From Detached ADUs to Garage Conversions, We Design, Permit, and Build Custom Accessory Dwelling Units in Mission Viejo and across Orange County – From Start to Finish.
Licensed • Insured • Bonded • 15+ Years Experience • Design-Build Experts • Serving Southern California
Building an ADU isn’t simply about adding another structure to your property. After evaluating properties throughout Mission Viejo, we’ve found that the biggest decisions are usually made before construction ever begins. The location of existing sewer and utility lines, lot slope, setbacks, grading, HOA requirements, and even where the new entrance should face can all influence the design, permitting process, construction timeline, and overall investment. Getting these details right early almost always leads to a smoother project.
Whether you’re planning a detached ADU, garage conversion, attached ADU, Junior ADU (JADU), guest house, backyard home, or in-law suite, our first step is understanding how you want the space to work—not simply how many square feet you can build. Some homeowners want long-term rental income, others are planning for multigenerational living, while many simply need additional living space without leaving the neighborhood they love.
As a licensed, insured, and bonded design-build contractor with more than 15 years of residential construction experience, Kol & Co. manages every phase of the project under one team—from feasibility studies and custom ADU design to architectural plans, structural engineering, permits, construction, inspections, and the final walkthrough. Instead of coordinating multiple companies, you’ll have one experienced team responsible for the entire process from start to finish.
If you’re thinking about building an ADU in Mission Viejo, we’d be happy to walk your property, discuss what’s realistically possible, and help you make informed decisions before investing in plans or construction.
Accessory Dwelling Units continue to grow in popularity throughout Orange County because they offer flexibility without requiring homeowners to move.
Many homeowners in Mission Viejo choose to build an ADU to:
With California’s ADU laws becoming more homeowner-friendly, many properties that previously couldn’t accommodate an ADU may now qualify.
A detached ADU is a standalone backyard home that offers the greatest privacy and flexibility. It’s often the preferred option for homeowners who want to maximize living space without changing the layout of the main house.
Popular uses include:
If you have an underused garage, converting it into a livable space can be one of the most efficient ways to build an ADU. Since the existing structure is already in place, garage conversion ADUs can reduce construction time while making better use of your property.
Garage conversion projects in Mission Viejo may include:
An attached ADU expands your existing home while creating a separate living space with its own entrance. This option works well when backyard space is limited or when homeowners want the new addition to blend seamlessly with the existing house.
Attached ADUs are ideal for:
A Junior ADU (JADU) converts part of an existing single-family home into a smaller, self-contained living space. For qualifying properties, it can be an excellent way to add functionality without building a separate structure.
A JADU may include:
Most ADUs we build in Mission Viejo fall between $200,000 and $500,000+, but there isn’t a one-size-fits-all price. Two ADUs with the same square footage can have very different budgets depending on the property, the amount of site work required, and the level of customization.
Your ADU investment may be influenced by:
Detached ADU, attached ADU, or garage conversion
ADU size, layout, and number of bedrooms
Architectural plans and structural engineering
Grading, drainage, retaining walls, and foundation requirements
Sewer, water, gas, and electrical connections
Electrical panel and utility capacity upgrades
Kitchen, bathroom, cabinetry, flooring, and finish selections
Title 24 energy compliance, solar, and building code requirements
Permit, utility, school, and development fees
Site access, material staging, and construction logistics
Our goal isn’t to provide the lowest estimate—it’s to provide one that’s accurate. By identifying site constraints, utility requirements, and permitting considerations upfront, we help homeowners avoid the unexpected costs and change orders that often arise when those details are overlooked.
In our experience, most ADU projects in Mission Viejo take approximately 12 months from the initial consultation to final inspection. While construction itself is only part of the process, careful planning before breaking ground is what keeps a project moving efficiently.
Yes. A new ADU, attached ADU, garage conversion, or Junior ADU must receive the required City of Mission Viejo approvals and building permits before construction begins.
