| Requirement | ADA, commercial | IRC, residential |
|---|---|---|
| Max running slope | 1:12 (8.33%) | 1:12 (1:8 if space-limited) |
| Max cross slope | 1:48 | — |
| Max rise per run | 30″ | No set limit |
| Landing length | 60″ min (60×60 at turns) | ≥ ramp width (36″ min) |
| Handrails | Both sides if rise > 6″ | ≥1 side if steeper than 1:12 |
| Min clear width | 36″ | 36″ |
| Edge protection | Required | Guards where drop > 30″ |
The maximum running slope of an ADA-compliant ramp is 1:12, or 8.33 percent: one inch of rise for every 12 inches of horizontal run. The cross slope (side to side) may not exceed 1:48. Where a 1:12 slope is used, the code also limits a single ramp run to 30 inches of rise before a level landing is required.
At the maximum 1:12 slope, every inch of rise needs one foot of ramp run, so a 24-inch rise needs 24 feet of sloped ramp. Gentler slopes need more: 1:16 needs 16 inches of run per inch of rise, 1:20 needs 20. Landings, which are 60 inches long minimum, add to the total footprint and are required at the top, the bottom and every 30 inches of rise.
Under the ADA, ramp runs with a rise greater than 6 inches require handrails on both sides, mounted 34 to 38 inches above the ramp surface with continuous graspable rails. In residential (IRC) construction, handrails are required on at least one side of any ramp steeper than 1:12; guards are required wherever the drop-off exceeds 30 inches.
An ADA ramp run may rise no more than 30 inches between landings. A rise taller than that must be broken into multiple runs separated by level landings at least 60 inches long. Where a ramp changes direction, the landing must be at least 60 by 60 inches so a wheelchair can turn.
ADA (commercial and public accommodation) ramps cap slope at 1:12, limit each run to 30 inches of rise, require 60-inch landings, handrails on both sides above a 6-inch rise, and a 36-inch minimum clear width. Residential ramps under the IRC also target 1:12 but permit up to 1:8 where space is genuinely constrained, require handrails on at least one side of ramps steeper than 1:12, and use landings sized to the ramp width.