If you own property in Los Angeles County and have been thinking about building an Accessory Dwelling Unit, 2026 is arguably the best year in history to do it. Owner-occupancy requirements are gone. Parking mandates are largely eliminated. Permitting is now a ministerial process with a legally mandated 60-day review window. And the California Housing Finance Agency is offering qualifying homeowners up to $40,000 in pre-development cost assistance — essentially for free.
But "simplified" does not mean "simple." The regulatory framework governing ADUs in Los Angeles County is still a layered system of state law, county code, and city-specific ordinances — and the rules that apply to your property depend on whether you are in an unincorporated area of the county, within the City of Los Angeles, or within one of the 87 other incorporated cities in LA County. This guide cuts through that complexity, with specific attention to the three areas Skyline Builders serves: Mid Wilshire, West Los Angeles, and the South Bay (San Pedro and Long Beach).
1. What Is an ADU? Types and Definitions
An Accessory Dwelling Unit is a secondary residential unit on a single-family or multifamily residential lot. It has its own living space, sleeping area, kitchen, and bathroom — making it a fully independent dwelling. California law recognizes four distinct categories of ADU, each with different size limits, cost profiles, and regulatory requirements.
| ADU Type | Description | Max Size | Typical Cost Range |
|---|---|---|---|
| Detached ADU | A standalone structure separate from the primary home | 1,200 sq ft | $175,000 – $400,000+ |
| Attached ADU | An addition physically connected to the primary home | 50% of primary home, max 1,200 sq ft | $140,000 – $280,000 |
| Garage Conversion ADU | An existing garage converted into a living unit | Existing garage footprint | $65,000 – $130,000 |
| Junior ADU (JADU) | A unit created within the existing walls of the primary home | 500 sq ft maximum | $40,000 – $100,000 |
2. State Law vs. Local Ordinance: Who Controls What
California state law — primarily Government Code Sections 65852.2 and 65852.22 — establishes a floor of rights that every city and county must honor. Local jurisdictions can add requirements on top of state law, but they cannot impose rules that are more restrictive than what state law permits. If a local ordinance conflicts with state ADU law, the state law prevails.
"A local agency shall ministerially approve an application for a building permit to create an accessory dwelling unit or junior accessory dwelling unit within 60 days from the date the local agency receives a completed application."
— California Government Code § 65852.2(a)(3)
For homeowners in unincorporated Los Angeles County, the applicable code is the LA County ADU Ordinance (Title 22). For homeowners within the City of Los Angeles, the applicable code is the LA City ADU Ordinance (LAMC Section 12.22 A.33). For homeowners in Long Beach, Torrance, Culver City, or other incorporated cities, each city has its own ordinance — though all must comply with state minimums.
3. Permitted Locations and Zoning Eligibility
Under California state law, ADUs are permitted by right on any lot zoned for single-family residential use that contains an existing or proposed single-family dwelling. "By right" means the city or county cannot deny an ADU application based on neighborhood character, design review, or discretionary judgment. If your project meets the objective standards, it must be approved.
Multifamily properties have different ADU rights. State law allows one detached ADU per multifamily lot (new construction), plus conversion of non-livable space within an existing multifamily structure into ADUs at a rate of up to 25% of existing units. Senate Bill 9 (effective January 2022) further allows homeowners on single-family lots in urban areas to split their lot into two parcels and build a duplex on each — potentially accommodating up to six units on a single original lot.
4. Size, Height, and Setback Requirements
State law establishes the following minimum size allowances. Local jurisdictions may allow larger units but cannot impose minimums that effectively prohibit ADUs.
| ADU Type | Max Size | Min Allowed (State Law) |
|---|---|---|
| Detached ADU | 1,200 sq ft | No minimum imposed by state |
| Attached ADU | 50% of primary, max 1,200 sq ft | No minimum imposed by state |
| Junior ADU (JADU) | 500 sq ft | Must be within existing walls |
| Studio / 1-BR ADU | — | Cannot be denied if ≥ 150 sq ft (studio) or ≥ 850 sq ft (1-BR) |
The City of Los Angeles and LA County both allow detached ADUs up to 25 feet in height (approximately two stories) in most residential zones. In hillside areas or Very High Fire Hazard Severity Zones, additional height and design requirements may apply.
