Prefab ADUs in Westminster
Westminster has permitted more ADUs every year since 2021 — and in 2025, 83% of new homes in the city were ADUs. We deliver an all-in prefab ADU from our factory in Lathrop — permits, foundation, delivery and installation included — at one fixed price.
Free lot check · zoning, setbacks, utilities · reply with a fixed price
Licensed builder · Our own factory in Lathrop, CA
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Quick answer
ADUs in Westminster — key facts for 2026
Most Westminster homeowners can add a detached ADU — state law guarantees at least 800 sq ft and 16 ft — with no impact fees under 750 sq ft. Bay Modular delivers a factory-built ADU all-in for $124,900–$271,900 — the same price anywhere in California.
- Can I build an ADU in Westminster?
- Yes, on most residential lots. State law guarantees a detached ADU of at least 800 sq ft and 16 ft with 4-ft side and rear setbacks; the City's own pre-approved plans go up to about 1,200 sq ft.
- How long does a Westminster ADU permit take?
- ADU-only projects go through a combined zoning clearance and building plan check; state law requires a decision within 60 days of a complete application.
- What fees does Westminster charge?
- No impact fees under 750 sq ft (state law); larger ADUs pay a proportional park fee. School fees apply only over 500 sq ft.
- How much does a prefab ADU cost in Westminster?
- Bay Modular: $124,900–$271,900 all-in, the same price as anywhere in California, permits and installation included.
- How many ADUs does Westminster build?
- 215 ADU permits in 2025 — 83% of all new homes permitted in the city — and 908 since 2021.
- What does an ADU rent for in Westminster?
- Average asking rent in Westminster was $2,787 a month in August 2026 (Zillow), up 4.3% in a year.
Sources: HCD APR 2025, Westminster ADU page (Ordinance No. 2572) and Standard Plan program, Zillow ZORI Aug 2026. Last reviewed October 2026.
Westminster in numbers
Westminster builds more ADUs every year
ADU permits grew every year, from 118 in 2021 to 215 in 2025 — most new homes permitted in Westminster are ADUs.
ADU permits issued in the City of Westminster
Source: California HCD Annual Progress Report data (Table A2), City of Westminster, permits issued per year. Percent = ADUs among all housing units permitted in the city that year.
average Westminster asking rent in one year ($2,673 → $2,787)
Zillow Observed Rent Index, City of Westminster, Aug 2026ADU permits issued in Westminster in five years (2021–2025)
HCD APR data, 2021–2025Can I build in Westminster?
Most Westminster lots with a house can add an ADU
Westminster’s ADU rules (Ordinance No. 2572) sit on top of state ADU law, which sets the floor. Here is what matters for most homeowners:
State law guarantees at least 800 sq ft; the City's own pre-approved plans run from 748 to 1,198 sq ft. All our models fit.
An 800 sq ft ADU with 4-ft side and rear setbacks and 16 ft of height can't be denied under state law.
ADU-only projects go through a combined Planning zoning clearance and Building plan check.
Lots in a flood zone follow extra building rules, and ADUs can't go in no-build easements — we check your title report.
Under state law, no parking is required within half a mile walking of public transit or for conversions.
Westminster offers City pre-approved standard ADU plans — we use our own HCD-approved designs.
Based on the City of Westminster ADU page and Standard Plan program and state ADU law (Gov. Code §§66314–66323). Not legal advice — rules depend on your exact lot. More in our ADU guides.
New in 2027: under AB 956 (Chapter 791, Statutes of 2026), from January 1, 2027 state law lets you build two detached ADUs on a lot with a single-family home, and HOA rules can’t block an ADU on a lot zoned to allow one.
Costs & fees in Westminster
What an ADU costs in Westminster
Same all-in price as anywhere in California. Our models are all under 750 sq ft, so none pays impact fees — and four of five pay no school fees.
| Model | All-in price | School fees | City impact fees |
|---|---|---|---|
| Backyard Studio120 sq ft · home office or guest studio, not a rentable ADU | $75,900 | $0 | $0 |
| Small Studio256 sq ft | $124,900 | $0 | $0 |
| Large Studio ADU320 sq ft | $154,900 | $0 | $0 |
| 1 Bedroom ADU480 sq ft | $214,900 | $0 | $0 |
| 2 Bedroom ADU640 sq ft | $271,900 | $3,443 | $0 |
Sources: Gov. Code §66311.5; Ed. Code §17620 and State Allocation Board 2026 school fee maximum; Gov. Code §66311.5. Launch pricing runs through December 31, 2026. Comparison is general — every project differs.
Renting in Westminster
Renting out an ADU in Westminster
average asking rent for all homes in Westminster — up 4.3% in a year. HUD's 2027 fair rent for a 2-bedroom in the area is $3,057.
Zillow Observed Rent Index, City of Westminster, Aug 2026 · HUD FY2027 FMR ADU for rental incomeLong-term tenants are the safe plan; a JADU can't be rented for less than 30 days under state law.
