What Is A Granny Flat? Granny Units Explained

As families grow and change, so do their living needs. Maybe you need to support aging parents, create private space for adult children, or add a cozy area for long-term visitors. Enter the granny flat.

But what is a granny flat? In this post, we’ll tell you what they are, how they can be used, and whether or not you can build one on your property.

A granny flat is a small, self-contained living space located on the same property as a primary home. Granny flats can be converted attics, basements, garages, or even an area sectioned off from the rest of a house.

Also known as an accessory dwelling unit (ADU) or a mother-in-law unit , these spaces are typically designed for aging family members to support independent living while remaining close to family. That’s where granny flats get their name — a living space for your granny!

A 2023 survey by Villa Homes found that 61% of ADUs are built to support multigenerational living. This highlights just how much families are looking for flexible, family-oriented housing in the modern age, rather than choosing retirement homes to take care of their aging relatives.

Granny flats and other ADUs offer privacy and independence while still being close to help when needed. They also remove the expense of buying and maintaining additional property, which is a huge help when money is tight.

However, these units have evolved to serve multiple purposes. For example, some people rent out their ADUs to supplement their income, while others use the space as an office or studio.

The same survey found that many ADU owners earn extra income by renting out their units long-term or through platforms like Airbnb.

Granny flats can take many forms, depending on your space, budget, and how you plan to use them. Some are created by converting existing parts of your home, like a garage or a basement. Other granny flats are new construction. Let’s break down the main types of granny flats to help you understand what might work well for your property.

One of the most popular and cost-effective ways to add a granny flat is by converting existing space in your home. This might include turning a garage, attic, basement, or even a portion of your main house into a private living area.

These conversions can be fairly affordable because the existing structure is already there. For example, garage-to-ADU conversions are a popular option that maximizes underused space while boosting property value. 

Building a new structure is another option if your home doesn’t have extra space to convert, but you have some extra land. These standalone or attached granny flats can be custom-designed or prefabricated, giving you plenty of options for layout and design.

Types of new granny flat structures include:

• Detached granny units: Standalone buildings in the backyard or elsewhere on the property. They offer the most privacy and independence.

• Attached ADUs: Built as extensions to the main home, often with a separate entrance. They offer a good balance of proximity and independence.

• Above-garage granny flat s: Built on top of an existing garage, making smart use of vertical space without expanding your home’s footprint.

• Modular or prefabricated units: Units pre-built off-site and installed on your property, helping reduce construction time and complexity.

Granny flats offer a flexible housing solution, but just like with any kind of property or renovation project, they come with benefits and trade-offs. Here’s a breakdown to help you decide if adding one to your property is the right move.

• Supports multigenerational living: Ideal for aging parents, adult children, or extended family members to live close by while maintaining independence.

• Increases property value: A well-designed granny flat can enhance your home’s appeal and resale potential.
  Generates rental income: Renting out the space can help offset your mortgage or boost monthly income.

• Flexible usage: Granny flats can serve as home offices, studios, guest accommodations, or even short-term rentals.

• Makes use of underutilized space: Get the full value out of your property by converting underused spaces.

• Environmental benefits: Smaller living spaces often mean lower utility consumption and a smaller carbon footprint.

• High upfront cost for new builds: Construction, design, and permits can add up quickly.

• Zoning restrictions: Not all neighborhoods or cities allow granny flats, so check local laws before starting any project.

• Permit and utility hurdles: You'll need to apply for permits, connect to plumbing and electricity, and meet building codes.

• Potential for higher property taxes: Adding livable square footage may increase your home's assessed value.

• Reduced outdoor space: Detached ADUs or extensions to your home will eat into your outdoor space.

• Ongoing maintenance: Like any other living space, a granny flat requires upkeep, including utilities, landscaping, and repairs.

In many cases, yes — but it depends on a few key factors. You may be able to build a granny flat if you:

• Have enough space on your property for an additional unit

• Have the budget for construction, permits, and utility connections

• Check your local zoning laws and confirm that ADUs are allowed in your area

• Obtain the proper permits to ensure your project complies with building codes
  
  

For a more detailed breakdown, read our guide to obtaining permits for an in-law unit .

Ready to get started on your granny flat? Get a detailed site plan from MySitePlan to help with permit applications!