Allowable spans for 2x4 top chord trusses using sheathing other than plywood e g.
Maximum roof span for 2x4.
For light load roofs 24 o c.
Maximum and use lumber properties as follows.
Spaced sheathing or 1x boards may be reduced slightly.
Also available for the android os.
1 ft 0 3048 m.
2 4 rafters can span up to 7.
Most roof framing is 24 on center and you can still build sheds up to 14 with 2 4 rafters at 24 on center.
Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.
2 are indicated below.
Live load is weight of furniture wind snow and more.
2x4f 2000psif 1100psie 1 8x10 2x6f 1750 psi f 950 psi f 1900 psi e 1 8x10.
For example in the rafter span table below the highlighted cell in the 40 live load table indicates that 2 x 8 southern yellow pine joists that have a grade of 2 that 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.
I used your formula backwards to calculate the max psf of a ceiling with 2x4 ceiling joists spanning 12 and spaced 24 o c.
While every effort has been made to insure the accuracy of the information presented and special effort has been made to assure that the information reflects the state of the art neither the west coast lumber inspection bureau the american wood council nor its members assume any responsibility for any particular design prepared from this online span calculator.
Span calculator for wood joists and rafters also available for the android os.
1 psf lb f ft 2 47 88 n m 2.
Assuming the fb of hemfir is maxxed at 1275 psi and i came up with 12 737 psf.
Spacing your 2 4 shed rafters at 24 on center limits the width of your roof.