The chicago ADU pilot program - reimagining the classic coach house
View of the coach house ADU from the rear yard
The City of Chicago has been grappling with a shortage of affordable housing options, as well as rising home prices and rents. To address this issue, Chicago has implemented a pilot program that allows for the construction of additional dwelling units (ADUs) on single-family lots. These are referred to as accessory dwelling units elsewhere, but we like to do things differently in Chicago. The program is part of the city's Affordable Requirements Ordinance (ARO), which aims to increase the supply of affordable housing in our city.
Site diagram showing a coach house ADU on a standard 25’ x125’ Chicago lot
First Floor Plan - Garage
Second Floor Plan - Dwelling Unit
Where does the city of Chicago allow ADUs?
The ADU pilot program allows homeowners in certain areas of the city to build a second unit on their property, either as a detached coach house, or as an attached unit within an existing building—referred to as a conversion unit. In effect since May 1, 2021, the pilot program is still in its infancy, and similar ADU programs in Seattle and Portland took time to gain momentum as design professionals gained familiarity with the zoning ordinance/restrictions, builders worked out construction logistics, and homeowners learned about their options.
We’re seeing a similar pattern occur in Chicago and we suspect the ADU will catch on in popularity and be adopted permanently in the Chicago Zoning Ordinance. We’ll likely see the ADU become much more common in the next decade. We can take cues from Seattle, a city which has continued to tweak and adapt their zoning ordinance over the past decade to accommodate the growing demand for housing. Chicago will get there, but those who pursue an ADU in Chicago now will be ahead of the curve.
View of kitchen/living room looking towards principal building
What are the different types of ADUs?
With very little built precedent, and limited information available beyond basic diagrams, we’ve developed a more detailed prototype for a coach house style ADU. For reference, Chicago ADUs generally fit in three categories:
1) Conversion Unit - an additional dwelling unit contained within an existing principal building, typically a garden style unit.
2) Coach House - a garage at grade with a dwelling unit on the second floor.
3) Granny Flat - A freestanding mini-house in a rear yard.
The prototype we’ve developed has the most utility as it does not eliminate parking and it’s developed for the RS-3 Zoning District (a common Chicago designation). Additionally, we made sure to consider the typical 25’ x125’ Chicago lot.
Obviously a bigger lot affords more options, but a well-planned unit can still pay huge dividends. In general, the zoning ordinance limits a homeowner's ability to go beyond 700sf, so it requires a focus on compact living. That 48” refrigerator and 72” freestanding bathtub probably won’t make the cut, but as a rental property, landing pad for a boomerang kid, or to keep an aging parent close by—an ADU is a smart option.
View of coach house dwelling unit from entry stair
How complicated is it to build an ADU?
An essential detail often ignored when pursuing the design and construction of an ADU is that we are building a building. This means everything necessary for any dwelling—electrical, domestic water, sewage, and natural gas—must be provided to the rear yard from the city infrastructure located at the street. Given the size of the unit, it makes practical sense to pursue an all electric dwelling unit. Electrical service can be pulled from the alley and the space requirements for a natural gas furnace and condensing unit are too extreme when dealing with a dwelling unit of this size.
We opted for a mini-split in our prototype for heating and cooling which is composed of a head located in the interior which can be wall hung and a heat pump which can be wall hung on the exterior of the building. The operating cost of the electric for an all-electric coach house can be offset with a solar array. Generous solar incentives in the state of Illinois bring such systems within reach for many homeowners.
View of garage from public alley
How much does an ADU cost to build?
Of course the first question is always, “ Yeah, but how much does it cost?” To put things in perspective, we performed a pricing exercise with our friends at Independiente Group for this coach house prototype which can be downloaded below. This budget is relative to this prototype only, but offers insight from experienced professionals as to what one can expect when building a coach house.