ADU vs JADU vs Garage Conversion in LA (2026)
Los Angeles homeowners have three distinct secondary-dwelling pathways under Gov Code §65852.2, and the labels matter. A detached new-build ADU, a JADU carved out of the primary house, and a garage conversion are all governed by the same statute but diverge sharply on cost, timeline, and post-construction rules. This guide pins down the definitions, cites the 2025 state amendments (SB 1211, AB 130, SB 543), walks through the fire-separation and utility-separation requirements, and shows where each pathway fits different homeowner goals. By the end you can tell a contractor which pathway you want and why — without being led by a sales pitch into the wrong one.
Detached ADU — the new-build path
Gov Code §65852.2(a)(1)(D) defines a detached ADU as a new structure physically separated from the primary dwelling, up to 1,200 sqft in city-of-LA per the 2022 ordinance. A detached ADU is what most homeowners picture — a backyard casita with its own entrance, kitchen, bath, and utility meters.
Timeline: 14–22 weeks typical for permit plus 12–24 weeks for construction. LADBS Standard Plan Program cuts permitting by 4–6 weeks.
Cost: $220–$520 per sqft in 2026 LA, typically $280,000–$620,000 all-in for an 800–1,000 sqft unit.
Parking: waived for ADUs within a half-mile of transit under Gov Code §65852.2(d)(1)(A), which covers nearly all urbanized city-of-LA parcels after the 2023 LADOT mapping update.
JADU — the junior path carved from inside the house
A Junior ADU (JADU) is defined in Gov Code §65852.22 as a unit no larger than 500 sqft contained entirely within the existing single-family residence, including conversion of an attached garage. A JADU must have its own exterior entrance and can share plumbing with the primary dwelling.
Timeline: 8–14 weeks for permit, 6–14 weeks construction. Much faster than a detached ADU because the shell already exists.
Cost: $60,000–$180,000 typical, heavily driven by whether plumbing needs to be extended to a new kitchenette and bath.
Owner-occupancy requirement: Gov Code §65852.22(a)(2) requires the owner to live in either the primary dwelling or the JADU. This rule was kept in place by SB 1211 (2024) even as owner-occupancy was eliminated for standard ADUs.
Garage conversion — the subset that lives in both camps
A garage conversion is any ADU pathway that starts from an existing garage. Detached garage conversion becomes a detached ADU. Attached garage conversion becomes either a JADU (if it stays under 500 sqft and the dwelling otherwise qualifies) or an attached ADU of up to 1,200 sqft.
Timeline and cost: generally faster and cheaper than a new-build detached ADU because the foundation, slab, and perimeter walls exist. Budget $120,000–$280,000 for a 400–500 sqft conversion.
Gotcha 1 — slab condition. Many pre-1980 LA garage slabs are 3–4 inches thick without a vapor barrier. Conversion to habitable space often requires demolishing and re-pouring the slab with proper moisture membrane per CBC §1805.4.
Gotcha 2 — parking replacement. State law (Gov Code §65852.2(d)(1)(D)) waives the replacement-parking requirement that used to make garage conversions infeasible. Pre-2017 garage conversions got stuck on this point; in 2026 it is no longer an issue.
The 2025 amendment stack — what changed in the last year
SB 1211 (effective January 1, 2025) raised the allowed detached-ADU count on multifamily parcels from one to eight, depending on parcel size. Applies to duplex, triplex, and fourplex properties, not single-family.
AB 130 (2025) tightened permit review timelines: 30 days for completeness check, 60 days for full decision, with deemed-approval if the agency misses.
SB 543 (2025) eliminated ALL development impact fees for ADUs statewide. For LA, that saves homeowners $8,000–$30,000 per project depending on whether LADWP water-service fees were previously treated as impact fees.
SB 1466 (pending 2026) would extend AB 1033 condo-sale pathways to more cities, but as of April 2026 city-of-LA has not opted in.
Side-by-side — pick the pathway that matches your goal
Rental income, maximum square footage, separate sale optionality later: go detached ADU. The 1,200 sqft cap beats JADU's 500 sqft and gives the tenant full separation.
Family member, fastest turnaround, lowest cost: go JADU. 500 sqft is enough for a one-bedroom unit for parents or an adult child, and the owner-occupancy rule matches the use case anyway.
Existing usable garage with intact slab and power: convert. The starting point is 30–50% cheaper than a new-build ADU of the same size.
Post-ADU property tax: only the new improvement is reassessed under Prop 13, not the whole property. LA County Assessor reassesses the added floor area at current market value.
Permit fees, impact fee elimination, and SB 543 economics
SB 543 (effective 2025) eliminated development impact fees for ADUs and JADUs statewide. The prior fee structure routinely added $8,000–$30,000 to an ADU project in LA.
Remaining fees after SB 543: LADBS building permit fee (scales with valuation, typically $4,500–$12,000 per ADU), LADBS plan-check fee (65% of permit fee), school fees (still collected, roughly $4.19 per sqft in LAUSD), and LADWP service-connection fees where new service is required.
