What additional plumbing fixture must be roughed in for men's and women's toilet facilities?

The additional plumbing fixture that must be roughed in for both men's and women's toilet facilities is a floor drain. In restroom designs, particularly in commercial settings, floor drains are essential for managing water that may accumulate on the floor. This helps in preventing flooding and maintaining hygiene by allowing for efficient drainage of any spills, leaks, or cleaning activities.

In men's facilities, while urinals are also common and essential, the question pertains to both men's and women's facilities, where floor drains are a universal requirement. Lavatories are important, but they primarily serve for handwashing rather than drainage. A sluice sink is typically used in clinical or laboratory settings, not standard restroom facilities. Therefore, having a floor drain ensures that both gender-specific facilities comply with appropriate plumbing codes and hygiene standards.