The Best Accessory Dwelling Unit Builders in California

Last updated on August 7th, 2024 at 01:55 am

The demand for Accessory Dwelling Units (ADUs) in California is skyrocketing, thanks to their affordability and versatility compared to traditional homes or apartments. Building an ADU in California is an excellent way to maximize your property’s potential, but the key to a successful project lies in selecting the right builder. A reputable and experienced ADU builder can provide accurate estimates, high-quality workmanship, and efficient navigation of the state’s complex regulatory requirements, ultimately saving you time, money, and stress.

In California, where the population reaches approximately 39.03 million, and the median home value is $904,210, the cost of building an ADU ranges from $100,000 to $350,000, with some projects costing up to $700,000. The average cost per square foot is $32.33, reflecting the substantial investment required for these projects. With an average completion time of 14 months, partnering with a skilled and reliable contractor is crucial to avoid delays and ensure your ADU meets all legal and quality standards. California has 56 relevant contractors who stand out for their expertise, reliability, and proven track records.

This article highlights some of the best ADU builders in California. Whether you want to add a small studio or a larger living space, these professionals can help you turn your vision into reality, ensuring your ADU project is handled with the utmost care and precision. Choosing the right builder is essential to creating a functional, aesthetically pleasing, and legally compliant ADU that enhances your property’s value and utility.

Overview: The Best Accessory Dwelling Unit Builders in California

See Ranking Methodology at the bottom of this article to learn more.

Santa Cruz Green Builders

303 Potrero St., Suite #45-105, Santa Cruz, CA 95060

Santa Cruz Green Builders is a locally owned family business with more than 12 years of experience building homes in Santa Cruz County. The firm specializes in sustainable design and construction and creates long-lasting, healthy, energy-efficient, environmentally sound homes and workplaces. It has received sterling reviews for its historic renovations, ground-up construction of new homes, and retail work. Well-versed in building accessory dwelling units in California, the company holds memberships in the Passive House Institute U.S., Build it Green, and the US Green Building Council. 

The company’s success lies in its excellent in-house team that possesses a wide variety of skills between members. The firm is led by owners Spencer Keenan and Taylor Darling. From the start, the duo put the principles of green building at the company’s core. Spencer graduated from San Francisco State University with a B.S. in Industrial Design. His education helped him to become a green builder. Taylor started at a young age in the building industry, having already built a number of projects in his high school years. Since then he has added experience working with a general contractor for five years. 

The firm’s impeccable work and sustainable ways have been featured in The Mercury News and This Old House. The company is well-versed in building ADUs in accordance with Santa Monica laws while also designing them for beauty and practicality. One of their best works is a 640-square-foot ADU with a comfortable living area, dining area, and kitchen. It even has a garage-style door that opens up one side of the structure to a deck and hot tub.

Acton ADU

808 E McGlincy Ln., Campbell, CA 95008

Acton ADU is the specialized arm of the premier remodeling company Acton Construction. Headed by principal Stan Acton, the company specializes in ADU residential design and interior design, navigating code regulations in 20 city or county jurisdictions, as well as the complete construction of fully liveable accessory homes. Constructing accessory dwelling units in California, the company was featured in a 2023 Los Angeles Times article.

With a focus on long-term family planning and multigenerational living, Acton ADU can deliver custom second homes that are fitted to address the varied needs of every family. From aging-in-place and universal design to providing affordable housing, the company personalizes each home for inclusivity. Additionally, the company offers Build Ready Plans, three of which are pre-approved by the city of San Jose, helping homeowners save time and money. Acton ADU also offers personalized designs, ADU financing options, and a Buy and Build program for new homeowners looking to purchase a new home and build an ADU.

Oliver Builders, Inc.

1428 Stannage Ave. Berkeley, CA 94702

Extensive experience and flexibility in project types make Oliver Builders a go-to contractor for many San Francisco East Bay residents. Principal owner Severin Oliver has more than thirty years of experience and vast know-how as a builder, project manager, and businessman. He has also assembled an expert team that can handle any type of residential project, from new homes to extensive second-story additions to beautiful kitchens and bathrooms. 

Oliver Builders proudly relies on local expertise. The firm is prepared for the challenges that arise in remodeling custom properties in an earthquake-prone area. The firm has also proven adept at integrating the latest technology into buildings. Fine woodwork, custom staircases, and high-end finishes define the company’s work.

