Converting a garage is usually the cheapest way to add a legal ADU in California — the structure, roof, and slab already exist. Here is the published cost range, what the money actually goes to, what the cities' own rules say about parking, and the cases where a conversion is not cheap after all.
San Diego builder guides put garage conversion ADUs at $100,000–$210,000 — the lowest of the common ADU types. That is a published educational range, not a quote for your garage. A basic one-car conversion with a short plumbing run lands low; a two-car conversion with a long sewer run, a panel upgrade, and premium finishes lands high or beyond.
The question every garage conversion raises — "where do the cars go?" — is answered in each city's official ADU rules:
None of these can be judged from a photo or a form — they are exactly what a builder's feasibility visit checks before anyone talks price.
All three published ranges, the educational cost estimator, cost drivers, and permit and utility fee notes.
Read the guide →Thinking bigger than the garage? The published $375–$600 per sq ft and the size math for a backyard build.
Read the guide →Eight quick questions and a plain-language likely / maybe / talk-to-the-city result.
Read the guide →That feasibility conversation — your lot, your city's current rules, your utilities, your budget — is the real answer to every cost and rules question. It is exactly what a match request starts: one licensed local builder, matched to your project, and nobody else.
The intake form lives on our main page — that page states whether intake is currently open.
San Diego ADU Match is a matching service, not a contractor. We never quote or estimate a price for your property, and we do not give feasibility or legal opinions — those calls belong to licensed builders and your city. Guides on this site are general information, not advice about your property.