The Complete ADU & Secondary Dwelling Guide for Los Angeles (2026)

An accessory dwelling unit (ADU) is a second, self-contained home on a residential lot, with its own entrance, kitchen, bathroom, and sleeping area. In Los Angeles in 2026, most single-family lots can add at least one ADU and one Junior ADU, a detached unit can be up to 1,200 square feet, and a typical project costs $150,000 to $400,000 and takes 12 to 18 months from first sketch to move-in. ACG plans and builds these projects through our ADU construction services.

This guide is the starting point for homeowners across our Los Angeles service area. It covers the types of ADUs, the rules that apply this year, realistic costs and financing, the permit and construction process, and what to know before you rent the unit out. Where a topic deserves more depth, we link to a dedicated guide.

Key Takeaways

• What you can build: a detached ADU up to 1,200 sq ft, an attached ADU up to 50% of the main home (1,200 sq ft maximum), or a Junior ADU up to 500 sq ft inside the existing house.
• Core rules: 4-foot side and rear setbacks, a 16-foot height limit for most detached units (18 feet near transit), and no parking required in many locations.
• Owner occupancy: not required for ADUs. Since January 1, 2026, a JADU needs an owner on site only if it shares a bathroom with the main house.
• Cost: about $150,000 to $220,000 for a garage conversion and $200,000 to $450,000 or more for a new detached unit, plus soft costs and contingency.
• Approval: ADUs are approved ministerially, with a 15-business-day completeness check and a decision within 60 days of a complete application.
• Renting: leases must be longer than 30 days. Short-term rental of a newer ADU is effectively not allowed in the City of Los Angeles.

What Is an ADU? Types and Definitions

An ADU, also called a granny flat, in-law suite, backyard home, or secondary dwelling, is a permanent residential unit that sits on the same lot as a primary home. Los Angeles recognizes several types, and the type you choose sets the budget, the timeline, and which rules apply.

ADU type	Maximum size	Where it goes	Typical cost	Best for
Detached ADU	1,200 sq ft	Separate structure in the yard	$200,000 – $450,000+	Privacy and rental income
Attached ADU	50% of main home, up to 1,200 sq ft	Addition sharing a wall with the house	Slightly below a detached unit of the same size	Lots with limited yard space
Garage conversion	Existing garage footprint	Converted attached or detached garage	$150,000 – $220,000	Lowest-cost full ADU
Junior ADU (JADU)	500 sq ft	Inside the walls of the existing home	$50,000 – $100,000	Family use, lowest entry cost

Detached ADUs are freestanding buildings. They offer the most privacy and usually the highest rent, and they cost the most because they need a new foundation, structure, roof, and utility runs. Attached ADUs share at least one wall with the main house and have their own entrance. Our comparison of detached vs. attached ADUs explains how the two differ on cost, privacy, and yard use.

Conversion ADUs reuse an existing structure, most often a garage. Because the slab, walls, and roof are already there, this is usually the fastest and least expensive route to a full unit. See our garage conversion ADU guide for details.

Junior ADUs are created within the existing walls of a single-family home, including an attached garage. A JADU needs an efficiency kitchen and its own entrance, and it can either share a bathroom with the main house or have its own.

Los Angeles ADU Rules and Zoning in 2026

ADU rules in Los Angeles come from two layers: California state law, which sets minimum rights that every city must honor, and the City of Los Angeles ordinance, which adds local detail. State law has been amended almost every year since 2019. The table summarizes what applies now.

