Ceiling Joist Span | What size do I need?

This ceiling joist span table is based on the 2012 IRC for uninhabitable attics with limited storage. It covers #2 common lumber species and sizes at 20 pounds per square foot load. Although 2 x 4’s are included in the official table, they are not listed because it is never advised to use them. 2 x 12’s are not listed because you can span pretty much whatever you want. Just know that this table requires a bearing stiffener. I prefer to call it a pig trough. This is a 2 x 4 nailed flat down against the top of the joist perpendicular and right along the center of the span, and  2 x 6 or more nailed into it and turned like a joist, or blocking (bridging) or similar “x” bracing.