The company is well-versed in building and creating ADUs in various styles and types. One example is an artist’s studio in Berkeley. Oliver Builders built a simple, serene space, perfect for creating and displaying the homeowner’s art. 

BMF Construction, Inc.

723 Camino Plaza, Suite #313, San Bruno CA, 94066

BMF Construction Inc. depends on the perfect balance of skilled team members, innovative methods, and fresh materials and design to provide premium San Francisco Bay Area construction services. 

Headed by veteran builders Derald Norton and Hugh “Tony” Bowen, the company started in the 80s with a focus on commercial projects, remodeling everything from offices and hospital facilities to schools and historic structures. During that time, the firm worked on Bay Area landmarks like the War Memorial Opera House and the Maritime Museum. The company soon brought its efficient process into residential work and has become a go-to contractor for many Bay Area residents. 

BMF creates striking detached and attached ADUs. It has provided backyard additions, conservatories, and other structures that can act as a place of retreat or a multigenerational space. One of their best works is a studio with zen design elements alongside a renovated 1906 cottage renovation.

Construction Consulting Services

3575 Cahuenga Blvd. W Suite #350, Los Angeles, CA 90068

Design-build company Construction Consulting Services has served the greater Los Angeles area for the last two decades with tailored construction services and great customer service. With its in-house team of architects, contractors, and project managers, the company can provide ample time and attention to ensure each residential and commercial project is successfully delivered. As a member of the Associated General Contractors of America and the Building Industry Association of Southern California, CCS adheres to the construction standards and ethics of trusted industry organizations.

CCS has a specialized team dedicated to creating key-ready ADUs. The firm can design diverse layouts and assist in every step, from permit expediting to architectural plans and construction. Among their most notable works is a one-story high-ceiling ADU the company created. The modern, private home’s exterior matches the existing house for a cohesive design. 

McDunn ADUs

1212 Glen Ave., Berkeley, CA 94708

Berkeley-based McDunn ADUs is a general contractor that does new construction of custom accessory dwelling units. It has completed nearly two dozen ADUs in all shapes and sizes in the San Francisco East Bay Area. Whether it’s a client in her 70s who wants to downsize and explore the world, a homeowner who dreams of a cozy art studio, or a client who needs a colorful aging-in-place home, McDunn rises to every challenge and delivers beautifully. 

Principal-owner Dan McDunn has been in the residential construction scene for two decades, and his experience ranges from production homebuilding for a Fortune 500 builder to luxury condominium construction as a small developer. In 2001, he started McDunn Construction and has built and remodeled beautiful homes across the area as well as commercial spaces. He transitioned to focusing on ADUs in 2017 and has built custom dwellings fitted for every need and desire of the client. 

Among the firm’s best projects is an award-winning work in Berkeley.  A collaboration with Larson Shores Architecture, the single-story backyard cottage was built so a grandmother can live with her children and grandchildren but still maintain independence. Some of its notable features are large skylights, a vaulted ceiling, and a welcoming patio. The project earned a 2019 Bay Area Remodeling Award and a 2020 NARI COTY Regional Award.

Canyon Design Build

3630 Park Blvd., Oakland, CA 94610

With more than 50 years in business and thousands of projects, East Bay remodeling company Canyon Design Build has established itself as one of San Francisco’s top builders and remodelers. This design-build company has completed numerous successful projects across the East Bay. The firm is also a recognized green building advocate. The US Green Building Council has recognized its work with LEED Platinum Certifications, including a 1915 Craftsman bungalow—dubbed the ‘greenest little house in America’ in 2012— and a historic Moraga barn. Magazines like Dwell, Metropolitan Home, and California Home and Design have also featured the firm’s work.

One of the company’s specialties is creating ADUs with the perfect balance of form and function. A great example is the Glass House, a 1200-square-foot customized ADU that acts as a guest house, office, and private gym. Canyon Design Build married industrial aesthetics and green design tactics to provide the client with a refreshing indoor/outdoor experience.

Levi Design Build

21118 Vanowen St., Canoga Park, CA 91303

Levi Design Build has completed more than 200 ADUs and remodeling projects in the Los Angeles and San Fernando Valley areas. One of the best ADU builders in Southern California, the company’s versatility in project type and wide geographic reach make it a dependable contractor for many Californians. 

Avi and Ester Levi established the firm. Avi’s experience includes being a former business partner in a commercial construction company. Clients praise them and the company for being trustworthy, knowledgeable, and professional. Their open communication and close collaboration approach fosters a great working relationship, resulting in projects being on time and budget every time. 

