FREE Architectural Design for Carlsbad ADU Projects • Licensed CSLB #1012379 • Call Today +1 800-959-6558

Carlsbad ADU Builder - Accessory Dwelling Units From $325/sq ft

Your dream ADU build is our specialty since 2008!

  • Free architectural design with every ADU project
  • Guaranteed budget and timeline or $250/day credit
  • 150+ five-star reviews from Carlsbad homeowners
Get Your Free Quote

16+ Years Experience

150+ 5-Star Google Reviews

On-Time Guarantee or $250/Day Credit

Licensed & Insured CSLB #1012379

Free In-Home Consultation Available

Complete ADU Construction Services in Carlsbad

Garage Conversions

Transform your existing garage into a beautiful accessory dwelling unit. Our ADU builders handle all permits, design, and construction for seamless garage-to-ADU transformations.

Detached New ADU Build

Custom detached accessory dwelling units built from the ground up. Professional ADU construction from foundation to finish with guaranteed timelines and budgets.

Attached ADU Suites

Expand your home with attached accessory dwelling unit additions. Our house addition contractors specialize in seamless integration with your existing home structure.

Junior ADUs (JADUs)

Efficient junior accessory dwelling units under 500 sq ft. Perfect for building an accessory dwelling unit on a budget while maximizing your property value.

Home Remodels

Complete home renovation and remodeling services. From kitchens to bathrooms, our building & design team handles all aspects of home improvement construction.

Room Additions

Professional room addition contractors for expanding your living space. Quality construction for house additions that blend perfectly with your existing home.

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Carlsbad's Most Trusted ADU Builder Since 2008

  • Carlsbad ADU builder with 16+ years of experience and 1,000+ completed projects.
  • Fully in-house team managing design, permits, construction, and inspections.
  • Free in-home consultation and architectural design for your ADU project.
  • Guaranteed budgets and timelines with $250/day credited for delays.

1,000+​

Completed Projects

16

Years in Business

150+

Five-Star Reviews

$325

Per Sq Ft Starting Price

Why Carlsbad Homeowners Choose TNT Design &
Build for ADU Construction

Guaranteed Budget and Timeline​

When building an accessory dwelling unit, cost overruns and delays are your biggest concerns. We're the only ADU builder in California offering guaranteed budgets and completion dates. If we don't finish your ADU build on schedule, we credit your account $250 for every day we're late — covering everything from garage conversions to detached new builds.​

Free Architectural Design With Every Project​

Every TNT Design & Build project includes complimentary architectural design services, saving homeowners thousands compared to other ADU builders in San Diego. Our in-house design team creates custom plans tailored to your property, local building codes, and your family's specific needs for building a house addition or standalone ADU.​

Complete In-House Construction Management​

Unlike other accessory dwelling unit builder companies that rely heavily on subcontractors, we manage every aspect of your construction project internally. From initial permits through final inspection, our ADU contractor team coordinates all trades, materials, and scheduling — eliminating communication gaps, reducing delays, and ensuring consistent quality.​

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Our Proven Step-by-Step Process for Building Your ADU

Step 1: Free Consultation & Design

We assess your property, discuss your ADU goals, and provide preliminary designs with a detailed quote.

Step 2: Permits & Project Planning

We handle permits, city approvals, inspections, and project scheduling before construction begins.

Step 3: Construction & Final Walkthrough

Our team builds your ADU on schedule, provides updates, and completes a final quality walkthrough.

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What Carlsbad Homeowners Say About Our ADU Construction

⭐⭐⭐⭐⭐

“TNT Design & Build exceeded every expectation for our garage conversion ADU. Avner and his team finished two days early, stayed within budget, and the quality is outstanding. The free architectural design saved us thousands, and their on-time guarantee gave us complete confidence throughout the process. I’d recommend them to anyone building an accessory dwelling unit in Carlsbad.”

— Sarah Mitchell, Carlsbad | Garage Conversion ADU

⭐⭐⭐⭐⭐

“After getting quotes from several ADU builders in San Diego, TNT was clearly the most professional and transparent. Their cost to build our 800 sq ft detached ADU was exactly as quoted, with no surprise charges. The construction quality is exceptional, and they handled all permits seamlessly. Our new accessory dwelling unit is now generating $3,200 monthly rental income.”

— Robert Chen, Carlsbad | Detached New ADU

⭐⭐⭐⭐⭐

“We chose TNT for our attached ADU addition after researching room addition contractors throughout San Diego County. Their building & design team created the perfect floor plan that flows seamlessly with our existing home. The project was completed on schedule with zero delays, and their daily cleanup kept our property neat throughout construction. Absolutely stellar service.”

— Maria Rodriguez, Carlsbad | Attached ADU Suite

ADU Construction Services Throughout North San Diego County

As Carlsbad’s premier ADU builder since 2008, we provide comprehensive accessory dwelling unit construction services throughout North San Diego County. Our local expertise in building codes, permit processes, and neighborhood requirements ensures smooth project completion for homeowners in every community we serve.

Carlsbad  ·  Encinitas  ·  Solana Beach  ·  Del Mar  ·  Rancho Santa Fe  ·  Cardiff  ·  Leucadia  ·  Olivenhain  ·  La Costa  ·  Aviara  ·  Carmel Valley  ·  UTC  ·  Village of La Jolla

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Frequently Asked Questions About ADU Construction in Carlsbad

The cost to build ADU projects in Carlsbad starts at $325 per square foot, including all permits, materials, and labor. A typical 600 sq ft garage conversion ranges from $195,000–$225,000, while detached new ADUs range from $260,000–$400,000 depending on size and finishes. Our transparent pricing includes architectural design, permits, construction, and project management with no hidden fees.
The complete timeline for building an accessory dwelling unit typically takes 4–7 months from initial consultation to final walkthrough. Permit approval takes 4–8 weeks, followed by 3–5 months of construction depending on project complexity. We provide guaranteed completion dates and credit $250 per day if we exceed our promised timeline.
Yes, all ADU construction requires building permits, and many projects need additional approvals for electrical, plumbing, and structural work. Our team handles all permit applications, city plan reviews, and inspection scheduling as part of our comprehensive service. We’re experts in Carlsbad’s specific ADU regulations and streamline the approval process.
Absolutely. Garage conversions are one of our most popular ADU services and one of the most cost-effective ways to add an accessory dwelling unit to your property. We handle everything from structural assessment and design through permits and final construction. Most garage conversions are completed in 3–4 months and start at $325 per square foot.

Ready to Build Your Carlsbad ADU?

  • Free in-home consultation and architectural design
  • Guaranteed budget and timeline on every project
  • $250/day credit if we miss your completion date
  • Licensed CSLB #1012379 — fully insured
Call Now +1 800-959-6558