Can I use tongue and groove boards for a vaulted ceiling?

If your ceiling is a cathedral-type or vaulted ceiling, you can still use tongue and groove boards on it. The application will be the same, except that you have to match the angle of the ceiling, and cut the wood accordingly. Use an angle finder, in order to be more accurate when measuring the angle. To give you an idea, a regular flat ceiling will have an angle of 90 degrees, so you don’t have to angle-cut the wood. On a vaulted ceiling however, the angle will be more, depending on how steep it is. Work on each tongue and groove board individually, cutting each with the angle measurements that you take for each section.