Custom ADUs across Orange County.

Orange County ADU questions, answered

What is an ADU?

An ADU (accessory dwelling unit) is a permitted, self-contained second home on a lot that already has a house: its own kitchen, its own full bath, and its own entrance. California state ADU law recognizes four typologies: detached (standalone, 500–1,200 sqft), attached (built off the primary residence), Junior ADU (converted inside the existing footprint), and garage conversion (an existing garage rebuilt as living space).

What is a Junior ADU (JADU)?

A Junior ADU is a conversion inside the existing footprint of the primary house: typically an unused interior wing or bedroom, 300–500 sqft, one bedroom, with a kitchenette and full bath. It's the tightest-scope path in Orange County, typically $135K–$220K+ over 4–6+ months, because no new foundation or exterior structure is involved.

What is a garage conversion ADU?

A garage conversion turns an existing garage into permitted living space: insulation, a conditioned envelope, and a full kitchen and bath, usually 350–600 sqft as a studio or one bedroom. In Orange County it typically runs $85K–$170K+ over 4–6+ months, and it's the fastest move when the existing garage frame is sound and you're ready to give up the parking.

What types of ADUs do you build in Orange County?

Detached ADUs, attached ADUs, Junior ADUs, and garage conversions, every permitted typology under California state ADU law.

What should I look for in an ADU builder in Orange County?

Three things matter most in Orange County: a California General-B license (Avorino holds #1107538), design + structural engineering + permitting handled in-house so nothing is lost between separate firms, and a fixed-price contract. Avorino keeps all of it under one roof across 37 OC cities, so your ADU is contracted and built by one company, not coordinated across subs.

What are typical ADU build windows in Orange County?

Detached: 5–8+ months. Attached: 5–8+ months. Junior ADU: 4–6+ months. Garage conversion: 4–6+ months. Windows vary with city, plan-check timing, and finish-level decisions.

What do ADUs typically cost in Orange County?

Detached ADUs typically run $245K–$440K+. Attached ADUs $200K–$350K+. Junior ADUs $135K–$220K+. Garage conversions $85K–$170K+. Use the Avorino cost estimator for a calibrated range on your specific project.

Do I need to hire an architect separately?

No. Avorino handles design, structural engineering, Title 24 calculations, and permitting in-house. Single point of accountability from concept through final inspection.

Do you build prefab ADUs in Orange County?

Avorino builds custom, site-built ADUs, not factory modules. If you're comparing prefab ADUs in Orange County, compare the total installed cost rather than the factory price: foundation, utility connections, crane or transport access, site work, and permits are typically added on top. Prefab pencils best on flat, open lots where a stock plan already fits; on the sloped, tight, or view-sensitive lots common across OC, custom site-built usually delivers better fit and finished value.

Do I need a specialized ADU contractor, or can any general contractor build one?

Any licensed general contractor can take the job, but ADU work is its own discipline. State ADU law, city-by-city overlays, setback and height exceptions, utility-connection rules, and layouts that actually rent are where budgets slip when a contractor is learning on your project. Avorino runs design, structural engineering, Title 24, permitting, and construction under one roof across 37 Orange County cities, on one fixed-price contract.

Still working out which type fits? What is an ADU compares detached, attached, Junior ADU and garage conversion by size, cost and build window.