ADU Regulations in Westminster, California
Orange County · CA · Pop. 90,000
Max ADU Size
1,200
sq ft detached
Rear Setback
4 ft
Permit Timeline
60 days
Build Cost
$165,000 – $335,000
Zoning
Allowed ADU Types
Westminster is nationally known as the heart of Little Saigon, home to the largest concentration of Vietnamese Americans outside Vietnam. Dense single-family neighborhoods with multigenerational households make ADUs especially practical for extended family housing. The city has embraced ADU development as a housing solution aligned with community values.
Source: City of Westminster — Accessory Dwelling Units · Westminster Municipal Code Chapter 9 (Zoning), Section 9-127
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 per underlying zone
side
4 ft
rear
4 ft
Max height: 16 ft
Lot coverage: Per underlying zone; typically 40–50% in R-1 zones
Westminster's residential lots tend to be modest in size; careful site planning is essential to maximize ADU square footage within coverage limits. Garage conversions are popular given the cultural norm of extended family living.
Permitting
Permit Process
Department
City of Westminster Planning & Building Department — Planning Division
Review Timeline
60 days
Permit Fees
$8,000 – $16,000
Impact Fees
Impact fees waived for ADUs under 750 sq ft; proportional fees apply above that threshold
Required Documents
- ›Site plan (to scale, showing lot dimensions, all structures, setbacks)
- ›Floor plans
- ›Elevations
- ›Title 24 energy compliance (residential)
- ›Structural drawings
Westminster processes ADU applications through its Planning & Building counter. The city's bilingual staff can assist Vietnamese-speaking applicants. Orange County Sanitation District serves Westminster — connect fee schedules apply for new ADU sewer laterals.
Visit City of Westminster Planning & Building Department — Planning Division →Infrastructure
Utilities & Requirements
Solar
Required
Parking
Not required
Separate Meter
Optional
Fire Sprinklers
See note
Financials
ADU Costs in Westminster
Typical Build Cost
$165,000 – $335,000
Cost per Sq Ft
$230 – $300
Monthly Rental
$1,700 – $2,700/mo/mo
Property Value Added
Adds $185,000 – $340,000 to property value
Available Grants & Programs
- ★CalHFA ADU Grant Program available (up to $40,000 for pre-development costs)
Westminster's strong multigenerational household culture drives consistent ADU demand — many are built for family use rather than market rental, which can lower effective vacancy risk. Little Saigon's commercial vitality and proximity to Garden Grove, Santa Ana, and Anaheim employment centers sustain healthy rental market fundamentals.
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Westminster Quick Facts
- Max size1,200 sq ft
- Rear setback4 ft
- Permit timeline60 days
- Build cost$165,000 – $335,000
- Rental income$1,700 – $2,700/mo/mo
- Owner occupancyNot required
Official Source
City of Westminster — Accessory Dwelling UnitsWestminster Municipal Code Chapter 9 (Zoning), Section 9-127
Last verified: March 14, 2026
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ADU rules change often.
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