What Is an ADU? A Modern Solution for Flexible Living

An Accessory Dwelling Unit (ADU) is a secondary housing unit located on the same lot as a single-family home. It is fully independent, with its own kitchen, bathroom, and entrance, yet remains connected legally and physically to the main property.

Modern backyard ADU exterior

ADUs come in many forms—converted basements, garage apartments, backyard cottages, or additions to the primary residence. Each configuration offers a flexible, private living space suitable for renters, extended family, or guests.

Basement apartments
Garage conversions
Detached backyard cottages
Attached additions or over-garage suites

Why Homeowners Build ADUs

Homeowners build ADUs for a variety of practical and financial reasons. Many use them to house aging parents (sometimes called “granny flats”) or young adult children. Others turn them into long-term rentals or Airbnb-style short stays for supplemental income.

Interior of a cozy ADU

With housing costs climbing in cities across the U.S., ADUs provide an affordable way to expand living space without having to move. They also increase long-term property value and flexibility.

Other Common Names for ADUs

You might hear ADUs referred to as granny flats, in-law units, casitas, carriage houses, or secondary suites. While the names differ, they all describe the same concept: a small, self-contained home that shares a lot with a primary residence.

ADU Popularity Is Rising

Thanks to statewide ADU legislation and local zoning reforms in places like California, Oregon, and Washington, building ADUs is easier and faster than ever. As a result, ADU permits and listings have surged since 2009, and demand continues to rise in urban and suburban areas alike.

Small modern home exterior at dusk

From repurposed historic carriage houses to sleek, minimalist backyard studios, ADUs are helping communities solve housing shortages while giving homeowners more control over their living space.

Unlock New Possibilities with an ADU

Whether you're looking to support family, generate passive income, or maximize your lot, an ADU can provide a cost-effective and flexible housing solution. Explore permit-ready house plans at adupatterns.com to get started.

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