ADU, junior ADU or garage conversion: which one fits your lot?
Four ways to add a unit to a single-family lot, compared on size, setbacks and rules.
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What is the difference between an ADU, a junior ADU and a garage conversion?
A detached ADU is a separate new building. An attached ADU is added onto the house. A garage conversion turns an existing garage into an ADU. A junior ADU is a unit of up to 500 square feet created inside the house itself. All four are permitted dwelling units with a kitchen.
| Type | Where it goes | Maximum size | Side and rear setbacks | Owner must live on site |
|---|---|---|---|---|
| Detached ADU | Separate new building | 1,200 sq ft | Four feet at most | No |
| Attached ADU | Added onto the house | 50 percent of the main house | Four feet at most | No |
| Garage conversion | Existing garage | The existing footprint | None required | No |
| Junior ADU | Inside the house | 500 sq ft | Not applicable | Only if the bathroom is shared |
Which type fits my property?
It depends on the lot. A detached ADU needs open space behind the house. An attached ADU suits narrower lots. A garage conversion uses a structure you already have and needs no setback. A junior ADU needs no new building at all. The free site assessment tells you which ones your lot allows.
Can I build more than one?
Yes. According to the state's ADU Handbook, a lot with a single-family home can combine one ADU converted from existing space, one junior ADU and one new detached ADU. Rentals of these units must be for terms longer than 30 days.
Which types does Siboni Development & Design build?
All four. Siboni Development & Design designs, permits and builds detached ADUs, attached ADUs, garage conversions and junior ADUs across Los Angeles, under California license CSLB #1085971. Each type has its own page with the rules that apply and how the project runs.
Sources
- California Government Code § 66314
- California Government Code § 66321
- California Government Code § 66323
- California Government Code § 66333
- California Department of Housing and Community Development, Accessory Dwelling Unit Handbook (March 2026)
Sources checked on . General information, not legal or financial advice. Rules change and each city applies its own standards: we confirm what applies to your lot during the free site assessment.
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