Although 2 x 4 s are included in the official table they are not listed because it is never advised to use them.
Ceiling joist support beam span.
View joist rafter tables.
Listed are 46 tables based on common loading conditions for floor joists ceiling joists and rafters.
This ceiling joist span table is based on the 2012 irc for uninhabitable attics with limited storage.
For example the highlighted cell below shows that a 2 x 6 southern yellow pine joist with a grade of 2 and spaced 24 apart can have a maximum span of 10 feet 0 inches 10 0 if you are designing your structure to support a plaster ceiling.
This will support a room ceiling that is 10 feet long on one side as in 10 foot by 15 foot or 10 foot by 17 foot rooms which is a standard dimension for many rooms in residential construction.
Simplified maximum span tables for selected visual and mechanical grades of southern pine lumber in sizes 2 4 thru 2 12.
2 x 12 s are not listed because you can span pretty much whatever you want.
It covers 2 common lumber species and sizes at 20 pounds per square foot load.
Large room joist spacing.
Sixteen inch oc spacing of ceiling joists made from 2 southern pine allows for a maximum 13 inch span length.