The 2010 ADA Standards and ICC A117.1 - Accessible and Usable Buildings and Facilities contain similar requirements regarding changes in level within an accessible route.  When thresholds are provided in a door opening, the maximum allowable threshold height is 1/2 inch, with the exception of existing or altered thresholds which are permitted to be 3/4-inch maximum in height (refer to the standards for additional criteria).*  These limitations on threshold height apply to manually-operated doors and automatic doors.