Like everything else in this game ( and the real world...) it varies.
Open the map editor and randomly place some buildings on a flat map. Now pass the cursor over the top of each hex they are in and the info bar at the top of the screen will tell you
The first number is the hex height
The second is the height of the object
The third is the total of the hex height and the object height ( could be a building...could be a tree )
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