HDR Remodeling

2952 Sacramento St., Berkeley, CA 94702

Established as Honey Do Repair, HDR Remodeling has become one of the premier remodeling companies in the greater East Bay Area. Remodeling Magazine rankings and national and regional accolades from the NARI and the Chrysalis Awards mark its three-decade tenure in the industry. The CBC, CNBC, Berkeley Times, and San Jose Mercury News have also highlighted the firm. Among the leading ADU builders in Southern California, clients praise the studio’s professional team, high customer service, and high-quality projects. 

The company has earned various awards for its remodeling projects including Chrysalis Awards, NARI Contractor of the Year Awards, and NARI Remmie Awards. The firm is also recognized as an LGBTQ company by the U.S. Senate and the State of California. A notable ADU project by HDR recently won a 2019 NARI COTY Award, a 2019 Regional Chrysalis Award, and a 2018 Remmies Award. The Oakland ADU was a collaboration with local architect Carrie Shores. The one-bedroom cottage was designed for aging-in-place, low maintenance, and low environmental impact. It features green building strategies, a galley kitchen, and a future green roof. 

Connect Homes

706 S. Hill St., Suite #1060, Los Angeles, CA 90014

Architects Jared Levy and Gordon Scott met working for a prefab home building company. During their six years working with modular homes, they saw many problems within the industry: inefficient design and soaring shipping costs. The duo sought to give Californians a better set of options and established Connect Homes to do it. The LA-based company now builds affordable, green, and accessible prefab homes. Among the top ADU builders in Southern California, it was featured in a 2023 Dwell article.

Connect Homes offers one- to four-bedroom dwellings, each designed to meet LEED Platinum status, with the option of making the structure net-zero as well. Rounding out the sustainable strategy, homes are equipped with water-efficient fixtures, a high-performance envelope, and energy-efficient appliances and systems. While most companies complete only 55% of prefab systems, Connect provides up to 90%, making each home ready to move in just under two months. Connect’s larger models can be used as main homes while its smaller models can be ADUs, in-law suites, backyard cottages, and more. 

A daughter for her aging mother commissioned this minimalist Sonoma home. The  1,600-square-foot in-law unit follows universal design principles and boasts minimalist aesthetics. Located just down the hill from the client’s own home, the beautiful home features red cedar siding and floor-to-ceiling windows. 

Cover Technologies

1219 W 135th St., Gardena, CA 90247

Cover is a technology company that reinvented how Los Angeles residents built their backyard homes. This prefab company merges cross-disciplinary expertise from design, architecture, software engineering, computational physics, automotive manufacturing, and professional services to custom-build accessory dwelling units and homes. Being the single point of contact for the entire process gives the company the edge in streamlining the process for homeowners. 

Using its own software, Cover uses geospatial and zoning data to determine whether and how big you can build on your property. The company’s algorithm takes answers from a 50-100-question survey and renders a bespoke floor plan within 3 days. The firm focuses on sustainability and fits its projects with features that adhere to passive house standards. Dwell, Curbed, and Architectural Digest have highlighted cover’s innovative technology.

Cover’s first completed project is a 320-square-foot outbuilding workspace. The white structure in the client’s backyard serves as a hybrid music studio and office space for a professional sound editor. 

Supreme Remodeling

14545 Victory Blvd. Suite #401, Van Nuys, CA 91411

Whether building a custom home on the hillside or remodeling an older one,  Supreme Remodeling consistently delivers high-quality projects and exceptional customer service. The Van Nuys-based construction company has over 30 years of experience serving Los Angeles and its surrounding areas, giving it expert know-how in all facets of construction. The company is led by owner Patrick Duhan, who has 20 years of experience in hillside construction. He is accompanied by a team with more than 20 years of experience in design and construction. 

Supreme Remodeling has earned excellent reviews from previous clients on third-party review sites. Many of these testimonials talk about the company’s reliability and upfront attitude on costs. Past clients also love how the company’s approachable attitude and friendliness.

Modative

8757 Washington Blvd., Culver City, CA 90232

Modative is a design/build operation in Los Angeles. Its ADU arm focuses on detached, ground-up ADUs and garage conversions. It offers semi-custom, predesigned models that are energy-efficient and affordable. Through a five-step process, homeowners can have their own ADUs that can be used as an in-law or granny home or as a home that can be rented out for income.

