ADU Builder in La Mirada, CA: County Plan Check, Fees and Costs

What ADU rules apply in La Mirada?

La Mirada does not run its own building department. The city contracts with Los Angeles County for Building and Safety services, and both building and structural plan checks happen at county offices: 12440 Imperial Highway, Suite 110 in Norwalk, or 900 S. Fremont Avenue, 3rd Floor in Alhambra. The city applies the 2022 California Building Code with the Los Angeles County 2023 Amendment. State law sets the outer limits. A detached ADU is capped at 1,200 sq ft under Section 66314(d)(5), side and rear setbacks are held to 4 ft under Section 66314(d)(7), and a detached ADU may reach 16 ft in height under Section 66321(b)(4)(A). A junior ADU is 500 sq ft or less under Section 66313(d). Under Section 66325(a), state ADU law supersedes any conflicting local ordinance.

How long does the La Mirada ADU permit process take?

Two clocks run in parallel. Section 66317(a)(2) gives the city 15 business days from submittal to say whether the application is complete. Section 66317(a)(3) then gives it 60 days from a complete application to approve or deny, and an application is deemed approved if the clock runs out with no applicant-requested delay. On the county side, plan check moves through the South Whittier district office or the Alhambra central office, and the city's Building and Safety counter is open Monday through Thursday and alternate Fridays from 7:30 a.m. until one hour before City Hall closes. City Hall closes at 5:30 p.m. Monday through Thursday and at 4:30 p.m. on alternating Fridays.

What will an ADU permit cost in La Mirada?

The city's Building Code Fee Schedule adds a $45.99 permit issuance fee to every building permit, and inspection of a Group R or U occupancy use is $364.33. Inspections outside normal business hours run $163.51 per hour. A geotechnical site review is $687.15, and a full geotechnical report, site and plan review is 0.50 percent of valuation with a $1,695.70 minimum and a $10,932.24 maximum. The city's valuation table sets a $250.89 minimum plan check fee for a standard plan and prices a combined permit for a one-family or two-family dwelling with attached garages at 1.6 times the building permit fee. The city's planning fee schedule lists a $113.00 zoning clearance or plan check application, $292.00 site plan review and a $355.00 zoning letter, with building plan review and building permit priced at the LA County fee schedule plus 15 percent overhead and general plan maintenance at 5.5 percent of the permit cost.

How much does an ADU cost in La Mirada?

L Square's published prefab ADU prices start at $180,000 for the 600 sq ft unit, $240,000 at 800 sq ft, $295,000 at 1,000 sq ft and $354,000 for the 1,200 sq ft unit. These are starting prices for the design-build scope, not a quote for a specific lot. Permit fees, plan check, utility work and site conditions move the final number. CSLB license number is 1095476.

What should I check before building an ADU in La Mirada?

Three items decide whether a La Mirada lot works. First, which county plan check office handles the project, since the city sends plans to Norwalk or Alhambra. Second, whether the county asks for a geotechnical review, which starts with a $687.15 site review and can add a report fee. Third, utilities and impact fees: under Section 66311.5(c)(1) an ADU of 750 sq ft or less carries no impact fee, and anything larger is charged proportionally to the primary dwelling. La Mirada's 2021 to 2029 Housing Element records 71 ADU permits issued between 2018 and 2022, with 33 in 2022 alone, and describes an Affordable Accessory Dwelling Unit Program that rebates planning and building fees when the owner signs a 10 year restrictive covenant. The city's Building and Safety counter is at 13700 La Mirada Boulevard.

Official La Mirada ADU sources

• The La Mirada Building and Safety Division states that the city contracts with the County of Los Angeles to provide Building and Safety services including engineering, that building and structural plan checks are performed at the county South Whittier District office at 12440 Imperial Highway, Suite 110 in Norwalk and the county central office at 900 S. Fremont Avenue, 3rd Floor in Alhambra, and that the city uses the 2022 California Building Code with the Los Angeles County 2023 Amendment. Official source
• The City of La Mirada Building Code Fee Schedule effective July 1, 2025 lists a permit issuance fee of $45.99 to be paid in addition to the other fees, $364.33 for inspection of any use, occupancy or change in use of Group R or U occupancy, $163.51 per hour for inspections outside normal business hours, a geotechnical site review of $687.15, and a geotechnical report, site and plan review fee of 0.50 percent of valuation with a minimum of $1,695.70 and a maximum of $10,932.24. Official source
• The City of La Mirada Community Development Department Fee Schedule lists a Zoning Clearance/Plan Check Application of $113.00, Site Plan Review of $292.00 and a Zoning Letter of $355.00, and states that Building Plan Review, Building Permit Inspection, Building Related Services and Building Permit are the LA County Fee Schedule plus 15 percent for building overhead under Resolution 09-03, with General Plan Maintenance at 5.5 percent of the actual building permit cost under Resolution 05-28. Official source
• The City of La Mirada Building Valuation Fee Table effective July 1, 2025 states that a permit issuance fee of $45.99 shall be added to all building permit fees, that a combined building permit for a one-family or two-family dwelling and attached garages shall be 1.6 times the building permit fee under Sections 106.5.6 and 107.1, and that the minimum plan check fee for a standard plan is $250.89. Official source
• The City of La Mirada 2021 to 2029 Housing Element records 71 ADU building permits issued between 2018 and 2022, with 6 in 2018, 8 in 2019, 9 in 2020, 15 in 2021 and 33 in 2022 for an average of 14.2, states the city expects to produce around 15 ADUs per year or 120 ADUs over the eight year planning period, and describes a proposed expanded Affordable Accessory Dwelling Unit Program that rebates all Planning and Building Fees upon execution of a restrictive covenant renting to qualified low and very low income tenants for the first 10 years. Official source
• California Government Code Section 66317(a)(2) requires a written completeness determination within 15 business days of submittal, and Section 66317(a)(3) gives the permitting agency 60 days from receipt of a complete application to approve or deny, with the application deemed approved if the 60 day clock runs out without an applicant-requested delay. Official source
• California Government Code Section 66314(d)(5) caps the total floor area of a detached accessory dwelling unit at 1,200 square feet, Section 66314(d)(7) allows a setback of no more than four feet from the side and rear lot lines, Section 66314(d)(10)(A) limits parking requirements to no more than one space per ADU or per bedroom, and Section 66314(d)(11) bars a local agency from requiring replacement parking when a garage, carport, covered parking structure or uncovered parking space is demolished for an ADU. Official source
• California Government Code Section 66311.5(c)(1) prohibits a local agency, special district or water corporation from imposing any impact fee on an accessory dwelling unit with 750 square feet of interior livable space or less or on a junior accessory dwelling unit with 500 square feet or less, and requires impact fees on a larger ADU to be charged proportionately against the square footage of the primary dwelling. Official source
• California Government Code Section 66321(b)(4)(A) requires a local agency to allow at least a height of 16 feet for a detached accessory dwelling unit on a lot with an existing or proposed single family dwelling, and Section 66321(b)(3) requires the agency to permit an accessory dwelling unit with at least 800 square feet of interior livable space and four-foot side and rear yard setbacks under all other local development standards. Official source
• California Government Code Section 66313(d) defines a junior accessory dwelling unit as a unit no more than 500 square feet of interior livable space contained entirely within a single-family residence, and Section 66325(a) provides that the ADU article supersedes a conflicting local ordinance. Official source
• California Government Code Section 66325(a) provides that the state ADU article supersedes a conflicting local ordinance, while Section 66325(b) preserves the authority of local agencies to adopt less restrictive ADU requirements. Official source