Building in San Diego County almost always involves a permit, and the permit process often takes longer than the construction itself. Homeowners adding an accessory dwelling unit, expanding a kitchen, converting a garage or trying to legalize work done years ago all face the same basic steps: preparing plans, submitting them to the right agency, responding to plan check comments and passing inspections. The details vary by city, and the county handles unincorporated areas under its own rules. This article explains how that process works, what state law now requires for ADUs, and where projects most often stall.
Who Reviews the Plans
San Diego County includes 18 incorporated cities plus a large unincorporated area. The City of San Diego’s Development Services Department reviews projects within city limits, while the County of San Diego’s Planning & Development Services handles unincorporated communities. Cities such as Chula Vista, Escondido, Oceanside and El Cajon each have their own building departments with separate submittal requirements, fee schedules and review times.
Knowing which agency has jurisdiction is the first step. A property with a San Diego mailing address may still be in the unincorporated county, and requirements for setbacks, parking, fire access and utility connections can differ significantly between jurisdictions. Firms such as Streamline Design & Permitting prepare plans and manage submittals across multiple jurisdictions, and one of the first questions in any project is which department will review it.
What State Law Requires for ADUs
California has changed its accessory dwelling unit laws repeatedly since 2017, and the current framework limits how much local governments can restrict ADUs. State law generally requires local agencies to approve or deny a complete ADU application within 60 days. Detached ADUs can generally be up to 1,200 square feet, and cities cannot require side and rear setbacks of more than four feet for most new ADUs. Parking requirements are waived in many situations, including when a property is within a half mile of public transit.
Owner-occupancy rules have also changed. State law no longer allows most local agencies to require that the owner live on the property to build an ADU, although junior ADUs, which are created within the existing space of a single-family home, still carry owner-occupancy requirements. Impact fees are waived for ADUs under 750 square feet, which can significantly reduce the cost of smaller units.
Types of ADUs
State law recognizes several forms of accessory units. A detached ADU is a separate structure in the yard. An attached ADU shares at least one wall with the main house. A conversion ADU uses existing space, such as a garage, basement or accessory structure. A junior ADU is created within the walls of a single-family home, is limited to 500 square feet and may share a bathroom with the main house. Each type has different design constraints, and a garage conversion, for example, often raises questions about ceiling height, foundation condition and the loss of covered parking.
Pre-Approved Plans
The County of San Diego offers pre-approved dwelling unit plans for use in unincorporated areas. These plans are largely complete and require the homeowner or designer to fill in project-specific information, such as site details and utility connections, which can shorten the review process. Several cities in the region offer similar programs. Pre-approved plans work well for many lots, although sloped sites, unusual lot shapes and properties with existing structures often need custom plans. Examples of custom ADU work in the region are available at streamlinedesigngroup.com/adu-designs-san-diego.
From Plans to Permit
A complete permit application usually includes architectural drawings, a site plan, structural calculations when needed, energy compliance documents under California’s Title 24 energy code, and plumbing and electrical details. Missing or inconsistent information is one of the most common causes of delay. Plan checkers issue correction comments, the designer revises the plans, and the cycle repeats until the plans are approved.
Other reviews may be required depending on the site. Properties in the coastal zone may need a coastal development permit or exemption. Lots in very high fire hazard severity zones must meet additional construction standards for fire resistance. Properties with sewer laterals, septic systems or wells may need separate approvals, and hillside lots can require grading permits or geotechnical reports.
Homeowners looking for permit services in San Diego County often ask how long review takes. Timelines vary by jurisdiction, project type and workload, and a well-prepared submittal with fewer correction cycles usually moves faster than one that needs repeated revisions.
Inspections During Construction
Approval of the plans is only the midpoint. Once construction starts, inspectors visit at defined stages, commonly including foundation, framing, rough plumbing, electrical and mechanical, insulation and final. Work that is covered before inspection may have to be opened again, which adds cost and delay. The approved plans must stay on site, and any significant change during construction usually requires a revision submitted to the building department before the work continues. A final inspection and, for new dwelling units, a certificate of occupancy or final sign-off complete the process.
Legalizing Unpermitted Work
Many older homes in San Diego County include additions, garage conversions or ADUs built without permits. Unpermitted work can create problems during a sale, complicate insurance claims and expose owners to code enforcement. Legalizing that work usually requires as-built drawings that show the structure as it exists, followed by a permit application and inspections. In some cases, walls or ceilings must be opened so inspectors can see framing, wiring or plumbing.
California law provides some relief for existing unpermitted ADUs. Owners of certain units built before 2020 can request a delay in enforcement of some building standards if correcting the violation is not necessary to protect health and safety, which gives time to bring the unit into compliance. Each jurisdiction applies these rules through its own procedures.
Additions and Remodels
Home additions and major remodels follow the same basic permit steps as new construction. Structural changes, such as removing a load-bearing wall or adding a second story, typically require engineering. Kitchen and bathroom remodels that move plumbing or add electrical circuits need permits even when the footprint does not change. Replacing a water heater, installing a new electrical panel or adding solar panels also requires permits in most jurisdictions.
Avoiding Common Delays
Several steps help projects move through review with fewer setbacks. A current survey or accurate site plan prevents disputes over setbacks and lot lines. Early confirmation of utility capacity, especially sewer and electrical service, can reveal the need for upgrades before plans are finalized. Consistency between architectural drawings, structural calculations and energy documents reduces correction comments. Responding promptly and completely to plan check comments keeps the review moving.
Budgeting for fees is also important. Permit fees, plan check fees, school fees and utility connection charges vary by jurisdiction and project size, and some fees are waived or reduced for smaller ADUs under state law.
San Diego County’s permit process can seem complicated, but it follows a predictable sequence. Understanding which agency has jurisdiction, what state ADU law requires and how to prepare a complete submittal helps homeowners avoid the delays that turn a months-long project into a year-long one.
