Kol & Co. is a trusted Accessory Dwelling Unit (ADU) builder in Costa Mesa, CA, specializing in custom ADU design, garage conversions, and turnkey construction services.
Licensed • Insured • Bonded • 15+ Years Experience • Design-Build Experts • Serving Southern California
Building an ADU isn’t just about finding a place to put another structure in your backyard. Before anyone starts drawing floor plans or pouring concrete, the first question we ask is, “Will this property support the ADU you actually want to build?”
Over the years, we’ve learned that no two ADU projects are ever the same. We’ve walked properties where a garage looked perfect for a conversion until we discovered foundation issues that needed to be addressed first. We’ve seen backyards with plenty of space, only to find utility easements or drainage requirements that changed the entire layout. Sometimes the best solution is a detached ADU. Other times, a garage conversion or attached ADU simply makes more sense for the property and the homeowner’s budget.
That’s why we spend time understanding the property before making recommendations. Looking at setbacks, utility connections, access, grading, existing structures, and how you plan to use the space helps us identify potential challenges early, before they become expensive surprises during design or construction.
As a licensed, insured, and bonded design-build contractor, Kol & Co. manages everything under one roof, from feasibility studies and architectural design to engineering, permits, construction, inspections, and the final walkthrough. Instead of coordinating multiple companies, you’ll work with one experienced team that’s focused on delivering an ADU that’s well planned, built to last, and designed to fit both your property and your long-term goals.
If you’re thinking about building an ADU in Costa Mesa, we’d be happy to visit your property, answer your questions, and help you understand what’s possible before you invest in plans or construction.
Homeowners choose to build Accessory Dwelling Unit (ADUs) for many different reasons, including:
The right ADU isn’t simply the largest one possible, it’s the one that fits your property, budget, and how you plan to use it for years to come.
A detached ADU is a separate residential structure built independently from the primary home. It’s one of the most popular choices for homeowners seeking maximum privacy, flexible living space, or long-term rental income.
Detached ADUs are commonly used for:
Because detached ADUs are built from the ground up, they offer the greatest flexibility in layout, size, architectural style, and interior finishes.
Converting an existing garage into a legal dwelling unit is often one of the most cost-effective ways to add living space while making use of an existing structure.
However, many garages built decades ago weren’t designed for full-time living. Depending on the existing condition, garage conversions frequently require:
An attached ADU shares at least one wall with the primary residence while functioning as an independent home with its own entrance, kitchen, bathroom, and living space.
Attached ADUs work well for homeowners who want to:
Because attached ADUs connect to the existing structure, careful planning is essential to integrate the new living space while maintaining the home’s architectural character.
Building above an existing garage allows homeowners to add living space while preserving valuable backyard area.
These projects often involve additional structural engineering to ensure the existing garage can safely support a second-story dwelling.
Above-garage ADUs are ideal for:
In general, Costa Mesa allows:
Setbacks determine how close an ADU can be built to your property lines and existing home.
For many new detached ADUs, Costa Mesa generally follows California’s minimum standards of:
If your project involves converting an existing garage or legally constructed accessory structure into an ADU, different rules may apply. In many cases, the existing building footprint can remain without requiring new side or rear setbacks, provided fire and life-safety requirements are satisfied.
Every property is different, which is why we verify setbacks during the feasibility study before design work begins.
Meeting the minimum size requirements is only one part of a successful ADU project. Every property has unique conditions that can influence design, engineering, permitting, construction costs, and the overall timeline.
When evaluating your property, we commonly review:
Addressing these items early helps reduce redesigns, avoid permit revisions, and minimize unexpected costs during construction.
Most custom ADU projects in Costa Mesa range from $200,000 to $500,000+, depending on the size, type of ADU, site conditions, structural requirements, and finish selections.
Your investment is typically influenced by:
Detached vs. attached ADU
Garage conversion vs. new construction
Utility connections
Structural engineering
Foundation requirements
Kitchen and bathroom finishes
Site grading and drainage
Permit and design requirements
Following a site visit, we’ll provide a detailed scope of work and transparent estimate based on your specific property.
A typical ADU project takes approximately 12 months from initial planning through final inspection, although timelines vary depending on design complexity, permitting, engineering, and construction.
Yes. Most detached ADUs, attached ADUs, and garage conversion ADUs require permits before construction begins.
Depending on your project, approvals may include:
Building permits
Structural review
Electrical
Plumbing
Mechanical
Energy compliance
Final inspections
Our team coordinates the permit process with the City of Costa Mesa and manages required documentation throughout the project.
We begin by visiting your property to understand your goals, evaluate site conditions, review zoning and setbacks, and determine the best ADU solution for your lot and budget.
Next, we develop a custom ADU design tailored to your property, refine the floor plan, discuss material selections, and establish a realistic project budget before construction begins.
Once the design is finalized, we coordinate structural engineering, prepare permit documents, and manage the approval process with the City of Costa Mesa to help keep your project moving forward.
Our experienced construction team manages every phase of the build, including foundation work, framing, roofing, electrical, plumbing, HVAC, insulation, interior finishes, and ongoing quality control.
Before completing the project, we perform a detailed walkthrough, address any final items, complete inspections, and ensure your new ADU is ready for occupancy.
Kol & Co. proudly designs and builds custom ADUs throughout Costa Mesa, including Eastside Costa Mesa, Mesa Verde, College Park, Halecrest, Mesa North, Westside Costa Mesa, Freedom Homes, State Streets, South Coast Metro, and surrounding communities. We also serve homeowners across Orange County, including Newport Beach, Irvine, Huntington Beach, Fountain Valley, Tustin, Santa Ana, Laguna Beach, Newport Coast, Corona del Mar, Orange, Anaheim, and nearby cities.
Whether you’re planning a detached ADU, garage conversion, attached ADU, or a fully custom accessory dwelling unit, choosing the right builder is one of the most important decisions you’ll make.
At Kol & Co., we believe every successful ADU begins with careful planning, transparent communication, and a design that’s tailored to your property—not a one-size-fits-all solution. From the initial feasibility study through architectural design, engineering, permits, construction, and final inspection, our experienced design-build team manages every stage with quality craftsmanship and attention to detail.
Let’s discuss your property, answer your questions, evaluate what’s possible for your lot, and create a custom ADU plan designed around your goals, budget, and future needs. Contact Kol & Co. today to schedule your consultation.
Most custom ADU projects in Costa Mesa range from $200,000 to $500,000+, depending on the size of the unit, structural requirements, utility connections, site conditions, and interior finishes. Following a site visit, we’ll provide a detailed proposal tailored to your property and project goals.
Not necessarily. Many ADUs can share water, sewer, gas, and electrical services with the primary residence, while others may require utility upgrades or separate connections depending on the project’s design, utility capacity, and local requirements. During the planning process, we’ll evaluate your property’s existing infrastructure and recommend the most practical and cost-effective solution for your ADU.
Yes. Garage conversions are a popular and cost-effective way to add living space. Kol & Co. evaluates:
Converted garages become fully functional ADUs with modern amenities.
Most Costa Mesa residential zones allow ADUs, but there are restrictions:
Our local expertise ensures your ADU is designed to comply with city rules and California ADU laws.
Suitability depends on lot size, zoning, setbacks, and utilities. Kol & Co. performs a site evaluation and feasibility assessment, identifying:
This ensures your ADU is efficient, legal, and optimized for your property.
