Edge support is how well the outside 20 cm of a mattress holds you up. It decides whether you can sleep right out to the side, sit on the edge to put your socks on, and get out of bed without sliding off. It's also the first thing to go on a cheap mattress, which is why we build it into ours three different ways.
Quick answer
- Good edge support means you can use the whole width of the mattress. A Queen with soft edges sleeps like a Double.
- We build it three ways: a border wire round the spring unit, firmer springs around the perimeter, or a foam encasement around the whole unit. Encasement gives the firmest edge.
- It matters most for couples, anyone who sits on the bed to dress, and anyone who finds getting up harder than it used to be.
- Test it in store: sit on the edge, then lie right on the edge. If you feel like you're rolling off, keep looking.
Why the edge matters more than you'd think
Most people sleep closer to the edge than they realise, especially couples, who drift outwards to make room. If the edge compresses under you, your body tilts, you tense up to stop rolling off, and you end up sleeping in a strip down the middle. On a Queen that can mean the two of you are effectively sharing a Double.
The edge also takes the hardest punishment: sitting to put shoes on, kids perching, getting in and out. A soft edge breaks down first and the mattress starts to look saggy at the sides long before the middle has worn.
The three ways we build firmer edges
Border wire
A heavy steel wire running round the top and bottom of the spring unit, tying the outer springs together so the edge compresses as a unit instead of one spring at a time. It's on our continuous coil beds and it's what "Triple Edge wire" means on the Citation Box Top, which has three of them. Our Down Under Trundler uses a 5 mm border wire because trundlers get sat on constantly.
Firmer perimeter springs
In a pocket spring mattress the outer rows can be wound from heavier wire than the rest, so the edge resists compression. This is the "firmer edges for maximum support allowing you to use all of the bed" line on the Anniversary Pocket (from $549, Single mattress only), Sense-A-Tech Pocket (from $659) and Spinal Luxury G-Top (from $989).
Foam encasement
A wall of high-density foam around the whole spring unit, so the edge is solid foam rather than springs. It gives the firmest, most sit-able edge and the most usable width. Our Windsor beds, including the Windsor Backcare, and the Opulence use a TheraFoam encasement; the Millennia Plush, Supreme Luxury and Body Care Ultra Plush have a high-density foam casing; and the iSleep Plush sits in a foam box so the edge stays firm even on an adjustable base.
Who should care most
- Couples. Firmer edges give you back the width you paid for. Our couples collection leans towards encased and pocket spring models for this reason.
- Anyone who finds getting up harder. A firm edge is something to push off. If you or a parent has a sore hip or knee, an encased mattress on a base with taller legs makes a real difference.
- People who sit on the bed. To dress, to read, to watch the kids. Border wire or encasement; perimeter springs alone soften faster under sitting.
- Smaller bedrooms. If you've bought a Queen because a King won't fit, you want every centimetre of it to be sleepable. See the Queen range.
Edge support isn't the same as overall support
A firm edge tells you nothing about how the middle will treat your back; that's down to the spring unit and comfort layers. And firm edges don't make the whole mattress firmer: the Supreme Luxury is a soft bed with a foam encasement. Choose your firmness for how you sleep, then check the edge.
The 30-second test in store
Sit on the edge, feet on the floor, and see how far you sink. Then lie on your side with your back right at the edge. If you feel secure, it's fine. If you're bracing not to roll off, it isn't. Do it on two or three beds at the same firmness and the difference is obvious.
Frequently asked questions
What does mattress edge support mean?
How firmly the outer edge holds you when you sit or sleep near it.
Is a mattress with reinforced edges better?
For couples and anyone who sits on the bed, yes. It gives you the full width and the edge lasts longer.
Which gives the firmest edge?
Foam encasement, then border wire, then firmer perimeter springs.
Does edge support make the mattress firmer overall?
No. The Supreme Luxury is soft with a firm edge. Firmness comes from the comfort layers.
How do I test it?
Sit on the edge, then lie on your side at the edge. If you're rolling off, keep looking.
Try the edge, not just the middle
Next time you're in store, finish every test nap by rolling to the edge. The Therawrap range is a good place to start.
Related guides: 3-zone vs 5-zone mattresses · Queen vs King for couples · Best mattress firmness for every sleeping position
