Prefab Accessory Dwelling Units (ADUs)

Add Livable Space to Your Southern California Property

Welcome home! As expert prefab housing builders in Southern California, US Modular, Inc. redefines modern living with our thoughtfully designed and swiftly constructed Accessory Dwelling Units (ADUs).

Whether you’re expanding your living space or investing in a profitable rental property, our team of seasoned ADU builders combines decades of experience with innovative prefab technologies to deliver high-quality, sustainable homes tailored to your lifestyle and needs. Explore the possibilities with us!

Call today to schedule an on-site evaluation and see if an ADU could be the perfect choice for you.

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What Is a Prefab ADU?

A prefabricated accessory dwelling unit (prefab ADU) is an affordable, high-quality way to extend your living space.

Often called a “granny flat” or “backyard home,” prefab ADU homes are factory-built off-site in a controlled factory environment and delivered to your property to sit on a permanent foundation.

Prebuilt ADUs are designed for quick assembly and customization. Choose from various layouts, from cozy studios to expansive four-bedroom homes, all constructed with precision and designed to blend with Southern California’s diverse architectural styles.

Whether you need space for a family member to age in place, an extra living area for guests, or even a rental income opportunity, prefab ADUs from US Modular offer limitless possibilities.

Browse Past Prefab ADU Builds

Why Choose US Modular ADU Builders

US Modular is a one-stop shop. As a full-service provider in Southern California, we handle the entire prefab ADU process, including design, permitting, contracting, and installation.
US Modular is licensed, bonded, and insured. We hold a California general contractor license and manufactured home dealer license, so you can be confident in our work.
We have more than 60 years of combined experience. We have seen it all! US Modular is your premier destination for prefab homes and ADUs.
The entire ADU process is much faster than most home construction. From design to delivery and installation, most clients can expect a timeline of only 6 to 9 months. Amazingly, once permits are secured, installation usually only takes around 3 months.
US Modular is committed to offering the best quality ADUs. Prefab ADUs are manufactured station-to-station with multiple sign-offs and inspections. They’re built from the same high-quality materials as site-built homes, but are often more energy-efficient to construct.
We offer competitive, transparent starting prices. ADUs are typically up to 40% less expensive than comparable site-built or modular options. Why pay more for a site-built home when you can get the same quality home with a faster delivery time?

Request ADU Pricing and Floor Plans

Our Full-Service Process

Understanding the prefab ADU building process can help you make an informed decision. US Modular’s process ensures efficiency, transparency, and a stress-free experience, from initial design to final inspection.

Here’s how it works:

Design & Consultation — Take advantage of our interactive tool to compare ADU floor plans and see how they might fit on your property, then call us to discuss your needs and schedule your on-site evaluation.

On-Site Evaluation — One of our building specialists will assess your property to see if an ADU is right for you. We will verify measurements, survey the area for utilities, and determine the full scope of the project.

Customization & Preparation — Now, the real fun begins, as you finalize your style and finish selections and fully personalize your build. All of the necessary permits are acquired to ensure full compliance with building regulations in your area, and your property undergoes preparation for construction.

Off-Site Construction — Your ADU is constructed off-site in our controlled factory environment to guarantee quality and speed.

On-Site Assembly — The prefab components of your ADU are delivered to your site and assembled quickly.

Final Touches and Inspection — The US Modular team completes the installation of your prebuilt ADU with attention to every detail, followed by a thorough inspection to ensure everything meets your expectations and local standards.

Ready to get started?

Call now to schedule your on-site evaluation

ADU Benefits & Use Cases

Keep Family Close — With a prefab ADU on your property, you can provide a beautiful, comfortable, safe living space for an aging parent, an adult child, or a relative in need.
With all the conveniences and amenities of a single-family home, a prebuilt ADU is the perfect option for keeping beloved family members close.
Rental Income — These days, everyone is looking for a way to generate additional income. A rental unit on your own property offers proximity and convenience.
With a long-term rental agreement on your ADU, you could potentially offset the cost of your own mortgage!
Value & Flexibility — ADUs make incredible offices, workshops, or guest suites, but no matter the use case, your new unit will add incredible property value to your existing space.
Boost the curb appeal and prestige of your property with a prefab ADU!

Ask If an ADU Is Right for You

ADU Success Stories

Prefab ADU buildings from US Modular offer flexibility and convenience for property owners in Southern California.

Learn about real ADU projects we’ve completed and the customers we’ve served!

Additional Space for Family Members (Orange County)

The US Modular team built a Bungalow ADU for a homeowner’s mother who’d been living 10 miles away in a small apartment.

Now she’s steps from family, feels safer, and enjoys daily time with the grandkids.

The household reports meaningful monthly savings ($1,000 in rent!) and a better quality of life; an ADU doing exactly what it’s meant to do.

Rental Income (San Diego)

A prefab ADU can turn one rental into two income streams.

An investor client added a 2-bedroom ADU behind an existing single-family rental in San Diego and immediately increased total monthly cash flow with one property, one lot, and one set of utilities. Smart density, predictable build, stronger return.

“Where can I buy a 2-bedroom rental property for under $225,000 in San Diego?” he asked. “Nowhere! But I could build a 2-bedroom ADU for this price; it’s a no-brainer.”

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