b'When applying an alteration to an existing building, it may not meet all the requirements of the latest code. The alteration must be such that the performance is improved in a cost-effective and practical manner.The following article originally appeared in the Fall 2022 issue of Roofing BC magazine. Its reprinted here with permission.T heNationalBuildingCodeofCanada(NBC)provides specificationsfornewroofconstruction.Whenapplying NRC Consultation with IndustryThean alteration to an existing building, it may not meet all the requirements of the latest code. The alteration must be such that the performance is improved in a cost-effective and practical manner. NBC provides examples of when the code can be applied to existing buildings:To rehabilitate a building; To change the use of a building; To build an addition; andWhen the enforcement authority requires alterations for pub- lic safety (A-1.1.1.1. (1)).The NBC also directs users to a number of publications that aim to aid the user in the application of alterations to existing buildings:Guidelines for Application of Part 3 of the National BuildingCode of Canada to Existing Buildings 1Commentary titled Application of NBC Part 4 of Division Bfor the Structural Evaluation and Upgrading of Existing Build-ings of the Structural Commentaries (Users GuideNBC 2015: Part 4 of Division B) 2CBD 230,3Applying Building Codes to Existing BuildingsORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ONTARIO ROOFING NEWSISSUE 1 202313'