Can You Add an ADU to Your San Diego Home?

By Rieder Homes

Dennis and Mance Rieder are the dynamic father-and-son duo behind Rieder Team Realty, bringing decades of combined experience and a genuine passion for the San Diego real estate market.

With home prices in San Diego as high as they are, a lot of homeowners are weighing the same question: do you buy something bigger, add on to what you own, build an ADU, or revamp the whole house? To dig in, we sat down with our friends and clients at Josh Renner Design, two native San Diego design pros who specialize in custom homes, additions, remodels, and, of course, ADUs (Accessory Dwelling Units).

Bring in a designer as early as possible. Before you remodel or build, identify your opportunities, constraints, and any issues up front, because catching them early saves real money. You don’t need everything figured out before you call. Part of a designer’s job is to research what’s buildable and guide you through the permitting maze across San Diego’s many municipalities.

The most expensive mistake is skipping permits. The costly cases come from owners who hire a contractor without plans or who do work without permits. It can feel silly to permit something as small as a single window, but unpermitted work resurfaces as a code enforcement case or a legal problem when it isn’t disclosed to a future buyer. A code enforcement case runs with the land. If you buy a property with an open case, rectifying it becomes your problem, not the previous owner’s.

Do your due diligence before you sign. As a property owner, you have the right to walk into your city municipality, whether that’s San Diego, La Mesa, Chula Vista, or the County, and ask about code violations or pull the permit history. Seller disclosures help, but sometimes even the seller doesn’t know about an old handshake easement or work done decades ago without a permit. A feasibility report from a designer saves you a lot, especially if you’re buying in San Diego’s more rural pockets.

What California actually lets you build. If you’ve got a single-family property, you’re entitled to an ADU. As a statewide baseline that cities must follow, you’re generally allowed a detached ADU up to 1,200 square feet, you can convert a garage or interior space to a junior ADU up to 500 square feet, and you can add an attached ADU up to 50% of your home’s existing square footage. Even at your maximum allowable build, state law protects a minimum size, so you can typically still add roughly an 800-square-foot ADU. Because ADUs generate income and raise property value, they now make up the majority of design work in San Diego.

Parking is the catch nobody plans for. Under state rules, parking is generally waived when a property is within half a mile of a transit station. That’s great for a developer, but a regular homeowner often wants that parking, especially in San Diego, where nearly everyone owns a car. A good design team tries to provide parking anyway, rather than squeezing six units onto a cul-de-sac with nowhere to park.

Pre-approved plans help, but they lock you in. Some municipalities offer free, pre-approved ADU plans that speed up permitting. The trade-off is that you still have to fit that design onto your lot and account for fire rating, and the moment you want to move a single window, it reverts to the regular, slower process, which matters in earthquake-conscious California.

Balance aesthetics, function, and budget, and keep communicating. The strongest projects come from real back-and-forth: bring your Pinterest boards, share what you love, and work with a team that listens rather than imposing an ego-driven design you can’t afford. Budget gets handled early by bringing in a trusted general contractor before you’re deep into plan check, and communication is the glue from the first meeting through permit issuance.

For an ADU, expect roughly six to eight months from the first meeting to the permit. If you’re thinking about adding an ADU, remodeling, or building new, the best first step is an open conversation.

Reach out to us at 858-779-0823 or info@riederhomes.com, or visit riederhomes.com. You can also connect with Josh Renner at 619-990-8942 or joshuarenner07@gmail.com, and Josh Percy at 619-306-6441 or joshapercy@gmail.com.