Locate the two joists nearest the new fixture location using a stud finder or tap on the wallboard until the sound indicates the general location of the joists. Use a drill and an eighth inch bit to drill through the plaster where the joists are estimated to be. Drill holes at 1" intervals until you meet resistance and wood from the joist is ejected. Mark the location of each joist with a pencil mark.
An easier alternative to repairing the damage is to use one coat of mud and then cover the rough repair with a preformed medallion. A plastic medallion can be installed using caulk to stick it to the surface or using the fixture cover plate to hold it in place. You can also get a plaster medallion, these should be installed using setting joint compound or plaster of Paris to attach it to the ceiling. Keep pressure on the medallion to hold it in place until the mud has set.
If the wiring is correct turn the power off and install the device in the outlet box. Carefully fold the wires to fit into the box and push the device with your palm until it sits flat and is aligned with the mounting holes. Drive the mounting strap screws and shift the replacement of the device left or right as necessary to square it in the box as you tighten them down. Install the cover plate, turn the circuit back on and test the device again.
Hold the fixture up to splice the wires. Usually the first wire splice will aid in supporting a small light, but have a helper assist with supporting a large, heavy fixture while making the connections. While still supporting the weight, attach the base to the mounting strap with the screws and tighten the base to the ceiling.
If no access is available from above you can work through the outlet hole to install a specially made, adjustable fan support. Using this method it can be difficult to secure the support and set the outlet box at the proper, finished level. An easier way to be sure of proper placement is to use the method here to install a wood frame. The ceiling must be cut to do this, after which the damage can be patched and/or covered with a decorative medallion.
At the floor the wallboard is cut to allow for boring a hole in the soleplate. Then the run can be made from an upper floor to the room below or vice versa.
To install a fixture using a coupler, thread the rod into the center hole in the mounting strap and set the rod depth so the fixture base will fit snuggly against the ceiling when it’s installed. Measure the depth of the cover plate to estimate placement, precision isn’t necessary here, small adjustments can be made to the position after the installation by turning the coupler nut. Be sure all the wires are stripped for splicing, hold the fixture up and feed them through the threaded rod into the outlet box.
A rigid, flat metal tape used to run electrical cable through a finished wall or ceiling. The rigid nature of the tape makes it possible to push it past most obstructions in the wall cavity by turning the reel to either side. See Run New Wiring for more about fishing cable.