Build types · San Diego, CA
Four ways to add a home to your San Diego lot.
Detached, converted, attached or junior. Each type trades cost, size and privacy differently. Here is how they compare.
How do the four ADU types stack up?
Rules summarized from state ADU law in the HCD ADU Handbook; cost ranges are published San Diego contractor estimates. All as of October 2026.
| Type | Location | State size rule | Published San Diego range |
|---|---|---|---|
| Detached ADU | New building in the yard | Limit must allow at least 850 sq ft (1,000 sq ft with 2+ bedrooms) | About $250,000 to $460,000 |
| Garage conversion | Inside the existing garage | Existing footprint, plus up to 150 sq ft for entry or stairs | About $100,000 to $225,000 |
| Attached ADU | Addition to the house | State default of 50% of the home, with the 850 / 1,000 sq ft floor | About $160,000 to $350,000 |
| Junior ADU | Inside the existing home | Up to 500 sq ft | About $90,000 to $200,000 |
Sources: HCD ADU Handbook (March 2026); Realm (March 2026) and Lars Remodeling & Design (October 2026). Ranges are not our prices; we give a written, itemized quote after a site visit. Details in the San Diego cost guide.
Which type should I start with?
If the garage is sound, a conversion or junior ADU usually keeps cost down because the shell exists. If you want two bedrooms, privacy or a second story, a detached unit is the usual answer. An attached ADU fits when the yard is shallow but the side or rear of the house has room. The garage-or-new guide walks through the trade-offs.
Find out what your lot allows
Tell us where the property is and what you have in mind. We read the zoning and ADU rules for that address, then reply with what could fit. Serving San Diego, Chula Vista, La Mesa, El Cajon and Escondido.