Framing & StructuralQuestion 368 of 700
CALCULATION: A stair has 15 risers. Using a 10-inch tread depth, what is the total horizontal run of the flight (number of treads times tread depth)?
a.150 inches
b.140 inches
c.110 inches
d.160 inches
Explanation
A straight flight has one fewer tread than risers: 15 - 1 = 14 treads. Total run = 14 x 10 inch = 140 inches. Using 15 treads (150 inches) forgets that the top riser lands on the floor, 110 and 160 inches use the wrong tread count.
Law Reference: 2025 CA Residential Code §R311.7.5.2Practice all 700 questions free — no signup required.
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