Skip to main content
Avorino
(714) 900-3676Get a Free Estimate
The Vietnam War Memorial, Little Saigon, Westminster — Westminster, Orange County

ADU Construction · Westminster

Westminster · Orange County

Westminster ADU construction

Westminster ADU Regulations.

Detached, attached, Junior ADU, and garage-conversion ADUs in Westminster, fully permitted, designed for your vision, and built end-to-end by Avorino.

Same-week free consultation Get your Westminster ADU quote
01 / Westminster37 Orange County cities & communities · B-#1107538Scroll to explore ↓

Talk To Us

Free Westminster ADU estimate.

Two minutes, no pressure. We reply as soon as possible. Westminster permits handled.

Start my free estimate Or call (714) 900-3676

  • Coverage Westminster, OC
  • Built by Avorino in-house
  • Scope Permits → final inspection

Westminster · Executive summary

What does an Avorino ADU in Westminster actually involve?

Avorino builds ADUs in Westminster, Orange County end-to-end — design, engineering, permits, and construction under one roof. ADU projects in Westminster typically run $85K – $440K+ depending on type — garage conversion at the low end, detached at the top — priced fixed in a single contract.Avorino designs, permits, and builds ADUs in Westminster: detached, attached, Junior ADU, and garage conversion. California state ADU law preempts most city setbacks (4-ft minimum side + rear) and starts a 60-day ministerial clock on a complete application (Gov. Code §66317), so each correction round delays when that clock begins. We carry the city correspondence and tiered warranty under one roof.7+ years of OC experience · 150+ projects · 4.8 Yelp average across 35+ reviews.

Plan your project
Detached ADU
$245K – $440K+
· 5–8+ mo
Attached ADU
$200K – $350K+
· 5–8+ mo
Junior ADU
$135K – $220K+
· 4–6+ mo
Garage conversion
$85K – $170K+
· 4–6+ mo
Plan check
4–6+ wk
· state 60-day clock starts once the file is complete
How to get a permitted ADU in Westminster.
  1. 01Permitting
  2. 02Timeline
  3. 03Zoning
  4. 04Investment

Local context

Building ADUs in Westminster.

Westminster's ADU story is a family-housing story. The city anchors Little Saigon, and multigenerational households are the norm rather than the exception here — which is why so many Westminster ADUs are built for parents and grown children instead of tenants. The flat 1960s tracts cooperate: regular lots, workable rear yards, and detached garages that convert cleanly.

The city runs a Pre-approved ADU Standard Plan program — a city-vetted design that trims drawing costs and review time for lots that fit it — alongside the standard ministerial path. State rules do the heavy lifting on entitlements: one ADU plus one JADU on single-family lots, two detached units plus conversions on multifamily parcels, four-foot side and rear setbacks, and impact-fee exemption for units of 750 square feet or less.

Westminster's code drew a state compliance review in 2023, which is worth knowing for one practical reason: where a local rule and state ADU law disagree, state law controls — and a builder who tracks that line saves you from over-designing to a rule that can't be enforced. We track it, and complete applications ride the 60-day clock.

@avorinoconstruction

Avorino builds across Orange County.

No published Westminster build yet — here’s recent Avorino work from across Orange County.

“These are the best people in the business. I used Avorino to build my own ADU. They beat every single price I got and on top of that did an excellent job finishing it in no time. Truly the best of the best — highly recommended.”
Shahin S. · Detached ADU · Orange County · 2023
Follow @avorinoconstruction
Years
7+
Orange County experience
License
B-#1107538
California General-B
OC Cities + Communities
37
Coverage across all of Orange County
Rating
4.8★
Yelp

Service fit (4)

Which ADU lands cleanly in Westminster.

Plan your project
AVORINO / SPATIAL STUDIESFIG. 01
Detached ADUConcept only · cutaway walls lowered to reveal the layout

01 Detached ADU

Standalone unit on the lot — biggest rental upside, longest schedule. Strongest fit when the Westminster lot has the room to give it.

02 Attached ADU

Addition off the primary residence — shares a wall, often shares a service line. Common Westminster fit when the lot is tighter or setbacks are unforgiving.

