Junior ADUs (JADUs) in Orange County: The Complete Guide
A JADU builder can convert up to 500 sq ft within a proposed or existing single-family home — including an attached garage — into a legal rental or in-law space.
A junior ADU is a compact unit of up to 500 sq ft created within a proposed or existing single-family residence, including an attached garage. It needs a separate entrance and an efficiency kitchen. Under California’s 2026 rules, owner occupancy applies only when the JADU shares sanitation facilities with the existing structure; it is not required when the JADU has separate sanitation facilities. Here is how JADU construction differs from a full ADU, what it costs, and which permit rules apply.
Junior ADU (JADU) construction in Orange County
A junior ADU (JADU) is a unit of 500 sq ft or less created within a proposed or existing single-family residence; an attached garage qualifies as part of the residence. L Square is a JADU builder that handles feasibility, design, the separate entrance and efficiency kitchen, permitting and construction in Orange County under one contract (CSLB #1095476). If the JADU shares sanitation facilities with the existing structure, an interior entry to the main living area is also required. For a larger family unit, compare a JADU with a full in-law suite or a granny flat.
JADU vs ADU
A JADU is up to 500 sq ft within a proposed or existing single-family residence, including an attached garage. It has a separate entrance and an efficiency kitchen. A full ADU can be larger and may be attached or detached. For a JADU in 2026, owner occupancy applies only when sanitation facilities are shared with the existing structure; it is not required when sanitation facilities are separate.
What JADU construction costs
Because it reuses existing space, JADU construction is typically the lowest-cost path to a legal unit — most run $60K–$130K in Orange County depending on kitchen, bath and entry work. Get a range in the cost calculator.
2026 permits & requirements
California requires a JADU to be no more than 500 sq ft, remain within a proposed or existing single-family residence, have a separate entrance and efficiency kitchen, and carry a recorded deed restriction. Rentals must be for terms longer than 30 days. Owner occupancy is required only when the JADU shares sanitation facilities with the existing structure, not when it has separate sanitation facilities. Review the official California HCD ADU Handbook and AB 1154 (Government Code 66333). We handle the JADU permit submittal and plan-check responses.
Why build with L Square
Design, permits and construction under one roof. L Square is a licensed Orange County design-build team (CSLB #1095476). One contract covers architecture, engineering, city approvals and our own build crews — so your ADU moves on a fixed schedule from first drawing to final inspection, across Orange County and Los Angeles.
- 01 · Architect-grade design
- Every unit is drawn around your lot, light and privacy.
- 02 · Permit-ready, OC-savvy
- We know each city’s ADU rules and clear the approvals for you.
- 03 · Built once, built right
- Our own crews deliver on a fixed schedule, foundation to finishes.
Licensed · Insured · Bonded · CSLB #1095476 · Orange County & Los Angeles
Frequently asked questions
What’s the difference between a JADU and an ADU?
How big can a JADU be?
Do I have to live on the property?
Can I have both a JADU and an ADU?
What does a JADU cost?
Building an ADU in your Orange County city
ADU rules vary by city — we handle the specifics for your address. Statewide, California allows ADUs up to about 1,200 sq ft with 4-ft side and rear setbacks (CA HCD); your city may add its own details. For the statewide rules, see the CA HCD ADU Handbook.
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