Attached ADU Builders in Northern California

Add smart, livable space to your home with a custom attached ADU. Sidex designs and builds seamless additions that feel like they’ve always been part of your home.

4.9/5 rating from 56+ online reviews.

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What Is an Attached ADU & Why It Works

An attached ADU is a self-contained living unit built as an extension of your existing home. Unlike detached units, an ADU attached to a house shares at least one wall with the main structure, making it a more cost-effective and space-efficient option.

Across attached ADU projects, homeowners are choosing this approach because it blends naturally with the home, simplifies utility connections, and often moves faster through approvals. At Sidex, we make sure your attached dwelling unit is designed right, built right, and fully compliant.

Complete Attached ADU Services

Custom Attached ADU Design

We design attached ADUs that integrate perfectly with your home’s layout and architecture. From private entrances to efficient floor plans, every detail is planned to maximize comfort, privacy, and functionality.

Full Attached ADU Construction

Our team handles complete attached ADU construction; from foundation extensions to framing, electrical, plumbing, and interior finishes. We build spaces that feel like a natural part of your home, not an add-on.

Permits & Code Compliance

Building an attached ADU California requires meeting local zoning and building codes. We manage permits, approvals, and inspections so your project moves forward without unnecessary delays.

Built with Precision, Designed for Real Living

Explore our projects to see how we build functional, durable, and visually seamless structures across Northern California.

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How We Build Your Attached ADU

Consultation & Assessment

We evaluate your home’s layout, available space, and goals to determine the best approach for your attached ADU.

Step 1

Design & Planning

Our team creates a custom plan for your attached accessory dwelling unit, including layout, materials, and utility integration. We also handle permit documentation.

Step 2

Construction & Integration

We carefully build and connect the ADU attached to the house, ensuring structural integrity, proper insulation, and seamless transitions between old and new spaces.

Step 3

Final Walkthrough

We complete inspections, ensure everything meets code, and walk you through your new attached dwelling unit so it’s ready for use.

Step 4

Attached ADU Construction Across Northern California

We design and build attached ADUs for homeowners throughout the region, serving over 57 locations.

The Bay Area

From San Francisco to San Jose, we create space-efficient attached dwelling units that increase property value without sacrificing design.

South Lake Tahoe

We build durable attached ADUs designed for colder climates, with proper insulation and weather-resistant construction.

Sacramento Region

In Sacramento and surrounding areas, we deliver practical and cost-effective attached accessory dwelling unit solutions for growing households and rental income.

Attached ADU FAQs

What is an attached ADU?

An attached ADU is a separate living unit connected to your main home, with its own entrance, kitchen, and bathroom.

Is an attached ADU cheaper than a detached ADU?

In many cases, yes. Because it shares a structure and utilities, an attached ADU can be more cost-effective to build.

Can I rent out my attached ADU?

Yes, many homeowners use attached ADUs as rental units, depending on local regulations.

Do attached ADUs require permits in California?

Yes. Every attached ADU California project must comply with zoning laws and building codes. We handle the process for you.

Will it look like an addition or part of my home?

When designed properly, an attached accessory dwelling unit blends seamlessly with your existing structure.

      EXCELLENT  
   Based on 38 reviews 
    
 
 
 
   
 
 
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   Tatyana P 
 
 
 
 Trustindex verifies that the original source of the review is Google. 
  
 
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   Vivi Babenko 
 
 
 
 Trustindex verifies that the original source of the review is Google. My grandparents backyard deck had taken a beating over the years, especially from all the snow and rough weather. It was definitely time for some love, and Sidex really came through for! What stood out most was the crew and how they treated my grandparents like family and were genuinely so kind throughout the whole project. Really glad we chose them!
  
 
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   Sara Yarmolyuk 
 
 
 
 Trustindex verifies that the original source of the review is Google. Extremely helpful employees and truly have honest work and craftsmanship.
  
 
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   Valya Stepanov 
 
 
 
 Trustindex verifies that the original source of the review is Google. I can’t say enough good things about Sidex Siding & Decking! From the first phone call to the final walkthrough, the entire experience was outstanding. The team was professional, punctual, and incredibly knowledgeable. They took the time to answer all of my questions, communicated clearly throughout the project, and paid close attention to every detail. The quality of their workmanship exceeded my expectations, and the finished deck looks absolutely amazing. They treated my home with respect, kept the work area clean, and completed everything on schedule. It’s rare to find a company that truly delivers on its promises, but Sidex Siding & Decking did exactly that. If you’re looking for a trustworthy, skilled, and reliable contractor, I highly recommend them. I couldn’t be happier with the results and will definitely use them again for future projects. Five stars all the way!
  
 
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   Max Gatsmanyuk 
 
 
 
 Trustindex verifies that the original source of the review is Google. Fast and professional
  
 
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   Vince Carterson 
 
 
 
 Trustindex verifies that the original source of the review is Google. Andrey and Nate were very helpful, would work with Sidex again. I am glad everything went as smooth as they said it would.
  
 
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   Sava Vashchuk 
 
 
 
 Trustindex verifies that the original source of the review is Google. We recently hired SIDEX to completely replace the old, worn-out siding on our home and we could not be happier with the results. They gave us a highly competitive and transparent quote with no hidden fees.
  
 
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   Rita Snizhko 
 
 
 
 Trustindex verifies that the original source of the review is Google. We couldn’t be happier with how our new deck turned out! From the very beginning, the whole process was so easy, and the Sidex Construction team was amazing to work with. They really listened to what we wanted and brought our vision to life exactly how we imagined it! Our outdoor space has completely transformed, and it’s now one of our favorite places to relax. It’s exactly what we had in mind for our home, and we honestly couldn’t have asked for a better result. We highly recommend Sidex Construction to anyone looking for quality work!
  
 
      Posted on Google  
   
   Amanda Kilgore 
 
 
 
 Trustindex verifies that the original source of the review is Google. Had a great experience working with Sidex. Nate was super helpful during the in-person site visit and took the time to explain everything clearly without making us feel rushed or pressured. Andrey was also very helpful with scheduling and keeping everything organized throughout the process. The whole team was professional, easy to work with, and communication was solid from start to finish. Really appreciated how smooth everything went. Would definitely recommend Sidex to anyone looking for quality work and good customer service.
  
 
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   Marjorie Siemsen 
 
 
 
 Trustindex verifies that the original source of the review is Google. Tim did a wonderful job fixing a leak on my skylight windows. Totally professional and very detailed in his work. I would definitely consider him for future work!