Arches – Where is the crown located? In arch terminology used in building construction, the “crown” refers to which specific location on an arch?

Introduction / Context:Precise terminology helps in detailing arches, calculating geometry, and communicating site instructions. Words like intrados, extrados, springing, skewback, haunch, crown, and keystone each point to a distinct feature of the arch geometry and construction sequence.

Given Data / Assumptions:

• An arch ring with clearly defined inner (intrados) and outer (extrados) curves.
• Symmetric arch for simplicity, though the definition holds in general.
• Conventional building construction terminology.

Concept / Approach:

The intrados (soffit) is the lower curved surface of the arch visible from below. The crown is the highest point along this inner curve—essentially the topmost point of the soffit. While the extrados also has a highest point, the term “crown” conventionally refers to the intrados position; detailing such as crown thickness or crown height relates to this location.

Step-by-Step Solution:

Verification / Alternative check:

Construction manuals and architectural dictionaries illustrate the crown at the highest intrados point; keystone sits near the crown in many arches but the term “crown” names the geometric location, not the specific stone.

Why Other Options Are Wrong:

Option A refers to the outer curve; Option C misplaces the term; Option E confuses impost with keystone location; “None” is inapplicable.

Common Pitfalls:

Equating the crown with the keystone only; mixing intrados and extrados; assuming the crown refers to the outer surface.

Final Answer:

The highest point on the intrados (soffit) of the arch