Recently we received many clients concerned about how to figure trusses,well this article may help you.Making the correct calculations for the angle and length of a truss is essential to the success of truss system construction.The angle and length is a product of two factors: the rise and the run. The rise refers to the vertical climb of the roof. The run refers to the horizontal distance from the center of the truss to the outside corner. This equation is typically expressed in one of three ways. It can be written out, as in "6-in-12," written as a fraction, e.g., "6/12," or written as a ratio, such as "6:12." In all three cases, this number represents a roof that rises six inches for every 12 inches of horizontal run. Gable trusses, with their three outside lines and two simple angles, are the simplest to calculate.And a few steps you need to take!

1.Consult your blueprint to determine how tall your truss needs to be from the bottom horizontal to the peak.
2.Take the width of your roof truss from the blueprint and divide it by two.
3.Divide the number from step one by the product of step two. The answer is the number of inches of rise for every foot of horizontal run.
4.Use a framing square to calculate the angles of your roof's pitch. Wrap a string tightly around the longer arm of the square at the dimension representing the rise. Stretch the string diagonally to the other arm and wrap the string tightly around the 12. Read the number the string intersects with in the center column of the long arm of the square.
5.Cut all the ends of your roof truss pieces to this angle.


6.Draw a triangle to figure the length of your pieces. For easy calculation, make a full-scale mock up on your driveway or garage floor. Draw the bottom horizontal as wide as the width of your truss. Draw the peak height at a right angle from the center of this horizontal line, up to a distance equal to the truss height from step one. Draw diagonal lines from this peak to the lower corners of the horizontal line to form a triangle. Use a chalk line to draw your lines.
7.Measure in 3 ½-inches from each side and draw a second triangle with its sides parallel to the first one. Overlap the intersecting corner lines. These two sets of lines represent the upper and lower cords of your truss. Measure the upper cords from the peak along the outside triangle to where the inside triangle intersects it at the bottom. Measure the lower cord by measuring the bottom line from corner to corner.