You can assign rooms to dwarves manually or automatically. For example, if you give a dwarf two bedrooms, the dwarf will prefer to use the room with the higher quality bed, regardless of the comparative quality values of each room. If you assign two or more rooms of the same type to a dwarf, the value of the piece of furniture that defines the room determines which room the dwarf will prefer to use. Also, most nobles require an assignment to a room. When dwarves have their own room, happy thoughts occur when they sleep in it (alternatively, unhappy thoughts can occur when they do not have their own room to sleep in). Rooms can be assigned to specific dwarves. Rooms can not span z-levels when you define a room it can only be on a single level. For instance, a communal dining room is defined from one table - just give the room a large enough radius to cover the whole space. In general, you only need to define a room from one object in the room. Rooms do not have to be blocked off on all sides, and can even overlap, but for various reasons you will usually want to avoid overlapping rooms and give them proper boundaries.

If you want to have a door dividing a single, defined room into multiple areas without blocking the room's zone, you can set the door to 'internal' in the door's q menu. If you first build the door to create a closed space, then the game will define the room so you won't need to resize it unless it is very big. The room's radius extends outward in a rectangle, but will stop when it hits walls or external doors. Then you must select the completed item in question with the q command and choose to create a room.

To create a room, you must first have built something capable of supporting a room from the build menu, such as a table or bed.

Dwarf fortress rooms