Guide to the ADA Standards

Slope [§405.2] and Cross Slope [§405.3]

Slope represents the proportion of vertical rise to horizontal length and is specified in the Standards as a ratio (e.g., 1:12). It also can be expressed as a percentage, pitch, or in degrees. The running slope is to be uniform along a run, although slight variations may occur with certain materials such as concrete. No other changes in level other than the running slope (1:12 max.) and cross slope (1:48 max.) are permitted. Variations in slope, such as grade breaks within runs, can disrupt wheelchair travel.

Recommendations:  Providing the least possible slope below the 1:12 (8.33%) maximum offers better usability for a wider range of users. Specifying a running slope of 7.5% maximum and a cross slope of 1.5% maximum for exterior ramps will accommodate most irregularities or variances due to construction methods or materials according to a study sponsored by the Board (“Dimensional Tolerances in Construction and for Surface Accessibility” by David Kent Ballast.)