How to Store a Mattress the Right Way

Whether it's a move, a guest bed waiting for a guest, or a mattress you're holding onto between apartments, storage is one of those chores people assume is simple and then get wrong in the same handful of ways. Most of the damage that shows up months later — a lean, a musty smell, a dent that won't pop back out — traces to one of two decisions made on the day the mattress went into storage, not to anything wrong with the mattress itself. The good news is the method is genuinely simple once you know the one rule that matters most. Get that right and the rest is just common sense about moisture and weight.

The one rule: store it flat, not on its side

Everything else on this page is a footnote to this. A foam or hybrid mattress isn't a rigid object — it's layers of foam and padding that hold their shape because they're supported evenly across the whole surface, the way a bed frame supports them. Stand that same mattress on its edge for weeks or months and gravity does something different: the filling and foam layers slowly shift and settle downward, unevenly, because one edge is now doing all the work that used to be spread across the whole underside. The result is a lean or a permanent sag baked into the mattress before it's even back in use — and unlike a body impression that builds up over years of ordinary sleeping, this kind of damage can set in over a single season in storage.

A short stint on its side — moving it between rooms, a few days in a moving truck — won't do this. It's sustained vertical storage, over weeks and months, that causes the damage, because that's how long it takes gravity to actually reshape the foam. If you have any choice in the matter, lay it flat. Innerspring mattresses hold up a little better on their side for short periods, because the coils maintain their own shape independent of gravity rather than relying on foam to hold a level surface, but flat is still the safer default for anything beyond a few days. Memory foam is the most vulnerable of the bunch here, since it's the softest and slowest to recover of the common mattress materials, and latex sits somewhere in the middle — more resilient than memory foam, but still a foam that will settle unevenly under sustained one-sided pressure.

If space genuinely forces the issue and a mattress has to go on its side for more than a few days, at least rotate which edge is bearing the weight every so often, and get it flat again as soon as the space situation allows. It's a compromise, not a solution — the safest number of days to leave any foam or hybrid mattress standing on its edge is as few as possible.

Before it goes into storage

A mattress that goes into storage dirty or damp comes out of storage worse, not better — storage doesn't improve anything, it just holds whatever condition the mattress was already in, for as long as it sits there. A few steps before you put it away:

• Clean it and let it fully dry first. Any sweat, spills, or spot-treatment moisture needs to be completely gone before storage, since trapped dampness sealed away for months is exactly how mold gets started. Our guide to cleaning a mattress covers the routine clean and stain fixes — do that first, and give it extra time to air out and dry completely before it's wrapped or moved. If you've just spot-treated a stain, wait longer than feels necessary; a mattress can feel dry on the surface while still holding moisture a layer or two down.
• Use a breathable cover, not sealed plastic. A fitted mattress bag or cotton cover keeps dust and dirt off while still letting the mattress breathe. Fully sealed plastic traps whatever moisture is already there — or any humidity that creeps in later, since temperature swings inside a sealed bag cause condensation the same way a cold drink sweats on a warm day — against the foam with nowhere to go, which is close to ideal conditions for mold and mildew.
• Note which side is up, if the mattress is one-sided. Most modern mattresses have a comfort layer on only one side. It's an easy thing to forget after months in storage, so a strip of tape or a marker note on the cover saves you from re-learning the hard way which side you're supposed to sleep on.

Where and how to store it

Once it's clean, dry, and covered, the storage spot itself decides most of what happens next.

• Lay it flat, and don't stack anything heavy on top. Boxes, furniture, or anything with real weight will compress the foam in whatever spot it's sitting, and unlike a body rotating around a bed over years, a static weight in one place for months can leave a permanent dent — the foam simply doesn't spring back the way it would from ordinary, evenly distributed use. If you must store other items in the same space, stack them beside the mattress, never on it.
• Choose a climate-controlled space over a damp garage or basement. Temperature swings and humidity are the two things that quietly damage stored mattresses — humidity feeds mold and mildew, and extreme heat can affect adhesives and foam over a long stretch. A spare room or a climate-controlled storage unit beats an unheated garage or a basement that floods every spring.
• Keep it off a bare concrete floor. Concrete pulls in ambient moisture and can stay slightly damp even when the room feels dry, and a mattress resting directly on it will wick up some of that moisture over time. A wooden pallet, a few boards, or even a tarp underneath breaks that contact and keeps the mattress drier.
• Keep it out of direct sunlight.A window that bakes one section of a covered mattress for months can dry out and weaken fabric and foam unevenly in that one spot, the same way upholstery fades and thins on a sun-facing side of a couch. It rarely ruins a mattress on its own, but it's an easy thing to avoid simply by picking a spot away from a window.

Bringing it back into use — and the honest limit

Don't remake the bed the moment the mattress comes out of storage. Unwrap it, stand it up briefly or lay it somewhere open, and let it air out for a few hours — longer if it's been in storage for months. This gives any residual moisture a chance to evaporate and lets a foam mattress that's been compressed or covered re-expand fully before you put sheets and a protector back on top of it. If it was stored properly — flat, dry, breathable cover, off the floor — it should feel essentially the same as it did going in.

Good storage preserves a mattress; it doesn't improve it, and it can't undo a bad setup after the fact. A long stretch of heat and humidity will degrade any mattress eventually, no matter how carefully you followed the rest of this list — that's just what happens to foam and fabric over time in a hostile environment. And if a mattress went into a garage already sagging or worn out, it'll come back out sagging or worn out; storage isn't a repair. If that's the situation you're in, our guide on fixing a sagging mattress walks through what's actually fixable versus what isn't, and our guide on how often to replace a mattress covers the broader signs it's past saving. If it's genuinely time for something new, a bed-in-a-box mattress ships compressed and is easy to store again down the line if you ever need to.