The intersection of toilet, bathing, and shower floors with walls must have a vertical base that extends a minimum of how many inches up the wall?

The correct answer is based on building codes and standards that dictate proper water containment and sanitation in bathrooms. Having a vertical base extending a minimum of 4 inches up the wall helps to prevent water from splashing onto the walls and causing damage, mold, or deterioration over time. This 4-inch height is a standard that strikes a balance between effective protection against water exposure and practical construction requirements. It creates a barrier that is high enough to manage typical water splashes and spills without being excessively high, which could complicate design or increase costs unnecessarily. This measure is essential for maintaining hygiene and safety in commercial buildings, ensuring they meet health standards and provide a durable environment.