What is the maximum slope for an ADA ramp?
The maximum running slope for an ADA-compliant ramp is 1:12 — one inch of rise for every 12 inches of run (8.33%) — under the 2010 ADA Standards (§405.2). A single ramp run may rise at most 30 inches (§405.6) before a level landing is required.
Source: 2010 ADA Standards §405.2 · Verify against your AHJ and the adopted code edition.
1:12 is the number to remember: for every inch a ramp rises, it needs at least 12 inches of horizontal run. That’s a running slope of 8.33%, and it’s the steepest the 2010 ADA Standards allow for new construction (§405.2).
A few rules travel with it:
- Cross slope (side-to-side) is capped at 1:48 — §405.3.
- Rise per run: 30 inches maximum — §405.6. Beyond that you must break the ramp with a level landing.
- Landings are at least 60 inches long, and 60 × 60 inches where the ramp turns — §405.7. Provide one at the top and bottom of every run.
- Handrails are required on both sides of any run that rises more than 6 inches — §405.8.
The existing-building gotcha: in an alteration where space is tight, the older ADAAG allowances permit steeper ramps (1:10 to 1:12 for a ≤6-inch rise). New construction is 1:12; a renovation may legally be steeper — verify with your AHJ.
Work it out: the ADA ramp calculator turns a rise into the run, the sloped ramp length, and the number of landings, and flags anything steeper than 1:12.
Sources
- U.S. Access Board — Ramps and Curb Ramps — 2010 ADA Standards §405