Does the Orthopedic Classic tight-top need a box spring or foundation?

Yes, an innerspring bed like this needs a solid, evenly supportive foundation: a sprung box spring on a frame, a platform, or closely spaced slats. The base must fully support the coil unit so it cannot flex or sag in spots, which protects the steel and the warranty. It is delivered flat rather than rolled, so it is ready to use the same day on a sound foundation with no expansion wait.