#1 ADU Contractor in Brea
Custom Builds by Horizon Remodeling
Horizon Construction & Remodeling Inc. builds accessory dwelling units and room additions throughout Brea, managing design coordination, budgeting, material selection, and permits through the City of Brea Building and Safety Division so you do not have to chase the paperwork yourself. Projects range from detached backyard cottages to converted interior spaces, and because parts of Brea sit within the former Brea-Olinda oil field, some addresses carry added soil gas review that we account for during planning. Safety and a well-run build are the standard on every project we take on.
Services We Offer
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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Working as your adu contractor in Brea means understanding that the rules governing this process come from two places at once: California state law and the City of Brea Building and Safety Division, which handles every application locally. State law, updated as of January 1, 2026, now measures square footage as interior livable space, and it sets firm deadlines: 15 business days for an agency to determine whether an application is complete, and 60 days to approve or deny it. Approval is ministerial, meaning no hearing and no discretionary design review.
State law also sets a floor on what a city can require. A local agency cannot cap an ADU below 850 square feet of interior livable space, or 1,000 square feet for a unit with more than one bedroom. Side and rear setbacks cannot exceed four feet. Building an ADU cannot trigger a fire sprinkler retrofit of the main house, and there are no impact fees on a unit of 750 square feet or less. Owner-occupancy cannot be required as a condition of approval.
Brea’s housing stock shapes what is practical on any given lot. The older single-story ranch houses in the flatlands near downtown tend to have detached garages and shallower utility runs, which often makes a garage conversion straightforward. The larger two-story plans in the developments east of the 57 Freeway sit on different grades with longer distances to existing connections, which changes the cost equation for a new detached build.
One factor specific to Brea that a homeowner should know early: the city publishes a mapped combustible soil gas guideline covering portions of the former Brea-Olinda oil field, and some addresses carry added review as a result. Before we draw anything, we walk the parcel, check setbacks, confirm grade and equipment access, and identify whether the address falls inside that mapped area, because the answer affects both the design and the permit timeline.
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 Brea ?
ADU Contractor in Brea
Horizon Construction and Remodeling is a licensed Class B general building contractor, bonded and in business since 2009. Our office is in Fullerton, which puts Brea a short drive away, not a long-distance commitment. A detached ADU is a complete small house built on a lot that already has a primary residence, covering foundation, framing, roof, electrical service, plumbing, a kitchen, and a bathroom. Specialty trade portions of that work are handled by appropriately licensed subcontractors we coordinate directly.
Brea’s housing stock shapes how ADU projects come together. The older single-story ranch homes near Downtown Brea typically sit on flatland lots with room to place a detached structure, while the larger two-story plans east of the 57 Freeway often require more site analysis before design begins. Permits go through the City of Brea Building and Safety Division, and properties in areas covered by the city’s combustible soil gas guideline may require additional review before a permit is issued.
Because design decisions and construction constraints are tied together on an ADU, we draw the plans, manage the permit process, and build the project under one agreement. Neighborhoods we regularly work around include Downtown Brea, Olinda Village, Carbon Canyon, and Brea-Olinda.
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ADU Contractor Services in Brea
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ADU Contractor in Brea FAQ
What is an ADU and why should I build one?
An ADU is a secondary unit on your own property, built as a backyard cottage, a garage conversion, or an in-law suite. Adding one in Brea lets you bring in rental income, house a family member independently, or simply gain usable living space, and because permits run through the City of Brea Building and Safety Division, working with an experienced ADU contractor keeps that process on track.
How much does it cost to build an ADU in California?
What an ADU Actually Costs in Brea and What the Law Protects You From
Pricing an ADU honestly requires seeing your specific property first. The cost shifts based on whether you are converting existing space, which is more common in the older single-story ranch homes near Downtown Brea, or building a new detached structure, which tends to come up on the larger lots in the planned developments east of the 57 Freeway. Site work, utility runs, and finish level all move the number. That said, state law does set clear limits on what you can be charged: ADUs of 750 square feet or less of interior livable space are exempt from impact fees, school fees apply only above 500 square feet, and connection fees for a conversion or junior ADU are limited because the state does not treat those as a new residential use. Building an ADU also cannot trigger a fire sprinkler retrofit of your existing home.
Anyone quoting a firm number before walking the parcel is guessing. We visit the property, confirm setbacks and utility conditions, and check any added review requirements the City of Brea Building and Safety Division may flag, including addresses that fall within the mapped combustible soil gas area tied to the former Brea-Olinda oil field. After that review we give you a fixed scope and price you can hold us to. One warning worth stating plainly: the CalHFA ADU grant program is closed, its funding fully allocated, and the agency itself has stated that anyone offering to help you obtain an ADU grant is running a scam.
Do I need permits for an ADU in Brea?
Yes, every ADU requires a building permit, but the approval process is ministerial rather than discretionary, meaning there is no public hearing and no design review board to satisfy. In Brea, applications go to the City of Brea Building and Safety Division, which has 15 business days to confirm completeness and 60 days to issue an approval or denial, a timeline that drops to 30 days when a pre-approved plan is used. Some addresses in parts of the former Brea-Olinda oil field carry added review under the city’s combustible soil gas guidelines, so early preparation matters. Horizon prepares and submits the permit package and stays with the project through every inspection rather than returning the paperwork to the homeowner.
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 Brea?
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. manages every stage of an ADU project in Brea, from initial design through permitting with the City of Brea Building and Safety Division and on to finished construction, coordinating all trades so the work meets building codes and stays within your budget.
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 Construction & Remodeling Inc. to schedule a free consultation, where we assess your property, discuss your goals, and deliver a detailed estimate. We then guide you through every phase of your ADU project, including any added review that applies to addresses in Brea’s former oil field areas.
Recent ADU and Garage Conversions
Three completed ADU and garage conversion projects from our Orange County portfolio. Every project below was built in San Clemente. Nothing loads from YouTube until you press play.
ADU project in San Clemente
ADU project in San Clemente
ADU project in San Clemente
Built by Horizon Construction & Remodeling, Inc. Licensed Class B general building contractor.
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Horizon is a licensed Class B general building contractor serving Brea and the surrounding Orange County communities.
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