Parts of an arch — name of the lower half between crown and skewback In masonry arches, what is the term for the lower half portion of the arch ring located between the crown and the skewback at the springing?

Introduction / Context:
Accurate terminology for arch components is essential for describing geometry, analysing thrust lines, and specifying construction details. Different portions of the arch carry different stress distributions and interact with the abutments or spandrel fill.

Given Data / Assumptions:

• Masonry arch with defined crown (topmost point) and skewback (bearing surface on the abutment).
• Focus is on the lower half portion between crown and skewback.

Concept / Approach:
The haunch is the part of an arch between the crown and the springing (or skewback). It is a structurally important zone because compressive thrusts pass through it toward the abutments. The spandrel is the space between the extrados of the arch and the horizontal line of the crown or adjacent wall; the soffit (or intrados) is the inner curved surface; springing is the point/level where the arch curve begins from the support.

Step-by-Step Solution:

Verification / Alternative check:
Structural analyses show the haunch carries significant compressive thrust; strengthening at haunches (e.g., thicker ring or backing) is common practice.

Why Other Options Are Wrong:

• spandrel: space outside the arch ring above the extrados.
• springing: the level/point where the arch starts from support.
• soffit: inner curved surface of the arch.

Common Pitfalls:
Confusing soffit (surface) with a region; misidentifying spandrel as part of the ring.

Final Answer:
haunch