The lengths and sizes of joists vary depending on the species and quality of the lumber used.
Lumber roof spans.
The above spans are based on american softwood lumber standard sizes.
View allowable load tables.
1 in 25 4 mm.
So this table could accommodate a house with a total rafter span or house width of 32 feet.
Trusses must be designed for any special loading such as concentrated loads from hanging partitions or air conditioning units and snow loads caused by driftingnearparapetorslide offfromhigherroofs.
View size selection tables.
Live load 20 lbs ft 2 956 n m 2.
These easy to use tables were compiled by the southern forest products association sfpa as a service to design build professionals and other southern pine users.
The spans in this table are based on a maximum supported rafter span of 16 feet where the supported span is the total horizontal distance spanned by the roof rafters divided in half not the diagonal distance or the length of the rafter.
1 psf lb f ft 2 47 88 n m 2.
Simplified span tables for southern pine lumber and glued laminated timber glulam headers beams and girders.
Tabulated spans apply to surfaced s4s lumber having dimensions which conform to the american softwood lumber standard ps 20 10.
1 ft 0 3048 m.
In the example the beam spans the 10 foot width of the roof.
Dead load weight of structure and fixed loads 15 lbs ft 2.
Using table f 2 figure 3 check each lumber size to see if a 16 inch spacing will permit a span of 15 feet 1 inch.
Start with the 16 0 line in the spacing column at the left of the table then go to the right until you reach an appropriate span at least 15 feet 1 inch in this case.
Spaced sheathing or 1x boards may be reduced slightly.
The total load is 4 000 pounds.
Nominal actual surfaced size dry size 2 x 4 1 1 2 x 3 1 2 2 x 6 1 1 2 x 5 1 2 2 x 8 1 1 2 x 7 1 4 2 x 10 1 1 2 x 9 1 4 2 x 12 1 1 2 x 11 1 4 4.
Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.
F stands for the beam s fiber strength in bending which depends on the species of wood.
These sizes are as follows.
Also available for the android os.
Span calculator for wood joists and rafters also available for the android os.
For example you can span a 1 grade no knots southern yellow pine a greater distance than a 2 grade with knots southern yellow pine.
Live load is weight of furniture wind snow and more.
For additional species of lumber check out the rafter span calculator from the american wood council website.
For the initial calculation f can be estimated at 1 000.
