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ADU Builders in Westminster, CA

53 builders · ranked by Google rating and review volume · 30 CSLB license verified

★ Featured ADU builder

Featured ADU builder — this spot is open

Put your ADU company at the top of this page, in front of Westminster homeowners who are comparing builders right now. Includes your logo, project photos, a direct call button and a link to your website.

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Westminster is home to about 90,911 people (2020 Census) in Orange County. We found 53 ADU builders and contractors that show up for Westminster homeowners on Google Maps, most of them based in nearby communities. Their average Google rating is 4.9 stars. 16 market themselves specifically as ADU builders, and 1 mention garage conversions. 30 have a matched, active CSLB license shown with a verified badge. The top-rated by our review-weighted score are OC Builders Group, RSF Construction Inc and Avalon Studio Design Build Corp.

In Orange County, HOA and design-standard questions come up often. State law voids CC&Rs that ban ADUs, but HOAs can still apply reasonable objective standards. Compact lots make attached units and garage conversions popular.

#1

OC Builders Group

5.0 (76 Google reviews)
✔ CSLB License Verified #1052090

600 W Santa Ana Blvd Ste 114-499, Santa Ana, CA 92701

Serves Westminster · based in Santa Ana
General contractor
CallWebsiteView profile
#3

Avalon Studio Design Build Corp

5.0 (26 Google reviews)
✔ CSLB License Verified #1101572

17081 Sims Lane Unit A, Huntington Beach, CA 92649

Serves Westminster · based in Huntington Beach
Design-buildRemodels & additionsHome builderGeneral contractor
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#4

HQ Remodeling & Design Inc

4.9 (70 Google reviews)
✔ CSLB License Verified #1041842

17011 Beach Blvd suite 900, Huntington Beach, CA 92647

Serves Westminster · based in Huntington Beach
Remodels & additionsGeneral contractor
CallWebsiteView profile
#9

Vision ADU

5.0 (14 Google reviews)
✔ CSLB License Verified #1115842

1440 S State College Blvd #6h, Anaheim, CA 92806

Serves Westminster · based in Anaheim
ADU specialist
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#15

A&A Builder

4.9 (16 Google reviews)

Service-area business · Seal Beach

Serves Westminster · based in Seal Beach
Remodels & additionsHome builder
CallWebsiteView profile
#20

Seib Construction

4.8 (17 Google reviews)
✔ CSLB License Verified #891787

1464 N Batavia St, Orange, CA 92867

Serves Westminster · based in Orange
Remodels & additionsGeneral contractor
CallWebsiteView profile
#24

ADUscale

5.0 (4 Google reviews)

528 W Hampshire Ave, Anaheim, CA 92805

Serves Westminster · based in Anaheim
ADU specialistHome builder
CallWebsiteView profile
#25

Dv construction

5.0 (4 Google reviews)
✔ CSLB License Verified #1116638

10055 Lampson Ave, Garden Grove, CA 92840

Serves Westminster · based in Garden Grove
CallView profile
#31

Pelican ADU Builders

5.0 (2 Google reviews)
✔ CSLB License Verified #1106515

1924 Barranca Pkwy Unit 1, Irvine, CA 92606

Serves Westminster · based in Irvine
ADU specialistGeneral contractor
CallWebsiteView profile
#43

Skye Construction

No rating yet (0 Google reviews)
✔ CSLB License Verified #1068435

1302 E Hunter Ave #C, Santa Ana, CA 92705

Serves Westminster · based in Santa Ana
General contractor
CallView profile
#44

Orange Innovation

No rating yet (0 Google reviews)
✔ CSLB License Verified #832810

15122 Starboard St, Garden Grove, CA 92843

Serves Westminster · based in Garden Grove
General contractor
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#48

OCADUSTUDIO

No rating yet (0 Google reviews)
✔ CSLB License Verified #1155045

13251 Pinto Rd, Garden Grove, CA 92843

Serves Westminster · based in Garden Grove
ADU specialistGeneral contractor
CallWebsiteView profile

Permits and pre-approved plans in Westminster

ADU permits in Westminster go through the city's building or planning department. Under AB 1332, every California city and county had to set up a pre-approved ADU plan program by January 1, 2025, so ask Westminster whether it has approved plans you can use. See our pre-approved plans guide and California ADU law summary.

Planning an ADU in Westminster? Start here

The ADU Permit Process in California: Step by Step (2026)JADU vs ADU in California: Size, Rules, Cost and Which to BuildAB 1033: Can You Sell an ADU Separately in California?Two-Story and Above-Garage ADUs in California: Height Rules, Costs and Design

All ADU guides →

Westminster ADU FAQ

How many ADU builders serve Westminster?

Our directory lists 53 ADU builders and contractors that appear for Westminster on Google Maps, including companies based in nearby Orange County communities.

Do I need a permit to build an ADU in Westminster?

Yes. ADUs need a building permit from the City of Westminster, which must approve or deny a complete application within 60 days under state law. Many cities also offer pre-approved plans that speed up review.

How much does an ADU cost in Westminster?

Most Southern California detached ADUs land around $350 to $550 per square foot all-in, garage conversions around $200 to $350, and JADUs around $50,000 to $150,000. Use our ADU cost estimator and get three itemized bids.

How are Westminster ADU builders ranked here?

By Google rating weighted by the number of reviews, so a 4.9 with 200 reviews ranks above a 5.0 with 3. Featured placements are clearly labeled and don't affect the organic ranking.

Nearby cities in Orange County

Anaheim 114Santa Ana 97Irvine 107Huntington Beach 88Garden Grove 97Fullerton 23Orange 95Costa Mesa 103Mission Viejo 59Lake Forest 60Newport Beach 96Buena Park 52
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