Definitions of "what makes an apartment a loft apartment?" will vary. There are several different types of lofts in Chicago. A Warehouse Loft (also called an Industrial Loft) is found in a converted factory building or warehouse, as the name implies. These types of lofts in Chicago have been carved out of formerly industrial buildings. Features like concrete floors, bare concrete columns, exposed brick, and factory windows are common in Warehouse and Industrial Lofts. The South Loop, Fulton Market, and River North neighborhoods of Chicago contain many good examples of this type of loft apartment.
A Timber Loft probably matches many renters' preconceptions of what lofts look like. Sturdy wooden beams and timber-clad ceilings are defining traits of Timber Lofts. These are spread across the city in various neighborhoods, with Bronzeville, Lakeview, and Noble Square containing some fine examples.
Then there are the Soft Loft apartments, which renters might encounter in areas with more recent construction like the West Loop, South Loop, and Chicago Loop. This is a loft apartment built in recent years to evoke a loft feel: high ceilings, generous natural light, and raw industrial materials are incorporated into the apartment even though it was never used in any industrial capacity.