Where Can ADUs be Built in San Diego, CA?

What Is an ADU? (Definition & Legal Foundation)

An Accessory Dwelling Unit (ADU) — sometimes called a granny flat, in-law suite, or secondary dwelling unit — is an independent housing unit built on a residential property that already contains a primary home. According to the California Department of Housing and Community Development (HCD), an ADU provides complete independent living facilities, including a kitchen, bathroom, and sleeping area, and can be attached to or detached from the main house. Conversions such as basement apartments or converted garages also qualify as ADUs under California’s zoning regulations.

State law mandates that ADUs must be allowed jurisdiction-wide in all areas zoned for residential use. Cities and counties cannot ban them through local zoning ordinances; instead, they may only apply objective standards such as setbacks, height limits, or utility capacity requirements that align with the California Residential Code. As the HCD emphasizes, “ADUs are an innovative and effective option for adding much needed housing”. This legal foundation ensures that virtually any homeowner with a single-family dwelling or multifamily lot can add an ADU, subject to placement and siting rules established in the permitting process.

Tip: Before building, verify your property’s zoning and confirm your ADU meets California’s independent living unit standards.

Where on My Property Can I Place an ADU? (Setbacks & Siting Basics)

In California, Accessory Dwelling Units (ADUs) can be built in several locations on a residential property, as long as they comply with state and local zoning codes and siting rules. The standard minimum setbacks are 4 feet from the side and rear property lines, although conversions of existing Accessory Structures such as garages or other legal buildings generally do not require new setbacks (Alameda County).

For lot coverage, state law guarantees that a single-family home may add one ADU plus one Junior ADU (JADU), while multifamily properties may include at least two detached ADUs plus interior conversions of non-livable areas. Beginning in 2025, updated ADU legislation expands multifamily allowances to as many as 8 detached units on qualifying lots (Revival Homes).

Common Placement Options

• Backyard detached unit (most common siting choice)
• Above a garage (new build or conversion)
• Side yard unit (if setbacks allow sufficient clearance)
• Internal conversion such as attic conversions or basement conversions within the primary dwelling

Easements and Restrictions

ADUs cannot block existing utility easements, sewer connections, or access points on the parcel. These areas must remain clear for service and legal access. And importantly, “An ADU cannot be the first structure on a vacant lot — it must be accessory to a primary dwelling” (California State Assembly).

Tip: Plan your ADU placement early — setbacks and utility access can greatly impact design and cost.

Where Are ADUs Allowed by Local Zoning?

In California, state law requires that Accessory Dwelling Units (ADUs) — also known as accessory apartments or Ancillary Dwelling Units — be permitted in all residential zones statewide. Cities and counties cannot prohibit these secondary housing options; instead, they may apply objective development standards like setbacks, height limits, or lot coverage under the zoning code and local zoning ordinances.

In the City of San Diego, ADUs are allowed in all base zones that permit residential uses, confirmed in the city’s ADU/JADU Information Bulletin 400 and planning toolkit. This ensures that whether a property is zoned for a single-family home or multifamily use, homeowners can move forward with an ADU permit application and Building Permit process in compliance with city guidelines.

Special Cases

• Homeowners Associations (HOAs): Under California Civil Code §4751 (AB 670), HOAs cannot prohibit ADUs but may enforce objective design standards, such as requiring compatible exterior materials with the primary home.
• Historic Districts: ADUs are allowed, but additional review under local zoning ordinances may apply to preserve neighborhood character. These requirements must remain objective and cannot be used to block a legal ADU.
• Coastal Zone: ADUs are also permitted in California’s Coastal Zone, though projects may require a Coastal Development Permit, including fire safety considerations like fire sprinklers and compliance with environmental protection policies.

See our full San Diego ADU Regulations Guide for more details.

Where Can Utilities Be Connected? (Infrastructure Considerations)

Utility connections are one of the most important factors in planning where to place your ADU, since siting directly impacts cost, feasibility, and the permit process.

• Water & Sewer: ADUs must connect to the existing laterals serving the primary home. Placement can affect trenching and cost — backyard ADUs often require longer runs, while garage or basement conversions may reuse existing lines. In some rural areas, a septic tank connection may be required instead of public sewer.
• Electricity: Most ADUs are powered by extending service from the main residence. Homeowners may choose to sub-meter for separate billing, but detached ADUs can add costs depending on utility meters and trenching distance.
• Gas: A gas connection is optional. Many new ADUs, including manufactured homes or converted garages, follow the electrification trend by relying on all-electric appliances instead of new gas lines.
• Drainage & Stormwater: Detached units, especially in backyards, may require grading, erosion control, or drainage improvements to comply with stormwater requirements and prevent flooding in flood zone areas.
• Impact Fees: California law exempts ADUs under 750 square feet from impact fees, reducing costs for homeowners who want compact units that still generate rental income.

