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Ask Cityscape: Could I build two ADUs at my house?

Published on Jul. 26, 2020 by Steven Vance

Updated on Jul. 27, 2020

One of the architects on our Accessory Dwelling Units service providers list emailed to explain that he had a client, a woman in her 60s, who wanted to build two ADUs. The architect wanted to know what kind of ADU she would be allowed to build, and if she could build both an interior apartment and a backyard home.

Scroll to the end if you just want to know the ADU ordinance’s status.

Sharon owns a single-unit house in Lakeview, and her property is zoned RS-3; she wants to (1) build a small interior apartment for herself to live in, (2) rent out the main part of the house to earn money, and then (3) use the money later on to pay for the construction of a backyard home, where she would live permanently. It conceptually would look like the drawing below.

A conceptual drawing showing the desired use of adding an apartment inside the single-unit house, and then later adding a backyard home (“future coach house”). Image by Silvestro Design Operations.

That’s a great idea, and it’s a use case we’ve promoted in the past. The AARP and Habitat for Humanity both recognize the need for senior citizens to be able to age in place and downsize, so that they can spend less money on housing during retirement and stay in their neighborhoods.

Sharon thinks ADUs are great for other reasons, she wrote:

“A lot of us who bought houses when it was affordable to live in Lakeview, but not Lincoln Park or Gold Coast, are being priced out by escalating taxes that show no sign of reversing. The ADU ordinance gives us an opportunity to stay in our neighborhood. It increases foot traffic in the alleys [see Rebel Garages]. Provides for greater density of population near public transportation. More people, more support for restuarants and local businesses. More people, greater tax base. What is not to like about this?”

Can Sharon build two ADUs on her property?

Let’s review Chicago’s proposed ADU ordinance to see if Sharon, and her architect, James Silvestro, might be able accomplish her goal.

The short answer is yes, but it’s not a simple conclusion.

The house is in an RS-3 zoning district, one of the zoning districts that would allow ADUs “as of right”, so that’s good for Sharon’s plan. As the proposed ordinance stands now, however, property owners in two zoning districts — RS-1 and RS-2 — would have to obtain a “special use” permit by applying to the Zoning Board of Appeals.

There are 162,500 single-unit houses and 6,036 two-to-six flats in RS-1/2 zoning districts across dozens of communities on the South, West, and Northwest Sides, and I think it is a bad policy to require that those owners spend additional time and money to obtain permission. Many people are in the same situation as Sharon, or will soon be in the same position, where downsizing or earning rental income is necessary to live where they are, and cover maintenance costs and property taxes.

The next step in the review is determining the house’s age. The proposed ordinance would allow interior apartments (a.k.a. an “attached ADU”) in houses that are 20 years or older. Sharon’s house was built in 1998.

Sharon wants to have an interior apartment and a backyard home. The proposed ordinance would allow one or the other, not both ADU types.

I can think of two possible zoning strategies to achieve Sharon’s goals.

A. Build the interior apartment now, deconvert it later

Under the proposed ADU ordinance, Sharon would be able to get a permit to build an interior apartment (small or large) as soon as the ordinance becomes effective. If the design carves out space in the existing footprint and exterior walls, then there won’t be a conflict with the zoning rules.

If the design expands the footprint or moves exterior walls, then the architect will need to conduct a zoning assessment to determine how much, if any, the house could be enlarged. When Sharon earns enough rental income to start building a backyard home, the apartment can be deconverted and “returned” to the main part of the house.

While building an interior apartment and then deconverting it later is an option, I’d rather that the proposed ordinance allow both on the same site, especially in the situation that the proposed ordinance offers where a property is allowed two or more interior ADUs. However, option “A” may be the only way forward when option “B” wouldn’t apply.

B. Use an obscure part of the RS-3 zoning code to build both

The RS-3 zoning district allows single-unit houses as of right, but it also allows two-flats with a condition that’s difficult to find amongst the city’s housing stock. We wrote about this option in 2017: the Chicago Zoning Ordinance allows a two-flat on a lot size of 3,000 s.f. or larger in an RS-3 zoning district if 60 percent or more of the buildings on the same block and the same side of the block have two or more units. (See 17–2–0303-B.)

Using our Property Finder map in Address Snapshot, one can easily count the number of units in each building on a block. I counted the ones on Sharon’s block and about 76 percent of the buildings have two or more units. The lot size is just over the minimum, at 3,025 s.f.

With option B, Sharon would be able build an interior apartment (a second flat and not an ADU) immediately with a permit, and then a backyard home when the ADU ordinance is adopted by City Council.

What’s the status with the ordinance?

The proposed ordinance’s earliest adoption date is September 9, 2020, and I predict that there will be some changes in it. Read articles on WTTW, The Daily Line, and Crain’s Chicago Business to better understand why the adoption timeline has been extended.

Some alders do not want this passed. You can see who on our map. If Sharon’s reason for wanting to build a backyard home resonates with you, or you would like to be able to build one for a different reason, please email your alder. I am now getting inquiries several times a week from families, and developers, who are preparing themselves for the time when they can improve how they live. They want to know how the ordinance might support their plan, like Sharon’s, and what the hold up is.

Are you considering adding an ADU to your property? Get to know the proposed rules (which are subject to change prior to adoption) and find an ADU service provider.


Ask Cityscape: Could I build two ADUs at my house? was originally published in Chicago Cityscape on Medium, where people are continuing the conversation by highlighting and responding to this story.

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