January 5, 2026
ADU vs JADU in California: Cost & Permit Comparison (2025)
Use this side-by-side comparison to quickly see the difference between an ADU and a JADU in California. Compare costs, permit rules, size limits, and Title 24 requirements, then decide which option fits your property.
ADU vs JADU California: Costs & Permit Rules at a Glance
| Feature | ADU | JADU |
|---|---|---|
| Typical cost | $120,000 – $350,000+ | $80,000 – $150,000+ |
| Size limit | Up to ~1,200 sq ft (varies by city) | Up to 500 sq ft |
| Location | Detached, attached, or garage conversion | Inside the existing main house |
| Kitchen | Full kitchen required | Efficiency kitchen (small sink, fridge, cooking appliance) |
| Bathroom | Private bathroom required | May share with main house or be private |
| Separate entrance | Required | Required |
| Permit required | Yes — building permit + zoning review | Yes — building permit + zoning review |
| Title 24 / CF1R | Required for most ADUs | Required for many JADUs |
| Owner occupancy | Not required (state law) | Owner must live on site (in main house or ADU) |
| Rental use | Long-term rental allowed | Long-term rental allowed |
Costs and rules vary by city. San Jose, Fremont, Newark, and other Bay Area jurisdictions may add local requirements on top of California state law.
What Is an ADU?
An ADU (Accessory Dwelling Unit) is a self-contained living unit on your property.
Common types:
- Detached ADU (backyard unit)
- Attached ADU (addition)
- Garage conversion ADU
Key features:
- Full kitchen and bathroom
- Separate entrance
- Up to ~1,200 sq ft (varies by city)
What Is a JADU?
A JADU (Junior ADU) is a smaller unit inside your existing home.
Key features:
- Up to 500 sq ft
- Efficiency kitchen
- Bathroom may be shared or private
- Uses existing space (bedroom, garage, etc.)
Do You Need a Permit?
Yes. Both ADUs and JADUs require permits. Most projects also require Title 24 energy compliance, including a CF1R energy report as part of the permit submittal.
This is where many projects get delayed—when plans and energy compliance don't match.
What zHeight Provides
zHeight helps homeowners get permit-ready by providing:
We don't provide construction or licensed architectural services—but we focus on clear, code-aware design documentation that cities can review efficiently.
How Much Do ADUs and JADUs Cost?
Very rough ranges (varies by site and scope):
JADU
$80k – $150k+
Garage ADU
$120k – $200k+
Detached ADU
$180k – $350k+
Costs depend on size, structure, utilities, and local requirements.
Why ADU / JADU Permits Get Delayed
- Zoning or setback issues
- Incomplete drawings or missing details
- Plans don't match the CF1R Title 24 report
Code-compliant plans can save weeks or months in permitting time.
How zHeight Helps You Move Faster
- Permit-ready design & drafting plans
- CF1R that matches your drawings
- Fewer city comments
- Faster approvals
- Less back-and-forth during plan check
Our focus is simple: help you get approved faster with fewer surprises.
Quick FAQ
Can I build both an ADU and a JADU?
Often yes, on single-family lots (subject to local rules).
Is a JADU cheaper than an ADU?
Usually yes—smaller size and existing space lower the cost.
Do I need Title 24 for an ADU or JADU?
Most ADUs and many JADUs require a CF1R Title 24 energy report.
Bottom Line
- ADU = Bigger, more flexible, higher cost
- JADU = Smaller, cheaper, inside your home
- Both need permits and Title 24 (CF1R)
- zHeight provides design & drafting plans + CF1R to help you get approved faster
Ready to Start Your ADU or JADU?
Get permit-ready design plans and a CF1R Title 24 report from zHeight.
Get Started Today