Materials such as gravel, wood chips, or sand, often used for outdoor walkways, are neither firm nor stable, nor can they generally be considered slip-resistant. Thus, walks surfaced in these materials could not constitute an accessible route. However, some natural surfaces, such as compacted earth, soil treated with consolidants, or materials  stabilized and retained by permanent or temporary geotextiles, gridforms, or similar construction may perform satisfactorily for persons using wheelchairs and walking aids.

ADAAG also contains provisions that limit surface discontinuities along an accessible route, including elevator cab leveling tolerances at landings, gaps between car and platform in transit facilities, the size and orientation of openings in walkway gratings, the profile of doorway thresholds, and the pile height and attachment of carpeting. ADAAG 4.5.3 specifies that carpet and carpet tile be securely attached. This provision does not require that each tile--or the entire carpet or pad--be adhered to the floor surface provided the method of securement results in a surface that is stable, firm, and slip-resistant and does not pose a tripping hazard.