What is the maximum cross slope for an ADA ramp?
An ADA ramp's cross slope — the slope perpendicular to the direction of travel — may be no steeper than 1:48, about 2.08% (2010 ADA §405.3). That nearly level cross slope keeps a wheelchair from drifting or tipping sideways. It's separate from the running slope, which can be as steep as 1:12.
Source: 2010 ADA §405.3 · Verify against your AHJ and the adopted code edition.
A ramp has two slopes, and people often forget the second one:
- Running slope — the grade along the ramp (the climb). Max 1:12 (§405.2).
- Cross slope — the grade across the ramp, side to side. Max 1:48 (~2.08%), per §405.3.
The cross slope is held nearly flat on purpose. Any real side-tilt makes a wheelchair drift downhill and forces the user to steer against it the whole way — and on a wet ramp it’s a tipping risk. 1:48 is about ¼ inch of fall per foot of width.
The same 1:48 maximum also applies to landings in every direction (§405.7.1) and to accessible routes generally — it’s the practical definition of “level” for drainage while staying usable. State codes and ICC A117.1 can differ — verify with your AHJ.
Work it out: the ADA ramp calculator checks the running slope and landings against the 1:12 and 1:48 limits as you enter the rise and length.
Sources
- U.S. Access Board — 2010 ADA Standards — 2010 ADA Standards §405.3