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 inches apart as that could cause sagging and could potentially void your warranty.