ADU Builder in Hermosa Beach, CA: City Rules, Fees and Permits

What are the ADU rules in Hermosa Beach?

Hermosa Beach put its ADU rules in Municipal Code Chapter 17.21 and rebuilt that chapter with Ordinance No. ORD-26-1498, adopted on March 24, 2026 and effective thirty days after adoption, to match state ADU law as amended effective January 1, 2026. The Department of Housing and Community Development reviewed the new ordinance on April 14, 2026 and wrote on May 8, 2026 that it is substantially compliant with state ADU law, and it closed its review under Government Code sections 66310-66342. The city's summary of the earlier chapter revision, Ordinance No. ORD-24-1484, adopted in January 2025, set a uniform 20 foot height limit for detached ADUs in the city and stopped the city from making you replace an uncovered parking space that is removed for a unit. That same ordinance stops the city from denying an ADU or JADU built before January 1, 2020 unless correcting the violation is needed to meet Health and Safety Code section 17920.3. The 2026 rewrite replaced that chapter in its entirety, so confirm the current numbers with the Planning Division before you design.

How big can an ADU be in Hermosa Beach?

State law sets the size floor and the ceiling. Government Code Section 66314 caps a detached accessory dwelling unit at 1,200 square feet and limits an attached unit to 50 percent of the existing primary dwelling. Section 66321 stops the city from setting a maximum unit size below 850 square feet of interior livable space, or 1,000 square feet for a unit with more than one bedroom, and requires the city to allow a unit with at least 800 square feet of interior livable space and four-foot side and rear yard setbacks. It also requires a detached height of 16 feet, or 18 feet within one-half of one mile walking distance of a major transit stop. Section 66323 adds that the city must ministerially approve one ADU and one junior ADU on a lot with a proposed or existing single-family dwelling when the unit sits inside the dwelling or an existing accessory structure, with an expansion of not more than 150 square feet, plus one detached new build unit that meets four-foot side and rear yard setbacks.

How long does an ADU permit take in Hermosa Beach?

State law sets the clock. Government Code Section 66317 gives a city 15 business days to tell you in writing whether your application is complete and 60 days to approve or deny a complete application, and a complete application the city has not acted on inside that window is treated as approved, with the clock stopped while you ask for more time. The city runs its own process on top of that. Hermosa Beach moved applications onto an online permit portal, and starting October 1, 2026 portal applications have to be submitted online by the applicant or an authorized representative. Submittals are reviewed concurrently by Planning, Building, and Public Works, and the city offers a separate Preliminary Planning Review that gives one review and one round of Planning comments before the concurrent review starts. Plan check fees have to be paid before the city will route an application for review, and every resubmittal needs revised plans, a written response to each city comment, and clouded changes.

What does Hermosa Beach charge for an ADU permit?

The city sets ADU fees in the Master Fee Schedule that took effect July 1, 2026. Its building permit table charges an Accessory Dwelling Unit or JADU on an existing structure at $2,187.00 and a new one at $3,054.00, and it lists building permit issuance as included in other permit fees. Plan check is charged at 80 percent of the building permit fee, and expedited plan check is priced at 150 percent of the standard plan check fee. Utility and impact fees follow state limits. Government Code Section 66311.5 says no impact fee may be charged on an ADU of 750 square feet of interior livable space or less, or on a junior ADU of 500 square feet or less, and any impact fee above 750 square feet has to be charged in proportion to the square footage of the primary dwelling. A sewer connection fee is collected by Los Angeles County for the services the city does not run itself.

How much does an ADU cost in Hermosa Beach?

L Square publishes six configured prefab model prices on its Orange County cost page, and they are the honest place to start a budget. The 600 square foot unit with 2 bedrooms and 1 bath is $180,000, the two 800 square foot units with 2 bedrooms and 2 baths are $240,000 each, the two 1,000 square foot units with 3 bedrooms and 2 baths are $295,000 each, and the 1,200 square foot unit with 3 bedrooms and 2 baths is $354,000. Those are configured model prices for a factory built shell and interior, not a quote for your lot. Site work, utility routing, foundation design, permits and finish choices are priced per property, and the city fees above sit on top of them.

What should I check before you build an ADU in Hermosa Beach?

Three checks decide whether a Hermosa Beach lot can hold a unit. First, the Coastal Zone. The city's local coastal plan says the Coastal Zone covers about 43 percent of Hermosa Beach land area, includes two miles of sandy shoreline, and reaches inland to Ardmore Avenue, and the city says new development that increases floor area more than 10 percent or height more than 10 percent, or affects coastal resources, may need a Coastal Development Permit from the California Coastal Commission after the city approves the proposal in concept, so check the zoning map for your address. Second, the building code. Hermosa Beach adopted the 2025 California Building Standards Codes effective January 1, 2026, and a project vests to the code edition in force when a complete building permit application and plan submittal are received. Third, the paperwork. Completeness at the city requires all required plans and supporting documents, fully completed permit forms, and full payment of building plan review fees, and online payments need 2 to 3 business days for staff to process.

