Lumber Roof Spans

So this table could accommodate a house with a total rafter span or house width of 32 feet.

Lumber roof spans.

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. The above spans are based on american softwood lumber standard sizes. F stands for the beam s fiber strength in bending which depends on the species of wood. 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.

For additional species of lumber check out the rafter span calculator from the american wood council website. 1 ft 0 3048 m. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. Allowable spans for 2x4 top chord trusses using sheathing other than plywood e g.

2 are indicated below. Dead load weight of structure and fixed loads 15 lbs ft 2. Span calculator for wood joists and rafters also available for the android os. For the initial calculation f can be estimated at 1 000.

The total load is 4 000 pounds. 1 in 25 4 mm. 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. The lengths and sizes of joists vary depending on the species and quality of the lumber used.

View allowable load tables. Tabulated spans apply to surfaced s4s lumber having dimensions which conform to the american softwood lumber standard ps 20 10. Live load is weight of furniture wind snow and more. Spaced sheathing or 1x boards may be reduced slightly.

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. Simplified span tables for southern pine lumber and glued laminated timber glulam headers beams and girders. Use these two tables for roof rafters with a slope greater than 3 in 12. These sizes are as follows.

View size selection tables. 1 psf lb f ft 2 47 88 n m 2. 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.

In the example the beam spans the 10 foot width of the roof.