Floor Joist Strength Calculator

Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads.

Floor joist strength calculator.

Finally the truss calculator will compute the best dimensional method to connect the pieces of the truss with steel joints and a bridge. Divide the total span of the floor joists in inches by 360 to determine the maximum amount the floor can give in the middle under a live load of 40 lb sq. These steel joints are needed to support the overall truss. This is how far apart they will be.

Ft plus any long term deflection due to the weight of the floor. The lowest is a plain ceiling joist with no storage 10 pounds per square foot. These small areas are usually door opening on the interior and people are trained that these areas are the strongest. Enter a specific joist size 2.

It has been my experience to never use a beam smaller than a two ply 2 x 8. The highest is a fully loaded floor 70 pounds per square foot. Calculations to bs 5268 2 2002. There are six choices.

While every effort has been made to insure the accuracy of the information presented and special effort has been made to assure that the information reflects the state of the art neither the west coast lumber inspection bureau the american wood council nor its members assume any responsibility for any particular design prepared from this online span calculator. The width is considerably more important than the thickness of a board. The more complex the truss framework is the greater quantity of these joints will be required. Most lay outs are on 16 so the field is pre selected.

For a given joist size and spacing the tables indicate the strength value called the fb value and stiffness called the e value of the joist. Usually 400 450 or 600mm but any value can be used up to 610mm max. Architects and engineers use these tables to determine the required size and spacing of joists as they design buildings but you can use them to work backwards and calculate the load capacity of an. Also available for the android os.

1 enter joist details. The same thing is true for the bridge of the truss. This calculator matches up with 90 of the applications in the 2012 international residential code book. The strength of a given joist board is most dramatically affected by the board s top to bottom width.

For example a joist made from doubled 2 x 6s can span a distance about 25 percent more than a single 2 x 6 but a 2 x 12 can span about 80 percent more than a 2 x 6 even. No matter what the specs say. You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths. Select the on center spacing for the joists.

Domestic floor joist calculator.