7 min read · updated 2026-04-15
JADU vs ADU vs detached ADU: the real differences
California recognizes three distinct accessory unit formats. Here's exactly what each is, what each allows, and why most LA homeowners pick the wrong one first.
Why three formats exist
California's ADU statute distinguishes between attached, detached, and junior ADUs because each was added to the law at a different time to solve a different problem. HCD's ADU Handbook walks through the distinctions HCD ADU Handbook and the underlying statute is in Government Code §65852.2 and §65852.22 California Gov Code §65852.2 + §65852.22.
For LA homeowners, the practical question is almost always: am I willing to give up interior space in my main house, or do I want a fully separate unit? The answer determines which format you should pursue.
JADU — Junior ADU
150 to 500 square feet, carved out of existing conditioned space inside the main single-family home. Must include a small efficiency kitchen. May share a bathroom with the main house. Requires owner-occupancy of either the main house or the JADU. Cannot be sold separately.
Best fit: a homeowner who has an underused bedroom or finished basement and wants to add a legal rentable or family-use unit at the lowest possible cost. Hard cost typically lands $50,000–$90,000 for a clean conversion. Maxable has a clear JADU explainer Maxable — JADU explainer and Symbium's lookup tool flags JADU eligibility Symbium — JADU eligibility tool.
Attached ADU
Shares at least one wall with the existing main house. Capped at 1,200 sqft, but in practice limited to 50% of the main house's existing floor area (whichever is smaller, with a 800 sqft minimum allowance regardless). Can be a conversion of attached garage space or new construction.
Best fit: lots where setback geometry rules out a detached structure, or homeowners who want to expand the main house footprint and create the ADU as part of the same project.
Detached ADU
A standalone structure separated from the main house. Capped at 1,200 sqft regardless of main-house size. No owner-occupancy requirement (in most jurisdictions including LA, through current law).
Best fit: lots with usable backyard depth, owners who want maximum flexibility (rental, family use, eventual condo conversion if the city ever opts into AB 1033), and projects where the unit's privacy and independence matter for either rent or use. UCLA Lewis Center research shows detached units make up the majority of new LA ADU construction UCLA Lewis Center — LA ADU production data.
The combination most people miss
California law allows one JADU and one ADU on the same single-family lot. That means a homeowner can carve a 400 sqft JADU out of the main house AND build a 1,200 sqft detached ADU in the back — three legal units on a single-family lot, all under ministerial approval. The statute is clear on this California Legislative Information and HCD's memos confirm HCD ADU technical assistance memo.
On a multifamily lot, SB 1211 expanded the count further — up to 8 detached ADUs depending on the existing unit count Terner Center SB 1211 analysis. The LA Times has covered the resulting density potential LA Times — density coverage and Curbed LA tracks specific projects Curbed LA — project tracking.
Frequently asked
- Which format is fastest to permit?
- JADU is usually fastest because the structural envelope already exists — typical timeline is 6–10 weeks. Detached new-build ADUs run 12–20 weeks for permit issuance.
- Can I have a JADU and an attached ADU?
- Yes — California allows one JADU plus one ADU (attached or detached) on a single-family lot. The ADU can share a wall with the main house even when a JADU exists inside the house.
- Do JADUs require their own utility meters?
- No — JADUs are explicitly exempt from separate utility connections. Attached and detached ADUs typically need at least separate sub-meters; some jurisdictions require fully separate meters.
- Where can I read more on ADU zoning after "JADU vs ADU vs detached ADU: the real differences"?
- The pillar hub is the field journal — filter by the ADU zoning pillar. Definitions of the terms in this post live in the glossary.
- How does "JADU vs ADU vs detached ADU: the real differences" translate to a real California project?
- See completed builds on the projects index, the full design-build sequence on the process page, and pricing bands in the 2026 California cost report.
- Which Alpha Dream studio covers my area for "JADU vs ADU vs detached ADU: the real differences"?
- Los Angeles studio for LA, Orange, Inland Empire, and Ventura. Bay Area studio for SF, Peninsula, East Bay, South Bay, and North Bay.
- What's the fastest path from "JADU vs ADU vs detached ADU: the real differences" to a quote?
- Run the ADU cost calculator for a band, then book a discovery call. We don't quote sight-unseen.
- Are the numbers in "JADU vs ADU vs detached ADU: the real differences" verified against real bids?
- Yes — we publish from closed bids, not market averages. The full methodology is in the 2026 California cost report.
- Which California city does "JADU vs ADU vs detached ADU: the real differences" apply best to?
- The post calls out its primary city; statewide context is on the locations index.
- Can I share "JADU vs ADU vs detached ADU: the real differences" with my architect or designer?
- Yes — public content, attributable to Alpha Dream Construction. Pair it with the relevant field guides when you share.
- Does "JADU vs ADU vs detached ADU: the real differences" replace a conversation with a contractor?
- No — it informs one. Book a discovery call to apply the post to your specific lot.
- Where do I find more posts on the same pillar as "JADU vs ADU vs detached ADU: the real differences"?
- Filter by pillar on the field journal index. The topic clusters view groups posts with their related guides and city pages.
- Has the law changed since "JADU vs ADU vs detached ADU: the real differences" was published?
- California ADU and remodel law shifts every session. Material changes get a new post on the journal; definitions update in the glossary.
- What's the related cost benchmark for "JADU vs ADU vs detached ADU: the real differences"?
- See the 2026 cost report for city-by-city bands and the ADU cost calculator for an instant band.
- Can I cite "JADU vs ADU vs detached ADU: the real differences" in a permit appeal or HOA letter?
- Yes — pair with the underlying statute. The permit directory links those sources.
Sources we cited
- 1.HCD ADU Handbook — California HCD
- 2.California Gov Code §65852.2 + §65852.22 — California Legislature
- 3.Maxable — JADU explainer — Maxable
- 4.Symbium — JADU eligibility tool — Symbium
- 5.UCLA Lewis Center — LA ADU production data — UCLA Lewis Center
- 6.California Legislative Information — California Legislature
- 7.HCD ADU technical assistance memo — California HCD
- 8.Terner Center SB 1211 analysis — UC Berkeley Terner Center
- 9.LA Times — density coverage — Los Angeles Times
- 10.Curbed LA — project tracking — Curbed Los Angeles
Related areas
Neighborhood guides that pair with this article — local code, lot patterns, and what we've actually built nearby.
Eastside / NELA — ADU Zoning →
Local rules, costs, and project notes for Eastside / NELA.
Area overview →Westside — ADU Zoning →
Local rules, costs, and project notes for Westside.
Area overview →San Fernando Valley — ADU Zoning →
Local rules, costs, and project notes for San Fernando Valley.
Area overview →San Gabriel Valley — ADU Zoning →
Local rules, costs, and project notes for San Gabriel Valley.
Area overview →South Bay — ADU Zoning →
Local rules, costs, and project notes for South Bay.
Area overview →