Structural Commentaries (User's Guide for the National Building Code of Canada 2020: Part 4 of Division B)

The Structural Commentaries (User's Guide for the National Building Code of Canada 2020: Part 4 of Division B) is intended to help Code users understand the design provisions provided in Part 4 of Division B of the National Building Code of Canada 2020 (NBC).

It contains information and suggested approaches to certain design questions related to structural sufficiency such as limit states design, snow, rain and wind loads, and design for seismic effects.

This new edition of the Structural Commentaries reflects technical changes incorporated into the NBC 2020. Topics covered include the following:

• Further information on the Importance Categories, including post-disaster buildings, in the context of Part 4 of the NBC
• Guidance to support the revisions in provisions for:
  • loads and load combinations for serviceability limit states
  • tributary areas and live load reduction factors for slabs
• Information to support new provisions for snow loads on roofs with solar panels, drift loads for canopies and small roofs adjacent to tall buildings, and wind loads on parapets and attached canopies

Commentary J has undergone a comprehensive update to reflect changes to the seismic design provisions in the NBC 2020, and provides guidance on the new and revised provisions. Significant changes include the following:

• Commentary on Canada's 6th Generation Seismic Hazard Model (CanadaSHM6), which formed the basis for changes in the NBC 2020
• Information and examples to support the new approach to the calculation of seismic hazard, including the use of site designation
• Guidance to support:
  • the use of the 2020 National Building Code of Canada Seismic Hazard Tool
  • the application of the new Seismic Categories
  • the application of provisions for sloped column irregularity and for buildings with gravity-induced lateral demand
• Commentary to help Code users understand the additional performance provisions introduced in the NBC 2020 for buildings in the Post-Disaster and High Importance Categories, and a subset of buildings in the Normal Importance Category

New Commentary M on large farm buildings, including bins and silos, is also introduced.