How do I stop a wooden door from swelling?

First mark the insde of the frame with chalk the close the door. You should find chalk on the door where it touches the frame.
Remove the door from and plane down the parts marked with chalk.
Ideally you should have just enough space between the door and frame to slip in a penny/cent. That should give enough space for expansion of the door in wet or humid conditions.

Big Softy
July 2006