ADU Construction Permits California: Complete 2026 Guide for San Diego Homeowners

Accessory Dwelling Units have become one of the most popular construction projects in California, and for good reason. State legislation has removed many of the barriers that previously made ADU construction difficult, creating a streamlined permit process that allows homeowners to add rental income, house family members, or increase property value.

This guide covers the current ADU permit requirements in California with specific detail for San Diego County homeowners. Whether you are planning a garage conversion, a detached backyard unit, or a Junior ADU within your existing home, understanding the permit landscape is essential before breaking ground.

California ADU Laws: What Changed and Why It Matters

California has passed multiple pieces of ADU legislation since 2017 that fundamentally changed how cities process ADU permits:

• AB 68 (2020): Reduced permit review timelines to 60 days and limited cities' ability to impose subjective design standards
• SB 13 (2020): Reduced impact fees for ADUs under 750 sq ft and prohibited owner-occupancy requirements until 2025
• AB 881 (2020): Eliminated parking requirements for ADUs and limited setback requirements
• AB 2221 (2022): Further clarified that cities cannot impose conditions that make ADU construction infeasible
• AB 1033 (2024): Allows ADUs to be sold separately from the primary home as condominiums in participating cities

The net effect: California homeowners have a legal right to build at least one ADU and one Junior ADU on single-family lots, and cities must approve compliant applications within 60 days.

ADU Types and Size Limits

Detached ADU

A standalone structure built in your backyard. California allows detached ADUs up to 1,200 square feet regardless of lot size. Maximum height is 16 feet, or up to 18 feet in certain circumstances (e.g., within half a mile of transit).

Attached ADU

An addition to your existing home. Attached ADUs can be up to 1,200 square feet or 50% of the primary dwelling's floor area, whichever is less.

Garage Conversion ADU

Converting an existing garage into living space. This is often the most cost-effective ADU option since the shell already exists. No replacement parking is required under state law.

Junior ADU (JADU)

A unit of up to 500 square feet created within the existing walls of a single-family home. JADUs require their own entrance and a cooking facility (can be an efficiency kitchen). You can build both a JADU and an ADU on the same property.

ADU Permit Requirements in San Diego

The City of San Diego processes ADU permits through its Development Services Department. Here is the step-by-step process:

Step 1: Pre-Application Research

• Verify your property zoning allows residential use (most single-family and multi-family zones qualify)
• Check for easements, setback requirements, and any HOA restrictions
• Determine if your property is in a coastal zone, historic district, or fire hazard area (additional review may apply)

Step 2: Plans and Design

• Hire a licensed architect or designer to prepare construction plans
• Plans must include structural, electrical, plumbing, and mechanical details
• Title 24 energy compliance calculations are required
• Plan costs: $5,000-$15,000 depending on complexity

Step 3: Permit Application

• Submit plans to the City of San Diego Development Services
• City has 60 days to approve or deny a complete application
• Permit fees for ADUs in San Diego: $3,000-$10,000 (impact fees are waived or reduced for ADUs under 750 sq ft)

Step 4: Construction and Inspections

• All work must be performed by or under the supervision of a licensed contractor
• Required inspections: foundation, framing, rough electrical, rough plumbing, insulation, final
• Certificate of Occupancy issued after final inspection passes

Our detailed permits and rules guide covers the full San Diego building permit process.

ADU Construction Costs in San Diego (2026)

These costs include design, permits, construction, and site work. Utility connections (sewer, water, electrical) can add $10,000-$30,000 if new connections are needed. Use our free construction calculators to estimate costs for your specific project.

Common ADU Permit Mistakes to Avoid

1. Not Checking Utility Capacity

Existing sewer and water lines may not support an additional unit. The San Diego sewer capacity verification process can take 2-4 weeks and should be started early.

2. Ignoring Setback Requirements

While California has reduced setback requirements for ADUs to 4 feet from side and rear property lines, some local conditions may impose additional requirements. Coastal zone properties often have different setback rules.

3. Underestimating Site Work

Grading, retaining walls, drainage, and utility trenching can add $20,000-$50,000+ to a detached ADU project, particularly on sloped lots common in San Diego neighborhoods like Mission Hills, Hillcrest, and La Mesa.

4. Skipping the Soil Report

San Diego soils vary dramatically by neighborhood. A geotechnical report ($3,000-$5,000) is often required and always recommended to avoid foundation problems.

ADU Rental Income Potential in San Diego

The financial case for ADUs in San Diego is strong. Current rental rates for ADUs in San Diego County:

• Studio / 1-bedroom (400-600 sq ft): $1,800-$2,500/month
• 1-bedroom / 2-bedroom (600-1,000 sq ft): $2,200-$3,500/month
• Large 2-bedroom (1,000-1,200 sq ft): $3,000-$4,500/month

At these rates, most ADUs generate a positive cash-on-cash return within 5-8 years, making them one of the best real estate investments available to California homeowners. Read our design-build ADU guide for more on the construction process.

Hiring an ADU Contractor in San Diego

ADU construction requires a licensed general contractor (CSLB B license) who understands the specific permit requirements and construction methods for accessory dwelling units. Look for:

• Experience with completed ADU projects in San Diego County
• Knowledge of current California ADU legislation
• Design-build capability to streamline the process
• References from past ADU clients

RemodelSD Construction holds CSLB License #1054602 and specializes in ADU construction throughout San Diego County. Call (858) 434-7166 for a free ADU feasibility assessment for your property.

Frequently Asked Questions

Do I need a permit to build an ADU in California?

Yes. All ADUs in California require building permits. However, California state law has streamlined the process, limiting local review to 60 days and removing many barriers that previously made ADU construction difficult.

How much does an ADU cost to build in San Diego?

ADU construction costs in San Diego range from $150,000 to $350,000+ for a detached unit. Garage conversions run $80,000 to $150,000. Costs depend on size, finishes, site conditions, and whether utility connections are needed.

How long does it take to get an ADU permit in California?

California law requires cities to approve or deny ADU permits within 60 days of a complete application. In San Diego, the typical timeline is 4-8 weeks for plan review plus 1-2 weeks for permit issuance.

Can I rent out my ADU in San Diego?

Yes. ADUs can be rented as long-term rentals in San Diego. Short-term rental rules vary by neighborhood and require a separate permit. Check current City of San Diego regulations for short-term rental eligibility in your zone.