Agree with what others have said about practibility.
Who said doors are flammable? Just because it's made of wood doesn't mean it's immediately flammable, especially from any old piss-mote of flame and a paltry 1d10. Without kindling, or an already roaring campfire, that solid door is not going to burn.
Yeah, it would probably actually be quicker to set a mundane fire beside the door, light the kindling with a firebolt, then watch it burn (from a safe distance).