How to Choose a Box Spring

Which base does your setup need?

Work through these in order — the first match is your answer.

• Platform bed with slats 3 inches apart or less: you need nothing more.
• Slatted frame with wider gaps: add a bunkie board, a thin rigid panel that converts it to a continuous deck.
• Metal frame with only perimeter rails: you need a rigid foundation (or a box spring if an innerspring warranty demands one).
• Traditional innerspring mattress whose warranty specifies a box spring: buy the sprung version.
• Adjustable base: no foundation of any kind — the base is the support.

Signs your current base has failed

A base failure is often mistaken for a mattress failure. Take the mattress off and look: sagging in the foundation surface, broken or cracked slats, a bowed center rail, or a center leg that no longer reaches the floor all cause a dip you feel through the mattress.

The cheap test is to lay the mattress on the floor for a couple of nights. If the sag disappears, the base is the problem — and replacing it costs a fraction of a new mattress.

Split foundations and tight spaces

King and California king foundations come as two pieces by default, which is why they get up stairs when a one-piece queen sometimes will not. If you have a tight stairwell or a sharp landing, a split queen foundation exists and solves it — worth confirming before delivery day rather than after.