Depending on the project, the permit package may include:
Site and architectural plans
Structural plans and calculations
Title 24 energy documentation
Mechanical, electrical, and plumbing plans
OCFA Residential Preliminary Form
Geotechnical report or soil memo
Utility information
Construction and demolition waste documentation
Permit disclosure and contractor information
At Kol & Co., we coordinate the design, engineering, permit submission, correction responses, construction inspections, and final completion under one experienced design-build team.
Mission Viejo’s published ADU reference guide allows a newly constructed attached or detached ADU of up to:
The City’s guide also states that an attached ADU extending beyond an existing home is generally limited to no more than 50% of the existing primary dwelling’s floor area. Converted interior areas may be treated differently because they use space within an existing or proposed structure.
Even when lot coverage, floor-area ratio, or open-space standards would otherwise limit construction, California law generally protects the ability to build an ADU of at least 800 square feet with compliant side and rear setbacks.
The largest unit allowed on paper is not always the best design. We also evaluate usable yard space, privacy, daylight, parking, utility routes, construction access, and how the ADU will relate to the main home. In many cases, an efficient 700- to 900-square-foot floor plan works better than simply maximizing square footage.
For most newly constructed attached and detached ADUs, Mission Viejo’s published standards show minimum 4-foot side-yard and 4-foot rear-yard setbacks. The front setback is generally based on the property’s underlying zoning requirements.
Important exceptions and additional requirements include:
California’s current ADU guidance similarly limits required side and rear setbacks to no more than four feet for most attached and detached ADUs and provides setback protections for qualifying conversions and replacement structures.
Setbacks should never be measured from an online map alone. Property lines, easements, slopes, existing improvements, and recorded surveys can change the actual buildable area.
Building an ADU in Mission Viejo involves more than meeting the minimum size and setback requirements. Before we begin design, we evaluate the property for factors that can affect the budget, timeline, and construction process, including:
Evaluating these details early allows us to design an ADU that’s practical to build, complies with local requirements, and helps minimize unexpected costs and delays during construction.
We evaluate your property, discuss your goals, review what's possible, and recommend the ADU solution that best fits your home and budget.
We develop the floor plan, architectural drawings, structural engineering, and all required documents for permit submission.
Our team prepares the permit package, coordinates with the City of Mission Viejo, responds to plan-check comments, and manages the approval process.
Once permits are approved, we oversee every phase of construction, including site work, utilities, inspections, subcontractors, scheduling, and quality control.
After the final inspections are complete, we walk through the finished ADU with you to ensure every detail meets our standards before turning over your new living space.
Kol & Co. provides ADU design and construction services throughout Mission Viejo, including Pacific Hills, Canyon Crest, Painted Trails, Madrid, Galicia, Aegean Hills, Cordova, La Paz, Mission Ridge, Mallorca, Palmia, Casta del Sol, and nearby Orange County communities.
A successful ADU begins with understanding the property—not choosing a floor plan from a catalog. Setbacks, utilities, slopes, access, privacy, and construction costs should all be evaluated before you invest in architectural plans.
Kol & Co. provides complete ADU design-build services in Mission Viejo, from the initial property assessment and custom design through engineering, permits, construction, and final inspection.
Schedule an ADU consultation today. We’ll review your goals, evaluate your property, and help you determine the most practical way to move forward.
Most professionally designed and built ADUs range from approximately $200,000 to $500,000+. The final cost depends on the ADU type, size, site conditions, utility connections, foundation work, finishes, and permitting requirements.
Most Mission Viejo ADU projects take approximately 12 months from initial planning through final inspection. Garage conversions may move faster, while custom detached ADUs involving grading or major utility work may take longer.
Yes. ADUs and Junior ADUs require City review, building permits, approved plans, inspections, and supporting documents applicable to the project. Mission Viejo processes ADUs through its building-permit and plan-check system.
Yes. We provide complete design-build ADU services, including feasibility review, design, architectural plans, engineering, permits, construction management, material coordination, inspections, and the final walkthrough.