Owner occupancy applies only to a JADU, not to an ADU, under state law.
A new ADU is exempt from California's statewide rent cap (AB 1482) for 15 years after its certificate of occupancy.
Same money, other options
Yearly income per dollar, before taxes and costs. An ADU wins because you already own the land. Full comparison →
Sources: Gov. Code §66333; Civil Code §1947.12. Comparison: HUD FY2027 2-bedroom Fair Market Rent, Santa Ana-Anaheim-Irvine area ($3,057) × 12 ÷ $271,900; U.S. Treasury (Oct 6, 2026); FTSE Nareit (Sep 2026); Zillow ZORI ÷ ZHVI, LA metro (Aug 2026); FDIC (Sep 2026). Not legal or investment advice.
Permits in Westminster
How your Westminster permit works — we handle it
Free lot check
Zoning, flood zone, easements, sewer and water for your Westminster address.
Plans & submittal
Our HCD-approved plans plus site plan and title-report easements, filed for the combined zoning clearance and plan check.
City review
Planning and Building review together; we answer comments.
Decision in 60 days
State law requires a decision on a complete ADU application within 60 days. Your ADU is built in our factory meanwhile.
Install & move in
Delivered from our Lathrop factory, installed in about a week, inspected, then your Certificate of Occupancy.
Based on the City of Westminster ADU page and Gov. Code §66317.
Why now
Start your Westminster ADU with zero risk
Lock in launch pricing, see exactly what you get, and only decide once you have a fixed price for your lot.
All-in from $75,900 — everything included
- Backyard Studio (home office)$75,900All-in · fixed in writing
- Small Studio$124,900All-in · fixed in writing
- Large Studio ADU$154,900All-in · fixed in writing
- 1 Bedroom ADU$214,900All-in · fixed in writing
- 2 Bedroom ADU$271,900All-in · fixed in writing
Zero-risk start
- Free lot check & quoteNo obligation, no credit card.
- One fixed all-in priceDesign, permits, delivery and install — one number.
- HCD-approved plansState approval #1585366, financed and appraised like a home.
- 2-year warrantyOn materials and workmanship.
Visit our factory in Lathrop, CA and walk through a finished ADU.
Westminster ADU questions
Read our ADU guides, see all of California, or call (209) 214-6845.
Can I build an ADU on my lot in Westminster?
Most Westminster residential lots can add an ADU. State law guarantees a detached ADU of at least 800 sq ft and 16 ft with 4-foot side and rear setbacks; the City's own pre-approved plans go up to about 1,200 sq ft. We check your address for free.
How much does an ADU cost in Westminster?
Our all-in prices are the same as anywhere in California: from $124,900 for a Small Studio to $271,900 for a 2 Bedroom ADU, with launch pricing through December 31, 2026. No impact fees under 750 sq ft, and school fees only above 500 sq ft.
How long does an ADU permit take in Westminster?
ADU-only projects go through a combined zoning clearance and building plan check, and state law requires a decision within 60 days of a complete application. Most projects take 4–6 months from signing to keys.
Is my Westminster lot in a flood zone?
Some Westminster lots are, which adds building requirements for the ADU. We check flood zone and easements as part of your free lot check.
Does Westminster have pre-approved ADU plans?
Yes — detached plans from 748 to 1,198 sq ft. Bay Modular uses its own HCD-approved, factory-built designs instead.
Do I need parking for an ADU in Westminster?
Under state law, no parking is required within half a mile walking of public transit or for conversions; we check your lot.
Can Bay Modular deliver to Westminster?
Yes. We build in our Lathrop factory and deliver statewide at the same all-in price, including Orange County.
Is an ADU a better investment than a rental property in Westminster?
For most homeowners with room on their lot, yes: you don't buy land. A 2 Bedroom ADU at HUD's 2027 fair rent for a 2-bedroom in the Santa Ana-Anaheim-Irvine area ($3,057) earns about 13.6% a year on its price before costs, vs. about 3.7% for a typical LA-metro rental home (Zillow, Aug 2026). Not investment advice.
Free · no obligation
Can you build an ADU on your Westminster lot?
Send your Westminster address. We'll check zoning, flood zone, easements and utilities, and send a fixed all-in price — permits included.
HCD-approved plans (#1585366) · 2-year warranty · factory in Lathrop, CA
Sources: California HCD Annual Progress Report data, Table A2 (City of Westminster, 2021–2025, updated Oct 2026); Zillow Observed Rent Index, City of Westminster (Aug 2026); HUD FY2027 Fair Market Rents (Santa Ana-Anaheim-Irvine); City of Westminster ADU page (Ordinance No. 2572, Park Fee Resolution No. 5057) and ADU Standard Plan program; Gov. Code §§66314–66333. Prices: Bay Modular, October 2026. Not legal advice.