California ADU rules · Los Angeles County
Can I Build an ADU in Hermosa Beach?
Yes — you can build an ADU in Hermosa Beach. California's statewide ADU law requires every city, including Hermosa Beach, to approve a qualifying accessory dwelling unit by right, plus a junior ADU (JADU) on a single-family lot. What varies city to city are the local specifics below.
Can you build one?
ADUs allowed
CA state lawYes — by right
ADUs and JADUs are allowed by right in all residential and mixed-use zones; ministerial approval, no hearing.
Units on a single-family lot
CA state law1 ADU + 1 JADU
At least one ADU and one JADU per single-family lot (a conversion ADU may also be possible).
Units on a multifamily lot
CA state lawConversion ADUs (≥1, up to 25% of units) + up to 8 detached
Conversions of non-livable space (at least 1, or up to 25% of existing units) plus up to 8 detached ADUs on a lot with existing multifamily — never exceeding the number of existing units. JADUs are single-family only.
Junior ADU (JADU)
CA state lawAllowed
Up to 500 sq ft, within the walls of an existing single-family home (single-family lots only).
Size & height
Max detached ADU size
Local rule1,000 sq ft
Hermosa Beach splits ADUs into Class 1 (state-exempt, Gov. Code § 66323 — a detached ADU ≤800 sq ft, conversions, etc., approved with a building permit only) and Class 2 (locally regulated). A Class 2 ADU is capped at 850 sq ft for a studio/1-bedroom unit and 1,000 sq ft for a 2+-bedroom unit, and an attached Class 2 ADU is further limited to 50% of the primary dwelling. The 800 sq ft Class 1 by-right ADU remains protected regardless of these caps.
Max attached ADU size
Local ruleClass 2: ≤850 sq ft (studio/1-BR) or ≤1,000 sq ft (2+ BR), and attached additionally ≤50% of the primary dwelling. State floors (800 sq ft; 850/1,000 sq ft attached) still control via the Class 1 pathway.
Guaranteed minimum size
CA state law800 sq ft
An 800 sq ft ADU must be allowed regardless of FAR/lot-coverage caps; a city also cannot cap an attached ADU below 850 sq ft (1,000 for 2+ bedrooms).
Max JADU size
CA state law500 sq ft
Max height
Local rule16 ft
Detached ADU: 16 ft base, 18 ft within ½ mi of a major transit stop, up to 20 ft to match the primary dwelling roof pitch; an attached ADU may reach 25 ft or the underlying zone limit, whichever is lower. The city does not provide an above-garage two-story detached path, so a standalone two-story detached ADU is effectively not buildable — two-story height requires an attached ADU within a two-story primary residence.
Setbacks
Side setback
CA state law4 ft
A city cannot require more than 4 ft side or rear setback; conversions of existing structures are exempt.
Rear setback
CA state law4 ft
Front setback
CA state lawNo front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone
Separation from main house
CA state lawNone required
No statewide separation requirement between the ADU and the primary dwelling.
Parking
Parking required
CA state lawUp to 1 space
At most 1 space per ADU (or per bedroom, whichever is less) — and waived in the common cases below.
Transit parking exemption
CA state lawYes — no parking required near transit & for conversions
No parking may be required within ½ mi walking distance of transit, in a historic district, for an ADU within an existing structure, within one block of car-share, or in certain permit-parking areas.
Garage-conversion replacement parking
CA state lawNot required
When a garage/carport is demolished or converted to build an ADU, replacement parking cannot be required.
Approval, timeline & cost
Approval path
CA state lawMinisterial (by right)
No public hearing or discretionary design review for a qualifying ADU.
Approval timeline
CA state law60 days
The agency must act within 60 days of a complete application — and the ADU is deemed approved if it does not.
Owner-occupancy
CA state lawOnly for a JADU
No owner-occupancy requirement for ADUs (the prior sunset was removed). A JADU may require owner-occupancy, principally where it shares sanitation with the main house.
