You might be suprised to learn that a memory foam mattress contains a layer or layers of conventional foam underneath the memory foam layers. This is because memory foam is too soft to use for the complete mattress, something is needed to support the memory foam and distribute the weight or else the user would bottom out on the hard platform support.

Conventional foam is used for the base of a memory foam mattress and in some cases it is used for the eggcrate layer on top of the base which allows for ventilation of air between the layers. It is best if these base layers have an IFD value of somewhere between 40 – 55 lbs. This is what is needed to ensure your memory foam mattress does not sag over time. These base layers are critical for the best performance of the visco elastic foam layers on top and are part of what makes these beds so unique – no metal springs at all.

Conventional foam is familiar to most people. It is the type of foam you might find inside a sofa cushion. It is spongy and tends to push back when you push into it whereas the top visco elastic memory foam layers conform to your shape without pushing back. The tendency of the conventional foam base layers to push back is exactly what you want for  the base. Once the top visco layers conform to your shape, the pressure on the base layers will distribute the weight over a wide area whereas a base made out of metal springs will not distribute the weight, rather each spring will depress and push back individually at the greatest pressure points. 

These base layers are essential components to a memory foam mattress. Simply putting a memory foam layer on top of a conventional mattress (like a memory foam topper on top of a spring mattress) will in no way produce the same effects as a proper memory foam mattress with a platform support frame.

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