Inspection guide
How to check mattress sagging and the support underneath
A dip can come from the mattress, the foundation, the frame, or more than one part at once. This inspection helps you locate the change before you decide what to replace.
Before you start
Read the mattress and bed-frame care instructions first. Ask for help with heavy lifting, and do not bend or move a mattress in a way the manufacturer warns against. This guide is for observation, not repair.
Step 1: inspect the uncovered surface
Remove pillows, sheets, protectors, and toppers. Let the mattress sit unloaded, then view it from the side and foot of the bed. Look for a depression that remains, a ridge between sleep positions, an uneven edge, or fabric that is pulled unusually tight.
Step 2: make the comparison repeatable
Place a straight, rigid object across the area without forcing the surface down. Photograph the gap from the same position. Do not use a generic depth threshold to make a warranty claim; brands define measurements and acceptable impressions differently.
Step 3: inspect the base
- Check whether slats are cracked, bowed, displaced, or spaced differently from the frame instructions.
- Check center rails and support legs for movement or loss of floor contact.
- Look for a foundation or platform that bends under the same area as the visible dip.
- Confirm that the mattress size and support system are compatible.
Step 4: remove simple confounders
A compressed topper, uneven protector, loose frame joint, or floor that is not level can change what you see and feel. Check those parts separately. Rotate the mattress only if its instructions allow rotation; do not flip a one-sided mattress unless the manufacturer says it is designed for that.
Step 5: decide what the evidence supports
If the base is damaged, correct support may need attention before the mattress can be judged fairly. If the base is stable and the mattress has a persistent dip together with reduced comfort or support, keep your photos and purchase information and review the warranty or compare replacement options.
Return to the SleepCheck calculator and answer the physical-change question using what you observed. For a wider decision, use the replacement-sign checklist.