In building construction and staircase design, what is the correct term for the horizontal part of a step on which the foot is placed?

Introduction / Context:
Understanding the terminology of stair components is fundamental in architecture and civil engineering. Accurate terms support correct detailing, safety compliance, and communication on drawings and at site. This question focuses on the name of the horizontal surface that a user steps on while ascending or descending a staircase.

Given Data / Assumptions:

• The question refers to a conventional staircase used in buildings.
• Standard architectural nomenclature is assumed.
• No special stair types (spiral, alternating tread, ship ladder) are implied; the terms remain consistent across common stair typologies.

Concept / Approach:

Each step has two primary dimensions: the vertical dimension (rise/riser) and the horizontal dimension (tread). Additional terms such as flight, landing, and winder describe groupings or special shapes of steps. By matching definitions to the options, we isolate the correct term for the horizontal surface where foot contact occurs during use.

Step-by-Step Solution:

Verification / Alternative check:

Building codes and handbooks (e.g., NBC/IBC handbooks) consistently define “tread” as the horizontal component of a step. Detailing conventions on drawings label the tread depth and riser height for ergonomic and code compliance checks.

Why Other Options Are Wrong:

Rise denotes the vertical height of a step, not the horizontal surface. Flight is a series of steps between landings. Winder is a wedge-shaped step used to turn a stair. Landing is a flat platform, not the individual horizontal part of a step.

Common Pitfalls:

Confusing “tread” with “landing,” and “rise” with “riser.” The “riser” is the vertical plate; the “rise” is the dimension. The “tread” is the surface and also a dimension (tread depth).

Final Answer:

Tread