Residential Roof Framing Spans

Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run.

Residential roof framing spans.

Span calculator for wood joists and rafters also available for the android os. Another option are 2 x 8 rafters spaced 24 inches o c. Continuous span beams are beams supported at three or more points along their length. Allowable spans for 2x4 top chord trusses using sheathing other than plywood e g.

For example in the rafter span table below the highlighted cell in the 40 live load table indicates that 2 x 8 southern yellow pine joists that have a grade of 2 that are spaced 24 apart can have a maximum span of 10 feet 3 inches 10 3 if designing for a live load of 40 lbs ft 2. These span tables assume installation of at least three joists or rafters that are spaced not more than 24 on center. 2 you must determine the snow load for your region. Rafter and joist span faq.

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. Also available for the android os. The table states that 2 x 6 rafters spaced 16 inches on center o c can span a maximum distance of 13 feet 5 inches. The provisions of this section shall control the construction of cold formed steel roof framing for buildings not greater than 60 feet 18 288 mm perpendicular to the joist rafter or truss span not greater than 40 feet 12 192 mm in width parallel to the joist span or truss less than or equal to three stories above grade plane and with.

Let s use this example and find a size of rafter that will work. Looking through the center of the table we can find a couple of options. Span may be interpreted as the clear distance between supports measured along the beam. The lengths and sizes of joists vary depending on the species and quality of the lumber used.

Spaced sheathing or 1x boards may be reduced slightly. This is the horizontal distance from the inside surface of the supporting wall to the inside surface of the ridge board. The international code council icc is a non profit organization dedicated to developing model codes and standards used in the design build and compliance process. The international codes i codes are the widely accepted comprehensive set of model codes used in the us and abroad to help ensure the engineering of safe sustainable affordable and resilient structures.

Range of values in the tables provides allowable spans for all species and grades of nominal 2 inch framing lumber customarily used in construction. The span would be 11 5 3 4. Continuous span values given in the. The calculated spans assume fully supported members.