Setbacks are the minimum distances an ADU must maintain from property lines. The 4-foot setback rule for new detached ADUs is a significant state-law provision that opened up thousands of lots previously ineligible under stricter local rules.
| ADU Type | Rear Setback | Side Setback | Front Setback |
|---|---|---|---|
| New Detached ADU | 4 feet | 4 feet | Must meet primary dwelling standards |
| Attached ADU | Same as primary dwelling | Same as primary dwelling | Same as primary dwelling |
| Garage Conversion | 0 feet (existing footprint) | 0 feet (existing footprint) | 0 feet (existing footprint) |
| JADU | 0 feet (within existing structure) | 0 feet | 0 feet |
5. Parking Requirements (and Exemptions)
State law has largely resolved the parking debate in favor of homeowners. No replacement parking is required when an ADU is created through the conversion of an existing garage, carport, or covered parking structure. No additional parking is required for an ADU in any of the following circumstances:
- The ADU is located within ½ mile walking distance of a public transit stop (bus stop or rail station)
- The ADU is located within a historic district
- The ADU is part of the existing primary residence or an existing accessory structure
- The property is located within one block of a car-share vehicle location
6. Owner-Occupancy: The Rule That No Longer Exists
Until January 1, 2020, California law allowed local jurisdictions to require that the property owner live on-site as a condition of ADU approval. That requirement is now gone. Neither the City of Los Angeles nor Los Angeles County can impose an owner-occupancy requirement for ADUs. Real estate investors, landlords with rental properties, and non-resident property owners can now build ADUs without any obligation to live on-site.
7. The Permitting Process: Timeline and Steps
Pre-Application & Feasibility
1–4 weeksSite feasibility assessment: lot configuration, setbacks, easements, utility connection points, soil conditions, and overlay zones. Typically included in the design-build contract at no additional cost.
Design & Plan Preparation
4–8 weeksConstruction documents prepared: site plan, floor plans, elevations, structural drawings, and MEP plans. Projects using pre-approved ADU plans (AB 1332) can compress this to 1–2 weeks.
Permit Application Submission
1 dayApplication submitted to LADBS (City of LA) or LA County Department of Public Works (unincorporated areas), with construction documents and applicable fees.
Plan Check & Approval
Up to 60 days (legally mandated)Ministerial review — no discretionary judgment. LADBS online portal and pre-approved plan programs can reduce this to 2–4 weeks for straightforward projects.
Construction
4–6 months (detached ADU)Licensed, insured crews build to code. Weekly progress updates and photo reports at each inspection milestone.
Final Inspection & Certificate of Occupancy
1–2 weeksBuilding department inspects at key milestones. Upon passing final inspection, a Certificate of Occupancy is issued — the legal document confirming the ADU is approved for habitation.
| Fee Type | City of LA | LA County (Unincorporated) |
|---|---|---|
| Plan check fee | $1,500 – $4,000 | $1,200 – $3,500 |
| Building permit fee | $2,000 – $6,000 | $1,800 – $5,500 |
| School fees | Waived for ADUs ≤ 500 sq ft | Waived for ADUs ≤ 500 sq ft |
| Total estimated fees | $4,000 – $12,000 | $3,500 – $10,000 |
8. Utility Connections and Fees
Every ADU requires independent utility connections for water, sewer, and electricity. The cost and complexity of these connections is one of the most frequently underestimated aspects of ADU construction.
Under state law (AB 670 and related legislation), water and sewer agencies cannot charge connection fees that are disproportionate to the ADU's projected demand. For ADUs under 750 square feet, many agencies are required to waive or significantly reduce connection fees. LADWP's current connection fees for ADUs are capped at approximately $1,500–$3,000 for standard residential service.
9. Financing Your ADU: Grants, Loans, and Programs
CalHFA ADU Grant Program
Covers pre-development costs including architectural design, engineering, permitting fees, and site preparation. Requires owner-occupancy at time of application and income eligibility (up to 120% AMI). Available on a first-come, first-served basis.
Home Equity Line of Credit (HELOC)
Often the most cost-effective option for homeowners with significant equity. Lower interest rates than construction loans; interest may be tax-deductible. Requires CLTV ratio of 80% or less.
Cash-Out Refinancing
Replaces existing mortgage with a larger one, providing the difference in cash. Effective when current rates are comparable to the homeowner's existing rate.
ADU-Specific Construction Loans
Converts to a standard mortgage upon ADU completion. More flexible underwriting than traditional construction loans. Several lenders now offer ADU-specific products.
Long Beach Backyard Builders Program
Provides free architectural plans, permit fee reductions, and technical assistance to qualifying Long Beach homeowners. Skyline Builders works directly with this program.
10. Key 2024–2026 Legislative Changes
Pre-Approved ADU Plans
Requires cities with populations over 100,000 — including the City of Los Angeles — to develop and offer a library of pre-approved ADU plans. Using a pre-approved plan can reduce design costs by $8,000–$20,000 and compress the plan check timeline from weeks to days.
Expanded Multifamily ADU Rights
Expanded the number of ADUs permitted on multifamily lots. Property owners can now convert up to 25% of existing units into ADUs through interior conversions of non-livable space, and can add multiple detached ADUs on larger multifamily lots.