03 Junior ADU

Conversion within the existing footprint of the primary residence. Tightest scope; clean fit when the Westminster primary has a spare bedroom or formal dining to convert.

04 Garage conversion

Existing garage rebuilt as living space. Fastest move when the Westminster garage frame is sound and the slab can be reused — typical 8–12+ week build when permits clear cleanly.

Built by Avorino · Brea, California

Inside a finished Avorino ADU.

The kitchen of a garage conversion in Brea, filmed as finished.

The finished kitchen of the Brea garage conversion: white shaker cabinets, a marble-look backsplash, stainless appliances and a slider to the yard
  1. 01 / 03The kitchenWhite shaker cabinets over a marble-look backsplash.
  2. 02 / 03StainlessA gas range, a dishwasher and a stainless refrigerator.
  3. 03 / 03To the yardA glass slider opens the kitchen to the yard.

Westminster ADU Regulations

How to get a permitted ADU in Westminster.

Avorino carries the city. Submission, plan-check corrections, and final inspection, all handled in our office, on your behalf. State law preempts city setbacks (4-ft floor) and starts a 60-day ministerial clock once the application is complete, so correction rounds delay when that clock starts.

AVORINO / SPATIAL STUDIESFIG. 01
Review set · layout for professional reviewConcept only · cutaway walls lowered to reveal the layout
04 Steps to a permitted ADU · One conceptual floor plan, developed through every step. Schematic, not an engineering detail.
Permits · a coordinated submission set

01 / 04

Permitting

City of Westminster Building & Safety Division. Avorino handles all submissions, plan-check corrections, and approvals on your behalf. You sign once at the start; the city correspondence is ours to carry.

  • Verify homeowners association + zoning rules
  • Pre-application consult
  • Submit plans
  • Plan check & corrections

Permit reality

How Westminster plan check actually runs.

Ministerial review on the state's 60-day clock, with the city's Pre-approved Standard Plan as a shortcut where the design fits your lot. State law fills any gap in the local code — a 2023 state review made that boundary explicit — so entitlement questions resolve faster than owners expect.

  • Submission is hybrid — in person or online — through the city-branded “Westminster Build” portal (Tyler EnerGov Self-Service). Avorino files whichever route fits.
  • City Pre-approved ADU Standard Plan available — cuts drawing cost + review time
  • One ADU + one JADU on single-family lots; 2 detached + conversions on multifamily
  • 4-ft side/rear setbacks; parking exempt within ½ mile of transit
  • Units of 750 sqft or less exempt from impact fees
  • Westminster runs a Preapproved ADU Standard Plan program: six city-reviewed detached plans in four sizes (748/791/998/1,198 sq ft) with three roof options each.
  • ADU-only projects use one combined Planning Zoning Clearance + Building Plan Check track (Planning, Building, and Public Works Engineering) instead of a separate discretionary review.

Westminster ADU rules

Six pre-approved plans, one combined track, and the quick facts.

Westminster pairs one of the county's largest pre-approved ADU plan libraries with a single combined review track. These are the rules a Westminster ADU actually runs on.

