City of Calabasas ADU: Regulations, Costs & Permits

In May 2026, California's housing department (HCD) found Calabasas's 2020 ADU ordinance inconsistent with state law in 20 ways, including a separate zoning clearance step, a subjective design-matching rule, a one-story 16 ft height cap, and limits on combining an ADU and JADU. The city had to respond by June 2026. Until an amended ordinance is adopted, state law controls wherever it's more permissive, for example allowing 18 ft near transit, 25 ft for attached units, and a JADU plus a converted ADU plus a detached ADU on one lot. Ask the city which local rules it's still applying.

• Citywide very high zone: the city's pre-approved ADU FAQ says all Calabasas properties are in a Very High Fire Hazard Severity Zone.
• Fuel modification: every ADU needs a fuel modification plan approved by LA County Fire's Fuel Modification Unit before the permit issues. It's a separate online review with its own timeline, so start it early.
• Fire plans: LA County Fire approves the fire plans (you show proof of submittal before city plan review) and signs off before the city's final inspection.
• Access: LA County Fire may require a fire access road or driveway if any part of the ADU is more than 150 ft from the street.

• Size: the city code allows ADUs up to 1,200 sq ft (attached ADUs up to 50% of the home's living area), with a 220 sq ft minimum. JADUs up to 500 sq ft.
• The 800 sq ft guarantee: regardless of other limits, one ADU up to 800 sq ft, 16 ft tall, with 4 ft side and rear setbacks must be allowed.
• Setbacks: 4 ft side and rear, including units above a garage. None for a unit built inside an existing legal garage.
• Separation: the code calls for 10 ft between a detached ADU and other buildings, which the director can reduce for an 800 sq ft unit.

Calabasas offers three free plans by RRM Design Group: a 554 sq ft studio, a 750 sq ft one-bedroom, and a 1,001 sq ft two-bedroom, each in Cottage, Ranch, or Spanish style with slab or raised foundations. They're all-electric. The city estimates about 5 business days for the first review and 5 for the second, and pre-approved plans reduce plan check fees. For a custom ADU, you first complete the city's Custom ADU Checklist, which has to come back yes on questions 1 through 8.

• Sewer or septic: if the house is on sewer, the ADU ties into the existing line. If a septic property has sewer available, it must connect and remove the septic. Where there's no sewer, a professional designs a system meeting state Tier 1 requirements, and the existing system needs a Plumbing Code analysis. The city notes existing septic systems are rarely documented well enough to prove they can handle an ADU.
• Old Topanga and Calabasas Highlands: ADUs served by septic in these overlay zones must meet the zoning code's site coverage standards.
• Oak trees: the city has oak tree regulations, and the site plan must label oaks and their protected zones.
• Other overlays: the code also includes Scenic Corridor and Park Moderne overlays.

• Online: Planning applications go through the city's Planning Portal, and building plans are submitted as PDFs through the Building and Safety Portal.
• Review time: the code requires review within 60 days of a complete submission.
• Before the permit: LA County Fire plan approval, fuel modification approval, and a Las Virgenes Unified school fee receipt.
• Grading: generally needs a plan and permit above 50 cubic yards.
• Solar: required on new detached ADUs under the 2025 Energy Code.
• Impact fees: none for 750 sq ft of living space or less under state law, and proportional above that. School fees only apply over 500 sq ft.
• Water and sewer: Las Virgenes Municipal Water District. An ADU isn't charged as a new use for connection fees unless it's built with a new home.

• No short-term rentals: rentals under 30 days are banned citywide, including in ADUs.
• No owner occupancy for ADUs: the city's FAQ confirms you don't have to live on the property.
• No separate sale: ADUs can be rented but not sold apart from the house.

Is every Calabasas property in a very high fire zone?

The city says yes. Every ADU needs LA County Fire fuel modification approval before the permit is issued.

Does Calabasas have free ADU plans?

Yes: a 554 sq ft studio, a 750 sq ft one-bedroom, and a 1,001 sq ft two-bedroom by RRM Design Group, with about 5 business days per review.

Are Calabasas's ADU rules current?

Not fully. The state found the 2020 ordinance out of compliance in May 2026, so state law controls wherever it's more permissive until the city adopts an amended ordinance.

Can I build an ADU on a Calabasas lot with septic?

Yes, but it's the hardest case. You'll need a Plumbing Code analysis of the existing system or a new state Tier 1 system, and in Old Topanga and the Calabasas Highlands, site coverage limits apply.

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