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ADU Builders in Fullerton, CA

23 builders · ranked by Google rating and review volume · 11 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 Fullerton 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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Fullerton is home to about 143,617 people (2020 Census) in Orange County. We found 23 ADU builders and contractors that show up for Fullerton homeowners on Google Maps, 4 of them based in the city itself. Their average Google rating is 4.9 stars. 15 market themselves specifically as ADU builders, and 4 mention garage conversions. 11 have a matched, active CSLB license shown with a verified badge. The top-rated by our review-weighted score are John Christopher Construction, Inc., Producers Construction Inc and Vision ADU.

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.

#3

Vision ADU

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

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

Serves Fullerton · based in Anaheim
ADU specialist
CallWebsiteView profile
#13

ADUscale

5.0 (4 Google reviews)

528 W Hampshire Ave, Anaheim, CA 92805

Serves Fullerton · based in Anaheim
ADU specialistHome builder
CallWebsiteView profile
#19

KoBolt Construction

4.6 (11 Google reviews)
✔ CSLB License Verified #1024785

406 E Commonwealth Ave #3, Fullerton, CA 92832

Based in Fullerton
Remodels & additionsHome builderGeneral contractor
CallWebsiteView profile
#21

Apex Construction

3.7 (6 Google reviews)
✔ CSLB License Verified #1020301

Service-area business · La Habra

Serves Fullerton · based in La Habra
ADU specialistRemodels & additionsGeneral contractor
CallWebsiteView profile

Permits and pre-approved plans in Fullerton

ADU permits in Fullerton 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 Fullerton whether it has approved plans you can use. See our pre-approved plans guide and California ADU law summary.

Planning an ADU in Fullerton? Start here

SB 9 vs ADU: Lot Splits, Duplexes and Backyard Units in CaliforniaGarage Conversion ADU Cost in Southern California (and What Drives It)AB 1033: Can You Sell an ADU Separately in California?How Much Does It Cost to Build an ADU in Southern California?

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Fullerton ADU FAQ

How many ADU builders serve Fullerton?

Our directory lists 23 ADU builders and contractors that appear for Fullerton on Google Maps, including companies based in nearby Orange County communities.

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

Yes. ADUs need a building permit from the City of Fullerton, 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 Fullerton?

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 Fullerton 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 97Orange 95Costa Mesa 103Mission Viejo 59Westminster 53Lake Forest 60Newport Beach 96Buena Park 52
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