Roof terminology in building construction: the line formed by the intersection of two sloping roof surfaces that meet to create an external angle greater than 180° is called what?

Introduction / Context:
Understanding roof terminology is essential in civil engineering and architecture for detailing, estimating, and site supervision. Roof surfaces intersect along characteristic lines with specific names that also hint at how rainwater will flow and how tiles or sheets are lapped.

Given Data / Assumptions:

• Two sloping roof planes meet and form an external angle exceeding 180°.
• Common roof intersection terms include ridge, hip, and valley.
• We are identifying the correct line of intersection by geometry and function.

Concept / Approach:
A hip is a convex, outward corner line where two roof slopes meet, creating an external (obtuse) angle greater than 180°. A valley is a concave, inward (re-entrant) junction forming an internal angle that channels water. A ridge is the horizontal apex where opposite roof slopes meet at the top.

Step-by-Step Solution:
Identify the geometry: 'external angle > 180°' denotes a convex roof edge.Map terms to geometry: convex intersection → hip; concave intersection → valley; top horizontal → ridge.Therefore, the correct term for the line described is 'hip'.

Verification / Alternative check:
Roof framing drawings show hips at outer corners of L- and T-shaped plans, carrying hip rafters; valleys occur at inner corners, carrying valley rafters or valley boards.

Why Other Options Are Wrong:

• Ridge: a horizontal apex line, not a convex corner.
• Valley: an internal, re-entrant angle that collects runoff.
• None of these: incorrect because 'hip' fits precisely.

Common Pitfalls:

• Confusing hip and valley because both are diagonal lines on plan; their cross-sectional geometry differs (convex versus concave).

Final Answer:
hip