Minimum Joist Size For Floor

The floor joist spacing is the distance between the centers of any two installed joists.

Minimum joist size for floor.

A live load of 60 pounds per square foot demands more support and shorter spans. 1 ft 0 3048 m. True floor joist span calculations can only be made by a structural engineer or contractor. 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.

You can always use bigger lumber closer spacing or a smaller span. 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. 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. Floor joists shall have a bearing support length of not less than 1 1 2 inches 38 mm for exterior wall supports and 3 1 2 inches 89 mm for interior wall supports.

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. 1 psf lb f ft 2 47 88 n m 2. You will need to determine. Maximum floor joist span for no.

Size of joist. Newer construction has floor joists spaced at 16 inches on center. 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. Dead load weight of structure and fixed loads 10 lbs ft 2.

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. 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. Just don t go smaller further apart or a longer span. How long can floor joists be without support.

Spaced at 12 inches the joist may only span 16 feet 8 inches. 2 grade of douglas fir are indicated below. See the image below for an example of joists spaced 16 on center 16 o c.