Rule	What applies in 2026
Units on a single-family lot	At least one ADU and one JADU. State law can also allow a conversion ADU and a new detached ADU of up to 800 sq ft on the same lot.
Units on a multifamily lot	Up to 8 detached ADUs, capped at the number of existing units, plus conversions of non-livable space such as storage rooms and garages (SB 1211).
Maximum size	Detached: 1,200 sq ft. Attached: 50% of the primary home, up to 1,200 sq ft. JADU: 500 sq ft. Since 2026, size is measured as interior livable space (SB 543).
Guaranteed minimum	An 800 sq ft ADU with 4-foot side and rear setbacks must be allowed even if lot coverage or floor area limits would otherwise block it.
Setbacks	4 feet from side and rear property lines for new construction. No additional setback for converting an existing legal structure.
Height	Detached: 16 feet, or 18 feet within a half mile of a major transit stop, plus 2 feet to match the main roof pitch. Attached: up to 25 feet or the zone limit, whichever is lower.
Parking	None required within a half mile walking distance of public transit, in historic districts, or for conversions. No replacement parking when a garage is converted.
Owner occupancy	Not required for ADUs (AB 976). For a JADU, required only if it shares a bathroom with the main house (AB 1154).
Approval	Ministerial review with no public hearing. Completeness check within 15 business days and a decision within 60 days of a complete application.
Impact fees	No impact fees for ADUs under 750 sq ft. Larger units pay fees proportional to their size.

Some properties face extra conditions. Lots in hillside areas and Very High Fire Hazard Severity Zones can generally still build, with added requirements covered in our guide to ADUs in hillside and fire hazard zones. Homes in Historic Preservation Overlay Zones and the Coastal Zone go through additional review. Owners of apartment buildings should read our guide to multifamily ADUs in Los Angeles.

Two other state laws are worth knowing. AB 2533 created a path to legalize unpermitted ADUs built before 2020. AB 1033 lets cities allow ADUs to be sold separately as condominiums, but only where the city has adopted a local ordinance, so confirm the current status with Los Angeles City Planning before counting on it.

How Much Does an ADU Cost in Los Angeles?

Most ADUs in Los Angeles cost between $150,000 and $400,000 to build in 2026, and large or high-finish detached units can exceed $450,000. New detached construction generally works out to roughly $350 to $500 or more per square foot. Smaller units cost more per square foot because every ADU needs a kitchen, a bathroom, and utility connections regardless of size.

ADU type	Typical total cost	What drives the range
Garage conversion	$150,000 – $220,000	Existing slab and structure lower the cost; utilities, insulation, and egress still required.
Small detached (400–500 sq ft)	$200,000 – $280,000	New foundation, full utility runs, one bedroom and one bath.
Mid-size detached (600–800 sq ft)	$280,000 – $380,000	Two bedrooms, full kitchen, larger HVAC and electrical loads.
Large detached (800–1,200 sq ft)	$330,000 – $450,000+	Multiple bedrooms, higher finish level, larger foundation and roof.

Budget soft costs separately. Architectural design typically runs $4,000 to $14,000, structural engineering $1,000 to $5,000, permits and plan check $3,000 to $11,000, and utility connections $3,600 to $7,200. Add a contingency of 10% to 15%. Hillside lots, long utility trenches, electrical panel upgrades, and sewer lateral replacement are the items that most often push a project above its first estimate.

For a full breakdown by line item, see what really drives ADU cost in Los Angeles.

Financing an ADU

Most homeowners pay for an ADU with home equity or a construction loan. Rates change with the market, so treat these as a starting point.

Option	Typical rate (2026)	Best for
HELOC	About 7.0% – 7.5%, variable	Owners with a low first-mortgage rate who want to draw funds in stages.
Home equity loan	About 7.0% – 8.0%, fixed	A fixed project cost and a predictable payment.
Cash-out refinance	Near current mortgage rates	Owners whose existing rate is already close to market.
Construction loan	About 7.5% – 9.5% during the build	Ground-up builds, often underwritten on the after-completion value.

One correction to older guides, including the previous version of this one: the CalHFA ADU Grant of up to $40,000 is not currently available. Its funding was fully allocated in December 2023 and no new round has been confirmed. Do not build it into your budget. Our ADU financing guide compares every option in detail.

The ADU Process: Permits, Timeline, and Phases

From first consultation to move-in, a ground-up ADU in Los Angeles typically takes 12 to 18 months. Garage conversions and JADUs are faster. The work falls into six phases.

