I'm always working on sets of symbols for my dungeon floor-plans, I've got sheets full of symbols for different genres, styles and scales.
Here for my gentle readers and fellow DMs out there is a comprehensive legend of dungeon doors.
THE OCD Dungeon Doors Legend.
Putting more info on the map is something I strive to do, hopefully there might be some utility to this table. I know it's not the last one I'll ever produce and this set will likely only look good for grids ruled between 3 to the inch and 6 to the inch as far as I currently tell. The legend certainly looks better if you open it in it's own window or download it.