Westminster ADU standards and quick facts
StandardWhat applies in Westminster
Detached ADU sizeUp to 1,200 sq ft.
Attached ADU sizeUp to 1,200 sq ft or 50% of the main home's living area, whichever is less. State size safeguards of 850 and 1,000 sq ft apply.
Height (detached)16 ft for a detached ADU. State law can allow a taller unit near major transit or on a multistory multifamily lot.
Side and rear setbacks4 ft from the side and rear lot lines for a new ADU.
Front setbackThe zoning district's front setback applies. State law's 800 sq ft safeguard also applies: a front setback cannot block an ADU of up to 800 sq ft.
ParkingGenerally 1 space unless a state exemption applies.
Short-term rentalsShort-term rental is not allowed. An ADU or junior ADU created under the ordinance may not be rented for less than 30 days.
Coastal ZoneNo California Coastal Zone land has been identified within the city.
Fees (state rule)No impact fees on an ADU of 750 sq ft or less of interior living space (Gov. Code §66311.5(c)(1)), and none of the state's school developer fees on one under 500 sq ft (Gov. Code §66311.5(c)(3); Ed. Code §17620). Larger units pay fees set by the city and the school district.
Review time (state rule)State law starts a 60-day ministerial clock once your application is complete (Gov. Code §66317); each correction round delays when that clock begins.
How permits are filedHybrid — in person or online — through the city-branded "Westminster Build" portal (Tyler EnerGov Self-Service). Avorino files whichever route fits.
Review trackADU-only projects use one combined Planning Zoning Clearance + Building Plan Check track (Planning, Building, and Public Works Engineering) instead of a separate discretionary review.
Pre-approved plansA Preapproved ADU Standard Plan program: six city-reviewed detached plans in four sizes — 748, 791, 998, and 1,198 sq ft — with three roof options each.
Flood complianceThe city's own ADU process makes flood-zone compliance a Step-1 item and links a Special Flood Hazard Area handout — low, flat Westminster sits near the water table with mapped flood areas.
Fees to knowSewer is a two-agency system (Midway City Sanitary District collection + OC San regional treatment): a new detached ADU making a new/separate connection can carry both a district capacity fee and OC San's charge, plus the city's own development impact fees.

Summarized from Westminster's ADU pages, Standard Plan program, and state ADU law; flood-zone status varies parcel to parcel. Avorino confirms what your exact lot carries in the free consultation.

Lot profile

What Westminster lots actually look like.

Flat, regular 1960s tract parcels across the city — modest frontages, usable rear yards, detached garages in the older blocks. Little Saigon's commercial spine concentrates the density; the residential grid behind it is classic single-story ranch fabric.

  • 1960s tract lots: flat pads, workable rear yards — detached units and conversions both fit
  • Detached garages in older blocks — conversion candidates at the value end of the range
  • Multigenerational-household demand — many units designed as family housing
  • Impact-fee exemption at 750 sqft or less — a real budget lever on this lot stock
  • Sewer is a two-agency system — the Midway City Sanitary District owns the local collection lines while OC San handles regional treatment — so a new detached ADU that makes a new/separate sewer connection can carry both a district capacity fee and OC San's charge.
  • Westminster's own ADU process makes flood-zone compliance a Step-1 item and links a Special Flood Hazard Area handout — low, flat Westminster sits near the water table with mapped flood areas.
  • Water is a city municipal utility, and the city routes every ADU through three divisions (Planning, Building, and Development Engineering) plus its own development impact fees.

Verify with the city

All Westminster ADU, custom-home, and construction details on this page, including fees, setbacks, timelines, and zoning, are based on the City of Westminster Building & Safety Division's published information and are subject to change. This information may not be fully up to date or accurate. For the latest requirements, visit the city's building and planning department directly, and confirm anything that affects your budget or schedule before you build.

Investment range

Where Avorino's ADU budgets in Westminster typically land.

Inland Westminster ADU work tracks the OC average. Flat-lot construction, straightforward foundations, and clean utility runs keep build budgets predictable. Detached unit budgets typically land in the $245K–$440K+ range; attached and Junior ADU options trim significantly.

Detached ADU:
$245K–$440K+ typical fixed-price contract
Attached ADU:
$200K–$350K+ typical
Junior ADU:
$135K–$220K+ typical
Permit + design fees:
$8K–$20K+ typical
  • Rental income (Orange County range): $2,500–$4,500+/mo, modeled on real OC long-term rents
  • Two school districts levy Level 1 developer fees on a 500+ sq ft ADU — Westminster (K-8) and Huntington Beach Union High (9-12) — on top of the city, water, and sewer fees.

How an Orange County ADU budget is built up, line by line — the same breakdown behind the Westminster range above.

Recent builds

ADUs, built for real life.

Explore completed Avorino projects, photographed as built. Different properties, personal priorities, and ways to make a home.

01 / 08

See more on Instagram@avorinoconstruction

Run your numbers

What would an ADU pencil out to in Westminster?

Two free tools, calibrated to 2026 Orange County bids — a cost range in about a minute, and the rental return behind it.

