Crossfield class decks
The decks of a  Federation starship. (, et al.)

 Deck 1 
 Bridge (, et al.)
 Captain's ready room, replaced by science lab (, et al.)
 Deck 2
 Deck 3
 Two-level science lab: Logic sciences, replaced by Paul Stamets' spore drive lab ()
 Guest quarters ()
 Deck 4
 Sickbay ()
 Transporter room ()
 Loading bay ()
 Deck 5
 Mess ()
 Deck 6
 Deck 7
 Deck 8
 Deck 9
 Deck 10
 Deck 11
 Deck 12
 Utility closet, replaced by Logic sciences lab ()
 Deck 13
 Deck 14
 Deck 15 ()
Deck 16
Deck 17 ()
Deck 18

Background
To account for set changes between season one and two,  art director Jody Clement has suggested that the mess hall seen during season one was on deck 2, and the mess hall from season two was on deck 5. 

The Art of Star Trek: Discovery (p. 28) featured a production diagram depicting what deck each of the Discoverys frequently used rooms was intended to be located on.