Accessible ramp: max 1:12 slope, 36 in clear width, 60 in landings at top + bottom + every 30 ft of run
US Access Board ABA §405 Ramps — slope, width, landingsDescription
Accessible ramps must have a running slope no steeper than 1:12 (8.33%). Cross slope (perpendicular to direction of travel) ≤ 1:48 (2%). Clear width ≥ 36 in between handrails. Landings ≥ 60 in × 60 in at the top + bottom of every ramp run + at every direction change. Maximum rise per single run = 30 in (then a landing must intervene). Handrails required on both sides where rise > 6 in. Edge protection (curb, wall, or projecting surface) required where the side opens to a drop.
Why this exists
The 1:12 slope means a 30-in rise needs a 30-ft ramp — quickly becomes a major site feature. Architects designing accessible homes should integrate the ramp into the architecture (front porch design, terraced landing) rather than appending it as an awkward attachment. Steeper-than-1:12 ramps (used in renovation cases) are sometimes allowed but require special justification + are harder to use.
Measurements
| Property | Operator | Value | Unit | Note |
|---|---|---|---|---|
maxSlope | max | 0.0833 | rise/run (1:12) | Maximum running slope |
maxCrossSlope | max | 0.0208 | rise/run (1:48) | Maximum cross slope |
minWidth | min | 36 | in between handrails | Minimum ramp clear width |
landingSize | min | 60 | in × 60 in | Landing minimum dimension (both axes) |
maxRiseSingleRun | max | 30 | in | Maximum rise per single run before landing |
Categories
Source
Solver enforcement
Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.
Related directives
- Bathroom entry doorway · NKBA Bath 1
- Kitchen walkway and work-aisle widths · NKBA Kitchen 6
- Single-door clear opening: 34" minimum (36" door leaf) · NKBA 4th ed §1.1 Doorways
- Wheelchair-maneuvering clearance at doorways · NKBA 4th ed §1.1 Doorways
- Flush flooring transitions; max 1/4" eased, 1/2" beveled · NKBA 4th ed §1.3 Floor Transitions
Last reviewed 2026-05-15.