Does this memory foam mattress need a box spring or foundation?

No box spring is needed or wanted. This medium memory-foam bed relies on even, gap-free support to hold its 6-out-of-10 feel, so use a platform bed, slats no wider than three inches apart, or a bunkie board. A worn box spring flexes under the foam, creates dips, and can void the 10-year warranty. The 7-inch Serta Foam Core needs a rigid, level surface beneath it to perform as designed.