"There are several sites that have a floor joist span chart. One such site is: http://www.countrylumber.net/TechRef/floorjoistspans.htmAnother is: http://www.trulinetruss.com/html/floor_span_tables_-_ijoist.htmI am not in construction so couldn't explain why they are needed. However, if you are looking for one then you must really need it. They must be important so pay attention! Have fun with
. your project!"
