Calculate the valley length where two roof planes intersect. Valleys require special flashing and waterproofing treatment.
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Length of the main roof.
Width of the intersecting roof section.
Angle where two roof planes meet (commonly 90° for perpendicular intersections).
How this calculator works
Valley length equals half the width divided by the sine of half the valley angle. The valley angle depends on the roof pitches meeting at the valley.
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