Height and Design Clarifications
ADUs located within ½ mile of transit can be built up to 25 feet in height regardless of the primary dwelling's height limit. Local jurisdictions cannot impose design standards that add more than 10% to the project cost.
VHFHSZ Construction Standards
Properties in Very High Fire Hazard Severity Zones now require enhanced fire hardening for new ADU construction: Class A fire-rated roofing, ember-resistant vents, dual-pane windows, and non-combustible exterior cladding. Applies to portions of hillside West LA and parts of the South Bay.
11. District-Specific Notes
Mid Wilshire encompasses Koreatown, Hancock Park, Windsor Square, and the Miracle Mile. Lots typically run 5,000–7,500 sq ft. The most common ADU type is the garage conversion, given the prevalence of detached rear garages and relatively small lot sizes. The area is well-served by Metro Rail (Purple Line, Expo Line), meaning most properties qualify for the transit proximity parking exemption. Homeowners in Koreatown should be aware that the City of LA's Rent Stabilization Ordinance (RSO) may apply to new ADUs in certain circumstances — Skyline Builders can advise during the consultation.
West LA — encompassing Brentwood, Westwood, Culver City, and Mar Vista — is characterized by higher property values, larger lots (6,000–10,000 sq ft), and homeowners who expect premium finishes. The most common ADU type is the detached ADU, often positioned at the rear of the lot above a new or existing garage. Culver City has its own ADU ordinance with specific design guidelines encouraging contemporary architecture. The Expo Line and multiple bus rapid transit routes provide transit proximity exemptions for most properties.
The South Bay presents a distinct market with strong multigenerational living traditions and active municipal ADU incentive programs. Long Beach is particularly notable for its Backyard Builders program — free pre-approved ADU plans, reduced permit fees, and technical assistance. Long Beach's online permitting portal has reduced plan check times to as little as 2 weeks for standard projects. San Pedro (City of LA jurisdiction) may have industrial overlay zones or coastal zone regulations on some properties that require additional review.
12. Common Mistakes Homeowners Make
Assuming the permit process is faster than it is
Even with the 60-day mandate, the total timeline from design start to permit issuance is typically 8–16 weeks for a custom ADU. Homeowners who begin construction before permits are issued risk stop-work orders, fines, and the cost of demolishing unpermitted work.
Underestimating utility connection costs
A new water meter, sewer lateral, and electrical service connection can add $15,000–$40,000 to a project budget, depending on the distance from the main lines. These costs should be included in any honest project estimate.
Choosing a contractor without ADU-specific experience
ADU permitting requires knowledge of state law, local ordinances, and the specific requirements of each building department. A generalist contractor who has never pulled an ADU permit will encounter delays, corrections, and surprises that an experienced ADU specialist would avoid.
Ignoring the CalHFA grant
Thousands of eligible homeowners in LA County leave $40,000 in free pre-development assistance unclaimed simply because they are unaware of the program. Any homeowner who meets the income eligibility requirements should apply before spending money on design or permits.
Designing without considering the rental market
An ADU that is too large, too small, or poorly configured for the local rental market will underperform financially. Skyline Builders provides rental market analysis as part of the design consultation.
13. Frequently Asked Questions
Q.Can I build an ADU on my property if I have an HOA?
HOAs cannot prohibit ADU construction under California Civil Code Section 4751. An HOA may impose reasonable design standards (exterior materials, colors, landscaping) but cannot outright ban ADUs or impose standards that effectively preclude construction.
Q.Can I use my ADU as a short-term rental (Airbnb, VRBO)?
The City of Los Angeles and most other LA County jurisdictions restrict short-term rentals to the homeowner's primary residence. An ADU on a property where the owner does not reside cannot generally be used as a short-term rental. Long-term rentals (30+ days) are unrestricted.
Q.Do I need to pay school fees for my ADU?
School fees are waived for ADUs that are 500 square feet or smaller. For ADUs larger than 500 square feet, school fees apply at the standard residential rate, which varies by school district.
Q.Can I sell my ADU separately from my primary home?
Under current law, ADUs cannot be sold separately from the primary dwelling on a single-family lot. Senate Bill 9 lot splits offer a partial workaround for some properties, but the rules are complex. This is expected to remain an area of legislative activity in 2026 and beyond.
Q.How long does the entire ADU project take from start to finish?
For a standard detached ADU, the realistic timeline is: design (4–8 weeks) + permitting (8–16 weeks) + construction (16–24 weeks) = 28–48 weeks total, or roughly 7–12 months. Garage conversions and JADUs are faster: typically 4–7 months from design start to Certificate of Occupancy.