A granny flat is a small house built on an existing property. It has its own entrance, kitchen, bathroom and living space.

Homeowners in cities across the U.S. are looking to their backyards for housing. Granny flats—now commonly called accessory dwelling units, or ADUs—are the answer to more room for family members or more income from renting the unit.

Granny flats range in size from about 250 to 1200 square feet. They can take many forms and be attached to the primary dwelling or detached from it, but they must have their own entrance, kitchen, bathroom and living space.

While granny flats can be new stand-alone homes, they are often converted from a space that once was a garage, basement or attic.

With California’s 2020 passage of AB 68 and a host of supportive legislature, almost anyone who owns a single-family home in that state must be allowed to build one ADU of at least 800 square feet, as well as a junior accessory dwelling unit (JADU). If you own a duplex or other multi-family housing, you can build two ADUs on the property!

In 2021 California passed another bill, SB9, that will allow even more small homes to be built on single-family properties. As the kinks are getting worked out of that bill, granny flats are the most reliable way to increase housing now.

Structural Forms of a Granny Flat

what is an accessory dwelling unit

What name are you familiar with?

  • Accessory Dwelling Unit (ADU): The technical, architectural term used by a city or permitting office.
  • In-Law Suite
  • Backyard Cottage
  • Guest house
  • Mother in-law Suite
  • Laneway House
  • Secondary Unit
  • Basement Apartment

Granny Flats Provide Flexibility & Affordable Housing

Although many people buy and live in their home for many decades, their needs change over time. Granny flats can complement your lifestyle while also providing solutions to life’s challenges.

For example, a young family may use the space for rental income. As the family grows perhaps a college student saves money by living in the granny flat. Later in life, parents might explore downsizing and renting out the main house for more financial freedom.

what is an accessory dwelling unit


What’s Great About Granny Flats?

According to recent surveys:

Monthly rental income and caring for an elderly family member are the top two reasons people choose to build a granny flat. Housing for an adult child is also becoming a major reason to build an ADU.

There are a lot of awesome reasons why someone might explore this project:

  1. Provide affordable housing to others
  2. Need more space but want to stay in a beloved neighborhood
  3. Work from home in an office separate from the house
  4. Flexibility of the space
  5. Help pay mortgage by renting the unit
  6. Fight gentrification
  7. Friends and relatives visit comfortably
  8. Affinity for tiny spaces, live minimally
  9. Garage not being well utilized and desire to get rid of extra junk

Cities stand to benefit from ADUs as well. Affordable housing, and lack thereof, is at the top of the list of reasons. Cities like San Francisco, San Diego, Los Angeles, Portland, Seattle, and Austin struggle with soaring housing prices and lack of availability.

Why are you interested in an accessory dwelling unit? Leave a comment below! We want to hear from you.

What Is a Granny Flat?