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A Guide to ADUs: Granny Flats, In-Law Suites, and More

Updated: Jan 23


Imagine a cozy little home in the backyard, a comfortable living space above a garage, or even a basement turned into a separate apartment. These are all examples of an accessory dwelling unit (ADU), a smaller, independent residential dwelling unit located on the same lot as a stand-alone (i.e., detached) single-family home. ADUs go by many names and serve multiple purposes, making them a fascinating and flexible solution in the current housing landscape. Let's dive into the world of ADUs, their myriad of names, and their role in addressing housing challenges.

What is an ADU?

An ADU is essentially a secondary housing unit on a single residential lot. They are known for their versatility and can be attached to or detached from the primary residence, or even a part of it, like a converted basement or attic. ADUs typically have their own independent living facilities, including a kitchen, sleeping area, and bathroom.

The Many Names of ADUs

ADUs are known by various affectionate and practical nicknames, reflecting their diverse forms and functions:

1. Granny Flat: Perhaps the most endearing term, "granny flat" often refers to a separate, self-contained living area created for elderly family members, allowing them to live close to their loved ones while maintaining independence.

2. In-Law Suite: Similar to a granny flat, an in-law suite is a private space for relatives, offering both closeness and privacy.

3. Backyard Cottage: This term typically refers to a small, detached unit located in the backyard of the main house, offering a quaint and separate living space.

4. Garage Apartment: When you convert the space above a garage into a living unit, it's often called a garage apartment, making use of an area that might otherwise be used for storage.

5. Laneway House: Particularly in Canada, a laneway house is a form of detached ADU located in the backyards of residential lots, often facing an alley.

6. Carriage House: Historically used to store carriages, these structures are now often converted into independent living spaces.

7. DADU (Detached Accessory Dwelling Unit): This term is used for a detached ADU, emphasizing its separate nature from the main house.

8. Fonzie Flat: Named after the character Fonzie from "Happy Days," who lived above the garage, this term is a playful reference to any small living unit above a garage.

The Role of ADUs in Solving the Housing Crisis

1. Affordability: ADUs are often less expensive to construct than buying a new home, making them an affordable housing option for renters and an economical choice for homeowners seeking extra income through rent.

2. Density: ADUs add housing options within existing neighborhoods, increasing density without altering the neighborhood character significantly.

3. Flexibility: They serve various needs, from housing aging parents close by to providing a separate workspace or rental income.

4. Sustainability: By making use of existing lots and infrastructure, ADUs are considered a sustainable form of development, reducing the need for new construction and preserving land.


ADUs are a charming and practical solution to many of today's housing challenges. They offer a unique blend of affordability, privacy, and flexibility, all while providing a touch of character and personalization to housing. Whether you call them granny flats, in-law suites, or any of the other myriad names, ADUs are making their mark as a creative solution in urban and suburban landscapes. By understanding the various forms and functions of ADUs, we can appreciate their potential in creating a more diverse and adaptable housing market. So, the next time you spot a quaint little dwelling nestled in a backyard or above a garage, you'll know the world of possibilities it represents in the broader context of housing solutions.


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