ADU Construction
Three different things are commonly called an ADU. Which one you are building changes almost every answer.
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Design by Astrid Lind. Construction by Jacob Construction Inc., a licensed California general contractor, CSLB #1073757.
Scope
A detached new structure, a conversion of an existing garage, and a junior unit created within the walls of the main house are all referred to loosely as ADUs. They differ in what they cost, how they are reviewed, what utilities they need and what they are practical for.
California state law sets a baseline that local jurisdictions must work within, but cities still control meaningful details. What applies to your property depends on which city you are in and on the specifics of the lot, so the useful first step is establishing which type is actually viable there.
Key Decisions
A garage conversion reuses an existing structure and foundation. A detached unit is new construction from the ground up. The two are rarely comparable on cost, schedule or what the finished space feels like.
Water, sewer, gas and electrical have to reach the unit, and whether it is separately metered is a decision with long-term consequences for renting, billing and resale. Trenching across a finished garden is easy to forget at estimate stage.
A unit for a family member, a long-term rental and a home office are designed differently — in layout, sound separation, entry and finish level. Deciding this first prevents a unit that suits none of them well.
Where the unit sits affects privacy for both households, what the main house looks out onto, and how much usable garden remains. It is worth studying on the actual site, not only on a plan.
Converting a garage removes covered parking and, usually, the household’s main storage. Where those functions go afterwards is a practical question that tends to surface only once the work is complete.
State law and local ordinances interact, and cities update their requirements. Confirm the current rules for your specific jurisdiction and lot rather than relying on general summaries, including ones written here.
ADU or JADU
State law treats a full accessory dwelling unit and a junior unit differently, and the difference shapes the whole project.
A junior accessory dwelling unit, or JADU, is carved out of space within an existing single-family home, and in some cases an attached garage. It is usually the smallest step: a bedroom suite with its own entrance and a simple kitchen. A JADU carries a deed restriction recorded on the property, so ask what that restriction says before you commit.
A full ADU can be detached, attached or a conversion of existing space. It has its own kitchen and bathroom and is a separate home on the lot, which is why foundations, utilities and placement matter far more.
Standard Plans
LADBS runs an ADU Standard Plan Program: designs prepared by architects and engineers that the department has already checked against the building, residential and green codes. Choosing one shortens plan check, but it does not skip it. Zoning and foundation requirements are still reviewed for your lot, and a standard plan may not suit every site. Ask whether a pre-approved design fits your lot before paying for a custom one.
State Law
California has rewritten its ADU rules repeatedly, and some limits homeowners expect no longer apply.
Building an ADU cannot by itself require sprinklers to be added to the existing house. Whether the new unit needs them can depend on whether the main house already has a system, so confirm it for your design.
Owner-occupancy requirements were removed for ADUs. Junior units are treated differently, which is one more reason to read the deed restriction.
Because the law changes often, confirm the current rules with your city or county before design, and treat older articles with caution.
Ask before you commit: has anyone confirmed whether a pre-approved plan fits this lot, and which state and local rules apply to this design today?
Before You Commit
Our guide to comparing remodeling estimates is worth reading before comparing ADU proposals, which vary widely in what they include.
Share the lot, what the unit is for and your timing. We will talk through which type makes sense and what to confirm first.
Astrid Lind by Jacob Construction is the design studio of Jacob Construction Inc., a licensed California general contractor (CSLB #1073757). Jacob Construction Inc. performs the work under a written contract with you.
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Astrid Lind by Jacob Construction is the design studio of Jacob Construction Inc., a licensed California general contractor, CSLB License #1073757 (Class B – General Building). All construction work is performed by Jacob Construction Inc. under a written contract signed directly with you. Verify our license at cslb.ca.gov.
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Astrid Lind by Jacob Construction · 7077 W Willoughby Ave, Los Angeles, CA 90038 · (424) 256-5005
Astrid Lind by Jacob Construction is the design studio of Jacob Construction Inc., a licensed California general contractor — CSLB License #1073757, Class B (General Building). Design consultations and project estimates are free and carry no obligation. All construction work is performed by Jacob Construction Inc. under a written home improvement contract signed directly with you.
Verify our license, bond and workers’ compensation insurance with the California Contractors State License Board: License #1073757 at cslb.ca.gov or 1-800-321-CSLB (2752).
Any figure, range or timeline shown on this site is preliminary and non-binding. A binding price comes only in a written home improvement contract that complies with California Business and Professions Code §7159, issued after we inspect the property. Nothing here is professional, engineering, architectural or legal advice.
Some images on this site are computer-generated visualisations produced to illustrate design concepts. They are illustrative and do not depict a specific completed project unless the caption says so.