“Do I have to replace my box spring when I replace my mattress?”
While all is fair in love and war when it comes to bedding and sleep, it's not a bad idea to replace both at the same time. Some mattress manufacturers require you to buy a box spring along with a mattress to qualify for a warranty anyway so it makes sense to do so if you want the warranty.
What Does a Box Spring Do Anyway?
Box springs lie underneath a mattress to give a layer of protection between the mattress and bed frame. They absorb body weight and provide more support to the mattress.
Also called bed bases, most don't actually include springs anymore but instead contain a kind of steel grid to evenly distribute weight from above. According to the blog Sleeping Like a Log, only the most high-end manufacturers still use spring coils.
Some people don't even use box springs at all. Platform beds pretty much eliminate the need for them.
Why Should I Replace the Springs?
Box springs wear out just like mattresses. Older ones can develop sagging, which means it's time find a replacement. But if yours is fairly new – you've had it for less than three years – and it's the only mattress that you're dissatisfied with, it's probably OK to keep it.
However, also consider the new mattress when you're buying a box spring. The “give” factor is important when matching them to a mattress. Most mattresses come with the springs and are featured with them in showrooms. The only difference is that you can buy a thicker or thinner bed base to meet your height requirements for your bed.
If you're going for a spring-free memory foam mattress, don't buy a box spring. These mattresses need firmer surfaces underneath them, like a foundation, which is a solid piece without coils, springs or grids, because they form to fit your body. Any “give” underneath defeats their purpose.
Bed bases must match the mattress size. What works for a twin won't work on a queen. Mattresses need to be evenly supported all the way around.
Older homes may not accommodate a queen-size bed so measure your hallways and stairways to see if a split-queen box spring set is needed. For king sizes, the split-box is the only offering.
Be careful to differentiate between a standard king size and a California king – they aren't the same. King-size mattresses are four inches wider than a California king, and California kings are five inches longer than regular kings.
Also consider the height that a bed base will add to your bed. Standard springs are about nine inches high, which may be too high for elderly people and people with disabilities. Many stores sell low-profile bases, which are about five inches thick. Since thickness has nothing to do with quality, focus on mattress thickness for your comfort factor.