Montana SB 528 Preempts Local ADU Bans Statewide

Senate Bill 528 from the 2023 legislature, codified at MCA 76-2-345, mandates that any city or county zoning single-family dwellings must also permit at least one ADU on the same lot, either attached or detached. Local governments cannot require the owner to occupy the primary dwelling, restrict ADU occupancy to family members, mandate more than one parking space for the ADU, or charge separate impact fees beyond actual cost. Setback and height standards must match those for the primary structure. This represents a major statewide preemption of municipal zoning.

Local ordinances conflicting with MCA 76-2-345 are unenforceable. Property owners may seek injunctive relief and attorney fees against non-compliant municipalities.