An adapter for a cable hanger includes: a housing having a floor, a vertical wall extending generally perpendicularly from the floor, and side walls extending generally perpendicularly from the floor and vertical wall, each of the side walls including a finger extending generally parallel to the floor, the fingers including first engagement features, the vertical wall including a mounting hole; and a plunger having a main panel and second engagement features on opposite sides of the main panel, the second engagement features configured to engage the first engagement features to restrict relative movement of the plunger relative to the housing.