ADU vs JADU: Which Is Right for Your Property?

If you have been thinking about adding living space to your property, you have probably come across the terms ADU and JADU. Both can add flexibility, functionality, and value to your home, but they serve different purposes and come with their own set of rules.

So which one makes the most sense for your property? Let’s walk through the basics.

What Is an ADU?

An Accessory Dwelling Unit (ADU) is a fully independent living space built on the same lot as a primary home. It includes its own kitchen, bathroom, sleeping area, and entrance.

ADUs come in several forms:

Detached: A separate structure, such as a backyard cottage or small house.
Attached: An addition that shares a wall with the main house.
Converted: A transformation of an existing space, like a garage or basement, into a livable unit.

An ADU is often used as a rental unit, a home for extended family, or a way to increase long-term property value. Because it is fully independent, it can function like a small home within your property.

What Is a JADU?

A Junior Accessory Dwelling Unit (JADU) is a smaller, more limited option. By law, JADUs are capped at 500 square feet and must be created within the walls of your existing home.

Common JADU features include:

A separate entrance to the outside.
A small kitchen or kitchenette.
The option to share a bathroom with the main house.

JADUs are popular for guest suites, live-in caregivers, or affordable family housing. They are often more budget-friendly than a full ADU since they use existing square footage instead of requiring new construction.

Feature	ADU	JADU
Size	Up to 1,200 sq. ft.	Up to 500 sq. ft.
Kitchen	Full kitchen	Small kitchen/kitchenette
Bathroom	Required	May share with main house
Entrance	Separate	Separate
Location	Detached, attached, or converted	Must be within existing home
Parking	May be required	Often exempt
Cost	Higher (new construction or major remodel)	Lower (uses existing space)
Owner Occupancy	Not required (until 2025 for most ADUs)	Required (owner must live in the home)

How to Decide Which One Works for You

Choosing between an ADU and a JADU often comes down to space, budget, and purpose.

If you need more square footage and want a fully independent rental or living space, an ADU is the better option.
If you want a cost-effective solution for a guest suite, live-in relative, or caregiver, a JADU may be the right fit.
If you are thinking about resale value, ADUs often add more long-term value to your property.

An architect can help you evaluate your lot, navigate zoning rules, and clarify what is feasible.

How Much Do ADUs and JADUs Cost?

Costs vary depending on the size, condition of your property, and the level of finish you want, but here are some rough ranges to help you compare:

ADUs - Typically range from $200,000 to $400,000 for a detached unit in the East Bay. Conversions (like a garage or basement) tend to be on the lower end, while new construction is at the higher end.
JADUs - Usually fall between $50,000 and $150,000, depending on whether plumbing or electrical work is needed and how much you update the finishes.

Keep in mind that these numbers include design, permits, and construction, but actual costs can vary. Talking with an architect early can help refine a realistic budget for your specific project.

How I Can Help

As a licensed architect based in Martinez, I work with East Bay homeowners to design and permit both ADUs and JADUs. I can help you assess your property, create plans that meet state and local requirements, and guide you through the permitting process so your project moves forward smoothly.

Thinking about adding an ADU or JADU?

Visit www.bluesquare.studio or reach out directly to schedule a consultation. Together, we can determine which option is the best fit for your property, your goals, and your budget.