#1 ADU Contractor in Orange County
Custom Builds by Horizon Remodeling
Horizon Construction & Remodeling Inc. builds accessory dwelling units across Orange County, handling everything from design and budgeting through permitting, material selection, and construction. If you have a backyard, a garage, or unused space on your lot, we coordinate the full scope of work so you end up with a finished, code-compliant unit without having to manage multiple contractors on your own.
Most homes in Orange County were built between the 1950s and the 1980s, when orange groves gave way to master-planned tracts. Those single-story and two-story homes typically sit on lots of 6,000 to 7,000 square feet, which often leaves enough room for a detached backyard cottage or an attached addition. We look at your existing footprint, your setbacks, and your goals before recommending which ADU type makes sense for your property.
Permitting in Orange County runs through each individual city, so a project in Anaheim follows a different process than one in Irvine or Huntington Beach, and unincorporated areas go through OC Public Works. If your home sits in a planned community, HOA architectural review is commonly required before construction begins, and work near the coast may also trigger a Coastal Development Permit. We account for all of that at the start of the project, not after plans are drawn.
Specialty trade work, including electrical, plumbing, and mechanical systems, is performed by appropriately licensed subcontractors we coordinate as part of the overall build. Our role as a licensed general contractor is to keep every trade on schedule, make sure inspections are passed in the right order, and deliver a finished unit that meets current California Title 24 energy requirements and local structural standards.
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How Our ADU Process Works
When it comes to enhancing your living space, room additions combined with Accessory Dwelling Unit (ADU) construction offer unparalleled versatility and value. These projects not only increase square footage but also provide additional living accommodations, whether for extended family, rental income, or work-from-home setups, making them a popular choice for homeowners seeking to maximize their property’s potential. According to California’s Department of Housing and Community Development, ADUs are a key solution to expanding housing options in urban and suburban neighborhoods.
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ADU construction in Orange County moves through two separate layers of rules: state law sets the floor, and your city or the county handles the actual permit. California’s ADU statutes, now codified in Government Code sections 66310 through 66342 and amended again effective January 1, 2026, prevent local agencies from capping allowable ADU size below 850 square feet of interior livable space, or below 1,000 square feet for a unit with more than one bedroom. Side and rear setbacks cannot exceed four feet, owner-occupancy cannot be required, and the local agency must deem an application complete within 15 business days and issue an approval or denial within 60.
If your property falls in unincorporated Orange County, OC Development Services is your permitting agency, and ADUs there are processed as a ministerial building permit with no separate entitlement. Applications go through the myOCeServices portal. The county also publishes six pre-approved detached plans ranging from a 393 square foot studio to a 1,200 square foot three-bedroom. State law gives pre-approved plans a 30-day review window instead of the standard 60, which can move a project along. One thing worth verifying before committing to those plans: they were drawn to the 2022 building code, and updated 2025 versions were still in development at the time of this writing.
Inside any of Orange County’s 34 cities, from Anaheim and Santa Ana to Huntington Beach and Irvine, the city itself issues the permit, and requirements can vary from one jurisdiction to the next. Homeowners in coastal cities should also expect to navigate a Coastal Development Permit for work that falls within the coastal zone, adding a step that inland projects do not face.
For many Orange County homeowners, though, the permit office is not the most complicated hurdle. Industry figures drawn from 2016 data put roughly 82 percent of county residents under a homeowners association, a figure that reflects how much of the county’s housing stock grew out of master-planned tracts built between the 1950s and the 1980s. An HOA architectural review committee will have opinions about a detached structure’s roofline, exterior finishes, and placement even in cases where the building department raises no objection. Planned communities in south county and Irvine tend to have particularly active review boards, so confirming HOA requirements early is a practical step before design work begins.
Other Remodeling Services We Offer
A modern kitchen adds functionality, comfort, and lasting value to your home. At Horizon Construction & Remodeling, our kitchen remodeling experts bring fresh ideas and professional project management tailored to your unique needs. From layout design to material selection, we prioritize delivering a high-standard kitchen that’s both beautiful and energy-efficient — enhancing the way you cook, gather, and live every day.
Whether you envision a classic Southern California pool or a fully customized backyard oasis, Horizon Construction & Remodeling delivers the highest level of quality and service. Our comprehensive pool design and remodeling services cover everything from layout and decking to built-in BBQs and final touches like landscaping. Let Horizon be your trusted partner in transforming your backyard into the perfect outdoor retreat.
