San Diego homeowners have more ADU options than they did a few years ago, but an ADU is still a regulated residential construction project. General eligibility does not prove that a particular design, budget or schedule will work on a specific property.

The property, zoning, overlays, existing structures, access, utilities and proposed configuration can all affect feasibility and the permit application.

This guide explains the approval process at a homeowner level. It is not a substitute for current City requirements, property-specific research or advice from qualified design and construction professionals.

First Confirm the Governing Jurisdiction

A San Diego mailing address does not necessarily mean a property is regulated by the City of San Diego. Some properties are within another incorporated city or the unincorporated County of San Diego.

Before relying on City guidance, confirm the governing jurisdiction and identify the agencies responsible for planning, building, fire, utilities and special approvals. For property within the City, the Zoning and Parcel Information Portal can help identify the zone and mapped conditions that may affect the project.

Understand the Basic ADU Options

The City recognizes accessory dwelling units and junior accessory dwelling units. An ADU provides independent living facilities and may be attached, detached or created through conversion of qualifying existing space. A JADU is a smaller, more limited unit associated with a single dwelling unit and is subject to its own requirements.

For a lot in a single-dwelling-unit zone, current City guidance generally allows one attached or detached ADU, one ADU converted from qualifying existing or proposed space, and one JADU. Different allowances apply to multiple-dwelling-unit properties and projects using the City’s ADU Home Density Bonus Program, so confirm the number and type of units permitted for the specific property. See Municipal Code §141.0302(b)(1) and (c)(1) and confirm the applicable coastal provisions with City Development Services.

Current City guidance describes attached and detached ADUs as ranging from 150 to 1,200 square feet, while JADUs generally range from 150 to 500 square feet. Conversions, existing conditions, floor-area rules and specific property circumstances can affect how these standards apply. See the size provisions in §141.0302(b)(7) and (c)(4); do not assume a conversion is subject to the same maximum as a new detached unit.

Do not choose a configuration based only on the maximum permitted size. The right approach should respond to intended use, privacy, access, budget, property relationships and utilities.

Begin With Property-Specific Feasibility

Before paying for a complete design, homeowners should establish a reliable feasibility picture.

Zone and allowable use

Confirm the base zone, planned district requirements and whether residential use is permitted. The number and type of units that may be allowed can depend on whether the property is in a single-dwelling or multiple-dwelling zone and what legally permitted structures already exist.

Overlay zones and special conditions

A property may be affected by the Coastal Overlay Zone, Beach Impact Area, High or Very High Fire Hazard Severity Zones, historic resources, environmentally sensitive lands, brush management requirements or other mapped conditions.

These conditions do not always prevent an ADU, but they may change the standards, documentation or review path. Coastal applicability can differ by provision and effective date. Confirm which regulations and coastal approvals apply with City Development Services using the Municipal Code, Information Bulletin 400, and the City’s regulatory updates.

Buildable location and setbacks

The proposed location must be evaluated against front, street-side, side and rear-yard requirements, along with building-code limitations related to fire separation, openings, height and allowable area.

Some ADUs may use reduced side or rear setbacks, but this does not mean every property-line location is automatically buildable. Fire, structure, drainage, easements, access and neighboring conditions still matter.

Existing structures

A garage or interior conversion may reduce new building area, but the existing structure must still be evaluated for residential use. Foundation, framing, ceiling height, moisture, fire separation, energy performance and utilities may require substantial work.

Utilities and drainage

The design team should investigate water, sewer, electrical, gas, stormwater and other infrastructure early. Connection routes, existing capacity, meters, trenching and required upgrades can materially affect the scope and budget.

Construction access

Plan how workers, materials and equipment will reach the ADU location. Tight side yards, slopes, walls, occupied homes and protected landscaping can complicate excavation, deliveries, staging and debris removal.

Parking Requirements Depend on the Property

Parking for an ordinary ADU

Under Municipal Code §141.0302(b)(10)(A)–(B), ADUs generally do not require parking. An ordinary new detached ADU may require one off-street parking space when the premises is both within the Beach Impact Area of the Parking Impact Overlay Zone and outside a transit priority area, unless a listed exemption applies.

The listed exemptions include:

  • The ADU is 500 square feet or less.
  • The premises is within a historical district that is a designated historical resource.
  • The ADU is attached to the proposed or existing primary dwelling unit or accessory structure.
  • The premises is within a residential permit-parking district.
  • A car-share vehicle is located within one block of the premises.

Being somewhere within the broader Coastal Overlay Zone does not by itself establish a parking requirement. Ask City Development Services to confirm the Beach Impact Area, transit-priority-area status, overlays, and applicable exemptions for the specific property before relying on a no-parking assumption.

Replacement parking after demolition or conversion

Replacement parking is a separate question from parking for the new ADU. Under §141.0302(b)(10)(C), demolishing a garage, carport, or covered parking structure in conjunction with an ADU, or converting it to an ADU, generally does not require replacing those off-street spaces. Replacement parking may be required when the premises is within the Beach Impact Area and outside a transit priority area. Confirm the affected spaces and applicable requirements with the City; do not assume the new-ADU exemptions resolve the separate replacement-parking question.

Affordable and bonus ADUs

The ADU Home Density Bonus Program has a separate parking rule. §141.0302(d)(6) requires one off-street space for each affordable ADU and bonus ADU outside a transit priority area. Confirm the project’s program status and property-specific requirements with City Development Services.

A Building Permit Is Required

City Information Bulletin 400 requires a building permit to create an ADU or JADU. Depending on the project and number of units, the City may issue a Combination Building Permit or another Building Permit type.

