Lay it flat if you can, completely dry and off the floor. Don't stack mattresses on top of each other, or put anything else on them. Flat is best because a mattress is built to carry weight lying down; stood on its side for weeks, a sprung or natural-filled mattress can have its filling shift. Standing it on its long edge saves floor space, which is why our own packing guides suggest it, but for a stay of months that's a compromise. Use a polythene bag for the move, then open it or swap it for a cotton sheet in the unit so moisture can escape. If you're a landlord, storing a mattress for someone else, or already have one in a unit, there's a section for you below.
Flat or on its side?
Flat is best for every type. Simba, a UK mattress maker, puts it plainly: "Store It Flat, Not on Its Side." It adds that moving a mattress on its edge into a van is fine, but "Leaving it that way for weeks is what causes damage," and that side storage may affect its guarantee. Mattress Online, a UK retailer, says flat matters most for pocket sprung and natural-filled mattresses, and that "storing foam and latex mattresses on their side is fine as the materials won't move much."
| Mattress type | Best | On its long edge |
|---|---|---|
| Pocket sprung, standard sprung, hybrid | Flat | To move it, and otherwise as briefly as you can |
| Natural fillings | Flat | To move it, and otherwise as briefly as you can |
| Memory foam, latex | Flat | Mattress Online: fine. Simba: not for weeks |
Check your own mattress's care guide or guarantee too, because some makers set their own rules. Never fold or roll a mattress that wasn't made to be folded: Simba warns folding can damage the inside permanently, and says a Simba mattress shouldn't be re-rolled once it has expanded.
Here's what flat costs you in floor space, using standard UK sizes:
| Size | Mattress (UK standard) | Floor it covers when flat |
|---|---|---|
| Single | 90 x 190cm (3ft x 6ft 3in) | about 18 sq ft |
| Double | 135 x 190cm (4ft 6in x 6ft 3in) | about 28 sq ft |
| King | 150 x 200cm (5ft x 6ft 6in) | about 32 sq ft |
| Super king | 180 x 200cm (6ft x 6ft 6in) | about 39 sq ft |
On its edge a mattress still needs a clear wall as long as it is; we don't list unit dimensions here, so ask when you book.
A double laid flat covers more floor than a whole 25 sq ft unit has. Our room-by-room size guide fits a one-bed flat, including a double bed and mattress, into about 50 sq ft only "provided you stack well and stand the mattress on its edge". On its own, a king covers about 32 sq ft; if the rest of a one-bed flat is going in too, flat storage for a double often means a size above the 50 sq ft example (the median (middle value) of the listed prices for 75 sq ft is about £176). The median (middle value) of the listed prices on our September 2026 price lists is about £78 per four weeks for 25 sq ft and about £143 for 50 sq ft. Prices vary by site (from about £44 to £188 for 25 sq ft on the same lists), so check your quote. Nothing is added at checkout: the total in your quote is what you pay, and our prices include VAT. For months, lay it flat and size the unit for it.
Before it goes in
Get it completely dry. A mattress holds moisture, and our guide to long-term storage is blunt: "Any moisture that goes in with the items will stay in the unit with them." Vacuum it, let any cleaned patches dry fully, air it for a day if you can, and check the underside.
Then bag it for the move. Our Box Shop sells two polythene covers: the "Single Mattress Cover – 3ft 6″" at £3.99, described as "ideal for most standard single beds", and the "Double Mattress Cover – 6ft Double/Super King" at £5.99, for "most double, king, and super king mattresses" (prices as listed in September 2026). A standard UK single is 3ft (90cm) wide. The shop doesn't list the covers' other dimensions, so check the fit on a deep or long mattress. The mattress bag glossary entry explains what these bags do.
In the unit
Polythene keeps dust and marks off, and it also keeps moisture in. Our furniture guide says: "Avoid plastic covers that trap moisture; use breathable fabrics instead to let air circulate." Simba says the same: a tightly sealed plastic cover traps moisture, so use a breathable bag or cotton sheets, and if plastic is all you have, "don't seal it airtight". Simba suggests cotton sheets for a shorter period and a breathable storage bag for longer. Our Box Shop describes its covers as ideal for storage too, but they are polythene, so once the mattress is in place, take the bag off and lay a cotton sheet or other breathable cover over it (see breathable cover).
Keep it off the floor. Our packing tips say to use pallets to keep furniture off the floor, and Simba notes that concrete draws moisture upwards. Our Box Shop doesn't sell pallets, so bring pallets, boards or battens; ask us when you book what your site has. Leave a little air between the mattress and the wall.
Put nothing on top. Simba says sustained weight compresses the comfort layers unevenly and leaves impressions you can't remove; Mattress Online says heavy objects on top can alter the support a mattress gives.
How long can it stay? Neither source sets a limit. Simba's advice is that the longer the stay, the more breathability matters, and to look at a stored mattress every month or two. Storing a divan base as well? Our sources don't cover bed bases, so ask us when you book about the space it and the mattress need.
Our units aren't heated or climate-controlled, so the temperature follows the seasons to some degree (see do storage units get cold in winter?). Both sources above prefer climate-controlled storage; ours isn't, so dryness going in and airflow matter more. A mattress that goes in damp, or sealed in airtight plastic, is the one that comes out smelling musty. If you're booking an outdoor container, our booking system describes the Chipping Norton and Shipston-on-Stour containers as insulated (for any other container, ask when you book); read our guide to condensation in container units.
Storing several mattresses (landlords and furnished lets)
Don't stack them: each mattress is weight on the one below. For a stay of months, lay each one flat, foam included, since the two sources disagree on foam on its side. Four singles and two doubles laid flat cover about 129 sq ft before you allow room to reach them. Prices at some sites are well above the middle figure, so get your own site's quote, and describe the load to us before you book, on 0800 2545585.
Keep each mattress's fire-safety label intact and legible, and check the labels before you let the mattresses again. If you store as a business, clause 30(a) of our terms excludes liability for "loss or damage to Your business, if any, including consequential loss, lost profits or business interruption". Clause 31 requires the mattresses to be insured, through our contents protection (clause 48) or your own policy; check whether your landlord policy covers goods kept away from the let property.
Storing a mattress for someone else
A parent clearing a student room: our student guide says a mattress is "the single item that pushes most students out of the smallest unit", so size up if one is going in. A family clearing a relative's home: check each mattress is dry, underside included.
Cot and Moses basket mattresses
Store a cot or Moses basket mattress the same way: flat, dry, loosely covered and with nothing on top. The Lullaby Trust says "If possible, it's best to buy a new mattress for each baby", and that "Some research has found a higher risk of SIDS when using a second-hand mattress from outside the family home, although the link hasn't been proven." If you do reuse one, check it against the Trust's list when it comes out of the unit, not when it goes in: "no rips or tears", "in good condition with no water damage", "firm and flat (no areas of sagging)", "Fit the cot or Moses basket well, with no gaps", with a "well fitting, 100% waterproof cover" and "a fire-resistant label on it".
Already in your unit?
If yours is a sprung mattress that has been on its edge for more than a week or two and it'll be staying months, lay it flat if the floor allows. If it doesn't, call us about a larger unit. Lift it off the floor, check it's dry, and loosen any sealed bag. Check it on your visits: a musty smell or marks on the cover mean moisture, so take it out and dry it.
The mattress is your responsibility while it's stored (clause 30 of our terms), and it must be insured for what it would cost to replace (clause 31). Whether damp damage is covered depends on the policy, so read does contents protection cover damp and mould?.
Ready to book? Get a price online, tell us if a mattress needs to lie flat, and pick up covers from the Box Shop. To find a site, see our locations.
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