#1 ADU Contractor in Fullerton
Custom Builds by Horizon Remodeling
Horizon Construction & Remodeling Inc. builds accessory dwelling units throughout Fullerton, managing everything from initial design and budgeting through permit submittal and final inspection. Whether the project involves converting a detached garage on a postwar ranch in Sunny Hills or adding a backyard cottage behind a pre-war bungalow in the Golden Hill area, we coordinate every trade involved so nothing falls through the cracks. Permit applications go through the City of Fullerton Building and Safety Division, and any work touching a locally designated property may also require a Certificate of Appropriateness from the Fullerton Landmarks Commission.
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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Hiring an adu contractor in Fullerton means working inside a permit process governed by California Government Code sections 66310 through 66342, which were updated January 1, 2026. Under the current rules, square footage is calculated as interior livable space, the City of Fullerton Building and Safety Division has 15 business days to determine whether your application is complete, and a final approval or denial must follow within 60 days. Approval is ministerial, meaning no public hearing and no discretionary design review.
State law also sets a floor on what a local agency can restrict. A unit cannot be capped below 850 square feet of interior livable space, or 1,000 square feet if it has more than one bedroom. Side and rear setbacks cannot exceed four feet, owner-occupancy cannot be required, building an ADU cannot trigger a fire sprinkler retrofit on the main house, and there are no impact fees on units of 750 square feet or less.
Fullerton’s housing stock adds another layer of planning. The city was founded in 1887, and its oldest neighborhoods carry pre-war bungalows and Spanish Colonial Revival homes from the 1900s through 1930s. Postwar ranch-style homes on slabs filled in most of the remaining parcels after World War II. Lot size, grade, and existing utility routes vary considerably between those two eras, and that affects whether a garage conversion or a new detached build makes more sense for your property.
One additional consideration applies to designated historic properties. Fullerton has a Landmarks Commission and a local landmark ordinance, so qualifying work on a designated parcel requires a Certificate of Appropriateness before permits move forward. We review every parcel for setbacks, utility routing, equipment access, and landmark status before a single drawing is produced.
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 Fullerton ?
Horizon Construction and Remodeling is a licensed Class B general building contractor, bonded, with over 15 years of design-build work behind us. Our office is at 614 S Euclid St in Fullerton, so projects here are local work, not a long drive. We draw, permit, and build ADUs as one coordinated effort, which matters because the design decisions and the construction realities have to move together from the start.
A detached ADU is essentially a small house placed on a lot that already has a primary residence. It needs a foundation, framing, a roof, a complete envelope, a kitchen, a bathroom, and separate utility connections, with specialty trade portions handled by appropriately licensed subcontractors we coordinate. Permits for ADU work in Fullerton go through the City of Fullerton Building and Safety Division, and properties covered under the local landmark ordinance may also require a Certificate of Appropriateness before work can begin.
Fullerton’s housing ranges from pre-war bungalows and Spanish Colonial Revival homes in older neighborhoods to postwar ranch houses on slabs in areas like Sunny Hills, Raymond Hills, Amerige Heights, and Golden Hill. Lot configurations and existing structures vary considerably across those eras, and we account for those differences early in the design process.
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ADU Contractor Services in Fullerton
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ADU Contractor in Fullerton FAQ
What is an ADU and why should I build one?
An ADU is a secondary housing unit on your property, such as a backyard cottage, garage conversion, or in-law suite. Building one with Horizon Construction & Remodeling gives Fullerton homeowners a way to generate rental income, house extended family, or gain extra living space on lots that have accommodated separate service structures since the city’s earliest neighborhoods took shape.
How much does it cost to build an ADU in California?
What an ADU Actually Costs in Fullerton
Pricing depends on details no contractor can know from a distance: whether you are converting an existing structure or building a detached unit from scratch, how far utility lines need to run across your lot, the size of the finished space, and the materials you choose. What state law does spell out is where fees are limited. An ADU with 750 square feet or less of livable space is exempt from impact fees. School fees apply only when the unit exceeds 500 square feet. Connection fees for a conversion or junior ADU are capped because the state does not classify those as a new residential use. Building an ADU also cannot force a fire sprinkler retrofit on your existing home.
Fullerton permits go through the City of Fullerton Building and Safety Division, and if your property carries a local landmark designation, the Landmarks Commission may require a Certificate of Appropriateness before work begins. Older bungalows and Spanish Colonial Revival homes in neighborhoods like Golden Hill or Raymond Hills sometimes fall under that ordinance, so confirming landmark status early matters. We walk the property, review the setback and utility situation, and then provide a fixed scope and price you can hold us to. One point worth stating plainly: the CalHFA ADU grant program is closed, its funding fully allocated, and the agency itself warns that anyone offering help obtaining an ADU grant is running a scam.
Do I need permits for an ADU in Fullerton?
Yes, an ADU always requires a building permit, but state law makes approval ministerial rather than discretionary, meaning no hearing and no design review board. Applications in Fullerton go to the City of Fullerton Building and Safety Division, which has 15 business days to confirm completeness and 60 days to approve or deny, though a pre-approved plan shortens that review to 30 days. One thing worth noting for owners of older properties in historic neighborhoods like Golden Hill: a designated landmark may require a Certificate of Appropriateness before the permit application moves forward. Horizon prepares and submits the full package and sees it through every 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 Fullerton?
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 ADU projects in Fullerton from design through final inspection, coordinating permitting with the City of Fullerton Building and Safety Division and keeping the work aligned with building codes and 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?
Reach out to Horizon Construction & Remodeling Inc. to schedule a free consultation, where we assess your property, talk through your goals, and deliver a detailed estimate covering every phase of your ADU project in Fullerton, including permit coordination with the City of Fullerton Building and Safety Division.
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 Fullerton and the surrounding Orange County communities.
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