When are stub stacks required in a building?

Stub stacks are required in a building when a vertical drainage system needs to be extended in the future but is not yet connected to the main sewer line. They are typically used in multi-story buildings to facilitate future Plumbing expansions, ensuring compliance with local building codes. Stub stacks help prevent the need for extensive renovations later by providing a designated space for future connections. Additionally, they can be useful for accommodating changes in building usage or layout.