California ADU Laws 2025: What Every Homeowner & Investor Must Know

California has done something remarkable over the past several years: it has systematically dismantled the zoning barriers that made it nearly impossible to build secondary housing on residential lots. The result is that today, almost every single-family homeowner in California has the legal right to build an Accessory Dwelling Unit (ADU) — and in many cases, a Junior ADU (JADU) as well.

If you own property in Greater Sacramento or anywhere in California, understanding the current ADU laws is one of the most valuable things you can do. An ADU can generate $1,500–$3,000 per month in rental income, house a family member, or significantly increase your property's resale value.

This guide covers the current legal landscape as of 2025, what you can actually build, and what the permit process looks like.

What Is an ADU? What Is a JADU?

An Accessory Dwelling Unit (ADU) is a secondary residential unit on a single-family or multifamily lot. It can be:

• Detached: A separate structure in the backyard (the classic "backyard cottage")
• Attached: An addition to the main house
• Conversion: Converting an existing garage, basement, or other space

A Junior ADU (JADU) is a smaller unit (up to 500 sq ft) created entirely within the walls of the existing primary residence. JADUs have their own entrance and kitchenette, but may share a bathroom with the main house.

The Key Laws That Changed Everything

AB 68 (2019) — The Game Changer

Assembly Bill 68 was the legislation that fundamentally opened up ADU development in California. Key provisions:

• Eliminated minimum lot size requirements for ADUs
• Prohibited local ordinances from imposing unreasonable restrictions on ADUs
• Required ministerial approval (no discretionary review, no public hearings) for ADUs that meet objective standards
• Reduced or eliminated parking requirements for ADUs within half a mile of public transit

Reference: AB 68 — California Legislative Information

SB 9 (2022) — Lot Splitting and Duplexes

Senate Bill 9 went even further, allowing homeowners in single-family zones to:

• Build a duplex on their lot (two units instead of one)
• Split their lot into two parcels and build on each

Combined with ADU rights, this means a single-family lot could theoretically support up to four units: two on each half of a split lot.

Reference: SB 9 — California Legislative Information

SB 13 (2020) — Owner-Occupancy Removed

Before SB 13, many jurisdictions required the property owner to live on-site to build an ADU. SB 13 eliminated owner-occupancy requirements through January 1, 2025, and subsequent legislation has extended these protections.

AB 2221 and SB 897 (2023) — Size and Height Increases

These bills increased the maximum allowable size for detached ADUs and raised height limits, particularly for ADUs located near transit corridors.

What Can You Actually Build in Sacramento?

Here are the current rules for most Sacramento-area jurisdictions (always verify with your specific city or county, as local ordinances can add requirements within the state framework):

Detached ADU

• Maximum size: Up to 1,200 sq ft (or 50% of the primary dwelling, whichever is less, with a minimum of 850 sq ft for a studio/1-bedroom)
• Height: Up to 16 feet (or up to 25 feet if within half a mile of a major transit stop)
• Setbacks: 4 feet from rear and side property lines
• Parking: Generally not required if within half a mile of transit

Attached ADU

• Maximum size: Up to 50% of the primary dwelling's floor area, minimum 800 sq ft
• Must meet current building code for the addition

Garage Conversion ADU

• No replacement parking required (this was a major barrier before 2020)
• Must meet habitability standards (insulation, egress, natural light)
• Existing structure can be used — no setback requirements for the existing footprint

Junior ADU (JADU)

• Maximum size: 500 sq ft
• Must be within the existing primary structure
• Requires owner-occupancy (either the main unit or the JADU)
• Separate entrance required
• Efficiency kitchen required (no full kitchen required)

The Permit Process: What to Expect

Step 1: Pre-Application Research

Before hiring anyone, verify your specific parcel's zoning, any HOA restrictions, and whether there are any deed restrictions. The Sacramento County Parcel Viewer is a useful starting point.

Step 2: Hire a Drafting Professional

You need permit-ready construction plans. For an ADU, this typically includes:

• Site plan
• Floor plans
• Exterior elevations
• Foundation plan
• Title 24 energy compliance
• Structural details (if required)

At Liberty Drafting Studios, ADU plans start at $1.80/sq ft with a typical turnaround of 10–15 business days.

Step 3: Submit for Plan Check

Submit your plans to your local building department. Under state law, jurisdictions must act on a complete ADU application within 60 days. Many Sacramento-area jurisdictions are faster.

Sacramento County Building Inspection: saccounty.gov

City of Sacramento Permit Center: cityofsacramento.gov

Step 4: Permit Issuance and Construction

Once approved, your permit is issued and construction can begin. Typical construction timeline for a detached ADU: 4–8 months depending on size and complexity.

Step 5: Final Inspection and Certificate of Occupancy

After construction, a final inspection is required before the unit can be occupied. Once passed, you receive a Certificate of Occupancy and the unit is legal to rent.

The Financial Case for Building an ADU

In Greater Sacramento, a well-built ADU can generate:

• Studio/1-bedroom (400–600 sq ft): $1,200–$1,800/month
• 1-bedroom/1-bath (600–800 sq ft): $1,500–$2,200/month
• 2-bedroom (800–1,200 sq ft): $1,800–$2,800/month

With construction costs typically ranging from $150,000–$350,000 for a detached ADU (depending on size and finishes), many homeowners see a return on investment within 8–12 years — while also significantly increasing their property value.

For investors, ADUs on multifamily properties can add even more units and rental income. Under current California law, multifamily properties can add ADUs equal to 25% of the existing unit count (minimum of 2 ADUs).

Use Our Online Calculator

Want to know what your ADU project might cost before you call anyone? Use our free online calculator at liberty-drafting.com/calculator. Enter your project type and square footage and get an instant estimate for drafting services — no email required.

---

References:

• AB 68 — California Legislative Information
• SB 9 — California Legislative Information
• California HCD — ADU Handbook
• Sacramento County ADU Information