Mello-Roos and community facility district fees still attach to parcels in those districts. Some LA County unincorporated areas and certain incorporated cities have active Mello-Roos obligations that pass through to ADUs.
Total soft cost for a detached 800-sqft ADU in 2026 city-of-LA: $35,000–$68,000 across architecture, engineering, permits, and school fees. Down from $55,000–$110,000 before SB 543.
Fire separation, sprinklers, and CBC Chapter 4 provisions
CBC §420 governs dwellings and sleeping units. An attached ADU or JADU built adjacent to the primary dwelling requires a 1-hour fire-rated separation per CBC Table 602, typically achieved with 5/8-inch Type X drywall on both sides of wood-framed wall with mineral wool insulation.
Detached ADUs set less than 10 feet from the primary dwelling face a similar fire-separation requirement across the setback.
Sprinklers: CBC §903.2.8 requires NFPA 13D residential sprinkler systems on any new dwelling built after 2011. Existing primary dwellings without sprinklers are grandfathered, but new ADUs must have sprinklers if the primary has them.
Smoke alarms per CBC §907.2.11: interconnected 120V hardwired with battery backup, one per bedroom, one in hallway outside bedrooms, one on each floor. Carbon monoxide alarms per CBC §915 near sleeping areas in dwellings with gas appliances or attached garages.
Egress: every sleeping room in the ADU needs an operable emergency escape and rescue opening per CBC §R310: minimum 5.7 sqft opening area, minimum height of 24 inches, minimum width of 20 inches, maximum sill height of 44 inches above floor.
Kitchen and bath minimums that affect layout
A JADU kitchenette under 500 sqft must have a food preparation sink, cooking appliance, and food storage per LAMC §12.03 definition. The cooking appliance can be an induction cooktop — a 120V plug-in unit satisfies the kitchen requirement without requiring a 240V circuit.
A full ADU (detached or attached, above 500 sqft) needs a full kitchen with stove or cooktop, refrigerator, sink with hot and cold water, and at least 24 inches of counter workspace per California Residential Code §R329.2.
Bathroom minimums under CBC §1208: 3-foot clearance in front of fixtures, 30-inch width at the toilet, operable window or mechanical ventilation at 50 CFM intermittent / 20 CFM continuous per ASHRAE 62.2.
A JADU in a former attached garage can share a bathroom with the primary dwelling under Gov Code §65852.22, but most JADU designs include a dedicated bathroom for marketability.
Utility separation and metering — the hidden cost line
LADWP requires every new dwelling (ADU or JADU) to have its own metered electrical service. Service upgrade from 100A single-family to two 100A meters runs $8,500–$18,000 depending on utility pole proximity and mast configuration.
SoCalGas meter separation costs $1,800–$4,200 plus service-line extension. Some JADUs skip the gas meter entirely by going all-electric (heat pump water heater, induction range, heat pump HVAC), which also aligns with the 2025 Title 24 Part 6 electrification push.
Water and sewer are often shared between primary and ADU on single-family parcels. LADWP charges a one-time capacity fee of $4,500–$12,500 for the separate water service even on shared domestic plumbing. Sewer connection fees vary by LA Bureau of Sanitation district.
State law (Gov Code §65852.2(h)) caps utility-related impact fees for ADUs under 750 sqft at zero for most public agencies, but LADWP treats some service fees as cost-of-service charges that fall outside the cap.
When you are planning the pathway, pick the contractor around it
A detached ADU requires a CSLB Class B general contractor, structural design, utility trenching, and full MEP. Most single-trade subs cannot general the project.
A JADU interior buildout sometimes qualifies for CSLB Class C-36 (plumbing) + C-10 (electrical) subcontractor chain under the owner-builder model, but city-of-LA discourages owner-builder ADUs because of inspection-coordination issues.
Garage conversion should always go through a licensed general — the permit pulls require someone to sign for structural and MEP jointly.
The 2025 LADBS ADU Permit Handbook consolidated JADU, detached ADU, and attached ADU under one pre-check checklist. A contractor who has completed ADU projects in the prior 24 months will have the handbook workflow memorized. Ask for specific permit numbers from recent LA-area ADUs as part of vetting.
See the ADU Construction pillar for the full design-build workflow: https://askbaily.com/adu-construction-los-angeles
Still have questions?
Ask Baily — pre-seeded for this topic.
Loading chat…
Who is Baily?
Baily is named after Francis Baily — an English stockbroker who retired at 51, became an astronomer, and in 1836 described something on the edge of a solar eclipse that nobody had properly articulated before: a string of bright beads of sunlight breaking through the valleys along the moon’s rim.
He wasn’t the first to see them. Edmond Halley saw them in 1715 and barely noticed. Baily’s contribution was clarity — describing exactly what was happening, in plain language, so vividly that the whole field of astronomy paid attention. The phenomenon is still called Baily’s beads.
That’s what we wanted our AI to do. Every inbound call and text has signal in it — a homeowner’s real question, a timeline, a budget, a hesitation that means “yes but.” Baily listens to every one, 24/7, and finds the beads of light.
Baily was a businessman before he was a scientist. That’s our vibe too.