Space ceiling fixtures 6 to 8 feet apart along the run, and set the first one about 3 feet in from the end wall so the corridor does not fall dark at the ends. A 20-foot hallway therefore takes three fixtures. If you are using wall sconces instead, place them every 8 to 10 feet, alternating sides on a wide corridor. Even spacing matters more than raw output here: several modest fixtures read far better than one bright one casting a single pool of light.