These infrastructure considerations show why early planning is essential. Property owners should weigh not only available space and setbacks, but also how easily connections for water, power, and sewer can be extended to serve the new unit.

Expert Insight: Position your ADU close to existing utilities to reduce trenching and connection expenses.

Where We Build ADUs: Our Service Areas

We build Accessory Dwelling Units (ADUs) citywide in San Diego, serving every neighborhood — from La Jolla to City Heights to Pacific Beach. Beyond the city, our team also works across Greater San Diego County, including unincorporated areas where California State Law now supports ADUs as a key housing solution. In fact, 30–45% of new housing permits in these areas are for ADUs, reflecting the region’s growing demand for flexible housing and additional rental income opportunities (Governing).

Permitting activity continues to rise across the county. Between 2020 and 2024, the number of ADUs approved in San Diego more than tripled, with most of the growth happening within the City and in unincorporated communities (chpd.ucsd.edu). For homeowners looking to maximize space on their primary residence, our team helps navigate the full ADU process, from zoning review and permit applications to working with a licensed contractor for construction.

For neighborhood-specific rules and examples, visit our internal landing pages (e.g., La Jolla, North Park, Chula Vista) or explore our San Diego ADU regulations overview for guidance on siting, zoning, and Building Permit requirements.

Tip: We build ADUs citywide — from La Jolla to Chula Vista — helping homeowners unlock space and value.

Parking, Access, and Easements

California’s ADU legislation has eased parking requirements, making it easier for homeowners to add secondary units. Under Section 65852.2, cities may only require one off-street parking space per ADU or per bedroom (whichever is fewer), but there are several exemptions — such as when a unit is near public transportation, built through garage conversions, or part of the Plus One ADU Program (New Avenue Homes).

In San Diego, ADU projects located within Transit Priority Areas (TPAs) or within half a mile of a major transit stop are not required to provide additional parking (ADU Marketing Pros). This policy supports affordable housing growth while reducing reliance on cars.

Driveways, access easements, and shared drives must remain open and unobstructed. An ADU cannot block public streets or restrict existing access rights when sited on a property. Additionally, under San Diego’s JADU Zoning Ordinance and ADU/JADU guidelines, front yard areas are rarely permitted to serve as ADU parking, except in limited cases of Legal Structures or conversions (City of San Diego).

Expert Insight: Use your driveway or shared access wisely — ADU parking exemptions near transit can save valuable space and costs.

Property-Level Examples

Below are real-world ADU placement examples and considerations to help you picture how siting impacts cost, design, and utility complexity. These scenarios are consistent with state guidelines and local zoning, including requirements under AB 2533 and city-level planning rules.

Sample Lot Siting Scenarios

• Backyard Detached ADU: A freestanding unit behind the primary home—common and flexible. Placement may increase trenching and utility costs but provides privacy and rental potential.
• Garage Conversion / Over-Garage ADU: Use or expand an existing garage or other Legal Structures to reduce excavation and utility runs. These projects often have a faster permit history and may qualify for simplified review under pre-approved plans.
• Side Yard ADU: A viable option if setbacks allow; may require careful spacing, fire safety considerations, and coordination with Planning & Development Services for site-specific approvals.

Where you place the ADU affects excavation, trenching, drainage, and parking costs. A backyard unit often means longer utility runs, while a garage conversion can reuse existing infrastructure. Financing tools such as a renovation loan or HomeStyle® Renovation mortgage may also support projects, particularly when significant upgrades are needed.

Tip: Strategic ADU placement can lower trenching and utility costs — plan for function, privacy, and long-term flexibility.

Conclusion: Getting Your Property Assessed

ADUs in California must follow key siting rules: setbacks (4 ft side/rear), residential zoning, utility connections, easement protection, and parking exemptions. Every property is unique, and factors such as slope, drainage, or overlays like historic, coastal, or even Stormwater Flood zones can affect feasibility. In some cases, additional documentation such as a geotechnical engineering report or GIS Planning Layers (Parcel Maps or Tentative Maps) may be required to move forward.

The best way to move forward is with a professional site assessment. Our team offers free ADU consultations across San Diego city and county, guiding homeowners through the ADU process, identifying potential challenges such as unpermitted ADUs or easement conflicts, and helping you maximize your property under California’s ADU laws. For some projects, financing options like a renovation loan, Construction-to-Permanent loan, or HomeReady loan may also support your build.

👉 Next Step: Schedule your free ADU consultation and see what’s possible for your lot.

Expert Advice: A professional site assessment helps identify zoning limits and utility connections early — saving time and money.