Last updated: October 2026
A rolled mattress takes a few hours to get most of its height back and up to a day or two to settle completely. How long you should wait before sleeping on it depends on the brand: some say 24 to 72 hours, while a REM-Fit hybrid is ready to sleep on three to four hours after you unroll it. This guide explains what happens inside the mattress as it expands, what you can and cannot do while it does, and what to make of any new-mattress smell.
Quick answer: Most rolled mattresses recover 80 to 90 per cent of their height within a few hours and are fully expanded within 24 to 72 hours. A REM-Fit hybrid can be slept on three to four hours after unrolling, because the pocket springs recover almost at once and only the foam comfort layer needs time. Sleeping on it early will not damage it; it just feels a little firmer and less even until the foam has fully relaxed.
How long does a mattress take to expand?
A rolled mattress expands in two stages. The springs and foam push out to most of their full depth within an hour or two of the plastic coming off, and the last few centimetres and the even, settled feel arrive over the following day. By the next morning it should look and feel like the mattress you ordered.
The time depends on what is inside. A hybrid expands faster than an all-foam mattress because the pocket springs are steel; they are held compressed by the packaging and return to shape as soon as it is cut. Memory foam is slower, because it has been squeezed with the air pushed out of it and needs to draw that air back in cell by cell. A thick all-foam mattress can take a full 72 hours; a hybrid with a single foam comfort layer takes a fraction of that.
Three things slow expansion down: a cold room, a very thick foam layer and sleeping on it straight away. Unrolling in a room at normal living temperature, around 18 to 21 degrees, is the one you can control.
How long should you wait before sleeping on a new mattress?
Follow the maker's guidance for your mattress, because it reflects the foam inside. The usual advice for all-foam bed-in-a-box mattresses is 24 to 72 hours, and some brands make the wait a condition of the trial.
For a REM-Fit hybrid the wait is three to four hours. The hybrid mattresses in the range all use full-height or dual-layer pocket springs under an open-cell memory foam comfort layer. Open-cell foam has an open structure that lets air pass through, which is why it sleeps cool, and the same structure lets it refill with air quickly after rolling.
If you have to sleep on it sooner, you can. An hour or two early will not harm the mattress; the foam carries on expanding under you and you simply get a slightly firmer first night. Our guide to bed-in-a-box mattresses covers what else to expect in the first 30 nights.
What should you do when a rolled mattress arrives?
Set it up where it will stay. Once a mattress has expanded, moving it through a doorway or up a staircase is much harder than carrying the roll, so get the roll into the bedroom before cutting anything.
- Check the base first. The slats or divan should be flat and sound; a sagging base undermines a new mattress from night one.
- Put the roll on the base with the label the right way up, then cut the outer plastic with scissors, not a knife, so you do not nick the cover.
- Unroll it fully and cut the inner vacuum bag. You will hear it draw air in; that is the foam starting to recover.
- Leave it uncovered for the first few hours. A sheet is fine once it has risen; a thick protector or topper on a half-expanded mattress slows the air getting in.
- Open a window if you can. Fresh air speeds expansion a little and clears any packaging smell.
Then rotate it head to toe every few months. Rotation evens out the gentle settling every mattress goes through, which our post on mattress settlement explains, and the hybrid mattress care guide covers the rest of the routine.
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Why does a new mattress smell?
The new-mattress smell is off-gassing: the release of volatile organic compounds, or VOCs, from foam and the adhesives that bond the layers, which build up inside the sealed packaging and escape when it is opened. The Sleep Foundation says the compounds are generally considered harmless, that most of the smell goes within a few hours of unpacking, and that faint traces can linger for a few days in a poorly ventilated room.
How strong it is depends on how much foam and glue the mattress contains. All-foam mattresses with several bonded layers are the ones that smell most. A REM-Fit hybrid uses one foam comfort layer over steel springs, bonded with a low-odour adhesive used sparingly, so most customers notice little or nothing on unboxing. If you are sensitive to smells, leave the window open for the first day and hold off putting the sheets on until the mattress has fully risen.
The smell is not a sign of a fault. If it has not faded after a week, or it is accompanied by any reaction, contact the retailer; that is what the trial period is for.
What if the mattress has not expanded properly?
Give it 72 hours in a warm room before deciding anything. A slight dip at the edge or a corner that looks lower than the rest usually fills out over the first day; the edges are the last part of a rolled mattress to recover because they were the tightest part of the roll.
If after three days there is still a visible dip, a crease across the surface, or a corner that stays folded, photograph it on the base and contact the retailer. That is a packaging or transit fault, not something sleeping on it will fix, and a mattress that was rolled for many months in a warehouse is the usual cause. Every REM-Fit mattress comes with a 100-night trial, so you are covered either way.
Do not confuse this with normal settling. Over the first weeks the comfort layer softens slightly where you sleep, and the mattress feels less firm than on night one. That is the foam adapting to you, not a defect, and rotating it keeps the wear even. The sleep trial is long enough to judge the mattress once it has settled, not on the first night.
New mattress questions answered
Last updated: October 2026
Can you sleep on a mattress while it is still expanding?
Yes, once it has recovered most of its height. It will feel a little firmer and less even than it will the next night, and your weight slows the last stage of expansion slightly, but it does no harm. For a REM-Fit hybrid, three to four hours after unrolling is enough; follow the maker's guidance for other mattresses.
Can you put sheets on a mattress while it is expanding?
Wait until it has risen to roughly its full height, usually a few hours. A fitted sheet on a half-expanded mattress compresses the edges and corners, which are the slowest parts to recover. A thick protector or topper should wait until the mattress is fully expanded.
Do you really have to wait 72 hours?
Only for some all-foam mattresses, where the maker specifies it. 72 hours is the time for a thick memory foam mattress to expand completely, not a safety rule. Hybrids with pocket springs are ready far sooner; REM-Fit's guidance is three to four hours.
What happens if you sleep on a mattress before 24 hours?
Nothing lasting. The first night may feel firmer, and a very early night on an all-foam mattress can leave a temporary impression that fills out as the foam finishes expanding. It does not void a guarantee and it does not shorten the mattress's life.
How long does a rolled mattress stay rolled before it is a problem?
Makers typically advise unrolling within a few weeks of delivery, and foam rolled for many months can take longer to recover or hold a crease. If you cannot set it up straight away, keep it in the box, flat, at room temperature, and unroll it as soon as you can.
How long does the new mattress smell last?
A few hours to a few days in a ventilated room for most mattresses, longer for thick all-foam builds with several bonded layers. A hybrid with one foam layer and a low-odour adhesive often has no noticeable smell at all. Contact the retailer if it has not faded after a week.
Sources: Sleep Foundation, Off-Gassing; REM-Fit delivery and set-up guidance, October 2026.
