2010 ADA Standards for Accessible Design Pocket Guide
206.7.5 Existing Site Constraints.
Platform lifts shall be permitted where existing exterior site constraints make use of a ramp or elevator infeasible.
Advisory 206.7.5 Existing Site Constraints. This exception applies where topography or other similar existing site constraints necessitate the use of a platform lift as the only feasible alternative. While the site constraint must reflect exterior conditions, the lift can be installed in the interior of a building. For example, a new building constructed between and connected to two existing buildings may have insufficient space to coordinate floor levels and also to provide ramped entry from the public way. In this example, an exterior or interior platform lift could be used to provide an accessible entrance or to coordinate one or more interior floor levels.