Mattress Edge Support: Why You’ve Been Choosing Wrong (Foam Boxes vs Springs-to-Edge)

The edge support obsession is backwards

Here’s something the mattress industry won’t tell you: they’ve convinced you to care about the wrong thing.

Every mattress review you read obsesses over “firm edge support.” Reviewers sit on the edge of display mattresses, bounce a bit, and declare whether it’s “strong” or not. Then they rank mattresses accordingly.

But here’s the reality—you spend about 8 hours sleeping on your mattress every night, and maybe 2 minutes sitting on the edge when you get in and out of bed.

So why are we optimising for those 2 minutes at the expense of the other 8 hours?

From someone who works with these materials all day, every day for over a decade, I can tell you the “sit test” in showrooms is pure marketing BS.

What creates “firm edge support” (and why it’s a problem)

Most mattresses get their firm edges from foam boxes—thick walls of foam (usually around 10cm) that run around the entire perimeter of the spring unit. These foam walls create that solid, stable feeling when you sit on the edge. Great for the showroom “sit test,” right?

But there are three massive problems with foam boxes that nobody talks about.

Problem 1: They steal your sleep surface

This one’s simple maths. If you’ve got a 10cm foam box on each side of your mattress, you’ve lost 10cm of usable sleep surface from both sides. That’s 20cm total width you’re paying for, but can’t actually use for sleeping.

Why? Because the feel of the mattress changes when you’re lying close to the edge. That foam box creates a completely different feel than the rest of the mattress. You’ve got pocket springs and comfort layers in the centre, but when you roll toward the edge, suddenly you’re on a wall of solid foam instead.

The mattress doesn’t feel consistent all the way across. So you unconsciously avoid sleeping near the edges, making your actual usable sleep surface significantly smaller than the mattress dimensions you paid for.

Problem 2: Ventilation suffers (and mould grows)

This is where my own experience changed everything I make.

When I started making mattresses, I used foam boxes. That’s what everyone does, right? Better edge support, solid feel, looks good in the showroom.

Then I started seeing mould under the mattresses. Not every one, but it happened. Even occasionally was too much for me.

Here’s what I realised—coils all the way to the edge mean air all the way to the edge. The top layers of a mattress are basically a big sponge. They absorb moisture from your body every night (you’re basically a wet sponge in the morning, that’s just biology). Having wire to the edge promotes the drying of the upper layers.

But when you wrap the entire spring unit in a foam box? You’ve just blocked airflow around the perimeter. The edges can’t breathe properly. Moisture gets trapped.

So I stopped using foam boxes. I switched to springs-to-edge with metal wire around the perimeter instead.

Guess what? Never saw mould again. Not once.

If your mattress has springs to the edge, you can put it on a completely flat piece of ply, on the ground, whatever—it won’t get mouldy because it ventilates out the sides. I was even telling people they could put it on solid bases, but then I realized that’s only true for spring-to-edge designs. Most mattresses with foam boxes need slatted bases because they need airflow from the bottom since the sides are blocked.

Problem 3: The feel changes when you actually sleep near the edge

This is the part that convinced me foam boxes were wrong for sleeping (even though they’re great for sitting).

I believe the edge of the mattress should feel consistent with the rest of the mattress for laying on. If someone rolls over in their sleep and ends up near the edge, I want them to have the same support, the same contouring, the same pressure relief they’d get in the middle.

With a 10cm foam box, the feel changes 10cm in from the side. You’re no longer sleeping on pocket springs that respond to your body weight. You’re sleeping on a foam wall. Different support, different feel, different everything.

Why bed-in-a-box mattresses structurally can’t have good edge support

Now here’s something most people don’t realise about bed-in-a-box mattresses—they can’t have proper edge support, and it’s not because the companies are cheap. It’s physics.

To get decent edge support, you need solid metal rods running around the perimeter of the top and bottom of the spring unit. These perimeter rods are what give a traditional mattress that firm, reinforced edge.

But anything rolled in a box won’t have those solid metal rods. Why? Because you can’t roll a mattress with rigid metal perimeter rods into a box. The metal frame makes it structurally impossible to compress and roll.

So bed-in-a-box companies have three options:

1. Use foam boxes (which have all the problems I just outlined)
2. Skip edge reinforcement entirely
3. Use all-foam mattresses (no springs at all)

This is why the side support is usually lacking in bed-in-a-box designs. It’s a structural limitation of the rolled-and-compressed format, not a cost-cutting measure. They literally can’t include the metal perimeter reinforcement that traditional spring mattresses use.

Many bed-in-a-box brands use memory foam or thick polyfoam layers instead of springs, and when you combine that with no perimeter support, you get what people call “roll-off.” The edges compress way down when you sit or sleep near them.

Understanding edge support construction in hybrid mattresses

When shopping for a hybrid mattress, you’ll encounter two main approaches to edge support: foam box perimeters and springs-to-edge construction. Edge support refers to how the mattress behaves when weight is applied near the perimeter, and perimeter shapes multiple facets of the sleeping experience.

Foam Box Construction: Many hybrid mattresses use a reinforced foam perimeter around the spring core. This creates a firmer sitting edge—that solid feeling when you sit on the side of the bed to put on your shoes.

Springs-to-Edge Construction: The pocket springs extend all the way to the mattress perimeter, with no foam box blocking airflow around the edges. This is what I use across all Cooper, Aurora, and Cloud models in the Ausbeds mattress range.

The trade-off: showroom feel vs. 8 hours of sleep

Look, I’m not going to pretend there’s no trade-off here. I look at things as pros and cons rather than wrongs or rights, and I’ve tried everything over the years.

