A good night's sleep can set the tone for the next day -- whether you will be rested and energized and ready for whatever might happen, or whether you will be tired and dragging. Setting up your bed properly helps to guarantee better sleep and better mornings. But adding a mattress to an existing mattress is not recommended.
The two main types of mattresses used in homes are traditional and latex. Traditional mattresses contain a core of metal springs or coils. This core is surrounded by layers of padding made from wool, linen or cotton. Latex mattresses are formed from vulcanized latex, which contains thousands of bubbles that make it soft and supportive. The latex is surrounded in cotton padding.
Traditional mattresses need the support of a box spring beneath them. Another mattress is not firm enough to prevent the top one from sagging over time, and it is not stable enough to use on a bed frame. What's more, laying a traditional mattress on top of another puts them both at risk for moisture buildup, which can lead to mold growth, destroying them. A latex mattress does not require any sort of under support from either a foundation or another mattress. It can lay flat against bed frame slats or a platform bed base on its own.
If you have a traditional mattress and do not have a box spring, you are best off laying slats of wood across a bed frame and putting the mattress on top of them. This provides even support along the underside of the mattress and allows for air circulation, which helps prevent mold growth. If you have to use a second mattress beneath it, run a fan and a dehumidifier in the room to reduce moisture levels.
If you do pile mattresses up, make sure they are the same size. This gives you the most stable sleeping surface possible. If you are considering layering mattresses to save the cost of buying a new box spring, just reuse your old foundation with the new mattresses. If you are trying to raise the height of your bed, extensions for your bed frame's legs are a better choice.