How To Calculate Floor Joist Span

Floor joist span tables for various sizes and species of wood joist span table use these tables to determine floor joist spans based on grade of lumber size of joist floor joist spacing and a live load of 30 lbs ft 2 or 40 lbs ft 2.

How to calculate floor joist span.

Live load is weight of furniture wind snow and more. Most of the time the length is divided by 360 inches. This is how far apart they will be. The formula looks like this.

Start by measuring the full length of your deck outside of bearer to outside of bearer and then subtract the thickness of one of the floor joists. Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads. Suspended ground floor with no partitions above 0 25 kn m. There are six choices.

The live load will depend according to the floor. Maximum floor joist span for no. 2 grade of douglas fir are indicated below. Intermediate floor first and 2nd floors etc with no partitions above 0 5 kn m.

Dead load weight of structure and fixed loads 10 lbs ft2. The highest is a fully loaded floor 70 pounds per square foot. To come up with the deflection limit divide the joist span length with a number. Remember to complete all calculations using millimetres.

Select the on center spacing for the joists. The lowest is a plain ceiling joist with no storage 10 pounds per square foot. Depth to width ratio should not be greater than 6. The optimum deflection limit on your floor joist is an inch for every 360 inches.

Next use the buttons in the table to select the maximum length in feet or metres in brackets that your floor joists must span. Step 4 determining the live load. The prescriptive tables found in chapter 5 of the international residential code irc can be used to determine the maximum span of a floor joist. Floor joist span calculator to use the joist span calculator below first select the species of lumber you will use for your construction project from the drop down list.

Intermediate floor with lightweight timber stud partitions above 0 75 kn m. These tables can also be used to determine deck joist span. 1 psf lbf ft2 47 88 n m2. True floor joist span calculations can only be made by a structural engineer or contractor.

Then divide this measurement by the maximum floor joist spacing that is mentioned on your drawings.