Glossary

Nonconforming Use

Also known as: Grandfathered Use, Legal Nonconforming Use

A lawful use, structure, or lot configuration that existed before a zoning ordinance was adopted or amended and no longer complies with current zoning requirements, but is permitted to continue under grandfathering protections.

Nonconforming use protections (often called grandfathering) allow an existing use to continue despite a subsequent zoning change that would otherwise prohibit it, but the protection is typically fragile: most zoning codes provide that a nonconforming use is lost permanently if the use is discontinued or abandoned for a specified period, if the structure is destroyed beyond a specified damage threshold (commonly 50%) and the owner seeks to rebuild, or if the nonconforming structure is expanded or substantially altered beyond limits the code allows for legal nonconforming structures. This fragility makes nonconforming status a significant and frequently underappreciated diligence item in CRE acquisitions — a buyer purchasing a property that generates above-market income specifically because of a legal nonconforming use (extra density, a use no longer permitted in the current zoning district, reduced parking ratios) needs to understand precisely what would trigger loss of that status, since losing it could force a costly redevelopment to a lesser, conforming use.