What is an Accessory Dwelling Unit (ADU)?

Mar 25, 2022

By Robinson Markus, The Evanston Development Cooperative (EDC)

Now, it is easier than ever for Evanston homeowners to build an accessory dwelling unit (known as an “ADU”) on their property. Last September, the City of Evanston passed regulations to open up new citywide opportunities for ADUs (a.k.a. “backyard homes”). 

An ADU is a detached, independent home on the same property as an existing residence. It has its own kitchen, bathroom, and areas for living and sleeping.

The Evanston Development Cooperative (EDC), a local cooperative business that focuses on ADUs, has seen homeowners explore these projects for a range of reasons, including homes for aging relatives, long-term rental units, family members with disabilities, or downsizing.

Here are the answers to some common questions about ADUs:

1. Could I build something in my backyard, or would this be a conversion of my existing house?

You could do either of these in Evanston today!

It depends on the property, though it is possible to build a detached unit in your backyard without garaged parking, convert your garage into a dwelling unit, or build a unit next to or on top of a garage.

When it comes to your existing house, you may be able to convert part of your primary residence into a separate living unit, or you build an additional ADU connected to the main structure.

2. How do I know if I can build an ADU on my property?

If you own a home in Evanston, it’s likely that you can build some type of ADU, but there are several factors that determine the type of structure that is allowable on your property.

Your zoning district (e.g., R1, R2, R3, etc.) affects the “building lot coverage” and “impervious surface coverage” amounts which can be on your property. In turn, these regulations (along with other rules, such as parking, setbacks, height, and building code regulations) will affect the size and shape of your unit.

If you live in an R1 district, for example, there is less allowable density on your property when compared to an R3 district. This may make it easier to convert an existing structure rather than to build an addition.

You can look up your zoning district via this free tool offered by the City of Evanston.

3. How much does an ADU cost?

Based on ADU construction data from Portland, Oregon, when adjusting for inflation, unit costs have typically ranged from $115,000 to $330,000. On average, a conversion of your existing garage or house would be less expensive than new construction (such as building a detached ADU). The size of your ADU will also affect the overall cost.

For a detached ADU, the fixed cost of several big line items – such as connecting water service and sewer – will affect the price. In addition, you‘ll need to add a new fire sprinkler suppression system when building new construction in Evanston. As a result, you might also need to upgrade the water service size on your entire property, which will add to the overall price.

4. How do people pay for their ADUs?

Most often, people finance ADUs through a home equity line of credit (HELOC), renovation mortgage (FannieMae HomeStyle, FreddieMac CHOICERenovation), or cash savings.

To determine the best financing option for you, it can be best to talk with your current mortgage holder, bank, and/or a trusted financial advisor.

5. How do I get started?

Before you reach out to a professional design-builder or architect, all stakeholders (e.g., family members involved in the project) should discuss and mutually agree upon the goals, purpose, and “sticking points” for your project. If you’re designing a unit for aging relatives, for example, are you open to foregoing garaged parking in order to have ground-level living? Additionally, it can be valuable to have a rough budget range in mind as you start your project.

Once you’ve gathered your ideal project details, you should then reach out to a design-builder or architect to begin initial design work. You can contact the City of Evanston’s zoning department with any questions, too, as you explore the feasibility of your project.

Note that if you hire a design-builder, they will serve as your architect and general contractor; if you hire an architect, then you will hire a different general contractor after the architect draws up your plans.

6. Where can I learn more?

Evanston’s Guide to Accessory Dwelling Units (ADUs), co-authored by EDC and the City of Evanston, is a comprehensive source of information on ADUs in our city, and you can access it via the City of Evanston’s website or contact EDC for a free copy of this 20-page guide.

Additionally, you can always contact the Evanston Development Cooperative (EDC) or the City of Evanston’s zoning department with questions about ADUs on your property.

About the Author:

The Evanston Development Cooperative (EDC) designs and builds small, energy efficient housing for Evanston homeowners and residents. As a community-owned worker cooperative, EDC pursues initiatives focused on housing affordability, racial equity, and climate resiliency. Its work on ADUs has been covered by Next City, Crain’s Chicago Business, and the Evanston RoundTable.

Explore other media:

  • videos

  • issuu

  • other media

Blog Links:

Everything Evanston:

Stay Fit: A Comprehensive Guide to Where to Workout in Evanston

January is a time when your New Year’s resolutions get inculcated into your daily habits. If you made a resolution to stay or get in shape, lose weight, reduce stress, be more mindful, or undertake another health enhancing goal, you might want to consider joining a...

A Dozen (Plus) Ways to Make the Holidays Even Happier in Evanston

Evanston truly becomes Heavanston during the holidays, especially with the many breathtaking displays throughout the city. But what makes Evanston even more wonderful are all the seasonal activities you can find this time of year. In fact, from shopping to...

Your Comprehensive Guide to the Cafes and Coffee Shops of Evanston

Evanston has been called the City of Trees. It is well known for its beaches, parks, and homes of every shape, size, style, and price range. The education institutions, from pre-school to college, are among the best in the nation. You can find a restaurant to satisfy...

Everything Home Selling:

How to Confidently Prepare for Your Home Inspection

A well-prepared home not only instills confidence in your potential buyer, but also ensures a smoother transaction. But it requires taking a proactive approach and attention to detail to get your home in order. By following the following nine steps, you will not only...

This Storage Guide Can Help You Sell Your Home Faster

When you are looking to buy a new home, you want to walk through the house or condo and be to visualize yourself inside it. You think about where your things will go, and how you’ll decorate it. In other words, you want to see if it “feels like home.” The same goes...

Your Complete Guide to Understanding Home Warranties

Home emergencies happen, and there is no exception. Anyone who’s had their AC bust in the heart of summer knows that trouble can arrive at the worst of times. While you cannot stop bad things from happening, you can be prepared for the worst with a home warranty. From...

Is Your First Offer Really Your Best Offer?

There is a saying in real estate you may have already picked up on: Your first offer is your best offer!  So, what is it? Well, just like most things in life: There’s not a clear answer, but the saying is often true. To best understand how to answer the question, we...

Everything Home Buying:

Will 2025 be the Year to Buy a New Home?

Homebuyers can expect to obtain a slightly lower mortgage rates in 2025, compared to 2024. CNBC reported that the average 30-year fixed-rate loan on December 30, 2024, was 7.11% and that many financial institutions are predicting somewhere between 6.2% and 6.6% for...

What is Fannie Mae & Freddie Mac and How Do They Work?

You may have heard of Fannie Mae and Freddie Mac before. Perhaps you even have a general understanding of them or just associate these terms with owning a home. But what are they? What do they actually do? And why you, as a homebuyer, should care? According to the...

Buying a Condo? You Might Want to Consider a Co-Op Instead

There are many benefits to living in a condo: They often require less maintenance than single-family homes, as the condo association often maintains the common interior and exterior areas. As a result, condos can often offer more flexibility than single family homes...

Everything Home Maintenance:

Stopping Ice Dams in Their Tracks: A Guide for Homeowners

Drip, drop, plop – what’s that sound? It’s a water leak in the ceiling! Sigh, grab the buckets. As Evanston residents, like the rest of the Chicagoland area, we’re no strangers to the Midwest winter. Once the beautiful layers of white snow hit Evanston and the...

Creating a Stylish and Functional Home Office

With the post-covid opportunity to continue working remotely at least part of the time, having a dedicated home office has become a necessity. A simple desk and chair won't cut it. Your home office should be comfortable and inspiring, so you can be productive.  Here...