Foam boxes are legitimately better for:

• Sitting on the edge of the bed (unless it’s low-density foam, which can sag)

• Showroom look and feel

• Making the whole mattress feel more stable and solid when you’re testing it in a store

Springs-to-edge are better for:

• Consistent feel all the way across when you’re actually sleeping

• Ventilation and mould prevention

• Maximizing your usable sleep surface

• Keeping the mattress breathable even on solid bases

• Better pressure relief near the edges because you’re still on springs, not foam

So the question becomes: are you optimising for 2 minutes of sitting per day, or 8 hours of sleeping?

As one customer noted in their review: “One downside is that the edge of the bed is not as firm as some other mattresses, so when you sit on the side of the bed it compresses down more than one that has a firmer border spring set.” That’s the honest trade-off. But the same customer was perfectly happy with the overall sleeping performance and pressure relief they got from the natural latex and micro springs.

What “better edge support” actually means for sleeping

Here’s what I think sturdy edge support should mean for sleeping (not sitting):

The edge should feel the same as the middle. If you’ve got pocket springs matched to your body weight in the centre, providing proper support and contouring, you should have that same support and contouring when you roll near the edge. That’s what relieves pressure points properly, all the way across the mattress.

That’s what springs-to-edge gives you. The pocket springs run all the way to the perimeter, so the support characteristics stay consistent across the entire sleeping surface. The wire around the edge provides structural integrity without creating a different feel.

Vs. a foam box where you’ve got one type of support (responsive springs) in the middle and a completely different type (dense foam wall) around the edges. When you’re near that edge, you’re not getting the same relieving pressure points that the centre provides.

Addressing mobility issues and getting in/out of Bed

If you have mobility concerns, arthritis, or difficulty getting in and out of bed, here’s what you need to know: the sitting edge softness is usually not a problem for actual mobility. Most people getting in and out of bed aren’t sitting right on the very edge—they’re sitting 4-6 inches in from the perimeter, where the spring support is identical to the rest of the mattress.

The mattress height (31cm) provides easier access than many lower-profile mattresses. You’re not sinking as far or having to climb up as high. The Slimline Bed Base adds another 15cm, bringing the total height to 46cm—approximately knee height for most adults, which is ideal for getting in and out of bed with minimal strain.

One customer with arthritis in her spine shared: “How many people can say they had the business owner deliver their mattress to accommodate their disability (I have arthritis in my spine), put the bed together and take their rubbish with them?”

If you have specific mobility needs, give me a call on 0414 364 722. I’ll work with you to make sure the mattress and base combination works for your situation.

The mattress edge support you don’t see in reviews

Mattress reviews focus on edge support you can measure in 30 seconds: sit on the edge, see if it collapses, rate it good or bad.

But they don’t test:

• Does the edge feel different than the middle when you’re actually laying down?

• How much sleep surface are you losing to foam boxes?

• Will moisture get trapped and cause problems in 2-3 years?

• Can you sleep comfortably all the way to the edge, or do you unconsciously avoid it?

• Do you get consistent pressure relief across the entire width?

These are the questions that actually matter for the 8 hours you’re using your mattress every night.

I’ve seen people spend thousands on latex mattresses with foam edge boxes, thinking they’re getting premium materials all the way through. But when you look at construction, you’ve got maybe 5cm of latex in the centre and dense polyfoam walls around the edges. The feel isn’t consistent, and the premium material you paid for doesn’t extend to where you might actually sleep.

My design choice (and why I won’t change my mind)

I use pocket springs all the way to the edge with metal wire reinforcement instead of foam boxes. Across the whole mattress range—Cooper with polyfoam layers, Aurora with natural latex and micro springs, Cloud with dual micro spring layers—they all use springs-to-edge construction.

The trade-off? Softer when you sit on the edge. Not as impressive in the showroom. Doesn’t pass the reviewer “sit test” as convincingly.

The benefit? I stopped seeing mould problems entirely. The mattress feels consistent all the way across when you’re sleeping. Better ventilation. And you get to actually use the full width of the mattress you paid for, with consistent pressure relief from edge to edge.

It won’t be easy to change my mind on this. I make them, I’ve tried everything, and when I saw mould under foam-box mattresses and then never saw it again after switching to springs-to-edge, that was pretty convincing evidence.

All just my opinion of course, but it’s based on over a decade of working with these materials every single day.

What this means for your next mattress

If you’re reading mattress reviews that rank “edge support” as a top priority, ask yourself:

1. Are they testing sitting or sleeping? Most reviews test sitting. You’ll be sleeping.

2. How much sleep surface are you losing? If there’s a foam box, you’re losing width. How much?

3. Can you sleep on it comfortably near the edges? Lay down near the edge in the store. Does it feel the same as the middle?

4. Is it a bed-in-a-box? If yes, it structurally can’t have metal perimeter rods, so the edge support will be limited by design. Many use memory foam or thick layers of mattress toppers to compensate, but that doesn’t solve the structural issue.

5. What materials are in the edges vs. the centre? If you’re paying for latex or premium foam in the middle, are you getting foam boxes around the perimeter instead?

Your mattress should be optimised for the 8 hours you’re sleeping on it, not the 30-second sit test in the showroom. Don’t let “firm edge support” marketing convince you to accept worse ventilation, a lost sleep surface, and an inconsistent feel just so the edges are impressive when you sit on them for 2 minutes a day.

I like to keep things simple, as this mattress stuff is complex enough: if you’re buying a mattress to sleep on, prioritise sleeping performance. If you’re buying a bench to sit on, that’s a different product entirely.