ADU Construction

An ADU, or accessory dwelling unit, is a small second home on the same lot as your house. It has its own kitchen, bathroom, and entrance. California law allows an ADU on most lots with a home, and cities must act on a complete permit application within 60 days. Builders handles the whole project, from first plan to final walkthrough.

What counts as an ADU in California?

California recognizes several ADU types: a detached backyard unit, an attached addition, a garage or interior conversion, and a junior ADU of 500 square feet or less inside the main home. Every type is a real living space with a kitchen, a bathroom, and a private entrance. The right one depends on your lot, your goals, and your budget.

Which type of ADU fits your property and budget?

A detached ADU gives you the most privacy and the most design freedom. It is a stand-alone home in your backyard, so it also costs the most to build. An attached ADU shares a wall with your house, which can save on foundation and utility work.

A garage conversion is usually the fastest, lowest-cost path. The slab, walls, and roof already exist, so the budget goes into insulation, plumbing, and finishes. A junior ADU converts space inside your home into a small separate unit. We help you compare these options on your actual lot before you commit to plans.

How does ADU construction work from design to move-in?

ADU construction runs in clear stages. First we check your lot: setbacks, utility locations, and where the unit fits best. Then we design the unit and prepare the plans the city needs. We submit the application and handle any corrections the plan checkers send back.

After the permit is issued, the build follows the same order as a new home: site work and foundation, framing and roof, rough plumbing and electrical, insulation and drywall, then kitchen, bathroom, and paint. City inspectors sign off at set points along the way. One crew and one contract carry the project from the first dig to the keys.

Do you need a permit to build an ADU?

Yes. Every ADU needs a building permit, even a garage conversion. The good news is that state law makes ADU approval ministerial. That means the city reviews your plans against written standards, with no public hearing. The state Department of Housing and Community Development explains these rules in its ADU handbook, and we build to them on every project.

We prepare the drawings, submit the application, and answer the city's correction notes for you. You never have to stand at a permit counter or decode plan-check comments on your own.

What does your lot need to support an ADU?

An ADU needs more than four walls. It needs water, sewer, and electric service, and some projects need an electrical panel upgrade at the main house. The foundation has to match your soil and slope. On sloped yards, a retaining wall can create the flat pad the unit sits on.

We also finish the outside so the ADU feels like part of the property, with walkways, patios, and other hardscape connecting it to the main house. Planning these pieces early keeps the budget honest and the schedule tight.

Why hire one ADU builder for the whole project?

An ADU is a whole house in miniature, so it touches every trade. The same team that runs our kitchen remodels and bathroom remodels builds your ADU's kitchen and bath. Our crews also handle the interior and exterior painting, so the finish matches the rest of your home.

One ADU builder means one contract, one schedule, and one point of contact. Our workmanship guarantee covers the finished unit for 2 years. See everything our remodeling team builds, or request your free estimate and we will walk your lot with you.

Why choose Builders?

• Family-owned and local to Corona.
• Fully licensed & insured for your protection.
• Upfront pricing you approve before any work starts.
• Serving Corona, Yorba Linda, Anaheim, Mission Viejo, San Dimas, Pasadena and surrounding areas.

Related services

• Hardscaping, Paver patios, walkways, driveways, and outdoor living areas built on a compacted base with real drainage, so the surface stays flat for years.
• Retaining Walls, Retaining walls built on a compacted base with real drainage behind them, so they hold your slope and stay straight for the long run.
• Interior & Exterior Painting, Interior and exterior painting done the remodeler's way. We repair the surface first, prep it right, then paint it clean, with one crew for walls, ceilings, trim, stucco, and siding, inside and out.

Explore our full range of Remodeling, or head back to the Builders home page.