The finished floor at the door is 27 inches above the walkway where the ramp will begin. Using the maximum slope the code allows for a ramp, what horizontal run does the sloped portion require?
- 27 feet 0 inches
- B22 feet 6 inches
This is a 1 in 10 slope, which is steeper than the code allows and is not one of the recognized figures. It typically comes from rounding the required run down to fit the space available.
- C18 feet 0 inches
Eighteen feet corresponds to the 1 in 8 exception. That slope is permitted only where the building official finds the standard slope technically infeasible, and it is not the answer to what the code allows as a maximum.
- D13 feet 6 inches
Thirteen and a half feet is a 1 in 6 slope, which is far steeper than anything the ramp provisions allow and would be unusable by the person the ramp is being built for.
Why A is correct
At the maximum slope of 1 vertical in 12 horizontal, the run equals twelve times the rise: 27 inches times 12 is 324 inches, or 27 feet. Landings at the top and bottom are additional, so the contractor needs 27 feet of sloped run before the landings are placed.
What this question is testing
Whether the candidate can convert a rise into a required run at the maximum permitted slope, and distinguishes the code maximum from the steeper slope allowed only under a documented exception.
On the job
This conversation happens at the door with a tape, and the answer usually surprises the contractor: 27 feet of ramp will not fit in most front yards, which is why real ramps switch back with an intermediate landing. Inspectors who work the arithmetic on the spot save a demolition, because a ramp poured at 1 in 8 without a documented infeasibility finding comes out.
Memory technique
One in twelve: a foot of ramp for every inch of rise.
Exam tip
Run equals rise times 12. Do it in inches, then convert.
Where to look it up
IRC Chapter 3, ramps, the maximum slope paragraph and its exception.