Although a foundation isn’t required, 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 firm, flat and thick slats. No matter which support system you choose, the slats should be no wider than 5.5 inches apart as that could cause sagging and could potentially void your warranty.