Quick Answer: An ADU (Accessory Dwelling Unit) is a complete, independent dwelling unit with its own kitchen and bathroom — can be detached (backyard cottage), attached (addition to the main home), or a garage conversion. Maximum size: 1,200 sq ft. A JADU (Junior ADU) is a smaller unit created within the existing primary dwelling (conversion of a bedroom or garage attached to the home), maximum 500 sq ft. JADUs must include an efficiency kitchen (can share a bathroom with the main house) and require an owner-occupancy deed restriction. ADUs have no owner-occupancy requirement (as of 2023). Both require permits but JADUs have streamlined approval.
ADU vs. JADU — Key Differences
Helpful Resources:
| Factor | ADU | JADU |
|---|---|---|
| Maximum size | 1,200 sq ft | 500 sq ft |
| Location | Detached, attached, or garage conversion | Within the existing primary dwelling only |
| Kitchen requirement | Full kitchen required (separate from main house) | Efficiency kitchen (can be wet bar/kitchenette) |
| Bathroom | Separate bathroom required | Can share bathroom with main house (with internal access) |
| Owner-occupancy | Not required (as of Jan 2020) | Required — owner must live on the property |
| Construction cost | $100,000–$350,000+ | $30,000–$100,000 |
| Rental potential | Full market rent ($1,800–$3,500/mo in Bay Area) | Similar to ADU; some tenants prefer privacy of separate ADU |
| Deed restriction | None (for new ADUs post-2020) | Owner-occupancy restriction recorded on title |
When a JADU Makes More Sense Than a Full ADU
- Budget is under $80,000: JADUs are significantly cheaper because they convert existing space within the main home rather than building a new structure or full addition.
- You want family nearby (not rentals): JADUs are ideal for aging parents or adult children who need proximity to the main household but their own private space. The shared bathroom option works well for family arrangements.
- Your lot lacks space for a detached ADU: JADUs are contained within the existing structure — they don’t require backyard space, setback compliance, or new utilities.
- Fastest permitting: California streamlines JADU approvals (cities must approve ministerially in 60 days) — JADUs often permit faster than full ADUs because they’re contained within the existing structure.
Can I have both an ADU and a JADU on my Bay Area property? Yes — California Government Code Section 65852.22 allows a single-family property to have one ADU AND one JADU simultaneously. This means a Bay Area homeowner could have: the main house, a JADU (bedroom converted within main house, 500 sq ft), and a detached ADU (backyard cottage, up to 1,200 sq ft) — three total dwelling units on a single-family lot. This is a powerful wealth-building strategy in Bay Area markets where rental income from two ADUs/JADUs can generate $4,000–$6,000/month in gross rent.
Does a JADU require a separate entrance in California? Yes — a California JADU must have its own exterior entrance (separate from the primary dwelling’s main entrance). The JADU can also have an interior doorway connecting it to the primary dwelling (which must be lockable from both sides to provide privacy), but the exterior entrance is mandatory. This ensures the JADU functions as a self-contained rental unit even when the internal connection is locked.
Quartz Construction & Remodeling (CSLB #1003436) designs and builds both ADUs and JADUs throughout San Jose and the Bay Area. Call (650) 749-7436 for a free ADU/JADU feasibility assessment — we’ll help you determine which type makes the most sense for your property and goals.
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"Quartz Construction did an amazing job on our kitchen remodel. The team was professional, on time, and the results exceeded our expectations. Highly recommend to any Bay Area homeowner!"
— Michael T. |
"We hired them for a bathroom remodel in our San Jose home. From permitting to final walkthrough, everything was handled perfectly. The tile work is stunning. 5 stars without hesitation."
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"Just finished our ADU garage conversion. The project came in on budget and on schedule — rare in the Bay Area! The rental income already started. Could not be happier with Quartz Construction."
— David R. |
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