A valley truss is a specialized truss used where two roof sections intersect at an interior angle, called a valley, providing the structural support needed at this transition point where water naturally concentrates and flows down toward the roof’s edge.
Because valleys are a common location for roof leaks if not properly constructed and flashed, the structural framing at this intersection needs to work in coordination with careful waterproofing detail during roofing installation.
This truss type is specifically engineered to fit the particular geometry created where two differently oriented roof sections come together, a condition common on homes with more complex roof shapes than a simple rectangle.
What Does a Valley Truss Involve?
- Specialized geometry fitting the specific roof intersection
- Coordination with adjacent standard and hip trusses
- Structural support for the valley flashing and roofing above
- Engineering specific to the particular roof shape involved
Why Are Valley Trusses Important?
Because a roof valley concentrates significant water flow during rain, adequate structural support at this location matters not just for the framing itself but for maintaining a stable, properly sloped surface that valley flashing can effectively seal against water intrusion. Poor structural support at a valley can lead to sagging that compromises the flashing’s effectiveness, contributing to leaks even when the flashing material itself is adequate.
Complex roof designs with multiple intersecting sections often require several valley trusses working in coordination with hip and common trusses, making the overall structural design considerably more involved than a simple gable roof with no intersecting sections at all. This coordination between structure and design is what makes complex roof shapes achievable without compromising performance.
Valley Truss vs. Hip Truss
A valley truss supports an interior angle where two roof sections meet. A hip truss supports the sloped exterior ends of a hip roof, addressing a structurally and geometrically different condition despite both being specialized trusses for complex roof shapes.