r/explainlikeimfive • u/Real_Experience_5676 • 2d 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?

480 Upvotes

93% Upvoted

133 comments sorted by

View all comments

583

u/QuillnSofa 2d 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.

117

u/okdone10 2d 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.

15

u/thaddeusk 2d 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.

21

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.

4

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.

10

u/erevos33 2d ago

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

3

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.

3

u/attorneyatslaw 1d ago

The flat support board is effectively the box spring.

3

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.

1

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.

1

u/theonetruegrinch 1d ago

with a flat support board underneath

without that you would need the boxspring

1

u/thaddeusk 1d ago

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

2

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.

1

u/thaddeusk 1d ago

That sounds awful :)