It depends on the mattress. Some Helix mattresses can be used with a box spring, but others advise to skip it. Here’s what Helix says about the issue.
Helix Elite Collection
Traditional box springs are not recommended for the Helix Elite Collection. For best support and to prevent sagging, use a solid, flat surface or a base with firm, thick slats no more than five inches apart. This helps your mattress perform its best and protects your warranty.
-Helix
Helix Core or Luxe Collection
We highly recommend using a solid support system like the Helix Foundation or a bunkie board with a box spring. Ensure any slats are firm, flat, thick, and no wider than 5.5 inches apart to prevent sagging.
Helix
Helix offers the following alternative foundations and bases:
