According to accessibility standards, the maximum running slope for a ramp is 1:12. This ratio means that for every 1 inch of vertical rise, a minimum of 12 inches (1 foot) of horizontal run is required. The given rise is 1'-6", which is equivalent to 18 inches (12" + 6"). To calculate the required ramp length (run), multiply the rise in inches by 12.

Calculation: 18 inches (rise) × 12 = 216 inches (run).

To convert the run to feet, divide by 12: 216 inches / 12 inches/foot = 18 feet. Therefore, a rise of 1'-6" requires a ramp length of 18 feet.

A. 12 feet [3.66 m]: This would be the correct length for a 1-foot (12-inch) rise, not the specified 1-foot 6-inch rise.

B. 16 feet [4.88 m]: This length does not correspond to the standard 1:12 slope requirement for the given 18-inch rise.

D. 36 feet [10.97 m]: This would be the required length for a 3-foot (36-inch) rise, which is double the actual rise in the question.

1. U.S. Department of Justice. (2010). 2010 ADA Standards for Accessible Design. Section 405.2 Slope. "Ramp runs shall have a running slope not steeper than 1:12."

2. International Code Council. (2021). 2021 International Building Code (IBC). Chapter 10

Section 1012.2 Slope. "The running slope of ramps shall not be steeper than one unit vertical in 12 units horizontal (8.3-percent slope)."

3. Ramsey

C. G.

& Sleeper

H. R. (2016). Architectural Graphic Standards (12th ed.). John Wiley & Sons. Chapter 3: Building Elements

Section: Accessible Ramps

p. 136. This standard reference text illustrates and specifies the 1:12 maximum slope for accessible ramps.