ADU Basics in California

Your quick guide to Accessory Dwelling Units (ADUs)—what they are, why people build them, which type fits your property, and how to get started with the right partner.

What Are ADUs?

An ADU (Accessory Dwelling Unit) is a small, self‑contained home on the same lot as an existing primary residence. Also called backyard homes, in‑law suites, casitas, or granny flats, ADUs include a kitchen, bathroom, living space, storage, and a dedicated entrance. In California, ADUs are permanent residences, not mobile “tiny homes”, and they’re designed to provide flexible, long‑term housing for family, guests, or tenants.

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Why People Build ADUs

Homeowners choose ADUs for practical, long‑term reasons. Popular goals include:

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Family First

Keep your family close and comfortable

Next‑gen housing

Provide a safe, nearby home for young adult children

Age-in-place

Downsize to the backyard and keep the main home

Guest & Caregiver Space

Host family or long-term guests with privacy and comfort

Long‑term Value

Increase property value with a real, code‑compliant residence

Rental income

Generate dependable, long‑term rental or retirement income

Types of ADUs

Choose the format that best fits your lot, goals, and budget.

Detached ADU (Stand‑Alone)
Detached ADU
A separate backyard home offering the utmost privacy, ideal for multigenerational living or generating rental income. Detached ADUs are the most popular option for homeowners.
Attached ADU (Addition)
Attached ADU
Shares a wall with the main home–great for creating a connected yet independent suite, but projects tend to have some complexities because you’re tying into an existing building.
Garage Conversion ADU
JADU
Transforms an existing garage into a living space. Often requires new foundation work, plumbing, electrical, insulation, and energy upgrades that can make these projects complex.
Over‑Garage ADU
A separate backyard home offering the utmost privacy, ideal for multigenerational living or generating rental income. Detached ADUs are the most popular option for homeowners.
Interior Conversion / JADU
Attached ADU
Shares a wall with the main home–great for creating a connected yet independent suite, but projects tend to have some complexities because you’re tying into an existing building.
Site‑Built vs. Prefab or Manufactured Housing
Transforms an existing garage into a living space. Often requires new foundation work, plumbing, electrical, insulation, and energy upgrades that can make these projects complex.
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ADU Adventures Podcast

Listen & Learn on the Go

Acton Adventures in ADUs Podcast

Real homeowner stories, helpful tips, and homeowner insights–from design choices to navigating California rules. Short, practical episodes to help you make confident decisions about your backyard home.

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Custom ADU

How to Choose the Right ADU Partner

ADUs are small homes with big implications for your property and family. Look for a partner who offers:

End‑to‑End Expertise

Feasibility, architecture, engineering, permits, construction, and warranty under one roof–so details don’t get lost

Local California ADU Focus

Proven expaerience with local zoning, utilities, and inspections across multiple Bay Area jurisdictions.

Site‑Built Quality

Traditional, code‑compliant construction for long‑term performance and real property value.

Predictable Process

Fixed scopes, curated selections, and transparent communication to control cost and schedule.

Human Approach

Clear guidance, respectful collaboration, and professional, experienced advocacy with cities, inspectors, and utilities.

Why Acton ADU?

Build Ready ADUs

Pre‑designed, site‑built models with curated finish packages for faster, more predictable builds–so you can save time and money without sacrificing quality.

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Custom ADUs

Bespoke architecture tailored to your lot, style, and goals.

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35+ Years of Design‑Build

A dedicated, accountable team from first feasibility to final keys.

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Get your ADU now

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