What angle does the valley rafter form with the main ridge board in a roof of uniform pitch?

In a roof of uniform pitch, the valley rafter is designed to handle the intersection of two roof sections, typically where one roof plane meets another at an angle. In standard residential construction, especially for roofs with common pitches, the valley rafter typically forms a 45-degree angle with the main ridge board. This is due to the nature of the roof's geometry where the slope of the roof contributes to the angle of the valley, maximizing the structure's strength and ensuring proper water drainage.

A 45-degree angle allows for effective load distribution and provides a balance between the roof's aesthetic appeal and its functional integrity. It's this consistent angle that makes it easier to construct and helps maintain uniformity across various sections of the roof. Other angles, such as 30 degrees, 60 degrees, or 90 degrees, are not standard for valley rafters in residential construction and could lead to various issues like inadequate support, improper water shedding, or severe design complications. Thus, the angle of 45 degrees is recognized as the correct and practical choice for valley rafters in roofs of uniform pitch.