Phase	Typical duration	What happens
1. Feasibility	2 – 4 weeks	Site visit, zoning check, utility review, ADU type and budget decided.
2. Design and construction documents	2 – 3 months	Floor plans, elevations, structural engineering, Title 24 energy report.
3. Permitting	2 – 4 months	Submission to LADBS, plan check, corrections, permit issued.
4. Site work and foundation	1 – 2 months	Demolition, grading, utility trenching, foundation.
5. Framing, systems, and finishes	3 – 5 months	Framing, roofing, plumbing, electrical, HVAC, insulation, drywall, finishes.
6. Final inspections	1 – 2 weeks	Final sign-offs and Certificate of Occupancy.

State law requires the city to act on a complete ADU application within 60 days, and since January 2026 it must tell you within 15 business days whether the application is complete. In practice the permit phase runs longer than 60 days, because the clock pauses each time plans go back for corrections. A complete, well-coordinated first submission is the best way to shorten it. Los Angeles also runs an ADU Standard Plan Program with pre-approved designs that can reduce plan check time. For more on timing, see how long a building permit takes in Los Angeles, and for a step-by-step walkthrough read how to build an ADU in Los Angeles.

Design and Planning Considerations

Good ADU design balances livability, cost, and compliance on a specific site. Four decisions matter most.

• Site analysis. Topography, utility locations, mature trees, and easements determine where the unit can go. On sloped lots, a stepped design that follows the grade usually costs less than heavy excavation.
• Architectural fit. An ADU does not need to copy the main house, but complementary rooflines, materials, and proportions make the property read as a whole and protect resale value.
• Space efficiency. Open plans, built-in storage, and well-placed windows make a 500-square-foot unit feel generous. Vaulted ceilings add volume without adding footprint where the height limit allows.
• Privacy. Window placement, entry location, and landscape screening protect both households and reduce friction with neighbors.

If your main goal is more space for your own household instead of a separate unit, compare the two paths in our ADU vs. home addition guide.

Renting Out Your ADU: Income and Rules

Rental income is the main reason many owners build. The figures below are planning estimates for a one-bedroom ADU. Check current listings in your own neighborhood before relying on them.

Area	Estimated monthly rent	Estimated annual income
Santa Monica	$2,800 – $3,800	$33,600 – $45,600
West LA / Brentwood	$2,500 – $3,500	$30,000 – $42,000
Culver City	$2,300 – $3,200	$27,600 – $38,400
Pasadena	$2,200 – $3,000	$26,400 – $36,000
Downtown LA	$2,200 – $3,000	$26,400 – $36,000
Silver Lake / Echo Park	$2,000 – $2,800	$24,000 – $33,600
San Fernando Valley (Sherman Oaks)	$1,800 – $2,500	$21,600 – $30,000
South LA	$1,400 – $2,000	$16,800 – $24,000

As a simple illustration, a $250,000 ADU that rents for $2,500 a month produces $30,000 a year in gross rent, a 12% gross yield before property tax, insurance, maintenance, vacancy, and financing costs. Net returns are lower, and they vary widely with how the project is financed. An ADU also adds to the assessed value of the property. Under Proposition 13 only the value of the new unit is added to your tax bill, and the main house is not reassessed.

Rent Control and Tenant Protections

The rules here are more nuanced than “new units are exempt”. According to the Los Angeles Housing Department (LAHD):

• A newly built detached ADU is generally not subject to the Rent Stabilization Ordinance (RSO).
• If the main house was built on or before October 1, 1978, adding an ADU means there are now two units on the lot, and the main house may become subject to the RSO when rented.
• An ADU converted from existing habitable space in a pre-1978 house may leave both units subject to the RSO.
• Units not covered by the RSO are generally covered by the city’s Just Cause Ordinance, which limits the reasons a tenancy can be ended.

Confirm how your specific property will be treated with LAHD before you set rents. If you use a property manager, fees commonly run 8% to 10% of collected rent.

