Live load 20 lbs ft 2 956 n m 2.
Lumber roof spans.
1 ft 0 3048 m.
Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.
The total load is 4 000 pounds.
Live load is weight of furniture wind snow and more.
For the initial calculation f can be estimated at 1 000.
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.
Tabulated spans apply to surfaced s4s lumber having dimensions which conform to the american softwood lumber standard ps 20 10.
1 in 25 4 mm.
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.
View size selection tables.
Dead load weight of structure and fixed loads 15 lbs ft 2.
Also available for the android os.
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.
In the example the beam spans the 10 foot width of the roof.
The above spans are based on american softwood lumber standard sizes.
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.
Use these two tables for roof rafters with a slope greater than 3 in 12.
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.
Spaced sheathing or 1x boards may be reduced slightly.
For additional species of lumber check out the rafter span calculator from the american wood council website.
The lengths and sizes of joists vary depending on the species and quality of the lumber used.
Span calculator for wood joists and rafters also available for the android os.
View allowable load tables.
These sizes are as follows.
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.
Allowable spans for 2x4 top chord trusses using sheathing other than plywood e g.
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.
F stands for the beam s fiber strength in bending which depends on the species of wood.
