Final answer:
Shaft enclosures must have a fire-resistance rating of not less than 2 hours when connecting four stories or more, to prevent fire spread in buildings.
Step-by-step explanation:
The original question pertains to the construction standards related to shaft enclosures in buildings, specifically about their fire-resistance rating requirements. According to the International Building Code (IBC) and similar regulations, shaft enclosures must have a fire-resistance rating of not less than 2 hours when connecting four stories or more. This means that any vertical opening between floors, such as stairways, elevator shafts, ductwork, etc., must be enclosed with materials that can resist the passage of fire for at least two hours, providing safety to occupants and preventing fire and smoke from spreading between floors in high-rise constructions.