The information technology system (ITS) designer should design conduits entering a building from below grade point to extend ________ above finished floor (AFF).

51 mm (2 in) AFF is insufficient to provide reliable protection against water infiltration and does not meet the minimum height specified in the standard.

100 mm (4 inches) above finished floor is the standard design specification for conduits entering a building from below grade, as required by BICSI OSP design guidelines. This height provides adequate protection against water intrusion and floor-level flooding while remaining practical for cable management and maintaining acceptable bend radius at the conduit exit point.

152 mm (6 in) AFF exceeds the standard specification, creating unnecessarily long exposed conduit stubs and potential cable management complications.

203 mm (8 in) AFF significantly exceeds the design requirement and introduces avoidable conduit protrusion and installation complexity.

254 mm (10 in) AFF is well above the standard specification and would cause excessive conduit exposure, complicating cable routing and termination.