#1 ADU Contractor in Montclair
Custom Builds by Horizon Remodeling
Horizon Construction & Remodeling Inc. builds accessory dwelling units and home additions for homeowners across Montclair, handling design coordination, budgeting, permitting through the City of Montclair Building Division, and material selection so the project moves forward without loose ends. Many of the compact postwar single-story homes here on former citrus-grove land were built with attached garages and tight floor plans that lend themselves well to ADU conversions or backyard units. Specialty trade portions are performed by appropriately licensed subcontractors we coordinate directly.
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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Finding the right adu contractor in Montclair starts with understanding the rules that actually govern your project, and those rules shifted significantly when California moved its ADU law into Government Code sections 66310 through 66342 in 2024, with further changes taking effect January 1, 2026. Square footage is now measured as interior livable space. An agency has 15 business days to decide whether your application is complete and 60 days to approve or deny it. Approval is ministerial, meaning no public hearing and no discretionary design review stands between you and a decision.
For a Montclair property, that application goes to the City of Montclair Building Division. No unusual local overlay applies here, so what governs your project is the California building code and the age of your house. That second point matters more than many homeowners expect. Most homes in Montclair were built during the postwar tract boom, compact single-story structures on what had been citrus groves before incorporation as Monte Vista in 1956 and the renaming to Montclair in 1958. The existing construction is what we are working with, and we review it carefully before a plan is drawn.
San Bernardino County adopted a new ADU chapter, Development Code Chapter 84.36, at the Board of Supervisors on January 13, 2026. Published standards allow an ADU from 200 to 1,200 square feet, a junior ADU to 500 square feet, 25 feet of height when attached and 18 feet detached with two additional feet permitted to match a roof pitch, and four-foot side and rear setbacks with five feet of separation between detached structures. Two ADUs per lot are allowed, and properties of five acres or more may have three units.
Sewer connection is often the question that decides feasibility before anything else. Connection is required when a sewer line runs within 200 feet of the property line, with that distance increasing by 100 feet for each additional dwelling unit. Where that threshold is not met, the project goes to septic or an advanced treatment system. We bring Environmental Health into the conversation early rather than after plans are already drafted.
The lot itself shapes most of the remaining decisions. The typical Montclair home is a compact single-story house with an attached garage and a small walled-off kitchen, and that layout directly affects where a detached unit can sit and how far utilities need to run. We work through those constraints at the start, so the plan we submit to the City of Montclair Building Division reflects what the site can actually support.
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 Montclair ?
Horizon Construction and Remodeling is a licensed Class B general building contractor, bonded, and in business since 2009. We handle ADU work in Montclair from a single point of contact: one team draws the plans, submits them to the City of Montclair Building Division, and carries the project through to the final inspection. Because no unusual local overlay applies here, what governs your project is the building code itself and the age of your home.
Most Montclair homes are compact, postwar single-story houses built during the tract boom that replaced the old citrus groves after the city’s incorporation in the mid-1950s. Many of those homes sit on lots with attached garages, which are among the most practical starting points for a garage conversion ADU. The age of the structure shapes every part of the plan, and we work through those details before design begins, not after.
California state law provides meaningful protections regardless of where your parcel sits: no owner-occupancy requirement for an ADU, no sprinkler retrofit of the main house triggered by adding one, and no impact fees on a unit with 750 square feet or less of interior livable space. We serve homeowners across North Montclair, Downtown Montclair, the Holt Boulevard corridor, and the Monte Vista Avenue corridor.
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ADU Contractor Services in Montclair
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ADU Contractor in Montclair FAQ
What is an ADU and why should I build one?
An accessory dwelling unit is a self-contained secondary home built on your existing property, taking the form of a backyard cottage, a converted garage, or an in-law suite attached to the main house. Building one with Horizon Construction and Remodeling can open a rental income stream, give family members independent living space, or simply add usable square footage to your property.
How much does it cost to build an ADU in California?
What an ADU project costs in Montclair depends on details no contractor can assess from a distance: whether you are converting the attached garage that is so common on postwar tract homes here or building a new detached unit, how much site work the lot requires, how far utility lines need to run, and what finish level you want inside. Those variables drive the numbers more than anything else. What the law does pin down is worth knowing. A unit with 750 square feet or less of interior livable space is exempt from impact fees. School fees apply only above 500 square feet. Connection fees for a conversion or junior ADU are limited because state law does not treat those as a new residential use, and adding an ADU cannot force a fire sprinkler retrofit on your existing house.
Because Montclair homes were built during the postwar tract boom, the age of the structure and the standard California building code are what govern your project through the City of Montclair Building Division, with no unusual local overlay complicating the process. Any contractor quoting a firm price before walking your property is guessing. We visit the site, confirm setbacks and utility conditions, and then give you a fixed scope and price. One warning worth stating plainly: the CalHFA ADU grant program is closed and fully allocated, and the agency itself says anyone offering to help you get that grant is running a scam.
Do I need permits for an ADU in Montclair?
Every ADU in Montclair requires a building permit, and the application goes directly to the City of Montclair Building Division. State law sets the review clock at 15 business days for a completeness determination and 60 days to approve or deny the project. Where septic or a well is involved, Environmental Health becomes part of the review, and the sewer proximity rule applies as well, meaning connection is required when a sewer line falls within 200 feet of the property line. Horizon manages the submittal, the corrections, and the inspections from start to finish.
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 Montclair?
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 design, permitting through the City of Montclair Building Division, and construction from start to finish, keeping your project on budget and up to code. In a neighborhood of compact postwar single-story homes, the age of the structure and current building code are what shape the work.
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 estimate, and we will assess your Montclair property, talk through your goals, and walk you step by step through every phase of your ADU project.
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Horizon is a licensed Class B general building contractor serving Montclair and the surrounding Orange County communities.
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