Tread Surface — Glossary entry
Category: Glossary entry
Horizontal walkable top of a step — the going plus the overlap above the riser below. Together they form the safely usable tread area required by DIN 18065.
The tread surface is the horizontal, walkable top of a step. It consists of the going plus the overlap: the going is the visible tread width in plan; the overlap is the projection over the riser below. Together they form the actually usable tread surface. For small goings DIN 18065 requires a sufficiently large overlap so that the sum of going and overlap delivers a safe tread width.