Westminster is one of 37 cities covered by our Orange County ADU construction service.

01 / Avorino in Westminster

Does Avorino build ADUs in Westminster?

Yes. Avorino builds ADUs in Westminster. Detached, attached, Junior ADU, and garage-conversion ADUs handled end-to-end from permits through certificate of occupancy.

Is Avorino a licensed ADU contractor in Westminster?

Yes. Avorino carries California General-B License #1107538 and builds ADUs in Westminster end-to-end. With Avorino as the Westminster ADU contractor on your project, design, engineering, permits, and construction stay under one roof, so the schedule and the outcome sit with one company, not a chain of subcontractors you'd manage yourself.

02 / Permits, time & cost

How does ADU permitting work in Westminster?

Avorino handles all submissions, plan-check corrections, and approvals on your behalf. You sign once at the start; the city correspondence is ours to carry. The path: Verify homeowners association + zoning rules → Pre-application consult → Submit plans → Plan check & corrections.

What's the typical Westminster ADU build timeline?

From initial consultation to a fully finished, move-in ready ADU in your backyard. City plan check: 4–6+ weeks, and longer once corrections come back. Construction — typically 8–12+ weeks on a garage conversion; detached builds run several months, inside the 5–8+ month project window. Avorino carries that schedule end-to-end, from permit submission through to certificate of occupancy.

What's the Westminster ADU investment range?

Architecture, engineering, permits, and construction — all included in a fixed-price contract. Range: $85K – $440K+. That is an Avorino quote for your own lot, not a market average.

03 / Westminster specifics

Does Westminster have a pre-approved ADU plan?

Yes — the city publishes a Pre-approved ADU Standard Plan that trims drawing costs and review time where it fits the lot. We'll tell you straight whether the standard plan or a custom design serves your parcel and household better.

Can I build an ADU for my parents in Westminster?

That's what most Westminster ADUs are — multigenerational family housing. Detached backyard units and garage conversions both work on the city's flat tract lots, and units of 750 square feet or less skip impact fees entirely.

What if Westminster's code conflicts with state ADU law?

State law controls — a 2023 state compliance review of the city's ordinance made that boundary explicit. Practically, it means your entitlement is usually stronger than a first read of the local code suggests; we design to the controlling rule.

What sizes are the Westminster pre-approved plans, and where do I file?

Six city-reviewed detached plans in four sizes (748, 791, 998, and 1,198 sq ft), each with three roof options. Submittal is hybrid, in person or online, through the “Westminster Build” portal, and ADU-only projects run through one combined Zoning Clearance + Building Plan Check track. Avorino files it and tells you whether a standard plan or a custom drawing fits your lot.

What fees does a Westminster ADU carry?

A layered stack: the Midway City Sanitary District's sewer capacity fee plus OC San's regional charge where the ADU makes a new connection, the city's own development impact fees, and two school districts' developer fees (Westminster K-8 and Huntington Beach Union High). Flood-zone compliance is a Step-1 item here too. Avorino budgets and files all of it.

Talk To Us

Tell us about your Westminster vision.

Drop the address and what you're picturing. We read it as soon as possible and come back with the strongest ADU type for your specific Westminster vision, and what Westminster permitting is known to throw at the project.

AVORINO / SPATIAL STUDIESFIG. 01
Detached ADUConcept only · cutaway walls lowered to reveal the layout
Designed concept · not your final plan
Call(714) 900-3676Book a free consultation
  1. 01Project
  2. 02Plans
  3. 03Context
  4. 04Contact

What kind of ADU are you considering?

A starting point is enough. We can confirm what fits your lot together.

ADU type

Nearby ADU markets

Other cities Avorino builds in.

Comparing ADU build options across the Westminster corridor? Here’s the same end-to-end Avorino build, in the cities right next door.

Same city, other services

Avorino also runs these in Westminster.

Service areas

Serving 37 Orange County cities & communities, plus unincorporated OC and nearby LA County.

Talk To UsFree estimate. Same-week free consultation.General-B License #1107538 · 7+ years of Orange County experience
Call(714) 900-3676Text us(714) 900-3676Get a Free EstimateGet a Free Estimate