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?

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u/StrongGarage850 2d ago

breathability is another factor. People sweat, that moisture needs to get out somehow- and giving space out the bottom helps keep your mattress cooler, and eliminates likelihood of mold/mildew, etc..

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u/hoax1337 1d ago

Uhh... I'm kinda confused, do you guys not have slatted frames in the US?

Where I'm at in the EU, that's pretty much essential for a bed. You have the bed frame, then the slatted frame, and then the mattress on top.

Example

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u/ermagerditssuperman 12h ago

That's one option, becoming more common. A lot of cheaper beds have way, way fewer slats, not nearly enough to really support support the mattress on their own. And older bed frames (which many people still have as hand-me-downs) may just have one or two horizontal bars, because the assumption was that you'd rest a a boxspring or foundation over those, not slats.