Accessory Dwelling Units (ADUs) have emerged as a critical tool in Michigan’s efforts to address housing shortages, create more diverse residential options, and support aging-in-place initiatives. As municipalities across the state respond to increasing housing demands, ADUs offer a flexible and sustainable solution. For builders and attorneys involved in property development and regulation, understanding the complex, highly localized legal frameworks governing ADUs is essential. This article provides an in-depth overview of Michigan’s enabling laws, key municipal regulations, permitting processes, zoning considerations, and other vital compliance issues, ensuring professionals are well-equipped to navigate this evolving landscape.
Accessory Dwelling Units (ADUs) are secondary housing structures built on single-family residential lots. These units can take the form of detached buildings, additions to existing homes, or conversions of internal spaces such as basements or garages. Their growing popularity in Michigan stems from their ability to address various housing needs, including providing affordable living spaces, offering accommodations for extended family, and generating rental income. With cities and townships each developing their own ADU rules, builders and attorneys must stay informed and precise when engaging in projects involving these units.
Please note this blog post should be used for learning and illustrative purposes. It is not a substitute for consultation with an attorney with expertise in this area. If you have questions about a specific legal issue, we always recommend that you consult an attorney to discuss the particulars of your case.
Michigan State Legal Framework
The authority for municipalities in Michigan to regulate ADUs primarily originates from the Michigan Zoning Enabling Act (MZEA). The MZEA empowers local governments to establish zoning ordinances that dictate land use, including the development and placement of different types of dwellings. Although the Act does not explicitly reference ADUs, its broad language permits local control over their regulation. Section 201 specifically grants local governments the right to regulate land and buildings, while Section 203 requires that zoning decisions align with a comprehensive plan focused on promoting public health, safety, and welfare. This legal foundation is supplemented by the Michigan Home Rule City Act, which allows cities and villages to draft and amend their own charters, further enabling detailed, localized control over ADU regulations. Consequently, Michigan does not operate under a uniform statewide ADU standard; each community retains autonomy, leading to significant regulatory variation.
Key Local Regulations
In Ann Arbor, the city has embraced ADUs as a strategy to increase housing diversity. Ann Arbor permits ADUs in various residential zones, including R1 through R4, contingent on the lot containing a single-family home. Size limitations depend on lot size, with a maximum of 600 square feet for smaller lots and 800 square feet for larger ones, or matching the main dwelling’s ground floor area, whichever is smaller. Detached ADUs must adhere to specific setback rules, including a minimum of three feet from lot lines, and occupancy limits restrict the combined residence to four persons, excluding offspring. Additionally, short-term rentals under 30 days are prohibited, and rental units must meet the city’s housing standards.
Grand Rapids takes a slightly different approach by permitting ADUs in nearly all residential zones, provided the primary structure is a single-family or duplex home. ADUs must measure between 400 and 850 square feet and cannot exceed 40 percent of the primary structure’s floor area. Detached ADUs must maintain six feet of distance from the primary structure and at least three feet from side and rear lot lines. Recent amendments have removed the previous owner-occupancy and additional parking requirements, reflecting a shift toward facilitating greater ADU development. However, short-term rentals of less than 30 days remain prohibited.
Detroit’s regulatory environment reflects a more cautious embrace of ADUs. While attached and detached ADUs are permitted, restrictions exist in residential districts like R1 and R2, where only pre-1940 carriage houses are generally allowed for dwelling purposes. Property owners must reside in either the primary or accessory dwelling, and rigorous building code standards apply, including compliance with the Michigan Residential Code and annual inspections to maintain safety standards.
Holland has opted for a narrower ADU policy, allowing only detached units. These must be smaller than the principal dwelling, with maximum sizes ranging from 200 to 800 square feet based on lot size. Height limits are set at 16 feet for ground-level units and 22 feet for second-story structures. Each ADU must include dedicated off-street parking, and the city prohibits concurrent short-term rental or bed-and-breakfast operations on the same property.
Traverse City’s regulations balance housing needs with tourism concerns. The city permits both attached and detached ADUs but requires registration and annual renewal. Owner-occupancy is mandatory, and properties with ADUs cannot be used for short-term rentals or tourist housing. ADUs must comply with dimensional standards typically applicable to accessory buildings, providing a more flexible design framework.
Lansing and Kalamazoo offer additional examples of local variation. Lansing permits detached ADUs up to 1,000 square feet, limiting them to two bedrooms and requiring one parking space. Kalamazoo permits both internal and detached ADUs, with detached units capped at 950 square feet and internal conversions limited to 30 percent of the main unit’s size or 600 square feet, whichever is larger. Parking is required for each unit, and detached structures must comply with setback rules.
Washtenaw County municipalities demonstrate further fragmentation, with townships like Bridgewater requiring site plan approval for ADUs, while others, like Lodi Township, restrict accessory dwellings to specific uses such as caretaker or farmworker housing.
The Permitting Process
The permitting process for ADUs in Michigan requires careful adherence to local procedures. Builders should begin by confirming the property’s zoning eligibility, which often involves preliminary consultations with municipal planning staff. Many cities encourage or require a pre-application meeting to clarify applicable requirements and identify potential obstacles.
Following initial consultations, builders must submit comprehensive site plans detailing the layout, setbacks, parking arrangements, and elevation drawings, alongside detailed construction plans. These documents undergo a zoning review to confirm compliance with all local ordinances and a building review to ensure adherence to the Michigan Residential Code. Builders must also secure separate permits for electrical, mechanical, and plumbing work, typically performed by licensed contractors.
Certain jurisdictions require special land use approval for ADUs that do not meet standard zoning requirements. This can involve public hearings before planning commissions, adding time and complexity to the process. After construction, the property must pass all required inspections before the municipality issues a Certificate of Occupancy, formally allowing the ADU to be occupied.