Impact-fee waiver
CA state lawWaived under 750 sq ft
An ADU of 750 sq ft or less pays no impact fees (the 750 sq ft threshold itself is exempt under § 66311.5); larger ADUs pay fees proportional to the primary dwelling. JADUs (≤ 500 sq ft) are exempt.
Permits required
CA state lawBuilding permit
Only a ministerial building permit — no conditional use permit or discretionary design review for a qualifying ADU.
Hermosa Beach-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
California Coastal Zone
Hermosa Beach lies in the Coastal Zone. A Coastal Development Permit must be processed concurrently with the ADU building permit, and Coastal Act / Local Coastal Program resource-protection standards apply on top of state ADU law (HBMC § 17.21.040(C)(6)). The city's Class 2 development standards still apply within the Coastal Zone.
Privacy / window-screening standards
Class 2 ADU windows or doors within 30 ft of a property line generally must be clerestory (sill ≥6 ft above the finished floor) or use frosted/obscure glass, and direct lines of sight to adjoining residential property must be screened — a real design constraint on Hermosa Beach's dense small lots.
Pending HCD compliance corrections
HCD's Dec. 2025 review found the prior ordinance (Ord. 1484) non-compliant in several respects — unit allowances limited to two units on a single-family lot (state law requires allowing one conversion ADU + one detached ≤800 sq ft + one JADU), a JADU owner-occupancy clause, an ADU deed-restriction requirement, and an incomplete size-exception list. Ord. 26-1498 was adopted to respond; confirm the current unit-count and owner-occupancy text directly with Planning.
Hermosa Beach regulates ADUs in HBMC Chapter 17.21 (Ord. 26-1498, eff. April 23, 2026) using a Class 1 (state-exempt, Gov. Code § 66323) vs Class 2 (local) split. Class 2 ADUs are capped at 850/1,000 sq ft (attached also ≤50% of the primary), a standalone two-story detached ADU is effectively not buildable, and privacy window-screening rules apply. Because the whole city is in the Coastal Zone, a Coastal Development Permit runs concurrently with the building permit. HCD flagged the prior ordinance on unit count, JADU owner-occupancy, and a deed restriction; verify the current text with Hermosa Beach Community Development.
Frequently asked questions
Can I build an ADU in Hermosa Beach?
Yes. California's statewide ADU law requires Hermosa Beach to approve a qualifying accessory dwelling unit ministerial (by right), plus a junior ADU (JADU) on a single-family lot.
How big can an ADU be in Hermosa Beach?
A detached ADU of at least 1,000 sq ft must be allowed, and an ADU of 800 sq ft can never be zoned out by floor-area or lot-coverage limits. A JADU can be up to 500 sq ft.
What are the setback requirements for an ADU in Hermosa Beach?
Side and rear setbacks are limited to 4 ft. No front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone.
Is parking required for an ADU in Hermosa Beach?
Up to 1 space. No parking can be required within ½ mile of transit, for conversions, or for units inside the primary home. When a garage is converted, replacement parking is not required.
How long does ADU approval take in Hermosa Beach?
A complete application must be acted on within 60 days, with ministerial (by right) — no public hearing or discretionary design review for a qualifying ADU.
Do I have to live on the property to build an ADU in Hermosa Beach?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Hermosa Beach Mun. Code ch. 17.21 (Accessory Dwelling Units, Ord. 26-1498)
- HBMC § 17.21.070(A) (Class 2 size limits)
- HBMC § 17.21.070(A)(1)–(2)
- HBMC § 17.21.060(B) (height)
- HBMC § 17.21.040(C)(6)
- HBMC § 17.21.070(H)(6)–(7)
- HCD ADU ordinance-review findings, City of Hermosa Beach (Dec. 29, 2025)
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
- Cal. Gov. Code § 66314 (local ordinance standards)
- Cal. Gov. Code § 66315 (owner-occupancy)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated 2026-06-28. This is an AI-assisted summary of Hermosa Beach's ADU rules, drawn from its published ordinance and California ADU law — general information, not legal advice, and it may be incomplete or out of date. Verify the controlling rule for your specific parcel with Hermosa Beach Planning before relying on it.
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