Moss Architecture and the Chicago ADU Renaissance
Moss Architecture has been closely following — and actively participating in — the revival of Accessory Dwelling Units (ADUs) and coach houses across Chicago. With a recent city ordinance lifting a 64-year ban on new ADU construction and basement or attic conversions, there is renewed interest in these secondary dwelling types, and Moss Architecture has positioned itself as an ADU contractor and design firm ready to take on these projects.
ADUs go by many names: granny flats, mother-in-law suites, coach houses, and casitas. They typically involve converting a basement, attic, or garage into a separate dwelling with a private entrance, full bath, and kitchen. They can also take the form of a newly constructed, smaller-scale building on the same lot as the primary residence — what many refer to as a detached ADU or backyard cottage.
The Chicago ADU ordinance, which went into effect in May 2021, permits the construction of ADUs and coach houses across five designated pilot zones covering the north, northwest, west, south, and southeast areas of the city. The ordinance is designed to support homeowners in generating rental income, accommodate multigenerational living, and gradually increase affordable housing density in neighborhoods experiencing housing shortages.
ADU Design and Construction Services by Moss Architecture
Moss Architecture currently has several ADU and coach house projects underway across the Chicago area. Their work spans new construction, full rehabilitation, and historic restoration — covering a range of project types that reflect the diversity of Chicago's housing stock.
- Ravenswood ADU – New Construction: As part of a larger residential renovation, Moss Architecture is demolishing an existing garage on a double-wide lot to make way for a new detached ADU builder project. The design prioritizes backyard privacy while maintaining a visual connection to the outdoor space. Warm-toned stucco, a deep overhang, and a balcony extend the living area outward. Site analysis informed placement and overhang depths to manage summer heat gain and preserve daylight.
- Lincoln Square ADU – Rehab with Addition: This project involves a total rehabilitation of an existing coach house, with a new addition built on top of an existing garage. The design includes a balcony and overhang for passive cooling and outdoor comfort. As an active construction site, utility connections for the new structure are more straightforward to integrate.
- Logan Square ADU – Historic Carriage House Restoration: An original brick carriage house, complete with a horse stable, is being restored and retrofitted with a second story. The main two-unit building on the lot remains untouched. Structural support for the new upper level and utility connections from existing on-site inputs are among the key challenges being addressed.
- Evanston ADU – New Coach House Construction: In this project, an existing coach house in poor condition is being demolished and replaced with a new structure in a more suitable location on the property. Based on site analysis, the new placement is more practical. The new building will include a garage with an accessory dwelling unit constructed above it.
Each of these projects reflects the range of possibilities that ADUs and coach houses offer. Beyond rental income, these spaces can serve as in-law suite accommodations, home offices, artist studios, caregiver quarters, or housing for adult children — making them a flexible addition to many residential properties.
Design Considerations for ADUs and Coach Houses in Chicago
Under the current ordinance, new coach houses must be no taller than 22 feet above grade and no larger than 700 square feet, with a footprint not exceeding 60% of the rear setback. New ADUs can only be built on properties at least 20 years old and must be located in areas zoned for multifamily residences.
For properties with two or more ADUs, half of the units must be reserved for residents earning no more than 60% of the area's median income. Loans of up to $25,000 are available for households earning up to 80% of the area's median income, intended to support new garage conversion contractor work or the restoration of existing coach houses.
Moss Architecture approaches each ADU project with site-specific analysis, examining sun paths, prevailing winds, privacy considerations, and the relationship between the new structure and the existing primary residence. Their work as an ADU builder in Chicago reflects both the technical requirements of the ordinance and the practical needs of homeowners looking to make the most of their properties.
