City Councilman Ben Kallos (D-Manhattan) introduced legislation Thursday to legalize so-called “flex apartments,” where temporary walls are installed. This longtime, unlawful Big Apple practice has historically provided greedy landlords with additional rooms to rent and enterprising tenants with extra privacy to attract roommates to help cover rent.

Under city law, it’s illegal to install temporary walls or other floor-to-ceiling dividers unless proposed changes are submitted to the city by a licensed engineer or architect and then greenlighted through a Buildings Department permit.