Official Hermosa Beach ADU sources

• The city's Accessory Dwelling Units page defines an ADU as a secondary residential unit located on the same lot as a primary single-family or multifamily home, says an ADU is not for short-term rental and that the minimum rental period is 30 days, and says Hermosa Beach ADU regulations are in the Municipal Code in Chapter 17.21. Official source
• The city adopted Ordinance No. ORD-26-1498 on March 24, 2026, repealing and replacing Chapter 17.21 of the Hermosa Beach Municipal Code on accessory dwelling units and junior accessory dwelling units, and says amendments to California ADU law effective January 1, 2026 required the update so the city could avoid statutory preemption. Official source
• The city says Ordinance No. ORD-24-1484 amends Chapter 17.21 to comply with state law, prohibits the city from denying an ADU or JADU constructed before January 1, 2020 unless correcting a violation is needed to meet Health and Safety Code section 17920.3, prohibits requiring replacement parking when an uncovered parking space is demolished for or replaced with an ADU, and sets a uniform 20 foot height limit for detached ADUs in the city. Official source
• The city Master Fee Schedule building permit table, effective 7-1-2026, lists Accessory Dwelling Unit or JADU (Existing) at $2,187.00 and Accessory Dwelling Unit or JADU (New) at $3,054.00, lists Building Permit Issuance as included in other permit fees, and states that plan check fees are 80% of the Building Permit fee and that the expedited plan check fee is 150% of the standard plan check fee. Official source
• The city's Application and Submittal Process page says that beginning October 1, 2026 applications available through the Online Permit Portal must be submitted online by the applicant or the applicant's authorized representative, that project submittals are reviewed concurrently by Planning, Building and Public Works, that the Preliminary Planning Review service includes one review and one round of Planning comments, and that plan check fees must be paid before the city can begin routing an application for review. Official source
• The city's Applications, Forms, Maps and Handouts page says the city adopted the 2025 California Building Standards Codes effective January 1, 2026, that a project vests to the building code edition in effect when a complete building permit application and building plan submittal are received, that completeness requires all required plans and supporting documents, fully completed permit forms and full payment of building plan review fees, and that online payment needs 2 to 3 business days for staff to process. Official source
• The city's Local Coastal Plan page says the Coastal Zone of Hermosa Beach represents approximately 43% of the city's land area and includes two miles of sandy shoreline, that the Coastal Zone extends inland to Ardmore Avenue, and that new development which increases floor area more than 10%, increases height more than 10%, or affects coastal resources may require a Coastal Development Permit with the California Coastal Commission after the city has approved the proposal in concept. Official source
• The city's 2021-2029 Housing Element page says the City Council adopted PLAN Hermosa, the city's General Plan, in August 2017, that HCD issued a findings letter on August 1, 2024 finding the city's Housing Element and accompanying rezoning in substantial compliance with state law, and that the Council approved the second reading of zoning text changes, Ordinance 24-1481, on July 23, 2024. Official source
• The Department of Housing and Community Development wrote on May 8, 2026 that it reviewed the city's Ordinance No. 26-1498, adopted on March 24, 2026, on April 14, 2026, and determined that the ordinance is substantially compliant with State ADU Law, and that HCD considers the matter of compliance with Government Code sections 66310-66342 closed. Official source
• In a December 29, 2025 findings letter on the city's Ordinance No. 1484, HCD wrote that the city had up to 30 days to respond and had to provide a written response no later than January 30, 2026 with a plan to either amend the ordinance or adopt a resolution with findings, and found the ordinance did not comply in five areas, including a limit of no more than two units on a lot with a single-family primary dwelling, a deed restriction requirement, an incomplete recreation of the Government Code section 66321 size exceptions, and architectural requirements. Official source
• California Government Code Section 66317 requires a permitting agency to give written notice of whether an accessory dwelling unit application is complete no later than 15 business days after receiving it, to approve or deny a completed application within 60 days, to treat a completed application it has not acted on in that time as approved, and to toll the 60 days while the applicant requests a delay. Official source
• California Government Code Section 66314 provides that the total floor area for a detached accessory dwelling unit shall not exceed 1,200 square feet, that an attached accessory dwelling unit shall not exceed 50 percent of the existing primary dwelling, that parking shall not exceed one space per unit or per bedroom whichever is less, and that a local agency shall not require off-street parking spaces to be replaced when a garage, carport, covered parking structure or uncovered parking space is demolished in conjunction with an accessory dwelling unit. Official source
• California Government Code Section 66321 provides that a local agency shall not set a maximum accessory dwelling unit size below 850 square feet of interior livable space, or 1,000 square feet for a unit that provides more than one bedroom, must permit an accessory dwelling unit with at least 800 square feet of interior livable space and four-foot side and rear yard setbacks, and must allow a height of 16 feet for a detached unit and 18 feet within one-half of one mile walking distance of a major transit stop. Official source
• California Government Code Section 66311.5 provides that a local agency shall not impose any impact fee upon the development of an accessory dwelling unit that has 750 square feet of interior livable space or less or a junior accessory dwelling unit that has 500 square feet or less, and that impact fees charged for a larger accessory dwelling unit must be charged proportionately in relation to the square footage of the primary dwelling unit. Official source
• California Government Code Section 66315 provides that no additional standards, other than those provided in Section 66314, shall be used or imposed, including an owner occupant requirement, except that a local agency may require that the property may be used for rentals of terms 30 days or longer. Official source
• California Government Code Section 66323 requires a local agency to ministerially approve an application for a building permit to create one accessory dwelling unit and one junior accessory dwelling unit per lot with a proposed or existing single-family dwelling where the unit is within the proposed space of the dwelling or the existing space of the dwelling or accessory structure, with an expansion of not more than 150 square feet, and one detached new construction accessory dwelling unit that does not exceed four-foot side and rear yard setbacks. Official source
• The Department of Housing and Community Development's ADU Handbook states that a local agency cannot impose an owner-occupancy requirement on an ADU under Government Code section 66315, that owner occupancy is required for a junior ADU that shares sanitation facilities with the primary structure under section 66333, that maximum unit size requirements must allow an ADU of at least 850 square feet of interior livable space, or 1,000 square feet of interior livable space for ADUs with more than one bedroom, and that rentals of 66323 ADUs and JADUs must be for terms longer than 30 days. Official source