ADU Builder in Calabasas, CA: Pre-Approved Plans, Permits and Costs

What ADU rules apply on a Calabasas residential lot?

Calabasas allows ADUs on lots with an existing or proposed single-family dwelling, and ADUs are also permitted on lots with an existing duplex or multifamily building, while JADUs are limited to single-family dwellings. State law sets the minimum floor: Section 66321(b)(3) requires local rules to permit at least 800 square feet of interior livable space with four-foot side and rear setbacks, and Section 66314(d)(5) caps a detached ADU at 1,200 square feet. A JADU is existing space of 500 square feet or less within a single-family dwelling, with an efficiency kitchen and separate exterior entrance.

Does Calabasas offer free pre-approved ADU plans?

Yes. The City's ADU page says Calabasas offers three pre-reviewed, pre-approved, code-compliant plans online at no cost, with three size configurations and three exterior design options. The plans cover a studio, one-bedroom and two-bedroom, with three architectural elevations for each option. The City says pre-approved plans reduce pre-construction fees, shorten plan review and lead to faster permit issuance, while custom plans must be prepared by a California licensed design professional and adapted to the property.

How long does Calabasas take to decide an ADU application?

California law gives the permitting agency 15 business days after receiving an application to provide a written completeness determination under Section 66317(a)(2)(A). Section 66317(a)(3) then requires a decision within 60 days after receipt of a complete application, and an application left undecided for 60 days is deemed approved. HCD's May 4, 2026 findings letter says Calabasas must remove its separate zoning clearance requirement because it is unauthorized under state law and can interfere with the 60-day deadline.

What does Calabasas charge for an ADU zoning clearance?

The City provides a current planning fee schedule and links it from its Building and Safety Division. Ask the City for the ADU zoning clearance, residential site plan review and Oak Tree Permit charges that apply to the proposed project before filing. A project may also need an Oak Tree Permit, so the city's review for protected oaks can affect the site plan.

How much does an ADU cost in Calabasas?

L Square's configured prefab model prices are $180,000 for Model 600, $240,000 for Models 800A and 800B, $295,000 for Models 1000A and 1000B, and $354,000 for Model 1200. These are model prices, not final project totals. Calabasas site conditions can add foundation, grading, utility, fire-zone and oak-protection work. L Square holds California Contractors State License Board number 1095476. Call (949) 374-7980 to discuss the lot.

What should a Calabasas homeowner check before applying?

Start with the City's Custom ADU Checklist, which asks eight project questions and requires an affirmative answer to each before the application can move forward. The City's Building and Safety Division accepts permit applications electronically through the City portal. The Housing Element records 22 ADU building permits issued between 2017 and June 2021, with nine more applications in process in July 2021, and projects at least 12 new ADUs each year, or 96 during the 2021-2029 planning period. HCD's May 4, 2026 findings letter also says the City must add missing standards for private sewage disposal, fire sprinklers and concurrent demolition permits for detached garage conversions.

Official Calabasas ADU sources

• The City of Calabasas states that ADUs are allowed on properties with existing or proposed single-family dwellings, ADUs are also permitted on lots with existing duplex or multifamily units, and JADUs are only allowed as part of a single-family dwelling. The page also says a JADU is existing space of 500 square feet or less with an efficiency kitchen and separate exterior entrance, and an ADU is existing or additional space of 1,200 square feet or less with separate sanitation and cooking facilities. Official source
• The City of Calabasas says its pre-approved program includes three pre-reviewed, pre-approved, code-compliant ADU plans available online for no cost, with three size configurations and three exterior design options. RRM Design Group prepared the plans for a studio, one-bedroom and two-bedroom, with three architectural elevations for each option. The City says pre-approved plans reduce pre-construction fees and shorten review, while custom plans must be prepared by a California licensed design professional. Official source
• The City's Building and Safety Division publishes a current planning fee schedule that covers zoning clearances for ADUs and JADUs, residential site plan review and Oak Tree Permits for single-family projects. Homeowners should confirm the current charges for their proposed project with the City before filing. Official source
• The City's adopted 2021-2029 Housing Element states that Calabasas issued 22 ADU building permits between 2017 and June 2021, with an additional nine applications in process in July 2021. It projects a minimum of 12 new ADUs per year, or 96 over the 2021-2029 planning period, and says the City will provide pre-packaged and pre-approvable construction plans free of charge for garage conversions. The Home Repair Program offers loans of up to $100,000 to income-qualified homeowners for an ADU or JADU. Official source
• HCD's May 4, 2026 findings letter says Calabasas ADU Ordinance No. 2020-382, adopted January 22, 2020, does not comply with state ADU law. The letter says the City's separate zoning clearance condition is unauthorized, requires removal and notes that local agencies have 60 days to decide an ADU application. It also finds the City's impact-fee wording fails to exempt an ADU at exactly 750 square feet of interior livable space and says the ordinance is missing standards for private sewage disposal, fire sprinklers and concurrent demolition permits for detached garage conversions. Official source
• HCD's December 5, 2025 technical assistance letter says the most recent Calabasas ADU ordinance on file is from 2020 and may be outdated and out of compliance. It says an HOA cannot influence approval of an ADU application, and if a local agency misses the 60-day ordinance submission or 30-day response timeline, the ordinance is null and void and the agency must apply state ADU law. HCD requested a response by January 4, 2026. Official source
• California Government Code Section 66317(a)(2)(A) requires a permitting agency to determine whether an ADU application is complete and give written notice no later than 15 business days after receiving it. Section 66317(a)(3) requires approval or denial within 60 days after receipt of a complete application and states that an application not acted on within 60 days is deemed approved. Official source
• California Government Code Section 66314(d)(5) states that the total floor area for a detached accessory dwelling unit shall not exceed 1,200 square feet. Section 66314(d)(10)(A) limits parking to no more than one space per accessory dwelling unit or per bedroom, whichever is less, and Section 66314(d)(11) bars required replacement parking when a garage, carport or covered parking structure is converted to an ADU. Official source
• California Government Code Section 66321(b)(3) states that local lot coverage, floor area ratio, open space, front setback and minimum lot size rules must permit an ADU with at least 800 square feet of interior livable space and four-foot side and rear setbacks. Section 66321(b)(4)(A) requires local agencies to allow a height of at least 16 feet for a detached ADU on a lot with an existing or proposed single-family or multifamily dwelling. Official source
• California Government Code Section 66311.5(c)(1) states that a local agency, special district or water corporation shall not impose an impact fee on an ADU with 750 square feet of interior livable space or less or a JADU with 500 square feet or less. Fees above the ADU threshold must be charged proportionately against the primary dwelling's square footage. Official source