The Building Regulations
Approved Document O, 2021 Edition (ADO:2021) allows the free area of the opening to be assessed by either:
a. Measurement of the product to BS EN 13141-1 (You have access to this British Standard via the ARU Library Database).
b. Calculation using Appendix D of ADO:2021
Explain the difference in these two technical approaches with the Building Regulations and when as a practitioner you would recommend the adoption in a full plans application of the BS EN 13141-1 approach over the Appendix D method?
