Ready to start calculating how much lumber you ll need for your joists.
Floor joist two equal span.
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.
How far can you span a 2 8 floor joist.
Joist span and spacing is set by your local building code.
Hem fir 2 joists with a live dead load of 40 10 psf.
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.
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 rule of thumb is 8 foot span with a 2 8 at 16 centers.
1 in 25 4 mm.
Maximum floor joist span for no.
Spans in this table were derived from the irc table r502 3 1 2 design criteria.
End web crippling check is based upon 3 5 inch end bearing.
Apply the same rules and make sure you add all necessary calculations to the equation.
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.
1 ft 0 3048 m.
See the image below for an example of joists spaced 16 on center 16 o c.
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.
For example joists spaced 16 inches from the center of the joist next to it can span 1 5 times in feet the depth of their inches.
2 grade of douglas fir are indicated below.
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.
Joist flanges must be fastened to the support.
As a rule the larger the deck the larger the joists.
Dead load weight of structure and fixed loads 10 lbs ft 2.
Joists must be braced against rotation at all supports.
You should check with your local building department for construction requirements in your area.
To learn more about deck joist sizing spacing and allowable span reference this chart.
1 psf lb f ft 2 47 88 n m 2.
Live load 30 lbs ft 2 1436 n m 2.
