ADA Ramp Slope, Runs, and Landings (IBC 1012 / ADA)
The full layout of an accessible ramp, not just the slope: run = rise x the slope ratio (max 1:12 / 8.33%), the number of runs = ceil(rise / 30 in) because a single run may rise only 30 in before a >=60 in landing, the landings that adds, and the total ramp length; handrails are required where the rise exceeds 6 in. A 24 in rise at 1:12 is one 24 ft run with handrails; a 40 in rise needs 2 runs and a 60 in landing for 45 ft of total ramp. A layout aid; the adopted code and ADA/ANSI A117.1 govern slope, width, and handrail details.
Formula and source
run = rise x slope_ratio; slope_pct = 100 / slope_ratio; runs = ceil(rise / 30); landings = (runs - 1) x landing_len; total = run + landings; handrails if rise > 6 in.
IBC §1012 (ramps) and the ADA Standards for Accessible Design (2010) §405 / ICC A117.1, by name.
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