Forbes recently called 2020 The Year of the ADU. Due to a heavy push for affordable housing—perfectly timed with state regulation adjustments and advancements in construction technology—building additional structures and living spaces will be easier for homeowners this year. From prefab to design-build, the options are endless for Californians who want in-law units, guesthouses, or additional housing income right in their backyard. 

In this list, we present the top 15 accessory dwelling unit builders based in California. From Los Angeles to the San Francisco Bay Area, these contractors can deliver high-quality ADUs through turnkey and streamlined processes. They create these modern city housing solutions through close collaborations with homeowners, providing clients assistance from permitting and design to building and commissioning. Our team researched and selected the best based after we looked at credentials, versatility in project types, work histories, principals, awards, and the attention these firms have received from the press. 

If you are thinking about building an accessory dwelling unit, we recommend checking each builder’s license with the local licensing board, speaking to past clients, and using our bidding system to get competitive quotes from at least 3 contractors. Getting multiple bids is the best way to ensure you get a fair price and that bids include the complete scope of work.

Acton ADU

808 E McGlincy Ln., Campbell, CA 95008

Acton ADU is a residential design and construction company that specialises in full-service, accessory dwelling unit projects throughout Silicon Valley. Headed by founder and housing advocate, Stan Acton, the company offers a variety of approaches from build ready plans to full custom designs with a focus on helping homeowners navigate code regulations in over 20 city and county jurisdictions throughout Northern California.

With a focus on long term family planning and multigenerational living, Acton ADU can deliver custom second homes 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 and a Buy and Build program for new homeowners looking to purchase a new home and build an ADU, as well as ADU financing options.

Below you can see where Acton created an ADU for a San Jose client that wanted a multigenerational home for the entire family. This smaller home is also a great option as a future home for the client as she herself ages. 

BMF Construction, Inc.

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

BMF Construction Inc. banks on the perfect balance of skilled team members, innovative methods, and fresh materials and design to provide premium construction services in the San Francisco Bay Area. The firm offers new construction and remodeling services for homes and businesses. It also custom builds ADUs, decks, and other additions. 

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. Pictured here is an artist studio with zen design elements alongside a renovated 1906 cottage renovation.

Canyon Design Build

3630 Park Blvd., Oakland, CA 94610

With more than 50 years in business and thousands of projects under its belt, 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: from kitchen remodels and bath remodels to room additions and whole-house remodels. Its expertise extends to green remodeling, creating rental units within existing spaces, in-law units, basement conversions, seismic retrofits, modular home installation, and site work development. 

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 such as Dwell, Metropolitan Home, and California Home and Design have also featured the firm’s work.

Creating ADUs with the perfect balance of form and function is one of the company’s specialties. 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 a refreshing indoor/outdoor experience for the client.

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 a better set of options to Californians and established Connect Homes to do it. The LA-based company now builds affordable, green, and accessible prefab homes. Their efforts to streamline the design and construction process have been recognized in Dwell, Builder, Newsweek, Time, Architectural Digest, and GQ. 

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% and makes each home ready to be moved 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. 

This minimalist Sonoma home was commissioned by a daughter for her aging mother. 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. 

Construction Consulting Services

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

For the last two decades, design-build company Construction Consulting Services has served the greater Los Angeles area with tailored construction services and great customer service. With its in-house team of architects, contractors, and project managers, the company is able to provide ample time and attention to ensure each residential and commercial project is successfully delivered. And 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 set by trusted industry organizations.

CCS has a specialized team dedicated to creating key-ready ADUs. The firm is able to design diverse layouts and assist in every step from permit expediting, architectural plans, and construction. Aside from the common types of ADUs, CCS also delivers Junior ADUs and multitenant ADUs. Featured is a one-story high-ceiling ADU the company created. The modern, private home has an exterior that matches the existing house for a cohesive design. 


1219 W 135th St., Gardena, CA 90247

Founded in 2014, Cover is a technology company that reinvented the way 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 uses them to render a bespoke floor plan within 3 days. The firm focuses on sustainability and fits its projects with features that adhere to passive house standards. Cover’s innovative technology has been highlighted by Dwell, Curbed, and Architectural Digest.

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

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 the needs and desires of each client and provide consistently excellent results. Its expertise is as diverse as its team: projects range from custom residences and historic renovations to education centers and healthcare buildings. 

The firm is led by principal Tyler Kobick. 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 on a panel at the East Bay AIA about ADUs. His expertise proved vital in the panel discussion covering the ADU process including planning, design, permitting, building, and finance. 

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 made recommendations for improving the process and making ADU development more feasible for homeowners. The firm can build any type of ADU: rentals, in-law units, detached, additions, and downsizing. This detached ADU below is in design development. The sleek free-standing two-bedroom ADU will feature multiple wood finishes and strong dark lines. 

