What Is an Accessory Dwelling Unit?
An Accessory Dwelling Unit (ADU) is a secondary, smaller residence that can be attached to, detached from, or built within a primary residence. In most locations, ADUs cannot be sold separately from the primary residence. While ADUs were a common building practice in the United States prior to World War II, increasing suburban development and zoning restrictions made it difficult — or in some cases impossible — to build them without special permits in many U.S. cities.
Monarch Architecture and ADU Advocacy in Columbia, MO
Monarch Architecture, LLC is a Columbia, Missouri-based architecture firm with a long-standing interest in accessory dwelling units. The firm's founder, Adrienne Stolwyk, has been an advocate for ADUs for over a decade. In 2013, Adrienne and a group of architects and engaged citizens formed an organization called ECHO (Enhancing Columbia Housing Options), which successfully lobbied the City of Columbia, Missouri to establish an ADU policy allowing accessory dwelling units by-right in R-2 and R-MF zones.
Consulting with ADU policy expert Kol Peterson was a key part of developing a framework that avoided common pitfalls seen in other municipalities. Some cities technically permit ADUs but impose restrictions — such as owner-occupancy requirements — that make construction legal in name but impractical in reality.
Despite the passage of Columbia's ADU ordinance and a subsequent incentive program waiving ADU permit fees, the city has issued only around a dozen ADU occupancy permits since legalization. Part of the challenge lies in the complexity of coordinating design and construction, even for a smaller residence. Banks' general unfamiliarity with ADUs and the limited availability of ADU-specific loan products have also been contributing factors, though this is beginning to change in some markets.
An additional limiting factor in Columbia is zoning. Currently, only around 2,000 lots qualify by-right to build an ADU. The majority of Columbia's lots are zoned R-1 (single family), where building an accessory dwelling unit requires obtaining a Conditional Use Permit — an added bureaucratic step that discourages many homeowners and developers from moving forward.
Monarch's Own ADU: A Straw-Cell Construction Project
In 2023, Adrienne and her husband Adam completed construction of a 24′ x 24′ straw-cell ADU — a structure combining straw bale and cellulose insulation — on their property. This building now serves as the Monarch Architecture headquarters, but because it is permitted as a residence, it can transition into residential use at any time.
Straw bale construction, while permitted under the International Residential Code, is new to the Columbia, MO market. Monarch's ADU is the first permitted straw bale residence in the city. For Adrienne and Adam, building a full-scale single-family straw bale house felt financially out of reach; the detached ADU format allowed them to experiment with the construction method on a smaller, more manageable scale.
For homeowners in Columbia, MO who are considering building an ADU — whether a backyard cottage, an in-law suite, a garage conversion, or another type of accessory dwelling unit — Monarch Architecture offers design services tailored to small-space residential projects. Designing compact living spaces presents its own set of challenges, and the firm brings direct, hands-on experience with the ADU process in the local market.