Zoning Requirements
Compliance with zoning regulations is a fundamental aspect of ADU development. Municipalities impose strict size, height, and setback standards to maintain neighborhood character and ensure safety. Builders must verify minimum and maximum size limitations specific to each municipality and ensure the ADU’s design falls within these parameters.
Height restrictions often vary depending on whether the ADU is a single- or two-story structure, and whether it is attached or detached from the primary dwelling. Builders must design units that comply with maximum height limits to avoid costly redesigns or zoning variances.
Setback requirements govern the distance between the ADU and property lines. These distances differ for front, side, and rear setbacks and may vary further based on the unit’s attached or detached status. Failure to comply with setback requirements can halt a project or trigger legal enforcement actions.
In addition to structural constraints, builders must account for occupancy restrictions. Municipalities may limit the number of residents within ADUs and combined dwellings. Some cities require that either the primary dwelling or the ADU be owner-occupied, affecting project feasibility for investor clients. Rental restrictions, particularly on short-term leases, are common and must be considered during planning.
Parking requirements also demand attention. Some cities require additional off-street parking spaces for ADUs, while others, recognizing the burden of added costs, have eliminated such mandates. Access provisions, including driveway design and location, may also be regulated.
Building Code Compliance
Building code compliance is essential for ADU construction. Units must meet all requirements of the Michigan Residential Code and any applicable local amendments. This includes structural stability for foundations, proper insulation, fire-rated separations between units, and adherence to energy efficiency standards.
Safety features are mandatory, including smoke detectors and carbon monoxide alarms in all living and sleeping areas. Emergency egress requirements necessitate specific window and door configurations to allow safe evacuation.
Electrical, plumbing, and HVAC systems must be installed by licensed professionals familiar with current codes. Builders must ensure separate air handling systems for ADUs when attached to primary residences to prevent shared air circulation, which may introduce health hazards.
Common Legal Issues
Builders must remain vigilant against potential legal conflicts arising from ADU projects. Homeowners Associations (HOAs) often restrict or outright prohibit ADUs through Covenants, Conditions, and Restrictions (CC&Rs). Builders should advise clients to review these documents and consult legal counsel if necessary to avoid future disputes.
Maintaining positive neighbor relations can preemptively address complaints related to privacy, noise, and parking. Builders should recommend proactive engagement with neighbors to explain project details and construction timelines, minimizing opposition.
Zoning violations pose serious risks. Constructing an ADU without proper permits or in violation of size, height, setback, or use regulations can result in fines, stop-work orders, or court-mandated removal. Builders must meticulously follow all local rules and ensure proper approvals are obtained before proceeding.
Financial Implications
Adding an ADU often leads to an increase in property taxes, as assessors reevaluate improved properties. Although this raises ownership costs, it is offset by potential rental income and increased property value. Builders should counsel homeowners to anticipate these changes and consult tax professionals as needed.
Financing options for ADU projects include cash-out refinancing, home equity loans, and construction loans. Each option carries distinct terms and implications that homeowners must evaluate carefully. Builders should encourage clients to consult lenders experienced with ADU projects to secure appropriate financing.
Best Practices for Builders
Builders engaging in ADU projects must undertake thorough research into local zoning regulations for each project site. Educating clients about applicable requirements and assisting with permit applications helps minimize delays and legal risks. During design, strict adherence to size, height, setback, occupancy, and rental regulations is critical.
Builders should verify parking and access compliance and ensure all construction meets the Michigan Residential Code. Using only licensed contractors for trades work further ensures compliance and project quality. Proactive neighbor communication, HOA consultation, diligent permit documentation, and securing a final Certificate of Occupancy are also essential.
Maintaining comprehensive records of permits, inspections, and correspondence supports legal protection and smooth project completion. Addressing property tax implications during client consultations adds value to the builder-client relationship.
Future Outlook
Although Michigan currently lacks statewide ADU legislation, future changes are possible. Builders and attorneys should monitor legislative developments and local zoning amendments that may expand ADU opportunities. The trend toward easing restrictions to promote affordable housing is likely to continue, creating new prospects for ADU development.
Organizations such as the Michigan Municipal League and Housing North advocate for ADU-friendly policies and provide valuable resources. Builders staying informed about these initiatives will position themselves to adapt and thrive as regulatory landscapes evolve.
Conclusion
Accessory Dwelling Units represent a critical opportunity for addressing Michigan’s housing needs, but the regulatory environment remains fragmented and complex. Builders and attorneys must approach each project with a thorough understanding of applicable local ordinances, state enabling laws, permitting procedures, and construction codes. By adhering to best practices and remaining attentive to emerging trends, professionals can successfully navigate the legal landscape surrounding ADUs and contribute to the creation of more diverse and sustainable housing solutions across the state.
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Further Reading
- Accessory Dwelling Unit in Michigan: A Comprehensive Guide – Gather ADU, https://www.gatheradu.com/blog/accessory-dwelling-unit-michigan
- Accessory dwelling units – Coming to a neighborhood near you? – Planning, https://www.canr.msu.edu/news/accessory_dwelling_units_coming_to_a_neighborhood_near_you
- Accessory Dwelling Units | City of Ann Arbor, https://www.a2gov.org/planning/accessory-dwelling-units/
- Accessory Dwelling Unit Guidebook – City of Ann Arbor, https://www.a2gov.org/media/vj2ff3ij/september-2023-adu-guidebook.pdf
- Accessory Dwelling Units (ADU) – City of Grand Rapids, https://www.grandrapidsmi.gov/files/sharedassets/public/v/1/gr-digital/digital-services/paper-forms/development-center/faqs-accessory-structures.pdf