Exterior grade Medium Density Fiberboard (MDF) is a type of MDF that’s designed to withstand outdoor elements like moisture, humidity, and temperature changes. It’s made with high-quality wood fibers, water-resistant resins, and additives that are combined under high heat and pressure. Exterior grade MDF is more durable than regular MDF because it’s denser and stronger, and it’s also resistant to moisture, termites, and fungus. It’s often colored pink to differentiate it from other grades.