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General guidelines

ISO 21542:2021. Building construction - Accessibility and usability of the built environment


Publication date
1 June 2021
Technical Committee : ISO/TC 59/SC 16 Accessibility and usability of the built environment
  • English
  • French
  • 2021


This international standard specifies a range of requirements and recommendations for the elements of construction, building assemblies, components, fittings and products that relate to the design and constructional aspects of usability and accessibility of buildings, i.e. access to buildings, circulation within buildings, egress from buildings during normal conditions, and evacuation in the event of a fire. It also applies to the common spaces in multi-unit residential buildings; its Annex A provides recommendations regarding residential units. 

The document also contains provisions with respect to outdoor features directly concerned with access to a building or a group of buildings from a relevant site boundary, or between such a group of buildings within a common site. However, it does not deal with elements of the external environment, such as public open spaces, whose function is self-contained and unrelated to the use of a specific building.

The standard is applicable to new buildings and new work in existing buildings. In fact, it introduces the concept of ‘exceptional considerations for existing buildings’ for situations where it is exceptionally difficult to meet the requirements specified and, thus, impossible to provide full accessibility. By means of ‘exceptional considerations for existing buildings’, an acceptable, though restricted, level of accessibility is specified. However, an exceptional consideration for existing buildings is not to be applied in other situations or invoked in an unjustified manner, or as an excuse for not achieving a higher level of accessibility, where this is economically and/or technically feasible.

Although the document is primarily written for adults with disabilities, it includes some recommendations on specific accessibility needs of children.

Note: The URL provided is the one of the store of ISO. However, it can be purchased at the websites of many National Standardisation Bodies, where it might be available in more languages.


ISO 21542:2021. Building construction — Accessibility and usability of the built environment