Building an ADU in San Diego: The 2026 Homeowner's Guide

An ADU (Accessory Dwelling Unit) is a fully independent secondary dwelling on the same lot as a primary single-family home. California's ADU laws, particularly AB 1332 (2023) and SB 423 (2023), have made ADU permitting substantially faster and more permissive than pre-2020. San Diego has approved thousands of ADUs over the last five years. This guide covers the three ADU types, the realistic cost ranges, the San Diego permit timeline, and the rentability math that determines whether an ADU pencils as an investment.

The three ADU types

San Diego recognizes three ADU types under state law:

**Detached ADU.** A new separate structure in the backyard (or side yard if the lot allows). The most common type in San Diego. Sizes typically range 400–1,200 sqft. Detached ADUs require new foundation, utility tie-ins (sewer, water, electric, sometimes gas), and full plan review.

**Attached ADU.** A new addition to the main house — a bedroom-and-bathroom-and-kitchen expansion that creates a separate living unit with its own exterior entry. Common when the lot has no good detached placement but the main house has a side or rear wall that can be expanded. Less expensive than detached because some utility tie-ins are shared with the main house.

**JADU (Junior ADU).** A California-specific category added by state law in 2019. A JADU is a bedroom addition up to 500 sqft within the existing primary residence, with its own exterior entry but **sharing the main house's bathroom**. JADUs are the fastest and cheapest ADU type to permit because they require fewer utility tie-ins and trigger fewer planning requirements.

There's also a **converted-space ADU** category: a garage conversion, basement conversion, or other conversion of existing habitable space to an ADU. Converted-space ADUs are typically the cheapest because no new foundation or framing is needed; the cost is the conversion work plus the egress windows, separate utility meter (if required), and code-compliance upgrades to the converted space.

Quick answer: what it costs in San Diego

For a San Diego ADU in 2026:

| Type | Size | Cost range | Typical timeline | |---|---|---|---| | JADU | 400 – 500 sqft | $80,000 – $150,000 | 4 – 6 months | | Converted-space ADU (garage, basement) | 400 – 800 sqft | $120,000 – $200,000 | 4 – 7 months | | Attached ADU | 500 – 800 sqft | $200,000 – $350,000 | 8 – 12 months | | Detached ADU (mid-range) | 600 – 800 sqft | $280,000 – $400,000 | 10 – 14 months | | Detached ADU (upscale, 1,000+ sqft) | 800 – 1,200 sqft | $400,000 – $600,000 | 12 – 18 months |

These ranges include design, permits, site work, foundation, framing, MEP (mechanical, electrical, plumbing), finishes, and a 12–18% contingency. They assume standard site conditions: a flat or gently-sloping lot with sewer and water available at the property line and no significant tree removal or easement issues.

What drives the cost

**1. Site work.** Most ADU cost surprises come from site work, not the ADU itself. Site work includes: utility tie-ins (running new sewer, water, and electric lines from the main to the ADU), grading and excavation, foundation (slab-on-grade is cheapest; raised foundation on a slope runs more), retaining walls if the lot is sloped, and tree removal or relocation.

**2. Square footage.** This is straightforward: a 600 sqft ADU runs roughly 60% the cost of a 1,000 sqft ADU for the structure and finishes, with site work being the more variable component.

**3. Finish level.** Stock cabinets and laminate counters vs. custom cabinets and quartz or natural stone can swing the per-sqft cost by $80–$200+. Appliance package (basic vs. premium) adds $5,000–$25,000.

**4. Separate utility meters vs. shared.** California ADU law allows ADUs to share the main house's utility connections (water, electric, gas) under most circumstances. But a separate meter (sometimes required by the local water district for ADUs over a certain size) adds $1,500–$5,000 per utility.

**5. Coastal Overlay Zone fees.** If your property is in the Coastal Overlay Zone (much of La Jolla, Del Mar, Ocean Beach, Pacific Beach, Mission Beach, parts of Point Loma), you need a Coastal Development Permit in addition to the standard ADU permit. CDPs add $5,000–$15,000 in fees and 60–120 days to the timeline.

San Diego permit timeline

The City of San Diego ADU process (as of 2026, under AB 1332 and SB 423):

1. **Pre-application review** (optional, 2–4 weeks) — meet with DSD staff to confirm your ADU is eligible for ministerial (over-the-counter) approval vs. discretionary review. 2. **Plan preparation** (4–8 weeks with a designer; longer for complex sites). 3. **Plan submission and review** — under AB 1332, San Diego must approve or deny ADU plans within 60 days of submittal. Most ADUs qualify for ministerial (over-the-counter) approval. 4. **Permit issuance and construction** (4–8 months for detached ADU construction).

Total: 8–14 months from kickoff to move-in for a typical detached ADU. Shorter for JADUs and converted-space ADUs.

Rentability

The rentability math for a San Diego ADU depends on the neighborhood and the finish level. Current market ranges (2026):

| Neighborhood | 1-bed ADU rent | 2-bed ADU rent | |---|---|---| | North Park, South Park, City Heights | $2,200 – $2,800 | $2,800 – $3,400 | | Normal Heights, University Heights | $2,400 – $3,000 | $3,000 – $3,600 | | Clairemont, Kearny Mesa | $2,400 – $3,000 | $3,000 – $3,600 | | Scripps Ranch, Rancho Bernardo, Poway | $2,600 – $3,200 | $3,200 – $3,800 | | La Jolla, Del Mar | $3,500 – $5,000+ | $4,500 – $6,000+ |

A $350,000 detached ADU in Scripps Ranch at $3,200/month rent has a gross yield of 11% — well above San Diego single-family rental yields of 4–6%. The math works even with 30–40% of gross rent going to property tax, insurance, vacancy, maintenance, and management.

Short-term rental restrictions

San Diego's short-term rental (STR) ordinance prohibits ADU short-term rentals (under 30 days) in most residential zones. Whole-home STRs are also restricted to primary residences in many zones. If your ADU investment thesis depends on Airbnb-style short-term rental income, the math won't work in most of San Diego. Long-term rental (12+ months) is unrestricted.

What Craft does for San Diego ADUs

Craft Home Remodel is a San Diego design-build firm. For ADU projects we handle design, permits, site work, and construction under one contract. We've completed ADU projects in Scripps Ranch, Clairemont, Normal Heights, and City Heights. See https://crafthomeremodel.com/crafted-projects for the portfolio. To start a conversation about your project, see https://crafthomeremodel.com/contact-us.

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Sources

- California Government Code § 65852.2 (ADU law), § 65852.22 (JADU law) — AB 1332, SB 423, AB 587 - City of San Diego Development Services Department — ADU permit process, fee schedule, and ministerial approval criteria - California Coastal Commission — Coastal Overlay Zone ADU rules - San Diego County Apartment Association — current ADU rental comps (2024–2026)

_Last updated: June 2026. CSLB license #1114525. Adheres to NKBA design and construction standards. This guide is for informational purposes and does not constitute a construction contract or estimate._