When routing backbone cabling vertically, which location should be avoided?

• A. Ceiling voids
• B. Elevator shafts
• C. Stairwells
• D. Exterior walls

Answer: (B)

Vertical backbone cabling should run in protected, dedicated vertical spaces such as building risers or shafts designed for cabling. Elevator shafts are not suitable because they are dynamic environments with moving parts and frequent vibration, which can damage cables. Access to elevator shafts is restricted and not suited for routine cable installation and maintenance, and fire/safety considerations in these spaces are harder to manage. In short, the risks of physical damage, maintenance difficulty, and safety/compliance concerns make elevator shafts the location to avoid.

Ceiling voids, stairwells, and exterior walls each have their own challenges, but they are generally considered more workable routes when properly rated, protected, and firestopped. Ceiling voids can be used if kept free of hazards and properly shielded; stairwells may be used with careful routing to avoid dust and moisture; exterior walls expose cables to weather and temperature changes, which is why they’re typically avoided for critical backbone runs unless specifically rated and protected.