What You Need to Know Before Building an ADU in San Francisco

As housing costs continue to rise and available space becomes increasingly limited, Accessory Dwelling Units (ADUs) have become one of the smartest ways to maximize your property’s value and functionality in the San Francisco Bay Area. Whether you’re looking to create a rental income stream, house extended family, or add a private workspace, building an ADU can offer long-term benefits — if you know how to navigate the process correctly.

At Persepolis Construction, we’ve helped homeowners throughout San Francisco, Oakland, San Jose, and San Rafael bring their ADU visions to life. Here’s what you need to know before getting started.

What is an ADU?

An Accessory Dwelling Unit is a secondary residential unit located on the same lot as a primary home. ADUs go by many names: granny flats, in-law units, backyard cottages, or garage conversions. They can be detached, attached, or even built above a garage or in a converted basement.

What Are the ADU Rules in San Francisco?

San Francisco has made it easier in recent years to approve and build ADUs, thanks to state housing laws that encourage more flexible residential zoning. However, there are still key requirements to consider:

• Maximum size: Most ADUs must be under 1,200 sq. ft., though the size allowed depends on the lot and zoning.

• Setbacks: Detached ADUs generally require 4-foot side and rear setbacks.

• Height limits: Single-story ADUs can go up to 16 feet, with some exceptions.

• Owner occupancy: As of recent updates, owner occupancy is not required for new ADUs through 2025.

• Permits: All ADUs must go through planning review, building permit approval, and inspections.

These rules vary slightly depending on the jurisdiction (Oakland, San Jose, etc.), so working with an experienced ADU contractor is crucial to ensure compliance.

What Does It Cost to Build an ADU in the Bay Area?

While costs vary by design, size, and site conditions, you can expect a garage conversion to start around $120,000–$160,000, while a new detached ADU may range from $200,000 to $350,000+. Factors that affect cost include:

• Foundation work

• Utility connections (water, sewer, electrical)

• Interior finishes (kitchen, bathroom, flooring)

• Permitting and design fees

At Persepolis Construction, we provide transparent pricing and full-service project management from concept to completion.

Common ADU Types We Build

• Detached Backyard Units – Ideal for privacy and rental income.

• Garage Conversions – Fastest, most affordable way to create an ADU.

• Above-Garage Additions – Great for tight lots with limited ground space.

• Basement ADUs – Smart use of underutilized space in older homes.

• Attached ADUs – Seamless extensions connected to your main home.

Why Choose Persepolis Construction for Your ADU Project?

With years of experience in residential construction across the Bay Area, we offer:

• Code-compliant ADU designs that meet state and local requirements

• Full permitting support to avoid costly delays

• High-quality craftsmanship and materials

• Expertise in structural work, seismic safety, and modern design

• Seamless integration with existing homes

We don’t just build — we guide you through every step, from zoning review to final inspections.

📞 Ready to Build Your ADU in San Francisco?

An ADU is more than just extra space — it’s long-term value. Whether you’re planning a backyard cottage, garage conversion, or second unit, Persepolis Construction is your trusted ADU builder in San Francisco and the Bay Area.

Contact us today for a free consultation and let’s turn your property into something more.