Wood ceilings are created in a similar way to wood floors, with tongue-and-groove boards that connect along their edges to form the surface. If your ceiling is a cathedral or vaulted ceiling, meaning it angles up to a peak, it's still generally the same process, except you have to length-cut the long edges of the boards at the top and bottom of each section of the ceiling to match the angles there. An angle finder (a small carpenter's square, hinged in the middle) will help find the correct angle.
Things You'll Need
Tongue-and-groove ceiling planks
Small trim nail gun
Locate and mark each of the ceiling joists with an studfinder. Mark out lines up the whole ceiling on both sides of the peak, using a level and pencil. (Note: If the ceiling as exposed joists, you can skip this step.)
Measure the length of the ceiling where it meets the wall on one side. Mark that measurement on a ceiling plank. Cut it to size on your miter saw.
Use your angle-finder to determine the angle between the edge of the ceiling and the wall. On a regular flat ceiling, it will be a 90 degree angle, but on a vaulted ceiling it will be something more than that, depending on how steep it is.
Tilt the blade of your table saw to the angle you found on the ceiling. Run the cut piece of ceiling plank through the table saw, trimming from the grooved side to make the edge of the board match the angle.
Hold the plank to the ceiling, with the angled edge facing the wall. Shoot trim nails through the surface of the board to install it, shooting two nails at each joist.
Cut the next plank to the right length. Don't run it through the table saw, but leave the long tongue and groove edges intact. Press the grooved side of the board over the tongue side of the first board. Secure it by shooting a trim nail just above the tongue at each joist.
Repeat the process to install each board, working you way up the ceiling. Length-cut the top boards (as the peak of the ceiling) as you did the first one, first taking the angle of the peak and then cutting from the tongue side instead of the grooved side of the board.
Repeat the whole process for the other side of the ceiling.