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ADU Builders in San Marcos, CA

66 builders · ranked by Google rating and review volume · 34 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 San Marcos 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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With roughly 94,833 residents at the 2020 Census, San Marcos is one of San Diego County's established communities. We found 66 ADU builders and contractors that show up for San Marcos homeowners on Google Maps, 10 of them based in the city itself. Their average Google rating is 4.8 stars. 24 market themselves specifically as ADU builders, and 2 mention garage conversions. 34 have a matched, active CSLB license shown with a verified badge. The top-rated by our review-weighted score are dmb Builders Inc, Cali Dream Construction and Ambar Builders Inc..

San Diego was an early ADU adopter. Coastal-zone lots may need a coastal development permit, which state law now requires within 60 days, and transit-area lots often qualify for the 18-foot detached height allowance.

#1

dmb Builders Inc

5.0 (62 Google reviews)
✔ CSLB License Verified #1078610

Service-area business · Encinitas

Serves San Marcos · based in Encinitas
Remodels & additionsHome builderGeneral contractor
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#7

TNT Design & Build

4.9 (175 Google reviews)
✔ CSLB License Verified #1012379

3142 Tiger Run Ct #108, Carlsbad, CA 92010

Serves San Marcos · based in Carlsbad
Design-buildRemodels & additionsHome builderGeneral contractor
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#10

CASITA ADU

5.0 (25 Google reviews)

Aviation Jet Complex, 2100 Palomar Airport Rd, Carlsbad, CA 92011

Serves San Marcos · based in Carlsbad
ADU specialist
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#13

Specialty Design Build

5.0 (17 Google reviews)
✔ CSLB License Verified #799853

243 S Escondido Blvd #308, Escondido, CA 92025

Serves San Marcos · based in Escondido
Design-buildRemodels & additionsHome builder
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#15

AE Carlson Design & Build

5.0 (17 Google reviews)
✔ CSLB License Verified #1115290

1902 Wright Pl Ste 200 #277, Carlsbad, CA 92008

Serves San Marcos · based in Carlsbad
Design-buildRemodels & additionsGeneral contractor
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#23

Aura Design Build LLC

5.0 (8 Google reviews)
✔ CSLB License Verified #1124838

16769 Bernardo Center Dr 1 292, San Diego, CA 92128

Serves San Marcos · based in San Diego
ADU specialistDesign-build
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#35

ADU O’SIDE

5.0 (3 Google reviews)
✔ CSLB License Verified #1129042

5074 Gold Dr, Oceanside, CA 92057

Serves San Marcos · based in Oceanside
ADU specialistHome builder
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#38

Eco Minded Solutions

5.0 (2 Google reviews)
✔ CSLB License Verified #948204

608 Crest Dr, Encinitas, CA 92024

Serves San Marcos · based in Encinitas
Remodels & additionsHome builderGeneral contractor
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#40

ADU Pros

5.0 (1 Google reviews)

500 La Terraza Blvd Suite 150, Escondido, CA 92025

Serves San Marcos · based in Escondido
ADU specialist
CallView profile
#43

Casita ADU

5.0 (1 Google reviews)

1255 E Vista Way, Vista, CA 92084

Serves San Marcos · based in Vista
ADU specialist
CallView profile
#50

House to Home

3.6 (17 Google reviews)

374 Encinitas Blvd Ste b, Encinitas, CA 92024

Serves San Marcos · based in Encinitas
Garage conversionsRemodels & additionsHome builderGeneral contractor
CallView profile
#51

Vista ADU Builders

No rating yet (0 Google reviews)

110 Civic Center Dr Ste 187, Vista, CA 92084

Serves San Marcos · based in Vista
ADU specialistHome builder
CallView profile
#57

ZOOM ADU

No rating yet (0 Google reviews)
✔ CSLB License Verified #1145664

2888 Loker Ave E Ste 110, Carlsbad, CA 92010

Serves San Marcos · based in Carlsbad
ADU specialistGeneral contractor
CallWebsiteView profile
#61

Turnkey ADU

No rating yet (0 Google reviews)

Service-area business · Encinitas

Serves San Marcos · based in Encinitas
ADU specialist
View profile
#62

ADUware

No rating yet (0 Google reviews)

1470 Encinitas Blvd, Encinitas, CA 92024

Serves San Marcos · based in Encinitas
ADU specialist
CallWebsiteView profile

Permits and pre-approved plans in San Marcos

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

Planning an ADU in San Marcos? Start here

The ADU Permit Process in California: Step by Step (2026)How to Choose an ADU Builder in Southern California: 15-Point ChecklistHow Much Does It Cost to Build an ADU in Southern California?SB 9 vs ADU: Lot Splits, Duplexes and Backyard Units in California

All ADU guides →

San Marcos ADU FAQ

How many ADU builders serve San Marcos?

Our directory lists 66 ADU builders and contractors that appear for San Marcos on Google Maps, including companies based in nearby San Diego County communities.

Do I need a permit to build an ADU in San Marcos?

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

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 San Marcos 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 San Diego County

San Diego 120Chula Vista 86Oceanside 56Escondido 110Carlsbad 67El Cajon 22Vista 60Encinitas 64La Mesa 41Santee 67National City 99Poway 49
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