Garage Conversion, Detached ADU or JADU: Which ADU Should You Build in Los Angeles?

What each kind of ADU actually is

A garage conversion turns an existing garage, detached or attached, into a dwelling: the slab repaired or replaced, the walls insulated, the garage-door opening framed in, a kitchen, a full bath, a sub-panel and a mini-split added. State law treats it as an ADU inside an existing accessory structure, which is why the City cannot ask you to replace the parking you lose. A typical two-car garage in the Valley yields a 400–480 sq ft studio or one-bedroom.

A detached ADU is a new building in the yard on its own foundation, with its own roof, kitchen, bath, address and utility connections. In the City of Los Angeles it can be up to 1,200 sq ft on a single-family lot, which is enough for two bedrooms, and it must keep 4-foot side and rear setbacks. An attached ADU follows the same rules but shares a wall with the house and is limited to half the house's floor area, with 800 sq ft always allowed.

A junior ADU is up to 500 sq ft carved out of the existing house, usually a bedroom and part of a hall: an efficiency kitchen, its own exterior entrance, and a bathroom that may be its own or shared with the main house. The owner must live on the property, in the house or in the JADU. It is the only ADU type with an owner-occupancy rule.

Garage conversion vs. detached ADU vs. JADU at a glance

Which costs the least, and why?

The JADU, at $90K–$180K, because it reuses the house's structure, roof, foundation and most of its systems; the money goes into the efficiency kitchen, the entrance, fire separation and, if it is not shared, the bath. You give up a bedroom to get it.

The garage conversion comes next at $130K–$240K. The slab, the walls and the roof already exist; the cost is in making them habitable: a moisture barrier and slab repair, insulation to Title 24, egress windows, the infill of the garage-door opening, a full kitchen and bath, a sub-panel and often a longer sewer run than people expect. Most conversions stay under the 750 sq ft line, so there are no city impact fees.

A detached unit at $250K–$500K+ pays for everything from the ground up: foundation, framing, roof, windows, trenching for sewer, water and power, plus the same kitchen and bath. The small units sit at the top of the per-square-foot band because the kitchen and bath cost the same whatever the floor area around them. The ADU cost guide shows the ranges for every neighborhood.

Which is fastest?

The conversion and the JADU. Both need about 6–10 weeks of design and plan check and 3–5 months of construction, about 5–8 months from the first visit to the Certificate of Occupancy. The work happens inside an existing shell, the inspections are fewer and the weather matters less.

A detached unit needs 3–5 months of design, structural engineering and plan check and 6–9 months of construction, 9–14 months in all. Two things shorten it: a site where the utility runs are short and level, and one of LADBS' pre-approved standard plans, which skips most of the architectural review when the plan fits the lot. State law also requires the City to act on any complete ADU application within 60 days, and ministerial review means no hearing and no neighbors' veto; see how we run an ADU project.

Parking, fees and the rules that decide it

Parking. A converted garage needs no replacement parking, by state law. Any ADU within half a mile of public transit needs no parking either, which covers most of the Valley near the Metro G Line busway, the B Line in North Hollywood and the Metrolink stations in Van Nuys, Northridge, Burbank and Glendale. Elsewhere a new detached unit may need one space, and a driveway or tandem space counts.

Fees. Units under 750 sq ft pay no city impact fees; larger units pay in proportion to the main house. School district fees apply only to units of 500 sq ft or more, from January 1, 2026. Plan-check and permit fees apply to every unit.

Size and height. Detached units go to 1,200 sq ft in the City of Los Angeles and may be at least 16 feet tall by right, 18 feet within half a mile of a major transit stop; attached units follow the house's height limit up to 25 feet. Setbacks are 4 feet at the sides and rear. In Burbank, Glendale and Beverly Hills the same state rules apply through each city's own ordinance and building department.

Use. Every type can be rented on terms of 30 days or more. Only the JADU carries an owner-occupancy requirement.

Which unit fits which Valley lot?

• Flat R1 tract lot with a detached rear garage (Van Nuys, Valley Glen, North Hollywood, Reseda, Lake Balboa): the simplest conversion in Los Angeles. The garage already sits at the back of the lot with its own access, and the sewer line often runs nearby.
• RA or RE estate lot (Encino, Tarzana, Northridge, Granada Hills): room for a full 1,200 sq ft detached unit with its own driveway, and often for a JADU inside the house as well.
• Hillside parcel (Sherman Oaks and Studio City south of Ventura Boulevard, the Hollywood Hills): the garage pad is often the only level ground, so a conversion, or a unit built over the garage, is the practical answer, with Baseline Hillside Ordinance review on top of the ADU rules.
• Attached garage in a Burbank or Glendale tract (Burbank): a conversion with a fire-rated wall to the house, permitted through the city's own building department rather than LADBS.
• A house with a spare bedroom and an owner who is staying: the JADU, often paired with a detached unit later.

Rental income, privacy and resale

A detached unit is the most private and the easiest to rent: its own path, its own yard, no shared walls. A garage conversion is separate but close, which suits a relative or a tenant who does not mind the proximity. A JADU shares the house and is best for family or a single long-term tenant. All three are permitted dwellings that an appraiser can count and a buyer can inspect, and all three can be rented the day the Certificate of Occupancy is issued.

Property tax rises only on the new unit: the Assessor adds the ADU as new construction to your existing Proposition 13 base. Whether the unit pays for itself depends on the rent in your neighborhood and the number you build to, which is why we give a written planning range before you spend on drawings.

Can you build more than one?

Yes. On a single-family lot, state law allows one ADU (detached, attached or converted) plus one junior ADU inside the house. The common Valley combination is a garage conversion or a detached unit in the yard and a JADU inside, each with its own entrance. Two full detached ADUs on one single-family lot is not allowed; a second full unit is a different conversation about zoning.

What we recommend

Start with the garage. If it is sound, sits at the back of the lot and you want the quickest legal unit for the least money, convert it. If you need a real one- or two-bedroom home with privacy and a yard and the lot has the room, build detached, and use a standard plan if one fits. If you are staying in the house, have a bedroom to spare and want the smallest budget, carve out a JADU. If the lot is large and the need is big, do the JADU now and the detached unit next.

Right Image Builders designs, permits and builds all three across the San Fernando Valley, Glendale and Burbank on one fixed-price contract. The free feasibility visit covers the parcel on ZIMAS, the utility routes, the garage and the panel, and ends with a written recommendation for your lot; the garage conversion page and the addition vs. ADU guide cover the neighboring decisions.

Sources (checked October 2026): California HCD ADU Handbook (state ADU law: ministerial review within 60 days, setbacks, parking, size limits, rentals of 30 days or more); Government Code §66311.5 (SB 543): school district fees apply only to ADUs of 500 sq ft or more, from January 1, 2026; Los Angeles City Planning, zoning (ZIMAS), ADU ordinance and the Baseline Mansionization and Hillside ordinances; Los Angeles Department of Building and Safety, plan check and permit information; Los Angeles County Assessor: new construction is assessed and added to the existing Proposition 13 base; Right Image Builders service and neighborhood pages (2026 planning ranges, timelines, permit authorities). Cost figures are Right Image Builders' 2026 planning ranges from its service and neighborhood pages.