A support system for your mattress is highly recommended. The best option is to use the Helix Foundation to provide proper support and avoid sagging. If you prefer to use a different support system, we recommend using a bunkie board with a box spring or any support system with a firm, flat and thick slats. No matter which support system you choose, the slats should be no wider than five inches apart as that could cause sagging and could potentially void your warranty. Traditional boxsprings typically do not provide enough support for Helix Mattresses.
If you have an existing foundation that has support beams with gaps wider than 4-5" apart, putting down a piece of plywood that fits the frame can do just the trick. This piece of wood is sometimes called a "bunkie board".