Sean, I think the door will catch most of the light - IF you run some sort of insulating material (foam, rubber, etc) around the door frame. That's what I did on mine..plus I added heavy dark cloth at the bottom. Been thinking of just using the black-out cloth from Calument (Porter's Cameras may have this, too!) and hang it over the doorway with a curtin rod. But then my dark room has only one door, and is only 8x10. With the monster enlarger, you need a monster dark room.