How big can an ADU be in Santa Rosa?

Detached ADUs in Santa Rosa can be up to 1,200 sq ft. Attached ADUs: 50% of primary home, max 1,200 sq ft. JADUs up to 500 sq ft.

How much does it cost to build an ADU in Santa Rosa?

Build costs typically range $170,000 – $360,000, or $240 – $330 per square foot.

Verified March 14, 2026

ADU Regulations in Santa Rosa, California

Q: What are the setback requirements for ADUs in Santa Rosa?

Front: Same as primary dwelling. Side: 4 ft. Rear: 4 ft.

Sonoma County · CA · Pop. 178,000

Max ADU Size

1,200

sq ft detached

Rear Setback

4 ft

Permit Timeline

60 days

Build Cost

$170,000 – $360,000

Zoning

Allowed ADU Types

✓Detached ADU

✓Attached ADU

✓JADU (Junior ADU)

✓Garage Conversion

Max per lot: 2 ADUs✓ No owner-occupancy required

Santa Rosa has one of the most active ADU programs in California — accelerated post-2017 fires to address housing shortage

Source: City of Santa Rosa — Accessory Dwelling Units · Santa Rosa City Code Section 20-42.050

Dimensions

Size & Setback Requirements

Detached

1,200

sq ft max

JADU

500

sq ft max

Attached

50% of primary home, max 1,200 sq ft

Setbacks

front

Same as primary dwelling

side

4 ft

rear

4 ft

Max height: 16 ft

Lot coverage: Per underlying zone

Post-fire rebuild areas may have expedited ADU approval

Permitting

Permit Process

Department

Santa Rosa Planning & Economic Development

Review Timeline

60 days; some pre-approved plans approved in 30 days

Permit Fees

$8,000 – $16,000

Impact Fees

Impact fees waived under 750 sq ft

Required Documents

›Site plan
›Floor plans
›Elevations
›Title 24 energy compliance
›Structural drawings

Santa Rosa has a robust pre-approved ADU plan library — use it to save time and money

Visit Santa Rosa Planning & Economic Development →

Infrastructure

Utilities & Requirements

Solar

Required

Parking

Not required

Separate Meter

Optional

Fire Sprinklers

See note

Sewer: City of Santa Rosa sewer system; connect to existing lateral

Fire Sprinklers: May be required in fire hazard areas; verify with fire department

Parking: No additional parking required

Financials

ADU Costs in Santa Rosa

Typical Build Cost

$170,000 – $360,000

Cost per Sq Ft

$240 – $330

Monthly Rental

$1,700 – $2,900/mo

Property Value Added

Adds $160,000 – $310,000 to property value

Available Grants & Programs

★CalHFA ADU Grant Program
★Sonoma County may have local housing assistance programs

Post-fire housing shortage drives strong ADU demand and rental rates in Santa Rosa

Use the free ADU Cost Calculator →

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Disclaimer: Information is compiled from publicly available municipal codes for general informational purposes only. It does not constitute legal, zoning, or construction advice. Regulations change frequently. Always verify with your local planning department. Last verified: March 14, 2026. Verify with Santa Rosa Planning & Economic Development

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Nearby Cities in Sonoma County

Petaluma

Max 1,200 sq ft · $165,000 – $330,000

Santa Rosa Quick Facts

Max size1,200 sq ft
Rear setback4 ft
Permit timeline60 days
Build cost$170,000 – $360,000
Rental income$1,700 – $2,900/mo
Owner occupancyNot required

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Official Source

City of Santa Rosa — Accessory Dwelling Units

Santa Rosa City Code Section 20-42.050

Last verified: March 14, 2026

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