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Crib Mattress Height Adjustment (2027)
How to adjust crib mattress height safely: when to lower, hardware checks, and spring-frame fixes.
Mattress height is a safety control, not a convenience setting: high for newborns you lift often, low before the baby can pull to stand. These fixes cover when to move it, stuck hardware, and sagging supports.
Not sure when to lower the mattress
Start at the highest setting for newborns. Lower to the middle when the baby sits up, and to the lowest setting before they pull to standing, usually around 8 to 10 months. The rule is simple: when the top rail is below the baby's chest while standing, the mattress is too high. With four-position cribs like the Kalani or Hudson, step down one level at a time.
Mattress support bolts will not budge
The bolts thread into metal inserts that can seize over time. Apply firm, steady pressure with the correct Allen key size; a stripped key is worse than a stuck bolt. If a bolt is truly frozen, a drop of penetrating oil on the threads, left for an hour, usually frees it. Never force with pliers, which rounds the bolt head.
Spring frame sags in the middle
Check that all four corners are seated on their brackets; a corner that slipped off its hook causes most sagging. Tighten every bolt, since seasonal wood movement loosens hardware. If the spring itself is bent, contact the manufacturer for a replacement frame rather than reinforcing it yourself, which can create uneven support.
Toddler rail does not align with pre-drilled holes
Conversion rails are model-specific; confirm the rail matches your exact crib model, since look-alike rails from sibling models often differ by millimeters. Assemble the rail loosely first, align all holes, then tighten in sequence. If holes are genuinely misaligned, the rail may be for a different model year; check with the manufacturer before drilling anything.
Questions, answered
How often should I check crib hardware?
Monthly. Wood expands and contracts with seasons, loosening bolts over time. A quick check with the Allen key takes two minutes and is the most important crib maintenance there is.
The mattress rocks slightly. Is that normal?
A tiny amount of play is normal in spring frames. If it rocks visibly, a corner is unseated or a bolt is loose; fix it before the next sleep. The mattress itself should never shift more than a finger's width.
Can I raise the mattress back up later?
Yes, for the daybed stage or a second child. Keep the manual and all hardware; the positions work in both directions. Just never raise it while a standing-age baby uses the crib.