ADU Alliance

2023 Complete Guide To ADU Laws In San Diego County

Accessory dwelling units (ADUs) have become an increasingly popular option for homeowners in San Diego County looking to add extra living space to their property. However, before you can build an ADU, you need to obtain the proper permits from the County of San Diego. This comprehensive guide provides everything you need to know about recent ADU laws in San Diego County, along with details on ADU permits, regulations, and requirements.

Key Takeaways: ADU Laws in San Diego County

  • Recent California laws allow taller detached 2-story ADUs to meet height limits
  • Must obtain permits verifying compliance with County ADU regulations
  • Attached and detached units have different size maximums
  • Budget $7k–$40k+ for permits, fees, and utility upgrades
  • Temporary fee waivers on plan checks until January 2024

What is an ADU?

An ADU, also known as a granny flat or in-law suite, is a secondary dwelling unit on the same lot as an existing single-family home. According to ADU laws in San Diego County, an ADU must contain complete independent living facilities, including a full kitchen, bedroom(s), and bathroom.

what is adu


ADUs can either be detached from the main house (such as a backyard cottage) or attached in some way, such as an addition, conversion of an attached garage, or repurposing basement or attic space.

Recent California ADU Legislative Changes

In January 2023, California enacted AB 2221, AB 916, and SB 897 which contained over a dozen impactful changes for ADU laws in San Diego. Most notably:

Height Restriction Overrides: The new laws allow homeowners in certain areas to build 2-story detached ADUs subject to maximum height limits such as 18 or 25 feet, depending on location specifics. This enables the construction of ADUs with enough height for a second level.

Expedited Review: The state mandated a 60-day limit for local agencies to approve or deny ADU permit applications after submittal. This stringent deadline aims to accelerate project approvals.california ADU legislative changes

Affordability Incentives: The ADU laws in San Diego County standardize an affordable housing density bonus that enables homeowners to build additional market-rate units if they designate some ADUs as income-restricted affordable housing.

San Diego County adopted guidelines to reflect these 2023 ADU laws. The county’s updated ADU regulations include specific height allowances for 2-story units based on their proximity to transit and application review deadlines.

Where Are ADUs Allowed in San Diego County?

You can only build an ADU on a residentially zoned property with an existing single-family home per county zoning regulations. Use this zoning lookup to verify your eligibility by entering your assessor’s parcel number (APN).

If your property qualifies, you may be able to have up to one detached ADU plus one junior ADU on the lot. A junior ADU (JADU) is a smaller dwelling (maximum 500 sq ft) created within the walls of the primary residence.

JADUs must include an efficient kitchen, separate entrance, and interior entry to the main home. The owner must reside on-site within either the JADU or primary dwelling.

ADU Laws in San Diego County: ADU Size Requirements

The maximum ADU sizes allowed depend on whether the unit is attached or detached:


Square Footage of Existing single-family residence (SFD) Maximum Allowed Square Footage for Detached ADU Maximum Allowed Square Footage for Attached ADU (up to 50% of SFD)
Studio or 1 Bedroom ADU 2 Bedrooms  or more  ADU
500 sq. ft. 1,200 sq. ft. 850 sq. ft. 1,000 sq. ft.
1,000 sq. ft. 1,200 sq. ft. 850 sq. ft. 1,000 sq. ft.
1,800 sq. ft. 1,200 sq. ft. 900 sq. ft. 1,000 sq. ft.
2,000 sq. ft. 1,200 sq. ft. 1,000 sq. ft. 1,000 sq. ft.
2,200 sq. ft. 1,200 sq. ft. 1,100 sq. ft. 1,100 sq. ft.
3,000 sq. ft. 1,200 sq. ft. 1,200 sq. ft. 1,200 sq. ft.
4,500 sq. ft. 1,200 sq. ft. 1,200 sq. ft. 1,200 sq. ft.

There are no explicit limits on the number of bedrooms in a detached ADU.

Building Permit Requirements

Yes, you need to obtain a building permit before any kind of ADU construction, as per ADU laws in San Diego County. This crucial process verifies your unit meets important health, safety, zoning, and building code regulations.

The County PDS department reviews all ADU permit applications. They ensure your project adheres to regulations around:

  • Maximum size
  • Height restrictions
  • Setback minimums (distance from property lines)
  • Utility requirements
  • Parking rules

PDS also enforces the state’s 60-day application review limit. At a minimum, detached ADUs must provide:adu building permit in san deigo county

Necessary Amenities

  • Complete kitchen
  • Bathroom (toilet, sink, shower)
  • Sleeping area(s)
  • Separate exterior entrance

Potential Other Requirements

  • Fire sprinklers
  • Parking space(s)
  • New utility meters and connections

Attached ADUs typically have lower amenity thresholds since they can share walls and systems with the main dwelling.

Utility Service Requirements

You will likely need independent utility infrastructure for a detached ADU, including:

  • Separate water line with a meter
  • Independent electrical panel and meter
  • Dedicated gas line, if applicable
  • Individual sewer/septic access

For attached ADUs, you can sometimes share utility connections with the primary dwelling or sub-meter of the ADU usage.

Utility connection costs often reach $5,000+ for detached ADUs but may be far less for attached units. Verify requirements and costs upfront with local utility companies.

ADU Permit Cost Breakdown

As part of a temporary county fee waiver program through January 2024, ADU laws in San Diego waive certain ADU plan check costs. However, you must still pay building permit fees, impact fees, and potentially utility connection and capacity charges.

Typical ADU permit costs include:

adu permit cost breakdown

Plan Check Fees

  • Review of construction plans
  • $800 – $2,500
  • Waived through January 2024

Building Permit Fees

  • Approval to begin construction
  • $2,500 – $5,000+

Impact Fees

  • Offset community facility impacts
  • $2,000 – $15,000+

Utility Connection Fees

  • Water, electrical, sewer, etc
  • $2,000 – $15,000

Total Budget: $7,000–$40,000+, depending significantly on size and whether utilities require upgrades. You can use ADU cost calculators to estimate expenses. Get proposals from reputable builders to dial in accurate pricing.

Financing Your ADU Project

Several financing options exist to fund your ADU project, including cash, loans, and alternative lenders.

  • For example, you can take out a home equity line of credit against your property value or use private lenders who fund as little as 50% of the project upfront, with the rest due upon completion. Many builders also offer payment plans to break up costs over time.financing adu project

Certain cities and non-profits additionally provide low-rate pre-development loans to pay for portions like permits and architectural plans if you meet affordability commitments.

Investigate multiple ADU financing solutions with reputable providers before breaking ground. Securing funding can be quick and easy with professional guidance.

Expediting Your ADU Approval

The web of county departments and regulations around permitting ADUs can quickly become hard to navigate, especially if you’re new to development—approval delays from lacking proper documentation further stall projects for months.

Instead, partnering with an experienced firm like ADU Alliance simplifies everything from initial design concepts to finalizing construction. Our full-service ADU team specializes specifically in navigating the ADU laws in San Diego County regulatory environment to facilitate quick permits often in 6-8 weeks.

After assessing your property, ADU Alliance generates 3D concept designs and a clear permitting roadmap tailored to your unique ADU project. our ADU experts assemble all required documentation, including zoning exhibits, utility planning, and architectural plans stamped for approval.

This comprehensive turnkey approach also extends to optional à la carte offerings like financing coordination, contractor introductions, interior design finishes, and furniture procuring, so you can fully outsource your ADU build.

Learn more about the complete range of ADU services available from ADU Alliance. We hope this comprehensive permit guide for ADU laws in San Diego County answers all your questions! Contact us if you need clarification or want customized guidance for your unique property situation.