SHEATHING CUT ANGLE AT VALLEY LINE

SHEATHING CUT ANGLES AT VALLEY LINE For roofs intersecting at 90 degrees

This angle is measured from a perpendicular to the ridge line, extending to the valley line. Often these angles are “eyeballed” and cut to fit by trial and error. The following table will help you avoid this frustrating, wasteful, and time consuming practice.

Roof pitches or slopes are measured in inches of vertical rise per foot of horizontal run. In the table, “S” equals the steepest roof pitch of the intersecting pair, and “F” equals the flattest. When the pitches are equal, obviously S = F. (Angle values in degrees.) Click picture for larger view; Click "back" to return







For combinations of other pitches, use the following equations to compute the angles:

S angle = ARCTAN [((S/F)12)/(S^2 +144)^0.5 ]

F angle = ARCTAN [12/(S^2(1+144/F^2))^0.5]

Example: A 3:12 roof intersects a 5:12 roof at 90 degrees. What is the cut angle for sheathing on the steepest roof?

S angle = ARCTAN [((5/3)12)/(5^2 + 144)^0.5]= ARCTAN [20/169)^0.5] = 57 degrees

Thanks to Dave Grazier and Martech Associates of Millheim, Pa. for this data.