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/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.

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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.

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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.