In the introduction of the International Standard 21542-2011 (page ix) is mentioned the relationship between the International Standard and the Local Standards:
This International Standard provides building users, architects, designers, engineers, builders, building owners and managers, manufacturers, policy makers and legislators with requirements and recommendations to create a sustainable built environment which is accessible.
The purpose of this International Standard is to define how the built environment should be designed, constructed and managed to enable people to approach, enter, use, egress from and evacuate a building independently, in an equitable and dignified manner and to the greatest extent possible.
The intention of this International Standard is to meet the needs of the majority of people. This goal is achieved by agreement on minimum standards of provision which are generally accepted to accommodate the diversities of age and of human condition. This agreement has been reached by consensus between different countries all over the world.
In some countries a higher level of technical specifications has been achieved due to their long history in developing accessible building standards and regulations. The requirements of this International Standard are not intended to replace more demanding requirements defined in those national standards or national regulations.
These principles are supported by Preamble (g) and Articles 9, 10 and 11 of the United Nations Convention on the Rights of Persons with Disabilities.
NOTE 1 The Convention on the Rights of Persons with Disabilities, with its Optional Protocol, was adopted by the General Assembly of the United Nations on 13 December 2006. It came into force, i.e. became an international legal instrument, on 3 May 2008. Furthermore, information about the Convention and its text can be found on the United Nations website: http://www.un.org/disabilities/. The Convention is serviced by a joint secretariat, consisting of staff from both the United Nations Department of Economic and Social Affairs (DESA), based in New York, and the Office of the High Commissioner for Human Rights (OHCHR) in Geneva.
From this it follows that it is possible that for the doors you
need to use the ISO and for the threshold for the local SANS 10400 part S
Accessibility is existing from several parts.: