#1 ADU Contractor in Los Angeles County
Custom Builds by Horizon Remodeling
Horizon Construction & Remodeling Inc. builds ADUs and home additions across Los Angeles County, handling everything from design and budgeting through permitting and construction so you end up with finished, usable space without having to coordinate a dozen separate contractors yourself.
Los Angeles County’s housing stock runs deep into the past, with bungalows from the 1920s and postwar tracts from the 1950s and 1960s making up a large share of the residential market. Many of those homes sit on narrow lots and still have their original detached garages, which are often strong candidates for an ADU conversion. A garage conversion, a backyard cottage, or a detached unit added behind the main house are all projects we coordinate from the first site visit to the final inspection.
Permitting in Los Angeles County is not a single process. Homes inside city limits go through the City of Los Angeles Department of Building and Safety, properties in unincorporated areas route to the county Building and Safety division, and every other city runs its own permit counter. We manage the application and inspection schedule regardless of which jurisdiction covers your property. Hillside and coastal lots add geotechnical reviews and, where applicable, Coastal Commission requirements, and we factor those into the project scope from the start.
Older homes throughout the county, particularly the stucco bungalows and Spanish-style houses common across the San Gabriel Valley, the South Bay, and the San Fernando Valley, frequently need electrical and plumbing brought up to current code during an ADU project. Specialty trade portions, including any electrical, plumbing, or mechanical work, are performed by appropriately licensed subcontractors we coordinate as part of the overall build. Contact us to request a free estimate for your ADU construction project in Los Angeles County.
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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ADU construction in Los Angeles County now operates under a significantly updated set of state rules, and knowing those rules before you apply saves time and avoids surprises at the permit counter. California consolidated its ADU statutes into Government Code sections 66310 through 66342 in 2024, replacing the old section 65852.2, and additional changes took effect January 1, 2026. Two of those updates come up on nearly every project we manage. Square footage limits are now calculated based on interior livable space rather than overall structure size, and the reviewing agency must notify you within 15 business days whether your application is complete, then issue a full approval or denial within 60 days. The approval itself is ministerial, meaning no public hearing and no discretionary design review stands between your application and a decision.
Where your application goes depends entirely on where your property sits. In unincorporated Los Angeles County, plan review runs through County Public Works, Building and Safety, and the EPIC-LA permit portal. The county also publishes three free pre-approved ADU plans at no cost to the applicant, one at 800 square feet with a single bedroom and two plans at 1,200 square feet. If your home sits inside any of the county’s 88 incorporated cities, that city’s own permit counter is your agency, not the county. Given that much of the housing stock in places like the San Gabriel Valley, the San Fernando Valley, and the South Bay was built during the postwar tract boom of the 1950s and 1960s, older electrical panels and galvanized plumbing often need to be brought up to current code as part of the project, which affects how we scope the work from the start.
One county-specific issue is worth understanding before you submit. The county’s ADU ordinance, amended in July 2025, was found out of compliance with state law by the California Department of Housing and Community Development in December 2025. One of the specific findings was that the county limits detached ADUs on multifamily lots to two units, while state law allows up to eight. When county rules conflict with state law, state law controls, but that is not an argument a homeowner should have to make alone at a permit counter. We know where those conflicts exist and how to address them as your general contractor coordinating the process.
Homeowners rebuilding in unincorporated Los Angeles County after the January 2025 Eaton and Palisades fires should be aware that the county approved permit fee deferrals and refunds covering plan review, permit, and inspection fees. ADUs are eligible under that program, including situations where the ADU or detached garage was the only structure lost on the property. Eligibility requirements apply, and we review those with you during the consultation so you know exactly where you stand before any fees are collected.
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 Los Angeles County ?
Horizon Construction & Remodeling builds ADUs throughout Los Angeles County as a licensed Class B general building contractor, bonded, and in business since 2009. We handle the plan, the permit submittal, and the construction under one roof, so you are not coordinating between separate design and build teams.
On most Los Angeles County lots, the site conditions drive the difficulty more than the structure itself. Grade changes, equipment access, existing utility locations, and whether the parcel falls within a very high fire hazard severity zone all have to be sorted out before drawings start. A plan that overlooks those conditions tends to come back for redesign, which costs time. We work through those questions in the field first. Hillside and coastal lots add another layer, since geotechnical review and in some cases Coastal Commission approval enter the process alongside the standard building permit. Los Angeles County routes permits through the City of Los Angeles Department of Building and Safety inside city limits, the county Building and Safety division for unincorporated areas, and one of the other 87 city permit counters everywhere else. Where state ADU law and a local ordinance point in different directions, we identify which controls and note it in the submittal.
State law also gives you a set of protections worth knowing. There is no owner-occupancy requirement attached to building an ADU. Adding an ADU does not trigger a fire sprinkler retrofit on the main house. And impact fees do not apply to a unit with 750 square feet or less of interior livable space. Many of the homes we work on in Los Angeles County are 60 to 100 years old, with original galvanized plumbing and undersized electrical panels, so those systems often need to be brought up to current code as part of the project. We coordinate that work with appropriately licensed specialty subcontractors so the ADU and the primary structure both come through the inspection process in good order.
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ADU Contractor Services in Los Angeles County
ADU cities we serve in Los Angeles County
ADU Contractor in Los Angeles County 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 residential lot, taking the form of a converted garage, a detached backyard structure, or an attached suite connected to the main house. For homeowners across Los Angeles County, building an ADU with Horizon Construction & Remodeling Inc. is one of the most practical ways to add a rental unit, house an aging parent, or free up space for an adult child without leaving the property you already own. Many of the county’s older one-story stucco homes and Spanish bungalows sit on lots that work well for this type of project, particularly in areas like the San Gabriel Valley, the South Bay, and the San Fernando Valley where detached garages are common and often good candidates for conversion.
How much does it cost to build an ADU in California?
ADU construction costs in Los Angeles County depend on factors we cannot determine from a web page alone: the size and type of unit, whether you are converting an existing structure or building a detached unit from the ground up, what site work and utility runs your specific lot requires, and the finish level you select. We can, however, explain where the money goes and what state law requires contractors to honor.
State law exempts ADUs of 750 square feet or less of interior livable space from impact fees. School fees apply only when the unit exceeds 500 square feet. Connection fees are limited for conversions and junior ADUs because the state does not classify those as a new residential use. Keep in mind that Los Angeles County’s older housing stock, much of it built during the postwar tract-home era of the 1950s and 1960s, often has galvanized plumbing and outdated electrical panels that may need to be brought up to current code as part of the project, so utility costs vary more here than in newer communities.
One protection worth knowing: adding an ADU cannot legally trigger a fire sprinkler retrofit of your main house. That rule holds whether your property sits in the San Gabriel Valley, the South Bay, the San Fernando Valley, or anywhere else in the county. Any contractor quoting a firm price before walking your parcel is working from guesswork. We visit the property, confirm setbacks, easements, and the utility situation on the ground, and then give you a fixed scope and price you can hold us to.
One warning deserves plain language: the CalHFA ADU grant program is closed and its funding has been fully allocated. The agency itself cautions that anyone offering to help you obtain an ADU grant is running a scam. If someone approaches you with that pitch, walk away.
Do I need permits for an ADU in Los Angeles County?
An ADU always 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 clear. For properties in unincorporated parts of Los Angeles County, the application goes to County Public Works, Building and Safety through the EPIC-LA portal. Inside any of the 88 incorporated cities, from Long Beach in the South Bay to Pasadena in the San Gabriel Valley, the application goes to that city’s own permit counter. The agency reviewing your application has 15 business days to tell you whether your submission is complete, then 60 days from a complete application to issue an approval or a denial. Any denial must spell out the specific deficiencies and explain what it takes to fix them. Because so many Los Angeles County homes date to the postwar tract era of the 1950s and 1960s, older electrical panels and galvanized plumbing lines often need to be brought up to current code as part of the project, which is something we account for before the application goes in. We handle the submission and manage every step of that review cycle, the process does not get handed back to you to figure out on your own.
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 Los Angeles 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?
We handle ADU construction in Los Angeles County from the first design conversation through the final inspection, coordinating every trade and every permit so you do not have to. Because the county spans more than 80 incorporated cities plus unincorporated areas governed by separate departments, knowing which counter to walk into and what each plan checker expects makes a real difference in how quickly a project moves forward. Horizon Construction and Remodeling Inc. manages that process end to end, keeping the work on budget and on track while specialty trade work is handled by appropriately licensed subcontractors we coordinate directly.
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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