The detached vs. attached ADU decision should start with the property and the owner's intended use. Each configuration changes privacy, site planning, utility routing, construction impact, and the relationship between the new unit and the main home.
California also recognizes conversion ADUs and the junior ADU, or JADU, category. The current California Department of Housing and Community Development ADU Handbook is the statewide reference point, while local agencies review property-specific proposals.
Detached ADU
A detached ADU is a separate structure. It can provide a clear physical separation between households and may offer flexible placement when the lot, access, and applicable rules support it.
Questions to resolve include:
- Where can the building fit relative to existing structures and site constraints?
- How will residents reach the entrance?
- Where will utilities run?
- How will windows, outdoor space, and privacy relate to the main home and neighboring properties?
- Can construction equipment and materials reach the work area?
A detached project typically requires a complete building enclosure and site connections. Do not assume that separation automatically produces better privacy or easier construction. Placement and design determine the lived result.
Attached ADU
An attached ADU connects to the primary dwelling. It may use a side, rear, or other addition strategy, depending on the property and approved design.
The shared interface deserves close attention. The team may need to coordinate foundations, framing, roof and wall connections, waterproofing, fire and sound separation, mechanical systems, and the effect on rooms inside the existing home.
An attached configuration can preserve a different portion of the yard than a detached building. It can also bring construction closer to the occupied house. Evaluate both the finished layout and the temporary disruption required to build it.
Conversion ADU
A conversion ADU repurposes qualifying existing space, such as a garage or other area, subject to current rules and the condition of the structure. The footprint may already exist, but living-space requirements can trigger substantial changes to structure, moisture protection, insulation, windows, doors, utilities, and interior systems.
For garage-specific planning, use the garage conversion ADU checklist .
Junior ADU
A JADU is a distinct California category associated with qualifying space within a proposed or existing single-family dwelling. It is not simply a marketing name for a small detached unit. Current state and local requirements govern its size, facilities, access, occupancy conditions, and other features.
Because ADU law changes, verify the current HCD handbook and responsible local agency guidance before designing around an older summary.
Compare the choices using owner priorities
Use one decision table rather than starting with a favorite floor plan.
Privacy
Consider entry paths, windows, outdoor areas, sound, parking or drop-off activity, and how the two households will encounter each other.
Site fit
Map existing buildings, grade, trees, utilities, access, easements, drainage, and other constraints. Confirm parcel information through the correct jurisdiction.
Construction impact
An attached or interior conversion can affect occupied portions of the home. A detached project may concentrate disruption in the yard but require more site work. Define how the owner will live during construction.
Utilities and operating systems
Identify feasible routes and capacity for water, sewer, electrical, communications, hot water, heating, cooling, and ventilation. Do not assume a particular connection arrangement is approved until the responsible parties confirm it.
Long-term use
Think beyond the first occupant. Accessibility, storage, privacy, maintenance access, flexible sleeping arrangements, and durable materials can influence how well the unit adapts over time.
Confirm the chosen path before pricing
Concept pricing is more useful when the basic type, program, site location, utility assumptions, and finish level are defined. If two contractors are pricing different ADU types, the totals are not directly comparable.
The Los Angeles ADU feasibility guide covers property-level due diligence. The ADU builder selection guide supports the next hiring decision.
Want to know what it's like to work with Jencor?
Choosing a builder is about more than the scope and the price. Read client reviews , then see what makes Jencor different .
Plan for cost and home value
Compare remodeling scope, published cost examples and the difference between estimated resale recovery and value while you own the home. The guide includes dated Los Angeles benchmarks and long-term planning considerations.
View the remodeling cost and value matrix
Related Jencor services
These service pages connect the planning topic to the project options, construction scope, and next steps Jencor can review.
Related reading
- Garage Conversion ADU Planning Checklist for Los Angeles
- What Drives ADU Cost in Los Angeles?
- Bathroom Remodel Waterproofing and Scope Checklist
Questions
What is the main difference between a detached and attached ADU?
A detached ADU is physically separate from the primary home. An attached ADU shares a connection with it, so design, structure, access, privacy, and construction interfaces differ.
Is a JADU the same as a small detached ADU?
No. California treats a junior accessory dwelling unit as a distinct category created within qualifying space in a proposed or existing single-family dwelling and subject to its own requirements.
Which ADU type is cheapest?
No type is automatically cheapest for every property. Existing conditions, structural changes, utilities, site access, design, approvals, and finish choices can change the result.
Planning a project in Los Angeles? Send Corey a note or call (310) 770-7707. Rules and requirements depend on the specific property; confirm with the city or county before you build.