California ADU Guide for 2026: Rules, Costs & Timelines

Accessory Dwelling Units (ADUs) are one of the fastest-growing segments of residential construction in California. New state laws have dramatically simplified the permitting process, making it easier — and more affordable — than ever to add a unit to your property.

What Is an ADU?

An ADU is a secondary housing unit on a single-family lot. They come in three types:

• Detached ADU: A standalone structure in your backyard (up to 1,200 sq ft)
• Attached ADU: An addition to your existing home
• JADU: A Junior ADU converted from existing space (up to 500 sq ft)

2026 Regulations

California AB 68, SB 13, and subsequent bills have established statewide ADU rules that override local restrictions:

• No owner-occupancy requirement for ADUs (JADUs still require it)
• No minimum lot size
• Reduced setback requirements (4 feet for rear and side)
• No parking requirements within 1/2 mile of transit
• Cities must approve or deny within 60 days
• Impact fees waived for ADUs under 750 sq ft

Typical Costs

A ground-up detached ADU in Southern California typically costs $175,000–$350,000 all-in (design, permits, construction, utilities). Garage conversions are less: $80,000–$150,000.

Why Peck General for Your ADU

We handle everything from feasibility study through final inspection. One contractor, every trade — foundation, framing, electrical, plumbing, HVAC, finish. No subcontractor juggling. Learn more about our ADU services.