The best mattress for couples who move differently: motion transfer explained
Motion transfer is the trade's name for the thing where your partner turns over and you feel it. It is the second most common complaint couples have about a mattress, after firmness, and unlike firmness it is decided almost entirely by the build. Some mattresses carry movement across the bed like a trampoline. Some barely carry it at all. Here is why, and what to buy if someone in your bed is always getting up.
Why a bed moves
A mattress carries movement when its layers are connected. An open-coil (Bonnell) spring unit is one piece of wire, every spring joined to the next, so when one corner goes down the whole unit responds. That is the trampoline. Pocket springs are each in their own fabric sleeve, joined at the fabric, so they move mostly on their own; a pocket-sprung mattress carries much less movement than an open-coil one. A foam core has no springs to join, and carries the least of all.
The comfort layer matters too. Memory foam absorbs movement, because it deforms slowly and locally. Latex is springy and carries a bit more. A thin comfort layer over any spring unit lets you feel the springs; a thick one damps them.
The scale, roughly
| Build | Movement carried | Feel |
|---|---|---|
| Open coil | A lot | Bouncy, connected, creaks with age |
| Pocket springs, thin comfort layer | Some | Responsive, you feel your partner turn |
| Pocket springs, 5 cm memory foam on top | Little | Most people's sweet spot |
| Micro-springs over a foam core | Very little | Quiet, still, some liveliness from the micro-springs |
| Solid memory foam | Almost none | Very still, but warm and hard to turn on |
Who needs the low end of the scale
New parents. Someone is getting up two, three, four times a night for a year, and the other person has to function in the morning. This is the case where a foam core earns its money, and where a firm edge matters too, because you will be sitting on the edge of the bed to feed at three in the morning and you do not want the mattress tipping.
Shift workers and early starters. One of you gets up at five. The other should not know.
Light sleepers married to restless ones. Some people turn forty times a night. Their partners can tell you the exact number.
Different weights. A big difference in weight makes movement transfer worse on a sprung bed, because the heavier person's side is always in motion relative to the lighter one's.
What to look for
- Pocket springs at minimum. Never open coil, whatever the price.
- At least 5 cm of memory foam of 55 kg/m³ or more on top of the springs. It damps what the springs pass up.
- Or a foam core with micro-springs, if movement is the main problem. This is what a motion-isolating build is: no main spring unit to carry movement, micro-springs for a bit of life, dense memory foam on top.
- A firm edge you can sit on. A 50 kg/m³ foam rail or a steel rod.
- A king or super king. Ten centimetres of extra width per person is worth more than any material.
- Split tension, if the problem is different weights or different backs rather than movement. That is a separate problem with a separate fix.
What about bounce?
A foam core does not bounce. Some people miss it. If you like a lively bed and movement is only a minor irritation, a pocket-sprung mattress with a thick memory foam top is the better compromise. If one of you is waking the other every night, stillness wins.
Bedside cribs
A practical note for the new-parent case. Side-sleeper cribs attach to the bed frame and need the mattress top within a stated height range, usually with a maximum around 25 to 30 cm above the base, and they need the mattress edge to stay put where the crib is strapped on. A firm edge and a 25 cm depth suit almost all of them. Check the crib's range before you buy.
How we built ours
The New Parent is the low end of the scale by design: a 10 cm reflex core, a layer of 1,000 micro-springs, 5 cm of 60 kg/m³ memory foam on top, a 50 kg firm rail you can sit on, and a zip-off cover that washes at 40 °C, because things happen. It is 25 cm deep for bedside cribs. It is quieter and stiller than any sprung bed we make, and it works just as well for light sleepers with no baby in sight. If you want springs and still want it quiet, The Single Life in a king has 3 cm of gel memory foam over pocket springs and carries very little.
The short version
- Open coil carries everything. Pocket springs carry some. A foam core carries almost none.
- Memory foam on top damps what the springs pass up.
- New parents and shift workers: foam core, micro-springs, firm edge, washable cover.
- Buy the width. A king solves more than any material.
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