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Grand Rapids, MI Accessory Structures: ADU Rules (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

ADU rules in Grand Rapids, MI, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

Units per lot: One ADU maximum per lot
Max height (detached): 25 feet
Max size: 850 sq ft or 40% of house
Bedrooms: Two bedrooms maximum
Eligible lots: Single- or two-family dwellings only

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Michigan under recent ADU streamlining laws. The Grand Rapids, MI rules below cover local size, height, and setback requirements.

Summary

Grand Rapids allows one accessory dwelling unit per lot with a single- or two-family home, capped at 850 square feet and 25 feet in height under Zoning Ordinance Section 5.9.03.

A.Not more than one (1) Accessory Dwelling Unit (ADU) may be permitted per lot.B.An ADU may be permitted only in association with a single-family or two-family dwelling.C.Minimum Lot Area. An ADU may be developed on a lot meeting the minimum lot size for the applicable zone district.D.Residential Density. An ADU shall be excluded from maximum residential density requirements.E.Setbacks.1.An attached ADU shall be subject to the zone district setback requirements for a primary structure.2.A detached ADU shall be subject to the zone district setback requirements for an accessory structure.F.Floor Area.1.The maximum permitted floor area for an accessory structure that contains a second floor ADU may be increased by one hundred (100) percent solely for the construction of a second-floor unit.2.Maximum ADU Size. The ADU shall not exceed forty (40) percent of the gross floor area of the primary structure or four hundred (400) square feet, whichever is larger. In no case shall the ADU exceed eight hundred fifty (850) square feet in gross floor area.G.Building Height. The maximum permitted height of a detached ADU is twenty-five (25) feet.H.Bedroom Maximum. A maximum of two (2) bedrooms are permitted within an ADU.

Source: Grand Rapids ADU RegulationsView official code

Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 70).

Full Breakdown

Section 5.9.03 of Grand Rapids' Zoning Ordinance permits only one ADU per lot, and it must be built in association with a single-family or two-family dwelling, not a stand-alone lot. The ADU can occupy a lot that meets the zone district's minimum lot size and is excluded from maximum density calculations. Setbacks follow the standard for a primary structure if attached, or an accessory structure if detached. A detached ADU is capped at 25 feet in height and two bedrooms, with floor area limited to 40 percent of the primary structure's gross floor area or 400 square feet, whichever is larger, up to an 850-square-foot ceiling.

Violations & Fines

Building an ADU without meeting these standards risks permit denial by the Planning Department; a second ADU on the same lot or a stand-alone ADU lot is not permitted under Section 5.9.03.

Frequently Asked Questions

Can I build more than one ADU on my Grand Rapids lot?

No. Section 5.9.03.A caps it at one accessory dwelling unit per lot, regardless of lot size or zone district.

How big can a Grand Rapids ADU be?

Up to 40% of the primary home's gross floor area or 400 square feet, whichever is larger, but never more than 850 square feet total.

Sources & Official References

[1]Grand Rapids Code of Ordinances, Chapter 61 Zoning Ordinance, Article 9 (Municode)

Other rules in Grand Rapids

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All Grand Rapids rules

How Grand Rapids compares: Easiest Cities to Build an ADU·Compare Grand Rapids to another location·View the Michigan accessory structures overview

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