Modative was founded as an architecture firm. After 12 years in the business, principals Christian Navar and Derek Leavitt saw the opportunity to focus on ADUs in the Los Angeles area. The firm’s specialization in helping create over 300 Small lot Subdivision Homes has equipped it with broad knowledge about designing, permitting, and building. The company brings this expertise into building efficient homes in small spaces. An expert in building an ADU in California, it was featured in a 2019 New York Times article.

Design Draw Build

2866 Webster St., Oakland, CA 94609

Design Draw Build Inc (DDB) is an architect-led design-build company serving the San Francisco East Bay area. It has a fully integrated team of highly adaptable architects and contractors. Its small size enables DDB to pay close attention to each client’s needs and desires and consistently provide excellent results. Its expertise is as diverse as its team: projects range from custom residences and historic renovations to education centers and healthcare buildings. 

Principal Tyler Kobick leads the firm. A licensed contractor and architect, Tyler’s construction experience includes building rural medical clinics in El Salvador and designing structures for Bonnaroo and Outside Lands. Recently, he spoke about ADUs on a panel at the East Bay AIA. His expertise proved vital in the panel discussion, which covered the ADU process, including planning, design, permitting, building, and finance. One of the best ADU builders in Southern California, the studio was awarded the 2024 California Preservation Foundation Design Award.

Design Draw Build is one of the few firms in the Bay Area that effectively addresses the increasing demand for ADUs. In 2019, the firm produced a research paper on behalf of the AIA that examined the bureaucratic and financial systems that affect ADU development. The paper recommended improving the process and making ADU development more feasible for homeowners. The firm can build any ADU: rentals, in-law units, detached, additions, and downsizing. 

Kaminskiy Design & Remodeling

12396 World Trade Dr., Suite #108, San Diego, CA 92128

Kaminskiy Design & Remodeling was founded as SDC Handyman Service Plus by Sergei and Elena Kaminskiy. What started as a small handyman operation has since become a full-service design and remodeling company. The firm has served thousands of clients in the San Diego area and has racked up awards such as Best Home Remodeler, Best Contractor, Best Kitchen and Bath Remodeler, and Best Local Construction Company as voted by readers of the San Diego Union Tribune for eight consecutive years. The company is a member of the NARI and the NKBA. Sergei is also a Certified Green Professional.

All of the company’s work is done in-house, from design to millwork. Doing so gives the firm complete control over the project, and results in highly detailed and personalized projects that fit every homeowner’s needs. Kaminskiy ADUs can be garage conversions or custom builds. The company also follows ADA and universal design guidelines for more inclusive spaces. One of their best works is a home addition that features a full kitchen, bathroom, and temperature-controlled wine cellar with wrought iron details on the door and bespoke wood carving details. 

Ranking Methodology

To evaluate the performance of builders, our methodology employs a systematic approach that considers various factors contributing to customer experience and satisfaction. We focused on assessing the accessory dwelling unit builders in the California area. The methodology involves assigning weightings to specific categories based on their significance in determining customer service quality. Here’s the breakdown of the categories and their respective weightings:

• Average Customer Satisfaction (35%): This metric represents the average rating given by customers across the same review platforms as the Average Customer Satisfaction Score. A higher average rating indicates greater overall satisfaction with the service provided.
• Service Rating Score (25%): We analyze the ratio of high (4-5 stars) to low (1-2 stars) ratings for each business across multiple review platforms: Google, Houzz, and Yelp. A higher percentage of positive reviews contributes to a higher score, reflecting better customer satisfaction.
• Complaint Percentage (25%): We analyze the ratio of complaints to total reviews for each business. A lower complaints ratio indicates better service quality and results in a higher score.
• Business Hours and Availability (10%): The operating hours of each business are assessed to gauge accessibility. Companies with extended operating hours are awarded a higher score, as they offer greater convenience to customers.
• License Status (5%): We verify the licensing status of each contractor with their local licensing board to ensure legal compliance. Companies with valid licenses receive a higher score, reflecting professionalism and adherence to regulations.
• Total Score: We determined the overall rating for every contractor by calculating a weighted average, with the category weight determining the amount the subscore contributed to the total score 

Additional Note: Service Rating Score, Average Customer Satisfaction, and Complaint Percentage are calculated with a Bayesian estimate to account for if the contractor has a low number of total reviews. A Bayesian average is a statistical method used to calculate the average of a set of data points while taking into account prior information or beliefs about the distribution of the data. It combines the observed data with a prior distribution to generate a more accurate estimate of the true average.