Can I add an ADU to my San Diego house?
Usually, yes. Whether it pencils out depends on your lot size, the setbacks, and what's already standing, because an existing garage can sometimes be converted instead of building from scratch. The City of San Diego caps a detached ADU at 1,200 square feet and requires no parking outside the coastal zone (City of San Diego). I'm Jared Harman.
Published . Last updated . Figures are from my own records unless a source is linked.
What tells me on the spot whether an ADU is realistic?
Space. Standing in the backyard, I'm looking for a clear, open area of at least roughly 15 by 15 feet, with room left around it. If that isn't there, a new detached ADU probably isn't happening. Narrow lots are the usual problem.
The city's setback rules are looser than most people think. A detached ADU 16 feet tall or less can go into the side and rear setbacks, up to the property line, unless building code says otherwise (IB 400).
Taller than 16 feet, next to residential property, it needs at least 4 feet from the side and rear lines. The front yard setback still applies, though one ADU of 800 square feet or less can go into it (IB 400).
Is it smarter to convert a garage than build new?
Often. It's the first thing I look at. If there's a detached garage, or in some cases an attached one, converting it can make a lot more sense than building from the ground up.
The city rules help. A converted structure can keep the setbacks it already has, and you can add up to 150 square feet just for getting in and out (IB 400).
What does a garage conversion actually cost?
A client of mine is looking at converting a big detached garage right now, about 600 square feet. The quote was roughly $180,000 to $200,000. (A contractor's quote to Jared Harman's client, 2026.)
So a conversion isn't automatically cheap. It depends on what's already there.
Is there plumbing? Power? Will it need a new electrical service, or proper drains? Every one of those moves the number.
That's why I get a professional involved early. I have an ADU contractor I trust and refer regularly.
What do older North Park and Normal Heights houses hide that kills an ADU plan?
The garage itself. Plenty of older houses come with a detached garage that is really old and would have to be completely rebuilt. That can blow up the budget you had in your head.
The city does let you tear down a structure and rebuild it as an ADU while keeping the old setbacks, but only in the same spot and to the same dimensions (IB 400).
Less often, it's alley access quirks or a utility easement. I don't see those much in North Park or Normal Heights, but they come up.
What should I do before I buy a house for an ADU?
Get your ADU contractor out for a feasibility study during escrow, while you can still walk away. That tells you what the property can actually hold before it is yours.
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How big can an ADU be in San Diego, and do I have to live there?
A detached ADU can be up to 1,200 square feet. On a lot with one house, it can't be more than two stories, and it has to stay within the zone's height limit (IB 400).
No parking is required outside the Coastal Overlay Zone, and the owner doesn't have to live on the property (IB 400).
In my opinion, a finished ADU is one of the bigger boosts you can give a home's value, and your equity with it. Curious what yours would do to your number? Start with a Net Number, back to you in 24 hours.
Who is Jared Harman?
Jared Harman is a real estate agent and REALTOR® in San Diego, California, licensed under DRE 02193879 with MatchPoint at eXp Realty of California, Inc. He is based in North Park and represents buyers and sellers across the San Diego metro, including small multi-unit property and lots with ADU potential. He personally toured more than 800 homes in 2025.