spancalc_google. Span Calculator for Wood Joists and Rafters available for the iPhone. spancalc. Span Calculator for Wood Joists and Rafters also available for the Android OS. read more
The maximum spans in the table above are for the horizontal distance the rafter can span (NOT the diagonal distance or actual length of the rafter). So if your house is 26 feet wide and the roof ridge beam is centered on the house, you will need a rafter that can span 13 feet. Let's use this example and find a size of rafter that will work. read more
For example, in the rafter span table below, the highlighted cell (in the 40# Live Load table), indicates that 2" x 8" Southern Yellow Pine joists, that have a grade of #2, that are spaced 24" apart, can have a maximum span of 10 feet - 3 inches (10-3) if designing for a live load of 40 lbs/ft 2. read more