Step 4 · Factor in the Nosing for Total Depth

The total tread depth is a combination of the 'run' you measured in Step 2 plus the 'nosing'—that part of the tread that hangs over the riser below. Building codes typically require this overhang (usually between 3/4 inch and 1-1/4 inches) because it adds crucial space for your foot, preventing slips. The formula is simple: Total Tread Depth = Actual Tread Depth + Nosing. This is how you achieve a professional, safe result.