Lumber Roof Spans

For the initial calculation f can be estimated at 1 000.

Lumber roof spans.

Allowable spans for 2x4 top chord trusses using sheathing other than plywood e g. In the example the beam spans the 10 foot width of the roof. Live load is weight of furniture wind snow and more. 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 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. 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. 1 ft 0 3048 m.

Use these two tables for roof rafters with a slope greater than 3 in 12. Tabulated spans apply to surfaced s4s lumber having dimensions which conform to the american softwood lumber standard ps 20 10. For additional species of lumber check out the rafter span calculator from the american wood council website. 2 are indicated below.

The lengths and sizes of joists vary depending on the species and quality of the lumber used. The above spans are based on american softwood lumber standard sizes. Span calculator for wood joists and rafters also available for the android os. Also available for the android os.

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. 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. F stands for the beam s fiber strength in bending which depends on the species of wood. View size selection tables.

These sizes are as follows. Spaced sheathing or 1x boards may be reduced slightly. The total load is 4 000 pounds. View allowable load tables.

Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. Live load 20 lbs ft 2 956 n m 2. So this table could accommodate a house with a total rafter span or house width of 32 feet. 1 psf lb f ft 2 47 88 n m 2.

Dead load weight of structure and fixed loads 15 lbs ft 2.