Lumber Roof Spans

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.

Lumber roof spans.

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

2 are indicated below. 1 psf lb f ft 2 47 88 n m 2. Allowable spans for 2x4 top chord trusses using sheathing other than plywood e g. Use these two tables for roof rafters with a slope greater than 3 in 12.

In the example the beam spans the 10 foot width of the roof. The above spans are based on american softwood lumber standard sizes. 1 ft 0 3048 m. So this table could accommodate a house with a total rafter span or house width of 32 feet.

Dead load weight of structure and fixed loads 15 lbs ft 2. F stands for the beam s fiber strength in bending which depends on the species of wood. 1 in 25 4 mm. These sizes are as follows.

Live load 20 lbs ft 2 956 n m 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. Simplified span tables for southern pine lumber and glued laminated timber glulam headers beams and girders. For the initial calculation f can be estimated at 1 000.

Spaced sheathing or 1x boards may be reduced slightly. Also available for the android os. For additional species of lumber check out the rafter span calculator from the american wood council website. 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.

View allowable load tables. 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. View size selection tables. 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.

Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.