Minimum Joist Size For Floor

Floor joist spacing has traditionally been 24 inches on center or from center to center of the joists.

Minimum joist size for floor.

1 ft 0 3048 m. Spaced at 12 inches the joist may only span 16 feet 8 inches. Maximum span of 2x8 floor joist maximum span of 2x10 floor joist maximum span of 2x12 floor joist the most important design choices to consider when building a home are the species and grade of wood that is being used as well as joist size and spacing. Dead load weight of structure and fixed loads 10 lbs ft 2.

True floor joist span calculations can only be made by a structural engineer or contractor. 2 grade of douglas fir are indicated below. You can always use bigger lumber closer spacing or a smaller span. You will need to determine.

See the image below for an example of joists spaced 16 on center 16 o c. Maximum floor joist span for no. Newer construction has floor joists spaced at 16 inches on center. A live load of 60 pounds per square foot demands more support and shorter spans.

Tracks shall be not less than 33 mils 0 84 mm thick except when used as part of a floor header or trimmer in accordance with section r505 3 8. The floor joist spacing is the distance between the centers of any two installed joists. If the joist spacing will be 16 inches 406 4 mm a joist size of 2 x 8 should be used even if the length is only 8 feet 2 44 m. This sample table gives minimum floor joist sizes for joists spaced at 16 inches and 24 inches on center o c for 2 grade lumber with 10 pounds per square foot of dead load and 40 pounds of live load which is typical of normal residential construction.

Most floor loads would be a minimum of 2x8 16 oc and most preferbaly 2x10. How long can floor joists be without support. Looking at this table you will see there is a choice in the size of floor joist 2 x 6 2 x 8 2 x 10 or 2 x 12 and there is a choice in the joist spacing 12 16 or 14. Below is a table giving the minimum size floor joists needed for 16 and 24 on center o c spacing when using 2 lumber with 10 pounds per square foot of dead load and 40 pounds of live load.

1 psf lb f ft 2 47 88 n m 2. A structure with a 10 foot 3 05 m length and joists set 12 inches 304 8 mm apart would require using a floor joist size of 2 x 8 50 8 x 203 mm. Just don t go smaller further apart or a longer span.