ADU Cost Per Square Foot in California (2026 City-by-City Breakdown)
By Majid Farooq | Updated October 12, 2026
⚡ Quick Answer
Complete 2026 analysis of detached ADU and garage conversion costs across Los Angeles, San Diego, Orange County, and the Bay Area, including Title 24 solar rules and pre-approved plan savings.
California remains the largest Accessory Dwelling Unit (ADU) market in the United States in 2026, accounting for over 24,000 permits annually. However, construction labor rates, seismic requirements, and Title 24 energy mandates create significant regional price differences between Southern and Northern California.
2026 California ADU Cost Per Square Foot by Region
| California Metro Region | Garage Conversion ADU ($/sq ft) | Detached Site-Built ADU ($/sq ft) | 600 Sq Ft Detached Total |
|---|---|---|---|
| Los Angeles & Orange County | $245 – $330 | $310 – $420 | $186,000 – $252,000 |
| San Diego Metro | $235 – $315 | $295 – $395 | $177,000 – $237,000 |
| Sacramento & Inland Empire | $210 – $280 | $265 – $350 | $159,000 – $210,000 |
| San Francisco Bay Area / San Jose | $290 – $390 | $375 – $510 | $225,000 – $306,000 |
How to Save $12,000–$22,000 Using AB 1332 Pre-Approved ADU Plans
Under California AB 1332, every city and county planning department now maintains a library of pre-approved detached ADU architectural plans. Selecting a pre-approved 400 to 800 sq ft floor plan reduces architectural engineering fees by 60% and guarantees a 30-day ministerial permit review window.
Impact Fee Exemptions Under 750 Square Feet
Under state law (SB 13), California cities cannot charge school district or municipal development impact fees on any ADU under 750 square feet. Designing a 749 sq ft 2-bedroom ADU instead of a 760 sq ft unit immediately saves $8,000 to $18,000 in city permit fees.
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