Sections 4.1.2 and 4.1.3 indicate which areas or elements of exterior sites and buildings are required to meet ADAAG's technical criteria in new construction. Compliance is required except where "structurally impracticable," a term intended to cover unique characteristics of the terrain that effectively prevent full compliance (e.g., structures built in flood plains that must be raised on stilts). Provisions in 4.1.2 and 4.1.3 are discussed in the relevant technical sections.

Each addition to an existing building is regarded as an alteration subject to ADAAG alterations requirements (including triggering of path of travel obligations, if applicable). To the extent that a space or element is newly constructed as part of an addition, it is also regarded as new construction and must comply with the applicable new construction provisions of ADAAG. Certain allowances made on the basis of technical infeasibility are permitted in alterations, but not in new construction. They are intended to cover portions of existing buildings altered in an addition, but not those portions that are newly built.