Which term best describes the required spacing of a higher building's outermost line from the property line?

The correct term for the required spacing of a higher building's outermost line from the property line is setback regulation. Setback regulations are a critical aspect of zoning laws that dictate how far structures must be set back from property lines. These regulations are established to ensure adequate space for light, air, and privacy, as well as to maintain the character of a neighborhood and reduce overcrowding.

In the context of zoning and building codes, setbacks can vary depending on the type of building, its height, the zoning classification of the area, and other factors. These regulations guide urban planning and contribute to orderly development. Given this context, the concept of setback is fundamental in determining how buildings interact with their surroundings, including their relationship with property lines and adjacent structures.