For example in the joist span table below the highlighted cell shows that 2 x 8 southern yellow pine joists that have a grade of 2 and are spaced 24 apart can have a maximum span of 10 feet 3 inches 10 3 if designing for a live load of 40 lbs ft 2.
Floor joist two equal span.
The rule of thumb is 8 foot span with a 2 8 at 16 centers.
Maximum floor joist span for no.
Joists must be braced against rotation at all supports.
Ready to start calculating how much lumber you ll need for your joists.
1 ft 0 3048 m.
Apply the same rules and make sure you add all necessary calculations to the equation.
1 psf lb f ft 2 47 88 n m 2.
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 though it has the same amount of wood as a doubled 2 x 6.
Hem fir 2 joists with a live dead load of 40 10 psf.
1 in 25 4 mm.
Joist span and spacing is set by your local building code.
Spans in this table were derived from the irc table r502 3 1 2 design criteria.
Joist flanges must be fastened to the support.
2 grade of douglas fir are indicated below.
While most residential construction uses 2x8 joists with 16 inch spacing there are many other factors you need to consider when determining the proper joist span length.
These tables can also be used to determine deck joist span.
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.
See the image below for an example of joists spaced 16 on center 16 o c.
Live load is weight of furniture wind snow and more.
For two equal spans the listed span is the center to center distance from either end to the center support with the joist continuous over the center support.
The floor joist spacing is the distance between the centers of any two installed joists.
Live load 30 lbs ft 2 1436 n m 2.
How far can you span a 2 8 floor joist.
You should check with your local building department for construction requirements in your area.
With everything being equal your maximum floor span using spf 2 8 will be 12 feet 8 inches with a minimum bearing length of 4 inches at 12 centers.
End web crippling check is based upon 3 5 inch end bearing.
As a rule the larger the deck the larger the joists.
