What height do you install Ada railing at?

Answer 1

If you mean dado rail the common height is

between 3 to 4 feet depends on ceiling height.

Hold a length up to the wall see what looks best.

I believe the questioner is not referring to a dado. ADA is the American Disabilities Act relating to issues of access and in particular, stairs, doors, sidewalks, and ramps, as well as relevant material changes of elevation, direction, surface and any edges or borders with inherent dangers such as the entrance to an elevator or flat sidewalk that transitions into a vehicular path or parking lot. It's also the reason you now find many office hallway signs with labels in braille. The original question needs to be more specific- are you talking about a stairs, balcony, bathroom stall, "grab bars", or a dedicated wheel chair only ramp? Is the location public or private? Generally speaking, most current codes will have already incorporated the ADA requirements into their current provisions.