ADU Alliance

Decoding ADU: What Does ADU Stand for in San Diego County?

ADUs, or Accessory Dwelling Units, play a pivotal role in San Diego County’s housing landscape. In this comprehensive guide, we dive deep into what ADU truly means for residents. From its definition to the benefits and legal aspects, this article serves as your go-to resource for understanding ADUs in San Diego County.

what does adu stand for in san diego county

Key Takeaways:

  • Definition of ADU: Unpacking the term and its implications.
  • Legal Aspects: Navigating the Regulations around ADUs in San Diego County.
  • Benefits: Exploring the advantages of having an ADU on your property.
  • Construction and Design: Understanding the process of building and designing ADUs.
  • ADU Services in San Diego County: An Overview of the Services Offered by ADU Alliance.

Unveiling the Significance of ADUs in San Diego County

The housing landscape in San Diego County has witnessed a transformative shift with the rise of Accessory Dwelling Units (ADUs). But what does ADU stand for in San Diego County, and why is it gaining so much attention?

Defining ADU: What Does ADU Stand For In San Diego County?

  • At its core, an ADU, or Accessory Dwelling Unit, is a secondary housing unit that can be either attached to or detached from the primary residence. The term encompasses various structures, from converted garages to standalone cottages.

ADU – Explained

  • ADUs, also known as granny flats or in-law units, have become a popular solution for homeowners looking to maximize their property’s potential. They serve as versatile living spaces that can house family members, provide rental income, or serve as a home office.

what does adu stand for in san diego county expert construction

Legal Aspects and Regulations:

  • Understanding the legalities surrounding ADUs is crucial for homeowners in San Diego County. The official regulations dictate the size, design, and placement of ADUs, ensuring they comply with local zoning laws.

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.
  • 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.

Navigating Regulations

  • The process of obtaining permits for ADUs involves adhering to specific guidelines. The ADU Regulatory Assistance provided by the ADU Alliance simplifies this intricate process, offering expert guidance to homeowners.

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:

what does adu stand for in san diego county local experts

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:


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.

Benefits of ADUs:

The advantages of having an ADU are multifaceted. From increased property value to additional income opportunities, ADUs contribute significantly to a homeowner’s overall experience.

Boosting Property Value

  • Research indicates that properties with ADUs often boast higher market values. The versatility of these units appeals to potential buyers, making them an attractive investment.

Rental Income Potential

  • For homeowners looking to supplement their income, renting out an ADU provides a steady revenue stream. The ADU Consultation services by ADU Alliance can guide you in optimizing your ADU for rental purposes.

Construction and Design:

Building an ADU involves intricate steps, from architectural planning to obtaining necessary permits. The expertise of professionals in ADU construction ensures a seamless process.

Designing Your ADU

ADU Services in San Diego County:

  • ADU Alliance stands as your go-to partner for all things ADU-related in San Diego County. From consultation to construction, their comprehensive services cover every aspect of ADU development.

Exploring ADU Services


In conclusion, deciphering what ADU stands for in San Diego County unveils a world of possibilities for homeowners. Whether it’s enhancing property value, creating rental income, or optimizing living spaces, ADUs redefine the way we approach housing.

Embrace the ADU revolution with ADU Alliance contact us today at (760) 456-8747, your trusted partner in bringing innovative and functional ADU solutions to San Diego County.