Building an ADU in Los Angeles: 2026 Homeowner Guide

An accessory dwelling unit (ADU) is a second, self-contained home on the same lot as a house or apartment building. It has its own entrance, kitchen, bathroom, and sleeping area. It can be a separate backyard building, part of the main house, or a converted garage. An ADU cannot be sold separately from the main home unless a city has opted into the condo program described below.

A junior accessory dwelling unit (JADU) is smaller and lives inside the walls of an existing or proposed single-family home. Under state law a JADU is capped at 500 sq ft. It needs its own exterior entrance and at least an efficiency kitchen, but it may share a bathroom with the main house.

The short version: an ADU is a full second home, and a JADU is a small unit carved out of the home you already have.

Which type fits depends on your lot size, slope, existing structures, and how you plan to use the space.

• Detached ADU: a new freestanding building, usually in the backyard. Most privacy and layout freedom, and usually the most site work.
• Attached ADU: an addition that shares at least one wall with the main house. Often a good fit on narrow lots.
• Garage conversion: an existing garage turned into a permitted unit. The slab, walls, and roof are already there, which often shortens the schedule. See our garage conversion service.
• JADU: up to 500 sq ft converted inside the existing home, such as a bedroom suite with a small kitchen added.
• Above-garage ADU: a unit built over a new or existing detached garage. The structure below usually needs engineering review, and height limits matter.

Many lots can combine types. A common Valley setup is a detached ADU in the back yard plus a JADU inside the house.

State ADU law sets a floor that cities must allow. Cities can be more generous, and some add their own design standards, so treat the points below as the general framework as of September 2026, not a guarantee for your address. We confirm the rules for your specific lot during feasibility.

• Units on a single-family lot: generally one ADU (attached, detached, or converted) plus one JADU.
• Units on a multifamily lot: owners can generally convert non-livable space (storage rooms, garages) into ADUs, up to 25% of the existing unit count, and under SB 1211 can add up to 8 detached ADUs, not exceeding the number of existing units.
• Size: detached ADUs are commonly allowed up to 1,200 sq ft. Attached ADUs are typically capped at 50% of the main home's floor area. Cities cannot use local limits to block a unit of at least 850 sq ft (studio or one bedroom) or 1,000 sq ft (two or more bedrooms).
• Height: state law protects at least 16 ft for a detached ADU, more in some cases (such as near qualifying transit or on multifamily lots), and up to 25 ft or the local zone limit, whichever is lower, for an attached ADU.
• Setbacks: side and rear setbacks of no more than 4 ft for new construction. Converting an existing legal structure in place generally requires no added setback.
• Owner occupancy: AB 976 removed owner occupancy requirements for ADUs. Starting January 1, 2026, AB 1154 limits the JADU owner occupancy requirement to JADUs that share a bathroom with the main home.
• Parking: no replacement parking is required when a garage is converted or demolished for an ADU. New ADU parking is also waived in many situations, including lots within a half mile walk of public transit.
• Review time: a city must approve or deny a complete ADU application within 60 days. SB 543, effective 2026, tightens the rules on how agencies handle completeness review.

The Department of Housing and Community Development (HCD) publishes an ADU Handbook, updated in 2026, that summarizes these rules.

If your home is in the City of Los Angeles, which includes Valley neighborhoods like Sherman Oaks, Studio City, Encino, and Van Nuys, your building permit goes through the Los Angeles Department of Building and Safety (LADBS). Planning and zoning questions, such as overlays and specific plans, sit with Los Angeles City Planning.

The City runs a Standard Plan Program with pre-approved ADU designs. Using one of these plans can shorten plan check, because the core design has already been reviewed. You still need a site plan and any site-specific engineering for your lot.

Hillside lots, including much of the area south of Ventura Boulevard in Sherman Oaks, Studio City, and Encino, can fall under the Baseline Hillside Ordinance and may sit in a Very High Fire Hazard Severity Zone. Those designations can affect grading, fire access, construction materials, and whether a detached ADU is practical at all, so they belong on the first feasibility checklist.

AB 1033 lets cities opt in to allowing ADUs to be sold separately as condominiums. It is not automatic. As of early 2026, published reports indicated the City of Los Angeles had not yet adopted an ordinance, so check current status before planning around a separate sale.

Many nearby homes are not in the City of LA at all. Burbank, Glendale, Pasadena, Santa Monica, and Beverly Hills each have their own building departments, fee schedules, and design rules. Unincorporated areas go through LA County Public Works Building & Safety. In Orange County, cities such as Irvine and Newport Beach run their own permitting, and coastal areas of Newport Beach and Santa Monica may need a coastal development permit. See our Orange County service area for more.

