Floor Joist Are What Size In Residential Construction. Below is a table giving the minimum size floor joists needed for 16 and 24 on center oc spacing when using 2 lumber with 10 pounds per square foot of dead load and 40 pounds of live load. You can always use bigger lumber closer spacing or a smaller span.
If your old joists do not meet the requirements set by the table they are either supported somewhere from underneath or they were installed pre regulations November 1985. Tracks shall be not less than 33 mils 084 mm thick except when used as part of a floor header or trimmer in accordance with Section R50538. Tabulated spans apply to surfaced S4S lumber having dimensions which conform to the American Softwood Lumber Standard PS 20-10.
A floors framework is made up mostly of wooden joists that run parallel to one another at regular intervals.
While homeowners may be able to repair minor joist problems most are best left to a professional. This should be compared to the table. If your old joists do not meet the requirements set by the table they are either supported somewhere from underneath or they were installed pre regulations November 1985. 210 to 15 feet and 212 to 18 feet.
