Planning to build an ADU in Orange County? As a licensed, insured, and bonded design-build contractor, we help homeowners design, permit, and build detached ADUs, garage conversions, and attached ADUs from start to finish.
Licensed • Insured • Bonded • 15+ Years Experience • Design-Build Experts • Serving Southern California
Building an ADU is one of the best ways to add flexible living space and long-term value to your property, but every home is different. Before deciding what to build, it’s important to understand what your lot can accommodate, what permits may be required, and which type of ADU makes the most sense for your goals.
At Kol & Co., we help homeowners throughout Orange County navigate that process with confidence. As a licensed, insured, and bonded design-build contractor with more than 15 years of experience, we manage everything from property evaluation and design to engineering, permits, construction of detached ADUs, attached ADUs, garage conversions, and other accessory dwelling units, and the final walkthrough, all with one team from start to finish.
One of the biggest misconceptions about building an ADU is that if you have enough backyard space, you’re ready to build. In reality, every property is different, and the best solution depends on more than just square footage.
When we evaluate a property, we look at things like the lot layout, existing structures, access, utility connections, site conditions, and local development requirements. These details help determine what type of ADU makes the most sense and can identify potential challenges before plans are drawn.
An ADU may be a great fit if you want to:
During your consultation, we’ll walk the property with you, discuss your goals, explain your options, and help you understand what’s realistically possible before you invest in design or construction.
A detached ADU is a separate structure built on your property, offering the greatest privacy and flexibility. It’s a popular choice for rental income, multigenerational living, guest accommodations, or anyone looking for a completely independent living space.
Common features may include:
An attached ADU is connected to the existing home while functioning as its own living space. This option works well for homeowners who want to keep family close while still providing privacy and independence.
Common features may include:
Converting an existing garage into an ADU is often one of the most efficient ways to add living space without expanding your home’s footprint. Depending on the condition of the garage and local requirements, it can be an excellent option for rental income, guest housing, or a home office.
Common features may include:
Building above an existing garage allows you to create additional living space while preserving valuable yard space. This option is ideal for properties where maximizing the lot is a priority.
Common features may include:
A Junior Accessory Dwelling Unit (JADU) is created within the existing home and is designed to make use of available interior space. For some properties, it’s a practical way to add independent living space with fewer structural changes than a traditional ADU.
Common features may include:
One of the first things homeowners ask us during a consultation is, “What should I expect to invest in an ADU?” Based on our experience, most ADU projects in Orange County range from $200,000 to $500,000+.
Your investment is typically influenced by:
The best way to determine your project’s cost is to evaluate your property first. Once we’ve seen the site and discussed your goals, we can provide a detailed proposal based on your home and the ADU you want to build.
Based on our experience, most ADU projects take about 12 months from the initial consultation to final inspection. While construction is only part of the timeline, design, engineering, permitting, and city plan review all happen before building begins.
The overall timeline can vary depending on your property’s conditions, the complexity of the design, and your city’s review process. Careful planning before construction is one of the best ways to keep your project moving efficiently.
Yes. In most cases, building an ADU in Orange County requires permits before construction can begin.
Depending on your project, the process may include architectural plans, structural engineering, Title 24 energy compliance, and city plan review. The specific requirements vary by property and local jurisdiction.
As a design-build contractor, we coordinate the design, engineering, permit applications, and plan review, so your project is ready before construction begins.
Under California law, local ADU rules must allow at least:
For a newly constructed detached ADU, the state default maximum is 1,200 square feet when a city or county does not have a compliant local ADU ordinance. Some Orange County cities may allow ADUs larger than 1,200 square feet under their local rules. A JADU is generally limited to 500 square feet.
The size that works on your property will still depend on the lot layout, setbacks, height limits, existing structures, and the city where the property is located. We review those conditions before developing the floor plan.
For most newly built attached and detached ADUs, a city may require no more than a 4-foot rear-yard setback and a 4-foot side-yard setback.
No additional setback is generally required when:
Cities may apply front-yard setbacks, but those rules cannot prevent the construction of an ADU of at least 800 square feet. Coastal properties may also be subject to additional requirements under an approved Local Coastal Program.
Every ADU must meet current California building and energy codes, but the requirements vary depending on your property and the type of ADU you’re building.
Some of the most common factors that can affect your project include:
We review these requirements during the planning stage so potential issues are identified early, not after plans have been submitted for approval.
We visit your property, discuss your goals, evaluate the site, and determine what type of ADU best fits your home and local requirements.
Once the direction is established, we develop the layout, prepare the plans, refine the project scope, and provide a detailed proposal based on your property and budget.
When required, we coordinate structural engineering, Title 24 documentation, permit applications, and city plan review to prepare your project for construction.
With approvals in place, our team manages every phase of construction, from site preparation and framing to utilities, finishes, inspections, and quality control.
Before we consider the project complete, we perform a final walkthrough, address any remaining details, and make sure your new ADU is ready to enjoy.
We’ve helped homeowners plan and build ADUs throughout Orange County, including Irvine, Newport Beach, Laguna Beach, Mission Viejo, Laguna Niguel, Costa Mesa, Huntington Beach, Anaheim, Orange, Tustin, Yorba Linda, Fullerton, Fountain Valley, Garden Grove, and nearby communities.
Building an ADU in Orange County is a significant investment, and it starts with understanding what’s possible on your property. During your in-home consultation, we’ll evaluate your site, discuss your goals, answer your questions, and recommend the best approach based on your home’s layout, local requirements, and budget.
If you decide to move forward, we’ll guide you through every step, from design and engineering to permits, construction, and the final walkthrough.
Most ADU projects range from $200,000 to $500,000+, depending on the type of ADU, site conditions, engineering requirements, and finish selections.
Most ADU projects take about 12 months from the initial consultation through final inspection, including design, permitting, and construction.
Yes. Most ADUs require architectural plans, permits, and city approval before construction can begin.
The allowable size depends on your property, local regulations, and the type of ADU you’re building. During your consultation, we’ll evaluate your property and explain what’s possible.
Permitting timelines vary depending on the city and project scope. On average, ADU permits can take a few weeks to a few months, depending on plan complexity and review workload. Our design-build team handles the entire permitting process for you, coordinating directly with local departments to keep your project moving efficiently.
California law makes ADUs possible on most properties with an existing or proposed residential use, but the final design must still comply with state law, local development standards, and applicable building codes.
Common requirements include:
Because requirements differ between Irvine, Costa Mesa, Anaheim, Mission Viejo, unincorporated Orange County, and other local jurisdictions, we review the property and applicable city standards before developing the plans. Kol & Co. manages the design, engineering, permitting, and construction process so the ADU is planned around the actual requirements affecting your property.
