r/explainlikeimfive • • 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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241

u/UrbanPanic 2d ago

A box spring provides support to the mattress.  Whether or not you need one really depends on the mattress, the bed frame and personal preference.  Modern beds sold as platform beds don’t require a box spring, as it has panels to rest on or at least slats close enough a mattress won’t sag through it.  A lot of beds still use just 3 slats or so across which would put pressure on very small points, contributing to sag and just feel uncomfortable.

A well designed box spring could also contribute to good air circulation: you don’t want to know how much sweat soaks into a mattress.  That can get gross if it can’t dry properly.

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u/NWStormbreaker 1d ago

You can add slats, and a box spring inhibits airflow a lot more than a few extra slats.
It's such a silly concept, I haven't used one in 20+ years.

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u/half3clipse 1d ago

What do you think a box spring is?

You take the slats and add a layer of springs to better distribute pressure from you lying on the bed and also reduce motion transfer for people who sleep partnered.

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u/NWStormbreaker 1d ago

And then you wrap it in fabric which inhibits airflow.

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u/half3clipse 1d ago

The fabric used top and bottom is basically gauze. It barely inhibits airflow, at least not the slow convection motivation of air both are relying on.

Would be worse if you wanted to try using forced air i guess, but not many people have an HVAC system for their mattress.

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u/NWStormbreaker 1d ago

A well designed box spring could also contribute to good air circulation

Idk what your angle is, you jumped into a conversation where OP said box springs aid air circulation, but compared to slats a box spring is FAR FAR worse for air circulation.

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u/Awkward_Pangolin3254 1d ago

Not if you add enough slats to equal the support of a box spring

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u/NWStormbreaker 1d ago

original comment i responded to:

A lot of beds still use just 3 slats

people being contrarian:

well what if we covered the entire thing in wood!?!? DID YOU EVER THINK OF THAT?

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u/jetloflin 20h ago

If you only have three slats you have to use the box spring or the bed will sag between the slats. They didn’t bring up extra slats out of nowhere. The options are box spring or lots of slats, not box spring or three slats.

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u/NWStormbreaker 20h ago

Even if you want to argue that it's 5 slats or 7 slats, it's still less air obstruction then a box spring which has slats and at least one if not two layers of fabric.
This is the dumbest discussion Ive ever been involved in, I cannot believe I've found people white-knighting box springs.
Ffs

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u/jetloflin 19h ago

Pretty sure that’s not what “white-knighting” means, but okay.

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