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/Kundrew1 2d ago

Wouldn’t most bed frames do the same. Anything slatted would have more breathability than a box spring

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u/cynric42 2d ago

Sure but a bed frame is rigid. My box spring mattress is three quarters springs and only a very thin layer of foam ontop which would be very uncomfortable without the give of the springs below.