Remove all existing light fixtures from the existing ceiling.
Measure the length and width of the space. Take the measurements along when purchasing the tongue and groove ceiling. Purchase slightly more than the measurements dictate to allow for any mistakes.
Prime and paint the tongue and groove ceiling prior to the installation.
Locate the joists using a stud finder.
Use a hammer and nail to locate the center of the joists.
Snap a chalk line the length of the joist, marking the center of the joist. Continue this process until all the joists are marked.
Place the first board on the ceiling with the tongue against the wall perpendicular to the floor joists. Have an assistant measure the distance from the groove side of the board to the opposite wall at the top and the bottom. Adjust the board until the two measurements are the same.
Nail the first board into place by nailing through the tongue and into the joists, and through the face of the board and into the joists.
Install the second board by sliding the tongue of the second board into the groove of the first board, making sure the two sections are tight together. Continue this process until the final board has been installed. Nail the last board to the joists in the same way as the first board.
Countersink the nails using a nail set. Fill the holes with putty and touch up with paint.
Add decorative trim around the perimeter of the room for a finished look that also hides any gaps caused by expansion and contractions.