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ADU Builders in Walnut, CA

20 builders · ranked by Google rating and review volume · 10 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 Walnut 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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Walnut is home to about 28,430 people (2020 Census) in Los Angeles County. We found 20 ADU builders and contractors that show up for Walnut homeowners on Google Maps, 2 of them based in the city itself. Their average Google rating is 4.8 stars. 8 market themselves specifically as ADU builders, and 1 mention garage conversions. 10 have a matched, active CSLB license shown with a verified badge. The top-rated by our review-weighted score are G-Man Development, Uni Construction + ADU Design and Skyline ADU Solutions.

Los Angeles leads California in ADU permits. Common projects here include garage conversions on older lots, detached backyard units on deep lots, and hillside sites where access and grading drive the cost.

#4

Capy Construction

5.0 (15 Google reviews)
✔ CSLB License Verified #1120565

Service-area business · Walnut

Serves Walnut · based in Walnut
Remodels & additionsHome builderGeneral contractor
CallWebsiteView profile
#9

The ADU Company

5.0 (6 Google reviews)
✔ CSLB License Verified #1118354

504 E Navilla Pl, Covina, CA 91723

Serves Walnut · based in Covina
ADU specialistRemodels & additionsHome builderGeneral contractor
CallWebsiteView profile
#11

B & D Construction

4.7 (13 Google reviews)
✔ CSLB License Verified #409057

1472 Avenida Loma Vista, San Dimas, CA 91773

Serves Walnut · based in San Dimas
Remodels & additionsHome builderGeneral contractor
CallWebsiteView profile

Permits and pre-approved plans in Walnut

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

Planning an ADU in Walnut? Start here

Prefab and Modular ADUs in California: Real Costs, Permits and PitfallsHow to Legalize an Unpermitted ADU in California (AB 2533)JADU vs ADU in California: Size, Rules, Cost and Which to BuildAB 1033: Can You Sell an ADU Separately in California?

All ADU guides →

Walnut ADU FAQ

How many ADU builders serve Walnut?

Our directory lists 20 ADU builders and contractors that appear for Walnut on Google Maps, including companies based in nearby Los Angeles County communities.

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

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

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 Walnut 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 Los Angeles County

Los Angeles 118Long Beach 119Santa Clarita 27Glendale 117Lancaster 12Palmdale 12Pomona 67Torrance 98Pasadena 100Downey 28West Covina 68El Monte 24
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