As of April 2015, for a wheelchair ramp to be compliant with ADA specifications, it must have a maximum slope ratio of 1:12. For every inch of rise, the ramp must have a foot of length to prevent the slope from being too steep.
Wheelchair ramps must also consist of a solid, regular, stable material. Soft, loose or irregular surfaces can lead to wheel mobility issues. Each end of the ramp must have a level landing area as wide as the ramp itself. If the ramp changes directions, the landing in between ramps must be a minimum of 60 inches long by 60 inches wide.
Ramps also have a maximum length of 30 feet. This means that for any height greater than 30 inches, multiple ramps are necessary. A collection of ramps can be as long as needed, but no single section of ramp can go beyond 30 feet without a landing for rest.
Specifications do not require handrails on all types of ramps. However, if the ramp stands higher than 6 inches, or is more than 72 inches wide, it must have handrails on both sides of the ramp. The upper gripping surface of the handrail should stand between 34 and 38 inches from the surface of the ramp. If handrails are not continuous, they must extend at least 12 inches at each end of the ramp, parallel with the ground.