If you are planning a complete bathroom remodel or simply want to change your tub, shower, update your plumbing fixtures, or make the space more efficient, our team at Horizon will help you through the process with expert advice, professional craftsmanship, and affordable options with beautiful results. Learn more about our bathroom remodeling services.
Transform your space with our expert interior work services. We offer a comprehensive range of solutions — from space planning and custom design to the selection of high-quality finishes and materials. Our team of experienced professionals works closely with you to create a space that’s both functional and stylish, tailored to your unique needs, goals, and budget. Whether you’re updating a single room or overhauling your entire interior, we bring precision, creativity, and craftsmanship to every project.
At Horizon, we believe your home is more than just four walls — it’s where life happens. It’s the place you relax, gather with family and friends, and create lasting memories. That’s why we offer a full range of exterior work services designed to elevate your outdoor living space. From patios and hardscaping to custom decks and exterior renovations, we help turn your vision into a dream yard that complements your lifestyle and enhances curb appeal.
At Horizon Construction & Remodeling, our expert team includes a dedicated design and planning division that works hand-in-hand with licensed architects and structural engineers. We take care of everything — from detailed plans and blueprints to securing city permits — so you don’t have to deal with delays or red tape. Our goal is to streamline the process and provide a fully approved set of documents that aligns with both your vision and city regulations, saving you time and stress.
Why Choose Horizon Remodeling As Your ADU Contractor in Orange County ?
Horizon Construction & Remodeling Inc. is based in Fullerton, which puts us squarely in Orange County, and we build ADUs here as a licensed Class B general building contractor, bonded and operating under. This is the county we work in every week, and that familiarity shapes how we approach each project from the first site visit forward.
A detached ADU is its own complete structure: foundation, framing, roof, exterior envelope, a kitchen, a bathroom, and separate electrical and plumbing service, all added to a lot that already has a primary home on it. Because Orange County’s residential stock grew mostly between the 1950s and the 1980s, a large share of those lots are single-story tract homes on 6,000 to 7,000 square feet of land, and understanding what that footprint can realistically hold is part of the design conversation. The design decisions and the construction constraints are not separate problems. We handle the plans, the permit applications, and the construction together, and we prepare any HOA architectural review submittal at the same time as the building permit package rather than treating it as an afterthought. In planned communities and coastal cities, skipping that step costs weeks.
Two state law protections are worth knowing before you start. First, ADUs of 750 square feet of interior livable space or less are not subject to impact fees. Second, there is no owner-occupancy requirement attached to building an ADU. If anyone tells you differently, the version of the law they are working from is no longer in effect. Orange County has 34 separate cities each issuing their own permits, from Anaheim and Santa Ana to Irvine and Huntington Beach, plus OC Public Works handling unincorporated areas, so confirming current local requirements at the start of your project is always the right move.
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ADU Contractor Services in Orange County
ADU cities we serve in Orange County
ADU Contractor in Orange County FAQ
What is an ADU and why should I build one?
A secondary housing unit built on your own property is called an ADU, or Accessory Dwelling Unit. It can take the form of a backyard cottage, a converted garage, or an in-law suite attached to the main house. For homeowners across Orange County, building an ADU with Horizon Construction and Remodeling is a practical way to add rental income, give a family member independent living space, or simply get more out of a lot that was already there.
Orange County’s housing stock leans heavily toward single-story and two-story tract homes built between the 1950s and the 1980s, many sitting on lots of 6,000 to 7,000 square feet. That footprint leaves real room for an ADU on a lot of that size, and the existing structure, whether it is a detached garage or an underused side yard, often gives us a practical starting point. We assess what is already on your property and work from there rather than applying a one-size approach.
Permits for ADU construction in Orange County run through whichever of the county’s 34 cities owns jurisdiction over your address, from Anaheim and Fullerton in the north to Irvine and the coastal cities in the south, with OC Public Works handling unincorporated areas separately. If your home sits in a planned community, HOA architectural review is a common additional step, and properties near the coast may also require a Coastal Development Permit. We coordinate with the appropriate permitting authorities and, where the project calls for electrical, plumbing, or other specialty trade work, we bring in appropriately licensed subcontractors to handle those portions.
