Different types of mattress foundations
What is a Box Spring
While the term "box spring" is generally used to describe any type of mattress foundation, it is technically a very specific type of foundation, so it can sometimes be confusing when looking for a "box spring". There are several different types of box springs but here is a brief description of the most common construction methods.
A true box spring, also called a "coil on coil" or coil spring design, literally uses stiff metal coiled springs to support the mattress. This design, which allows the mattress to flex as weight is applied, makes the mattress feel softer and bounce more. Unfortunately, most people do not want their bed to be bouncy and the flexibility of a coil spring box can have a negative affect on the durability of your mattress because most modern mattresses are designed to sit on a solid foundation. In fact, the coil spring design has become very uncommon in modern bedding. You will see that many of the links within this site are for "box springs" but we do not actually sell any of the coil spring design boxes. All of our "box spring" foundations are built to maximize the durability and comfort of your mattress.
This is the most common type of box spring for modern mattresses because it offers the most support and minimizes motion transfer across the mattress. They can be constructed of metal wire supports but are most often made of wooden slats. On top of the slats is a layer of fiberboard to prevent the mattress from sagging down into the box. These boxes are light weight, durable, and exactly what most mattresses are engineered to sit on.
Knock Down Foundation
A knock down foundation, often using the acronym KD, is one that arrives in several pieces that must be assembled into a box foundation. When they are disassembled they can be shipped for a low cost and easily carried through tight staircases into the desired room before assembly begins. Once assembled, the best KD assemblies will look and feel just like a normal zero-deflection foundation.
A semi-flex grid combines a wooden base with a tight web of low guage metal wire on top. This design allows less flex and bounce than a coil spring box and is much lighter weight, but it does bend more than a solid foundation, allowing more motion to be transferred through the mattress when a partner rolls over or exits the bed. A semi-flex grid can be good with thick memory foam mattresses but is much more expensive than a solid wood box spring and should not be used with thinner mattresses.