Short-Term Rentals

Do not plan on Airbnb income. State law requires ADU rentals to be longer than 30 days. Under the city’s Home-Sharing Ordinance, an ADU whose permit application was filed on or after January 1, 2017 cannot be used for home-sharing unless it is the host’s own primary residence, and units subject to the RSO cannot be home-shared at all.

Energy Code, Solar, and Sustainable Building

Every new ADU must meet California’s Title 24 energy code, which sets requirements for insulation, windows, HVAC efficiency, water heating, and lighting. The current code strongly favors all-electric designs with heat pump space and water heating.

• Solar. Newly built detached ADUs generally must include a solar photovoltaic system. Conversions of existing space and JADUs are generally exempt. See our guide to ADU solar requirements in California for sizing and exceptions.
• Water. Low-flow fixtures are mandatory under CALGreen. Drought-tolerant landscaping lowers water use and maintenance, which matters for a rental.
• Materials. Low-VOC finishes and durable, easily cleaned surfaces improve indoor air quality and reduce turnover costs.
• Electric readiness. Sizing the electrical service for EV charging and future battery storage costs little during construction and is expensive to add later.

Prefab and Modular ADU Options

Prefabricated ADUs are built partly or fully in a factory and then delivered and set on a site-built foundation. Their main advantage is speed: factory work can proceed while the site is being prepared, and on-site installation takes days or weeks instead of months.

Savings are less certain than marketing suggests. The foundation, utility connections, permits, crane or delivery access, and site work cost about the same as for a site-built unit, and those items make up a large share of the budget. Transport limits module width, which constrains layouts, and tight or hillside lots may not allow delivery at all. Compare total installed cost, not the factory price.

Our prefab ADU guide covers when prefab makes sense and when a site-built unit is the better choice.

Common ADU Challenges and How to Handle Them

Challenge	Why it happens	How to handle it
Utility capacity	Older homes often have undersized electrical panels or aging sewer laterals.	Check panel capacity and camera-inspect the sewer line during feasibility, before design is final.
Unexpected site conditions	Poor soil, buried debris, or undocumented utilities appear during excavation.	Order a survey and, on sloped or uncertain sites, a soils report early.
Permit delays	Incomplete submissions trigger repeated correction cycles.	Submit a complete, coordinated set of plans, or use a pre-approved standard plan.
Budget overruns	Scope changes and unknowns found during construction.	Finalize selections before work starts, use a fixed-price contract, and hold a 10% to 15% contingency.
Construction access	Narrow side yards and hillside lots limit equipment and deliveries.	Evaluate access at the first site visit; it affects both method and cost.
Neighbor concerns	Privacy, parking, and construction noise.	Share plans early, place windows carefully, and keep the site clean.

Future-Proofing Your ADU Investment

An ADU will be in use for decades, and its use will change. A few decisions at the design stage keep it valuable.

• Flexible layout. A plan that works as a rental, a guest suite, a home office, or housing for a parent keeps your options open.
• Aging in place. A zero-step entry, wider doorways, a curbless shower, and blocking in the walls for future grab bars add little cost during construction and widen the pool of future occupants.
• Climate resilience. Ignition-resistant materials and defensible space matter in fire-prone areas, and good insulation and shading keep the unit comfortable in heat waves.
• Technology. Conduit and wiring for high-speed internet, smart controls, and battery storage are simple to include now.

Conclusion: Planning Your ADU

State and city rules now make an ADU possible on most Los Angeles residential lots, with clear size limits, modest setbacks, no owner-occupancy requirement, and a defined approval timeline. The decisions that determine whether a project succeeds are practical ones: choosing the right type for your lot, setting a budget that includes soft costs and contingency, submitting complete plans, and understanding the rental rules before you sign a lease.

Aggregate Construction Group designs, permits, and builds ADUs across Greater Los Angeles. To see completed work, visit our project portfolio. To find out what your lot allows and what it would cost, request a free ADU consultation.