A mattress foundation is the base that supports your mattress, typically sitting inside or on top of a bed frame.
Foundations serve several purposes: providing even support, adding bed height, improving airflow, and protecting your mattress warranty.
Common types include box springs (coils in a frame), platform bases (solid or slatted), bunkie boards (thin solid platforms), and adjustable bases.
Using the wrong foundation can void your mattress warranty and lead to premature sagging.
Foundations serve as the critical interface between your mattress and bed frame. A proper foundation distributes weight evenly, prevents sagging, and extends mattress life. Using the wrong foundation is one of the most common causes of premature mattress failure.
Most modern direct-to-consumer mattress brands recommend a solid platform or closely-spaced slatted foundation. The shift away from box springs reflects changes in mattress construction — newer designs don't need the flex that box springs provide.
When shopping for a foundation, check your mattress warranty requirements first. Many warranties specify exact foundation types and maximum slat spacing. Non-compliant foundations can void your warranty, leaving you unprotected against manufacturing defects.