Lumber Roof Spans

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.

Lumber roof spans.

Dead load weight of structure and fixed loads 15 lbs ft 2. For additional species of lumber check out the rafter span calculator from the american wood council website. Live load is weight of furniture wind snow and more. 1 in 25 4 mm.

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 lengths and sizes of joists vary depending on the species and quality of the lumber used. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. Tabulated spans apply to surfaced s4s lumber having dimensions which conform to the american softwood lumber standard ps 20 10.

View allowable load tables. Span calculator for wood joists and rafters also available for the android os. Allowable spans for 2x4 top chord trusses using sheathing other than plywood e g. Spaced sheathing or 1x boards may be reduced slightly.

Use these two tables for roof rafters with a slope greater than 3 in 12. 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. 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.

Also available for the android os. 1 ft 0 3048 m. The above spans are based on american softwood lumber standard sizes. So this table could accommodate a house with a total rafter span or house width of 32 feet.

Live load 20 lbs ft 2 956 n m 2. 2 are indicated below. View size selection tables. 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.

For the initial calculation f can be estimated at 1 000. These sizes are as follows. 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. In the example the beam spans the 10 foot width of the roof.

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.