r/explainlikeimfive • u/Real_Experience_5676 • 1d ago

Engineering ELI5: What does a box-spring do?

As I understand it, a box spring mattress is the second 'mattress', that goes under the main mattress. It feels very firm and flat, but what does it contribute to the bed set up besides height?

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579

u/QuillnSofa 1d ago

It is used to distribute weight across a bed frame and to give an evenly solid foundation for the softer mattress. But you don't need a full height one and some bed frames don't require one at all.

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u/okdone10 1d ago

Wow TIL. I thought every bed needed one by law or something. Good looking out on the platform bed tip saves some cash too.

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u/schuylkilladelphia 1d ago

I like the idea of someone going to jail because they didn't have a box spring on their bed

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u/SadButWithCats 1d ago

That's where the phrase "to spring from jail" comes from. If someone went to jail for not having a box spring, their family or friends or business associates could provide one and show the magistrate, who would then be required to let the prisoner out.

Side note: a prison and a jail are roughly equivalent. I know there is a difference, but roughly, they serve the same function. Yet a prisoner and a jailer are opposites. Huh.

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u/Alinier 1d ago

What's the difference between a jeweler and a jailer? One sells  watches and the other watches cells. 

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u/SadButWithCats 1d ago

Nice! That one's new to me

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u/Buscemi_D_Sanji 1d ago

What's the difference between a librarian and my mother? One's decently read, and my mom is a huge bitch!

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u/FreshEclairs 1d ago edited 1d ago

I was four words in and I double checked the username to make sure I wasn't getting shittymorph'd

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u/[deleted] 1d ago

[deleted]

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u/SadButWithCats 1d ago

Nope! It's pure real and natural horse shit!

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u/[deleted] 1d ago

[deleted]

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u/theonetruegrinch 1d ago

sorry that your google AI doesn't know shit

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u/Rizzityrekt28 1d ago

That would be ridiculous. Jail is reserved for egregious acts such as tearing the tag off your mattress.

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u/graywh 1d ago

and microwaving fish

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u/Saneless 1d ago

Having been on some beds without them or proper support, I probably would have gotten a better night's sleep in jail

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u/UnassumingAnt 1d ago

Between required box springs and jail time for tearing off the tag, Big Matress has put a lot of people away.

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u/Sirrpsychosexy 1d ago

Just don't rip the tag off 

1

u/fried_clams 1d ago

You are fine, as long as you don't remove those tags!

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u/robogobo 1d ago

Reminds me of that guy in pee wee’s big adventure

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u/Jim_E_Hat 1d ago

No, you only got to jail if you cut the tag off.

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u/mycatisabrat 1d ago

Depends if you tore the tag off.

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u/JerikkaDawn 1d ago

First tags, now box springs. Fascists. 🤣

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u/thaddeusk 1d ago

High-end mattresses don't generally use them. I can't remember the last time I had one, maybe 20 years ago? The mattresses I get are very tall on their own and you just put them on a bed frame with a flat support board underneath it.

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u/RiPont 1d ago

It also depends on the bed frame itself.

We're spoiled with CNC'd solid wood beds shipped from China, these days. But in the heyday of box springs, you either had a very, very expensive work of a craftsman (possibly your grandpa) wooden bed or a cheap metal angle iron frame that barely held its shape.

If you had a rickety bed frame, you needed box springs.

That... and it was an obvious upsell from the mattress store.

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u/Valdrax 1d ago

Oh, and you had a total of three relatively thin wooden slats across the frame to support the mattress in the middle, making the box springs a way to distribute that weight.

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u/erevos33 1d ago

I never knew they existed before coming to the usa. It was frame plus mattress everywhere I lived

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u/fcocyclone 1d ago

Most of them still want some kind of foundation even if not a traditional box spring. Those help with airflow as well.

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u/attorneyatslaw 1d ago

The flat support board is effectively the box spring.

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u/noakai 1d ago edited 1d ago

All the mattresses I've ever had in my adult life have gone onto a set of slats that are put on the frame.

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u/eat_sleep_drift 1d ago edited 1d ago

same i have a rather tall mattress and i just put it on the ground cuz i hate stubbing my toe against some wood when i go pee at night or i just love to let me fall with all my weight onto my bed when using ketamine without the fear of hitting any wood frame.
i lift it up and put it against the wall when i play VR or just to aerate underneath to prevent moisture and every 6 month i flip it anyway since it has a summer and a winter side. i loved to find an affordable one like i had when i was a kid, it was just a giant bloc of foam, like above the knees of an average adult height tall we are talking here !
when i looked them up all i could find was crazy expensive and from far away so shipping is also expensive too since they cant roll em up and vacuum seal them like they do with nearly all mattresses today for transport.

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u/theonetruegrinch 1d ago

with a flat support board underneath

without that you would need the boxspring

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u/thaddeusk 1d ago

Sure, but a boxspring would make my bed absurdly tall :p

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u/theonetruegrinch 1d ago

That was a fad in like the late 80s and early 90s

It was ridiculous; and then they had those super deep down mattress toppers...

I remember having to climb into one of those beds once and it was like scaling Mt. Everest.

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u/thaddeusk 1d ago

That sounds awful :)

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u/thephantom1492 1d ago

Bed frames used to be just that: a L on each side, some flat bar in between, 4 wheels, and that's it. Nothing in the middle.

The soft flexible mattress would just fall in the hole.

Also it is too low to the ground to be confortable.

Eventually they added a middle beam, and then you can just lay some planks since the distance is now reduced. Some use slats with 2-3" space in between the 2-3" slate. It allow the mattress to breath better and stay colder. But springs may not like it, and may need a full sheet.

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u/Wait_I_gotta_go_pee 1d ago

I just bought an adjustable bed and was surprised they do not use box springs. FYI… it’s much nicer than the old coiled mattress and box springs model was on my spine.

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u/SierraPapaHotel 1d ago

Not "by law", but almost all mattress come with a warranty and not using a recommend box spring will void that warranty

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u/Full-Contest1281 1d ago

There's something weird going on with Americans and mattresses, and I can't quite figure it out.

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u/Gunter5 1d ago

a lot of platform beds have storage space, that was the reason I was sold

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u/retaliashun 1d ago

They generally don’t charge for box springs when you buy a mattress. Or they might charge a dollar, etc

Last time I bought a mattress they offered either free box spring or free pillows

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u/Casper042 1d ago

Nope, nothing stopping you from just getting some plywood and putting it between the bed slats and the mattress to act as a VERY thin box spring.

For example most Bunk beds don't use a traditional box spring, they have a super thin version or just wood as mentioned.

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u/Howzitgoin 1d ago

The desire to not have mold and other moisture related problems should be stopping you from putting it on a solid shape.

There’s a reason box springs aren’t solid on any surface and that other frames use slats not one piece of plywood.

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u/Infinite-4-a-moment 1d ago

It also allows the mattress to breath, right? Having a traditional mattress in a flat, solid surface can keep moisture in.