How much does it cost to build an ADU in California?
ADU construction costs in Orange County vary based on factors no contractor can assess from a web page alone: the unit’s size and type, whether the project is a conversion or new detached construction, the utility runs your specific lot requires, and the finish level you select. What we can tell you is where your money goes and what state law already protects you from.
State law limits certain costs in ways worth knowing before you budget. Any ADU with 750 square feet or less of interior livable space is exempt from impact fees. School fees only apply to units above 500 square feet. Connection fees for a conversion or a junior ADU are capped because the state does not classify those as a new residential use. Building an ADU on your property also cannot force a fire sprinkler retrofit on your existing home.
Orange County’s 34 cities each issue their own permits, so the process in Anaheim looks different from the process in Irvine, and coastal cities from Seal Beach to San Clemente typically require a Coastal Development Permit for work near the water. Planned communities throughout the county often add an HOA architectural review step on top of city permitting. Any contractor quoting you a firm number before walking your parcel is guessing. We visit the site, confirm setbacks and utility conditions, and then give you a fixed scope and price you can hold us to.
One point worth stating clearly: the CalHFA ADU grant program is closed, with its funding fully allocated. The agency itself warns that anyone offering to help you obtain an ADU grant is running a scam.
Do I need permits for an ADU in Orange County?
Yes, every ADU requires a building permit. Where you file depends on where your property sits. Homeowners in the unincorporated parts of Orange County submit through OC Public Works, and the process runs as a ministerial building permit with no entitlement hearing required. If your home is inside one of the county’s 34 cities, from Anaheim and Huntington Beach to Irvine and Santa Ana, you file directly with that city’s building department instead.
State law sets the review clock once your package goes in. The agency has 15 business days to confirm the application is complete and 60 days from that point to issue an approval or denial. Choosing a pre-approved ADU plan shortens that second window to 30 days, which can matter on those mid-century tract lots in north county or south county where homeowners want to move quickly. Horizon prepares the permit package, submits it to the correct agency, and stays with the project through every required inspection.
How long does ADU construction take with Horizon Remodeling?
Most ADU construction projects take between 4 to 8 months from design to completion, depending on scope and permit approvals. Horizon Remodeling prioritizes efficient timelines while maintaining quality workmanship.
What types of ADUs can Horizon Remodeling build?
We specialize in building detached ADUs, attached ADUs, garage conversions, backyard cottages, and junior ADUs (JADUs). Our team can help you choose the right ADU style for your property and goals.
Can I build a detached ADU on my property in Orange County?
Yes, if your property meets California zoning and space requirements. Horizon Remodeling will assess your site, secure the necessary permits, and build a fully detached ADU tailored to your preferences.
Is Horizon Remodeling licensed to build ADUs in my area?
Yes, Horizon Remodeling is fully licensed, bonded, and insured to build ADUs throughout Orange County and surrounding areas. We have over 18 years of experience delivering high-quality ADU projects.
What are the benefits of hiring Horizon Remodeling for my ADU project?
Horizon Construction & Remodeling Inc. handles ADU construction in Orange County from the first design conversation through the final inspection, coordinating every trade involved so you do not have to manage multiple contractors on your own. The goal is an accessory dwelling unit that meets California building codes, fits within your approved budget, and moves through the construction phase without unnecessary delays.
Orange County’s permitting landscape adds a layer of complexity that homeowners often underestimate. Each of the county’s 34 cities runs its own building department, so a project in Anaheim follows a different submittal process than one in Irvine or Huntington Beach, and unincorporated areas fall under OC Public Works. If your property sits in a planned community, an HOA architectural review may be required before construction drawings even reach the city, and properties near the coast typically require a Coastal Development Permit on top of the standard building permit. We track those requirements from the start so nothing stalls your project mid-process.
Does Horizon Remodeling handle ADU design and permitting?
Absolutely! Horizon Remodeling provides complete ADU design services, including architectural plans and 3D renderings. We also handle city permits and inspections, streamlining your project and reducing stress.
How do I get started on an ADU with Horizon Remodeling?
Contact Horizon Remodeling to schedule a free consultation. We’ll assess your property, discuss your goals, provide design recommendations, and deliver a detailed estimate. From there, our team guides you step-by-step through every phase of your ADU project.
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