combined with one further ADU created under § 66314. On a lot with an existing multifamily building the numbers are different again, running up to eight detached ADUs, not exceeding the number of existing units. Treat the local one-unit limit as the thing that has to give way, and get the city's position in writing before you design around it.

The ordinance says yes. The State says the city cannot require it. This is HCD finding number 6, and it is the sharpest one on the list, because it is procedural rather than dimensional. Gov. Code § 66321(b)(3) prohibits "any requirement for a zoning clearance or separate zoning review" that would prevent an 800 square foot ADU being built, and HCD's letter says a separate clearance "is unauthorized by State ADU Law and would thwart the 60-day approval deadline," concluding that "the City must remove the unlawful condition and timely review ADU applications consistent with statutory deadlines." If you are asked for a separate zoning clearance, that is the paragraph to quote — politely, in writing, early.

No. Much of Calabasas sits in the Santa Monica Mountains and the city applies a standard condition to projects in a Very High Fire Hazard Severity Zone, routing them through the requirements of CMC Chapter 15.04.900. Those are construction standards — materials, defensible space, access — not a prohibition, and no California city may use a fire zone designation to refuse a state ADU outright. Two related points worth knowing. State law limits what sprinkler requirements a city may impose on an ADU, and HCD listed those limits among the four required provisions missing from the Calabasas ordinance entirely. And fire-zone construction standards are a real cost line rather than a real barrier, so get them priced early rather than treated as a formality.

Usually not, and the local list is missing one of the ways out. At most one space per ADU may be required, and Gov. Code § 66322(a) sets out exemptions that each stand on their own: within a half-mile walking distance of public transit; within one block of a car share vehicle; where the ADU is part of the existing primary residence or an accessory structure; where on-street parking permits are required but not offered to the ADU's occupant; inside an architecturally and historically significant historic district; and where the ADU is permitted alongside a new primary dwelling, provided the lot also meets one of the others. That last one is the exemption HCD found missing from the city's table. No parking of any kind may be required for a Gov. Code § 66323 unit, and a junior ADU may never be required to provide parking on any route. One more point that saves people a parking pad: when you convert or demolish a garage or carport to build the ADU, you are not required to replace the parking it held. The Calabasas ordinance already says so, and Gov. Code § 66314(d)(11) says it too.

Building permit and plan check fees are valuation-based, so they scale with what your project is worth and are better quoted against real drawings than guessed from a table. Two things are worth knowing on the protective side. An ADU with 750 square feet of interior livable space or less pays no development impact fees at all under Gov. Code § 66311.5(c)(1), and a junior ADU at 500 square feet or less of interior livable space is treated the same. HCD found the local fee provision wrong on both counts — it does not measure in interior livable space, and it exempts units "less than 750 sq. ft." rather than 750 or less, which quietly loses the exemption for a unit built at exactly 750. If you are anywhere near that line, model the fees just under and just over it, and check which measure the city is applying.

Sixty days from a complete application, and the review is ministerial — a checklist rather than a judgment call, with no hearing and no neighbors to win over. Gov. Code § 66317 sets that clock and it binds the permitting agency as a whole rather than one department, so any clearance the city asks for sits inside the sixty days rather than in front of them. If the city misses the deadline without acting, the application is deemed approved. The Calabasas-specific risk is the separate zoning clearance the ordinance still calls for, which is exactly what HCD said would thwart the sixty-day deadline. If your project drifts past sixty days on a complete application, say so in writing and cite § 66317.

We would not, and here is the reasoning rather than just the advice. The replacement has already been drafted twice and has not reached the City Council as of this writing — the second rewrite was the City's own decision after reading the State's findings — and those findings analysed the 2020 ordinance, not the March draft. Nobody can tell you when it lands. More to the point, the direction of travel is toward the state standards rather than away from them: the changes described in the June 2026 draft include stating plainly that nothing in the local standards precludes an ADU of 800 square feet of living space with four-foot side and rear setbacks and a height of at least 16 feet, and measuring all sizes as interior habitable space. If you design to the state floor now, a compliant new ordinance should not undercut you.

Largely not, and this matters more in Calabasas than in most places we work, because so much of the city sits in gated tracts with recorded covenants. Civil Code § 4751 makes covenants, conditions and restrictions that either effectively prohibit or unreasonably restrict the construction or use of an ADU or junior ADU on a lot zoned for single-family residential use void and unenforceable. Separately, HCD has stated that a homeowners association, as a third party, cannot influence the approval of an ADU application at all, and that third-party review by an HOA or its agents would violate state ADU law. An association can still enforce reasonable, genuinely aesthetic standards. It cannot ban the unit, and it is not a step in your permit. If your association tells you otherwise, that is worth resolving in writing before you spend money on drawings.

For an ADU, no. Gov. Code § 66315 prohibits a local agency from requiring owner occupancy for an accessory dwelling unit. For a junior ADU the answer changed recently and the local ordinance has not caught up. CMC § 17.12.170.D.2 says flatly that "the owner must reside in the single-family residence." Under Gov. Code § 66333(b), owner-occupancy may not be required where the junior ADU has separate sanitation facilities, or where the owner is a governmental agency, land trust or housing organization. So if the junior ADU has its own bathroom, the requirement falls away. HCD listed the local provision among its findings. Junior ADU tenancies must also be for terms longer than 30 days.

Calabasas is one of the highest-value markets we work in, which cuts both ways for an ADU. The Zillow home value index for ZIP 91302 was about $1.97 million in June 2026 and the rent index about $3,600 a month. High values support strong rents, but they also mean ADU activity here is thin in absolute terms — the city's own June 2026 staff report says approximately 110 ADUs and junior ADUs have been permitted since 2022, and the city's own annual report to the State records 15 ADU permits in 2025. That is a small market with high per-project value, which is a different proposition from a high-volume one. We are not going to publish a bedroom-level asking rent, because the sources we trust are either blended across all unit sizes or are voucher standards rather than market rents. Start from HUD's Small Area Fair Market Rents for your own ZIP, then check live listings nearby.