Guide To Granny Flats, ADUs & More

Accessory Dwelling Units are separate living spaces built on or outside your home. Learn about the different types and costs of ADU construction.

Accessory dwelling units (ADU) have many different names. In some areas, they are known as granny flats, while others refer to them as in-law apartments. This is because ADUs are commonly used as homes for older family members. Despite the familial titles, ADUs are not limited to family members, with many homeowners building an ADU as home studios, or renting the space out as a secondary income source.

An ADU is an additional space built on your property that functions as a second household. Some ADUs are connected to your home while others are separate units. There are multiple types of ADUs available, each with different costs and benefits. Every state has slightly different regulations regarding ADUs. While this may seem intimidating, the regulations are fairly basic and rarely get in the way of a project.

Basement ADU

One of the most common types of ADU is a basement dwelling. A basement ADU is not the same as a refinished basement. Basement ADUs have much stricter requirements, such as plumbing and ventilation and main access. Basement ADUs must adhere to certain special requirements as well, which vary depending on your state. With many basements, height is an issue, requiring you to dig down past the existing floor to add extra headroom.

Another option is to lift your home to increase the ceiling height. With basements, this is a popular option because it also allows you to install larger windows and increase the amount of natural light, which basements commonly lack. Basement ADUs typically cost between $100,000 and $200,000.

Backyard ADU

A backyard ADU is a small living space detached from your home. Most backyard ADUs resemble small cottages. Because it is separate from your main house, a backyard ADU must have its own sewer, water and electrical utilities. Most homeowners choose a single story ADU, but multilevel options are available. If you want multiple levels, you must check with your state regulations to make sure you stay within height limits. Some states also limit how close you can build an ADU on your lot line. A single story ADU typically costs between $125,000 and $300,000, while a two-story unit costs $200,000 to $500,000.

Attached ADU

An attached ADU is similar to a backyard ADU, except it is connected to your home. A common place to build an attached ADU is above a garage. This is because the layout of a traditional garage provides plenty of space for an ADU.

In order to qualify as an ADU, the attached building must have a separate entry from the existing home. Some homeowners create a shared access point, turning the space between the two entrances into a small mudroom. Attached ADUs are a good choice if you have limited property space or are unable to build a separate structure on your property. An attached ADU typically costs the same as a single-story backyard ADU, $125,000 to $300,000.

Benefits of an ADU

There are many benefits to building an ADU. Many families use an ADU to provide an independent living space to family members, while being close enough to help in case of an emergency. They are especially popular among senior citizens, who are healthy enough to live on their own, but require some assistance with their day-to-day tasks. ADUs are also popular among homeowners who want to make extra income. You can rent out an ADU for the same price as a similarly sized apartment. Depending on where you live, you can make an extra $800 to $1,500 a month renting out your space. If you work from home, you can build an ADU as a separate workspace to avoid distractions around the house. There are also various tax benefits available if you have a separate space solely used for work.

Budgeting for an ADU

Constructing an ADU is a large project, which requires planning and budgeting. Before you speak with a contractor, have a maximum limit in mind. Ask your contractor about building regulations and whether there are any fees you must pay to construct your ADU. You also want to consider how much it will cost to get utilities set up in the ADU. You must also check whether your existing home insurance extends to the ADU.

Another decision you must make when budgeting is whether you want a custom or a pre-designed ADU. Pre-designed ADUs are less expensive than custom ADUs, but you have less control over the final appearance of the pre-designed ADU.

ADU Contractors

One of the best ways to find qualified contractors is word of mouth. If you know someone who has recently had an ADU built or a portion of their house remodeled, ask what firm they used. This method is preferred, since you can see their work beforehand. If you cannot get any recommendations, research local construction firms. Be sure to check for pictures of previous projects, or even see if there are local projects you can see in person. There are also a few ADU specialized contractors you can contact if you are having trouble finding a local contractor.

Acton ADU started as a general construction firm, but transitioned into exclusively building ADUs. The company primarily builds custom ADUs, but in recent years, have started to sell pre-designed units. As of writing, only three of these units are available. The company received favorable reviews from customers because they are upfront with fees and do not tack on additional labor charges at the end of a project.

Blackline Renovations largely focuses on attached and basement ADUs. The company originally worked on commercial properties, gaining plenty of experience working on larger projects. They are one of the best contractors if you need to make changes to your existing home to meet state regulations to add an ADU.

Canyon Design Build is one of the oldest contracting companies. Unlike other companies, they exclusively worked on residential properties. The company prides itself on using progressive technologies and sustainable building practices to preserve the environment during construction projects.