More in Bathroom
Before starting, make sure the power is off at the electrical panel. Remove the cover from the switch. Use an electrician's wire tester to double check that the circuit is safe to touch. Use a screwdriver to remove the switch toggle.
Once the switch is removed, use a wire nut to mark and keep track of the wires.
Measure to install a new double work box. Make marks on the wall, and check with a level.
Using a utility knife cut the drywall hole for the new double box.
With the wires for the light switch and exhaust fan separated, pull the wires through the new double work box and screw them into place.
Wire the new switch and the new timer attaching the hot, neutral and ground wires for each following the manufacturer's specifications.
Adjust the toggle switch for the light and the shaft for the timer accordingly to make them line up with the switch cover. Then screw on the switch cover and attach the timer plate and knob. Turn on the power and test your work.