Most ADU projects in Los Angeles follow the same path. The order matters, because skipping early steps is how projects stall in plan check.

• Step 1, feasibility: confirm the permitting agency, zoning, lot dimensions, setbacks, easements, hillside or fire zone status, and where utilities connect.
• Step 2, survey and site data: a survey or site plan, and a soils report if the site or agency calls for one.
• Step 3, design: floor plan, elevations, and a budget check before drawings are finalized. Decide between a custom design and a pre-approved plan.
• Step 4, engineering and energy: structural calculations, Title 24 energy compliance, and any required fire sprinkler or utility plans.
• Step 5, plan check: submit to the building department, respond to corrections, and pay permit fees.
• Step 6, utility coordination: water, sewer, and electrical service may need upgrades or new connections.
• Step 7, construction: site prep, foundation, framing, rough mechanical, electrical, and plumbing, insulation, drywall, and finishes, with city inspections at each required stage.
• Step 8, final inspection: the inspector signs off and the agency issues a certificate of occupancy or final approval so the unit can be legally lived in.

For a detached ADU in Los Angeles, design and permitting commonly take 2 to 6 months, and construction commonly takes 4 to 8 months. Garage conversions and JADUs are usually faster, because much of the structure already exists.

The biggest schedule swings come from plan check corrections, utility upgrades, hillside or fire zone reviews, and change requests after construction starts. A pre-approved plan and a complete first submittal are the two most reliable ways to save time. State law requires a decision within 60 days of a complete application, but reaching a complete application is part of the work.

ADU costs in Los Angeles and Orange County vary widely. Garage conversions often land in the low six figures, while larger detached new-build units commonly reach the mid six figures. Your number depends on your lot and your choices, and a real figure comes from a written estimate after a site visit.

• Type and size: a conversion reuses structure, while a detached unit starts from the ground.
• Site conditions: slope, soils, access for equipment, and demolition of existing structures.
• Utilities: sewer lateral distance, electrical panel capacity, and whether water or gas service needs upgrading.
• Design and engineering: custom plans cost more than a pre-approved plan, and hillside sites need more engineering.
• Finishes: cabinets, flooring, windows, and fixtures can move a budget more than homeowners expect.
• Agency requirements: fire sprinklers, fire zone materials, and local design standards.

You will pay plan check and permit fees to your building department, and possibly utility connection fees. State law limits some of the rest.

• Impact fees: ADUs of 750 sq ft or less of interior livable space are exempt from development impact fees. Larger ADUs can be charged proportionally to the size of the main home.
• School fees: starting January 1, 2026, SB 543 exempts ADUs and JADUs under 500 sq ft from school impact fees. Larger units may still be charged.
• JADUs: because they are capped at 500 sq ft, JADUs are generally not charged impact fees.

Fee schedules change, so confirm current amounts with your agency before you finalize the size of your unit. Sometimes trimming a design to 750 sq ft is worth a look.

An ADU can house a family member, provide rental income, or give you flexibility later. With owner occupancy removed for ADUs, you can generally rent the ADU, the main house, or both, subject to local rules such as short-term rental limits and, in some cases, rent stabilization. The City of Los Angeles generally prohibits renting ADUs as short-term rentals.

A permitted ADU adds legal living space, which can support property value, but the effect varies by neighborhood and market. Homeowners commonly pay for ADUs with cash, home equity loans or lines of credit, cash-out refinancing, or construction loans. This is general information, not financial or tax advice. Talk to a lender, appraiser, and tax professional before you commit.

If you have an older unit that was built without permits, AB 2533 creates a path to legalize some unpermitted ADUs. That route still requires an inspection and any work needed for health and safety.

An ADU is a new home, and the contractor you hire shapes both the schedule and the result.

• Check the license: look up the contractor on the California Contractors State License Board (CSLB) website and confirm it is active. KR's license is #1127167.
• Ask who handles permits: find out whether the contractor manages plan check corrections and inspections or leaves that to you.
• Ask about local experience: LADBS, hillside, and fire zone projects each have their own requirements.
• Get a written, itemized estimate: it should state what is included and what is excluded, such as utility upgrades or city fees.
• Get a written contract: California requires a written contract for home improvement work, with a payment schedule tied to completed work.

The fastest way to know what your lot allows is a feasibility check at your address. KR brings over 10 years of construction experience to ADU construction, from permits and plans to final construction. Contact us to schedule a site visit and get a written estimate.