The subfloor is the foundation of any indoor basketball court. It provides stability, supports the hardwood surface, and contributes to shock absorption.

There are several types of subfloors, including plywood, OSB (oriented strand board), and concrete. Plywood is the most common choice due to its strength, durability, and ability to flex slightly under load. It also helps distribute weight evenly, reducing the risk of floor damage. The subfloor must be properly installed and leveled to ensure a smooth, even surface for the hardwood to be laid on.