HDR Remodeling

2952 Sacramento St., Berkeley, CA 94702

Established in 1987 as Honey Do Repair, HDR Remodeling has become one of the premier remodeling companies in the greater East Bay Area. Its three-decade tenure in the industry is marked by rankings in Remodeling Magazine and by national and regional accolades from the NARI and the Chrysalis Awards. The CBC, CNBC, Berkeley Times, and San Jose Mercury News have also highlighted the firm. 

Clients praise the full-service residential design-build remodeling contractor for its professional team, high level of customer service, and high-quality projects. HDR re-imagines kitchens, bathrooms, and even whole houses, providing the perfect blend of form and function for every unique client. It also provides garage and basement conversions, ADUs, and backyard cottages. 

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 a recognized LGBTQ company by the US Senate and the State of California. Recently, a notable ADU project by HDR 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. 

Kaminskiy Design & Remodeling

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

Kaminskiy Design & Remodeling was founded in 2005 by Sergei and Elena Kaminskiy. What started out as a small handyman operation has since grown into 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.

The company provides whole home renovations and additions as well as smaller remodeling projects like kitchens, bathrooms, and outdoor living spaces. All of the work the company carries out is done by a team of professionals that Kaminskiy assembled over the last 15 years. This 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. Pictured below, you’ll see a home addition that features a full kitchen, bathroom, and a temperature-controlled wine cellar with wrought iron details on the door, as well as bespoke wood carving details. For more information on Kaminsky Design & Remodeling, you can visit their website here.

Levi Design Build

21118 Vanowen St., Canoga Park, CA 91303

Since 1999, Levi Design Build has specialized in remodeling, ADUs, and home additions. The Canoga Park-based design-build firm has completed more than 200 ADUs and remodeling projects in the Los Angeles and San Fernando Valley areas. These include detached, attached, garage conversions, and internal ADUs. Levi Design Build’s versatility in project type and its wide location reach makes it a dependable design-build firm for many Californians.

The firm was established by Avi and Ester Levi. 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 foster a great working relationship, resulting in projects being on time and on budget every time. For more information on Levi Design Building, you can visit their website here.

McDunn ADUs

1212 Glen Ave., Berkeley, CA 94708

Berkeley-based McDunn ADUs is a general contractor that specializes in the 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. From farmhouse to modern contemporary, its ADUs vary in style, much like custom homes. McDunn has also catered to a variety of clients who have used ADUs for a variety of unique purposes. 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 up 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. 

Featured here is the company’s 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. Large skylights, a vaulted ceiling, and a welcoming patio are just some of its notable features. The project earned a 2019 Bay Area Remodeling Award and a 2020 NARI COTY Regional Award.

Modative ADU

8757 Washington Blvd., Culver City, CA 90232

Modative is a design/build operation in Los Angeles that offers architecture, general contracting, and custom home building services. 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 in 2006. After 12 years in the business, principals Christian Navar and Derek Leavitt saw the opportunity to focus on ADUs in the Los Angeles area. Its specialization in helping create over 300 Small lot Subdivision Homes has equipped the firm with broad knowledge about designing, permitting, and building. The company brings this expertise into building efficient homes in small spaces. 

This garage conversion is a 310-square-foot studio apartment with a full-size kitchen and bath, in-unit laundry, built-in heating and air conditioning, and a uniquely designed patio. 

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 residents of the San Francisco East Bay area. Principal-owner Severin Oliver has more than three decades 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. 

Local expertise is what Oliver Builders proudly relies on. 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 in building. Its portfolio features a mix of architectural styles, ranging from modern contemporary to European classic. 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. Here, you’ll find an artist’s studio in Berkeley. Oliver Builders built a simple, serene space: perfect for the creation and display of the homeowner’s art. 

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 in 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, its ground-up construction of new homes, and its retail work. The company holds memberships in the Passive House Institute US, 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, already building 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 on 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. This 640-square-foot ADU has a comfortable living area, dining area, and a kitchen. It even has a garage-style door that opens up one side of the structure to a deck and hot tub.

Supreme Remodeling

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

Whether it’s 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 captained by owner Patrick Duhan who possesses 20 years of experience in hillside construction. He is accompanied by a team whose members have 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.

About Our Rankings

This list takes a range of ranking criteria into consideration, including but not limited to: work history, customer satisfaction, awards and recognition, geographic area of work, cost, building permits, and clientele. We spent over 40 hours researching local contractors before calculating the final ranking for this post. If there is additional information about your business that could affect these rankings, please fill out this form and we will take it into consideration.

Get Bids For Your Build

If you are thinking about building an accessory dwelling unit, we recommend checking each builder’s license with the local licensing board, speaking to past clients, and using our bidding system to get competitive quotes from at least 3 contractors. Getting multiple bids is the best way to ensure you get a fair price and that bids include the complete scope of work.