2010 ADA Standards for Accessible Design Pocket Guide

206.2.3.1 Stairs and Escalators in Existing Buildings.

In alterations and additions, where an escalator or stair is provided where none existed previously and major structural modifications are necessary for the installation, an accessible route shall be provided between the levels served by the escalator or stair unless exempted by 206.2.3 Exceptions 1 through 7.