A permit application needs coordinated documents sufficient to demonstrate compliance with the planning, building, structural, energy, fire, utility and site requirements applicable to the project.

An ADU submittal may require some combination of:

  • Site information showing property lines, structures, access, setbacks and relevant conditions
  • Architectural plans showing the proposed use, layout, dimensions and elevations
  • Structural information and calculations where required
  • Energy-code documentation
  • Utility, plumbing, electrical and mechanical information
  • Drainage, grading or civil information when site work requires it
  • Supporting documentation for overlays, easements, historic conditions or other special reviews
  • City forms, ownership information and project declarations

A complete-looking drawing set is not necessarily a coordinated permit package. Clarify who is responsible for each discipline and who will assemble responses when reviewing agencies request corrections.

Preapproved Plans Do Not Eliminate Site Work

The City accepts certain preapproved ADU plans. These may reduce part of the plan-review effort, but the selected design must still be adapted to the property and comply with current development regulations.

Homeowners may still need site planning, foundation adaptation, utility design, energy documentation, grading or drainage information and other property-specific work. A preapproved building design is not the same as a complete, permit-ready project for a particular lot.

The Typical Approval Process

1. Define the project

Clarify intended use, desired configuration, privacy, accessibility and preliminary budget.

2. Research the property

Confirm jurisdiction, zoning, overlays, legal structures, easements, utilities, fire conditions and site constraints.

3. Establish feasibility

Evaluate likely location, size, access, building relationships, utility routes, site work and professional requirements before committing to full design.

4. Develop coordinated documents

The design team prepares the drawings and calculations required for the selected project. Product decisions and system assumptions should be developed far enough to support a realistic application and budget.

5. Submit the application

The application is submitted through the City’s current permitting system with the required forms, plans and supporting information.

6. Respond to review comments

City reviewers may request corrections or clarification. The project team must coordinate responses across architectural, structural, energy, fire, utility and site disciplines without creating conflicts elsewhere in the documents.

7. Obtain permit issuance

After required corrections, approvals, fees and administrative items are completed, the permit can be issued. Permit issuance does not replace the need for a complete construction scope and qualified contractor.

8. Complete construction and inspections

Work proceeds under the issued permit and is inspected at required milestones. Changes during construction may require documentation or permit revisions.

9. Final approval and closeout

The project should not be treated as complete until required inspections and approvals are finalized and the homeowner has received relevant records, warranties, operating information and closeout documentation.

What Commonly Delays Approval?

  • Property conditions were not investigated before design
  • The proposed location conflicts with an easement, drainage path, fire condition or utility
  • Architectural, structural and energy documents are not coordinated
  • Utility scope or service capacity remains unresolved
  • Coastal, historic, fire or environmental requirements are identified late
  • The design changes after consultants complete their work
  • No one is clearly responsible for consolidating review comments
  • The budget assumes the permit plans represent the complete construction scope

Good planning cannot eliminate every correction or surprise. It can reduce avoidable gaps that cause redesign, delay and budget pressure.

Define Responsibilities Before Signing Agreements

Homeowners should identify who will:

  • Research zoning and overlays
  • Verify existing conditions and property information
  • Coordinate architecture, structure, energy and utilities
  • Prepare and submit the permit application
  • Respond to City comments
  • Update the budget and communicate schedule impacts
  • Coordinate plan revisions during construction

The architect, designer, engineer, ADU company or contractor may perform some or all of these tasks. The important point is that responsibility should be explicit rather than assumed.

How Foundation Can Help

A Foundation Strategy Session™ helps San Diego homeowners organize the goals, priorities and early decisions that come before ADU design, permitting and construction. The session results in a written Foundation Renovation Roadmap™ that identifies risks, unresolved questions and practical next steps.

For a San Diego ADU project, that may include:

  • Clarifying goals, priorities and intended use
  • Organizing feasibility questions for qualified professionals
  • Developing a complete preliminary budget framework
  • Identifying responsibilities that need to be assigned
  • Preparing for architect, designer, ADU company and contractor interviews
  • Preparing to compare proposals, assumptions, exclusions and deliverables

For property-specific preliminary due diligence, homeowners may add a Foundation Feasibility Report™ to the Strategy Session. The report can organize available zoning and property research, mapped constraints, apparent opportunities, likely professional or permit needs, major risks and recommended next steps before the homeowner invests heavily in design. It does not determine zoning compliance, provide a survey or engineering, prepare permit documents or guarantee City approval.

Foundation provides independent education, organization and decision support. Foundation does not act as the permitting authority or replace the architect, designer, engineer, surveyor, contractor, utility provider or other qualified professionals, and does not guarantee approvals, pricing, schedules or outcomes.

Start With Clarity, Not a Floor Plan

San Diego’s ADU rules create meaningful opportunities, but general eligibility does not prove that a particular design, budget or schedule will work on a specific property.

Before selecting a plan or requesting construction prices, confirm the jurisdiction, investigate the property, understand the approval path and assign responsibility for the work ahead.

That early clarity gives the design and permitting team a stronger foundation—and gives the homeowner a more realistic picture of the complete project.

Regulatory Note

This article is specific to San Diego and provides general educational information, not guidance for other jurisdictions. Regulatory references were reviewed on September 18, 2026. ADU laws, ordinances, bulletins and agency procedures can change. Property-specific requirements should be confirmed with the City of San Diego, other applicable agencies and qualified project professionals. Readers outside San Diego should consult their own state and local jurisdiction.

Official Regulatory Sources