ADU Cost in San Francisco: A 2026 Homeowner's Guide

Accessory Dwelling Units (ADUs) have become one of the most popular ways San Francisco homeowners add living space and rental income. But building one in SF involves real cost and a permit process worth understanding before you start. Here's a practical breakdown for 2026.

Types of ADUs allowed in San Francisco

San Francisco permits several ADU configurations, and which one fits depends on your lot, existing structure, and budget:

• Garage or ground-floor conversion — turning existing space into a unit, usually the most affordable option.
• Interior conversion — carving an ADU out of an existing basement or storage area.
• Attached addition — building new square footage onto the existing home.
• Detached new construction — a standalone unit in the rear yard, typically the most expensive.

What an ADU costs in San Francisco

In 2026, most San Francisco ADU projects fall between $150,000 and $400,000+ depending on type, size, and finishes. Garage conversions sit at the lower end, while detached new builds with full foundations, utilities, and finishes reach the higher end. SF's labor costs, permit fees, and the need to run new utilities all contribute.

The SF ADU permit process

California has streamlined ADU approvals, and San Francisco has a dedicated ADU program. Still, you'll go through plan review with the Department of Building Inspection and Planning, and detached units may trigger additional review. The process typically takes several months from application to permit, which is why working with a contractor experienced in SF ADUs matters.

Is an ADU worth it?

Beyond rental income — significant in San Francisco's housing market — an ADU adds long-term property value and flexibility for family, guests, or a home office. Many homeowners find the unit pays for itself over time through rent. If you're considering an ADU, we offer free consultations to assess your property and outline a realistic budget and timeline.