The granny flat is an old idea that is currently experiencing a new life in the U.S. As property values around the country continue to climb, granny flats – also known as accessory dwelling units (ADUs) – allow homeowners to create additional living space for themselves and loved ones, or to use as an income-generating rental unit

In this article, we go over the ins and outs of what a granny flat is, the different types of granny flats, and whether or not a prefabricated granny flat is a wise decision. You’ll also find information about some of the most popular granny flat floor plans to inspire your ADU plans.

What Is a Granny Flat?

A granny flat is a structure that creates an additional living space on an existing property. You may have also heard other terms for granny flats, such as ADUs or in-law suites. These additions can come in several different forms and are typically small in comparison to a conventional home.

In general, they are meant to provide an independent living space close to or attached to the primary home. As such, they typically include all the amenities you’d find in a home, such as a bathroom, bedroom, and kitchen.

Why Is It Called a Granny Flat?

“Granny flat” are named as such because one of the most common uses of an ADU is to provide a space for a family member to live close to a primary home while still being completely independent. This is often a grandparent, or “granny,” but can also be adult children or in-laws. Many people build ADUs to house an aging parent nearby to help care for them, get help from them, or simply to keep them close. 

What Can You Do With a Granny Flat?

Granny flats offer many possibilities for homeowners. While, as the name suggests, they make an excellent option for a living space for one’s parents (or one’s children’s grandparents), there are several other uses for these structures, including:

  • Home office: As working from home becomes more the norm, a granny flat can provide an ideal space for a dedicated home office. They allow homeowners to have an office that’s right next to or attached to their home, but still provides enough separation to keep it private and quiet.
  • Studio space: Granny flats are a popular choice for artists, musicians, and other makers and creatives as a space to engage in their hobbies. Because they are separate from the main home, they allow people to keep messy or noisy activities from interfering with the rest of the living space.
  • Rental unit: When outfitted properly, a granny flat can serve as a rental unit that can generate passive income for a homeowner without having to invest in an additional property. Cheaper to build than the cost of buying an investment property, they can often generate a strong return on investment, especially in high cost of living areas.

Granny Flat Designs

Technically, a granny flat can be designed any way you’d like. But as typically small structures, ADUs are often designed to make efficient use of limited space. As a result, you’re likely to find many similarities between granny flat designs – even among different types of structures.

Types of Granny Flats

Generally speaking, there are four main types of granny flats you can build. These include:

  • Standalone unit: A standalone, or detached, granny flat is a fully independent building that doesn’t share any structural elements such as walls or roofs with the primary home. These are the best type of ADU to use as a rental property due to their complete separation from the main home.
  • Over-the-garage unit: Another popular way to build a granny flat is over an existing garage or carport. Over-the-garage ADUs are often less expensive to build than detached units, but are limited to the square footage and floor plan of the garage underneath it.
  • Garage conversion: Instead of building an additional structure on top of a garage, some people choose to convert their garage to a living space. Since they are fairly large, open, unfinished spaces, adding walls and making modifications is relatively easy.
  • Basement or attic conversion: People who have an unfinished or underutilized attic or basement can also convert them into a living space. Since they are existing structures, most of the work needed to convert them is interior finishing work. However, for it to be a truly independent living space, you’ll also need to install plumbing for a bathroom and kitchen. 

Granny Flat Floor Plans

When converting or building on top of an existing space, the floor plan of a granny flat is limited by the dimensions of the space being converted or built upon. But when you build a detached granny flat, you have much more freedom and control over how it is laid out.

Typically, granny flat floor plans can be as small as 400 square feet and can be as large as 2,000 square feet. However, many areas have restrictions on how large a granny flat can be. These limits are sometimes a specific size, such as 1,000 square feet. However, many cities and towns regulate the size of a granny flat as a percentage of the square footage of the primary residence.

Many ADU builders offer several granny flat floor plans to choose from and may allow you to make modifications. Some may even design a custom ADU floor plan for you – albeit at an additional cost.

Is a Prefabricated Granny Flat a Good Idea?

With the rise in popularity of granny flats, manufacturers have started producing prefabricated ADUs. You can find these granny flat kits in big box stores, online, and with specialty vendors. Usually, prefab ADUs can be shipped to your building site for installation. 

Prefab Granny Flat Pros and Cons

A prefabricated granny flat can be a good option for some homeowners. However, they come with significant drawbacks compared to ADUs built by an experienced contractor.

Prefab Granny Flat ProsPrefab Granny Flat Cons
Can be less expensive than spec built ADUsMay not meet local restrictions or requirements
May be quicker to buildStill requires foundation and site work, which may negate the price difference
Easy to shop forOften made of poor-quality materials or designed carelessly
Typically comes with all materials neededNot designed with your building site in mind

Granny Flats: Conclusion

Granny flat, ADU, or in-law suite; whatever you choose to call it, these structures offer homeowners a way to get more out of their existing property. They can serve as fully-functional independent living spaces for friends, renters, and of course, grandparents. There are several different types of granny flats, but standalone ADUs make the best choice for people looking to build one as a rental unit.

At Feel Love Homes, we offer a range of granny flat designs and floor plans. Our team works with each and every client to ensure that the granny flat we build matches the granny flat of their dreams. If you’re ready to start looking into building an ADU, we’re ready to get the conversation started. Click the button below to reach out to a team member.