The San Diego Homeowner's Guide to Building an ADU

Few home projects deliver as much flexibility as an accessory dwelling unit. An ADU — sometimes called a granny flat, backyard home, or in-law suite — can house aging parents, give adult children a foothold in an impossible housing market, generate rental income, or simply add usable square footage and long-term value to your property. In San Diego, where land is scarce and rents are high, the math is especially compelling.

California and the City of San Diego have spent recent years streamlining ADU rules to encourage construction, which means the path is more navigable than most homeowners expect. This guide walks through what you need to know before you break ground in 2026.

What counts as an ADU in San Diego?

San Diego recognizes a few distinct ADU types, and the one you choose shapes both your budget and your permitting path. Understanding the categories early helps you match the project to your lot and your goals.

• Detached ADU: A freestanding structure in your yard — the most private and flexible option.
• Attached ADU: An addition that shares a wall with your existing home.
• Garage conversion: Transforming an existing garage into living space, often the most cost-effective route.
• Junior ADU (JADU): A smaller unit (up to 500 sq ft) created within the existing footprint of your home, with its own entrance.

Permits and rules you should know

San Diego's bonus ADU program is one of the most generous in the state, and in many neighborhoods it allows more than one additional unit. Still, the rules reward homeowners who plan carefully. A few essentials to keep in mind.

• Most ADUs no longer require additional off-street parking when near transit.
• Owner-occupancy requirements have been relaxed for many unit types.
• Coastal-zone properties (think La Jolla, Del Mar, Point Loma) may need a Coastal Development Permit.
• Setback, height, and size limits still apply and vary by zone and ADU type.

Because the details shift by parcel, we always start with a feasibility review of your specific lot before any design work begins.

What does an ADU cost in San Diego?

In 2026, most quality ADUs in San Diego fall between $150,000 and $400,000, depending on type, size, and finish level. Garage conversions sit at the lower end; fully detached, custom-built units with premium finishes reach the top. Beyond construction, budget for design and engineering, permit and impact fees, and utility connections.

• Garage conversion: roughly $150,000–$220,000.
• Detached ADU (600–1,000 sq ft): roughly $250,000–$400,000+.
• Soft costs: design, engineering, and permits typically add 10–15%.

Designing an ADU people actually want to live in

The best ADUs feel like real homes, not afterthoughts. Smart space planning, abundant natural light, and quality finishes make a small footprint live much larger — and command stronger rents. We focus on full-height windows, efficient kitchens, generous storage, and a private outdoor connection wherever the lot allows. Matching the ADU's architecture to your main home also protects curb appeal and resale value.

Is an ADU worth it?

For most San Diego homeowners, yes. A well-built ADU can add substantial property value, generate $2,500–$4,000+ per month in rent depending on size and location, and provide flexibility as your family's needs change. It's one of the rare projects that pays you back in both income and lifestyle — provided it's designed and built to last.