Junior ADU (JADU): What It Costs & 2026 Rule Changes

What Is a Junior ADU (JADU)?

A Junior ADU (JADU) is a small unit created within the existing walls of a single-family home — typically a converted bedroom, basement, or ground-floor space. Unlike a full ADU, a JADU:

• Is capped at 500 square feet
• Must be created within the existing structure (no additions)
• Requires a separate exterior entrance
• Needs an efficiency kitchen (sink + cooking surface — not a full range)
• May share a bathroom with the primary home (though a private bath is better)

JADUs are the lowest-cost ADU option because you're converting existing livable space, not building new square footage.

JADU vs Full ADU: Key Differences

	JADU	Full ADU
Max size	500 sq ft	1,200 sq ft (CA)
Location	Inside existing home	Inside, attached, or detached
Kitchen	Efficiency kitchen	Full kitchen allowed
Bathroom	Can share with main home	Must be private
Cost	$20,000–$80,000	$80,000–$350,000
Permit complexity	Lower	Higher
Owner-occupancy	See 2026 changes below	Not required (CA)

2026 JADU Rule Changes — What's New

California (Most Significant)

California made a major change effective 2025: owner-occupancy is no longer required for JADUs.

Previously, homeowners had to live in either the main home or the JADU. AB 976 eliminated this requirement — you can now build a JADU and rent both the primary home and the JADU without living on the property.

This significantly improves the investment case for JADUs in California.

Other 2026 California JADU rules:

• No impact fees for JADUs
• Ministerial approval required (no discretionary review)
• Cannot be sold separately from the primary home
• Must include a recorded deed restriction prohibiting separate sale

Oregon

Oregon allows JADUs as part of its statewide ADU mandate (HB 2001). Local rules vary — Portland has specific JADU standards worth reviewing before starting a project.

Washington

Washington's HB 1337 (2023) expanded ADU rights to include internal conversions similar to JADUs. Cities must allow at least two ADUs per lot, which typically includes one internal unit.

Texas / Colorado

No statewide JADU framework — rules vary by city. Austin allows internal ADUs with similar parameters to JADUs.

How Much Does a JADU Cost?

JADUs are the most affordable ADU option. Typical costs:

Scope	Cost Range
Bedroom conversion (no plumbing move)	$20,000–$40,000
Bedroom + new bathroom	$40,000–$70,000
Basement conversion	$35,000–$80,000
Ground floor with new entrance	$30,000–$60,000

What drives cost up:

• Adding a new bathroom (plumbing rough-in is expensive)
• Creating a separate entrance that requires structural work
• HVAC for a previously unconditioned space
• Soundproofing between units

What keeps cost down:

• Using an existing bathroom (shared or with interior connecting door)
• Converting a room with existing windows
• Minimal kitchen (efficiency kitchenette vs. full kitchen)

JADU Permit Requirements

JADUs require permits, but the process is typically simpler than a full ADU:

• Building permit — change of use, framing modifications
• Electrical permit — separate circuit for kitchen, lighting
• Plumbing permit — if adding or modifying bathroom/kitchen

In California, cities must process JADU permits ministerially — no public hearings, no discretionary review. This speeds up the process significantly.

Typical permit timeline: 30–90 days

Designing a JADU That Rents Well

The key to a successful JADU is creating a genuine sense of separation from the main home.

Must-haves:

• Private exterior entrance — ideally on a different side of the house from the main entry
• Door between JADU and main home — with a keyed lock on both sides (required in California)
• Soundproofing — add mass-loaded vinyl or extra drywall between shared walls and ceilings
• Efficiency kitchen — at minimum: sink, mini-fridge, two-burner induction cooktop, microwave
• Private bathroom — technically optional in some states, but a shared bathroom dramatically reduces rentability

Nice-to-haves:

• In-unit laundry (stacked washer/dryer — adds $1,500–$3,000 installed)
• Mini-split for independent climate control
• Separate utility meters (gas/electric) — adds cost but simplifies billing

JADU ROI: Is It Worth It?

JADUs offer some of the best returns in ADU investing because the cost basis is so low.

Example (California):

• JADU conversion cost: $55,000
• Monthly rent: $1,400 (shared-bathroom unit would be less)
• Annual net income: ~$15,120
• Break-even: ~3.6 years
• Cap rate: ~27.5%

Even at lower rents than a full ADU, the dramatically lower cost produces better returns.

Run your numbers with our ROI calculator.

JADU Limitations to Know

Cannot be sold separately. A JADU must remain part of the primary parcel — you can't condo-ize and sell it independently.

Size cap is firm. 500 sq ft is the maximum in California and most states. If your conversion space is larger, you'd need to permit it as a full ADU.

Kitchen limitations. A JADU kitchen can't have a full residential range (in some jurisdictions). A countertop induction cooktop + sink + mini-fridge typically qualifies.

Interior door required (California). California requires a door between the JADU and the primary home — it must have locks on both sides. This is a fire/safety requirement.

Should You Build a JADU or a Full ADU?

Choose a JADU if:

• You have an underused bedroom, basement, or ground floor space
• Budget is under $80,000
• You want the fastest path to rental income
• Your lot doesn't have room for a detached structure

Choose a full ADU if:

• You want maximum rental income potential
• You have a garage or extra lot space
• You want a completely independent unit with full kitchen
• You plan to house family members long-term

Not sure which is right for your property? Use our ADU feasibility advisor to get a personalized recommendation.