Key Updates to the 2020 Quebec Construction Code and Relevant Standards

by on November 6, 2025 with No Comments

On April 17, 2025, the 2020 Quebec Construction Code came into effect, with an 18-month grace period, thereby implementing the revisions brought to the 2020 National Building Code of Canada (NBC 2020) in the province of Quebec. These updates reflect significant advancements in structural engineering practices, seismic design, and material standards. Below is a detailed breakdown of the key changes and their implications.

 

Key Differences in the NBC 2020 Relevant to Structural Engineering

The NBC 2020 introduces several critical updates, including references to revised standards and enhanced seismic requirements:

  • Reference to Updated Standards:
    • CSA S16:19, Design of Steel Structures
    • CSA A23.3:19, Design of Concrete Structures
    • CSA O86:19, Engineering Design in Wood
    • CSA S832:20, Seismic Risk Reduction of Operational Support Buildings
  • Updated Seismic Hazard Values
  • Updated seismic requirements

For a comprehensive understanding, a video explaining the main differences is available here.

 

Insights from ISM Conference: Seismic Design Provisions

The following notes are from the ISM conference Nouvelles dispositions du CNB 2020 pour la conception parasismique des structures de bâtiments, presented by Professor Robert Tremblay on March 13, 2024:

  • For each site, the shear wave velocity (Vs30) must be measured directly. The categories A, B, C, D, E no longer formally exist (the categories can still be used, but the highest shear wave velocity of the category will now need to be used instead of the average as per the past building code).
  • When interpolating between Vs values, it is more accurate to use logarithmic interpolation (ln) rather than linear interpolation.
  • In general, the seismic values have gone up everywhere in Canada, notably in the Montreal (1.5x) and the Vancouver regions (1.4x higher). 
  • Seismic values are no longer included in Annex C.
  • Wind values and wind pressure values remain largely unchanged.
  • Seismic categories have now been defined: SC1 – SC4.
  • Two new bracing systems: moderately ductile plate wall and an EBF using a truss.
  • Irregularity 9 was added – example is cantilever wall with load on one side.
  • 4.1.8.23: New clauses for high importance buildings to ensure structures don’t fall into inelastic behavior for small earthquakes.
  • 4.1.8.23 clause 4: seismic category CS4 and[a] higher than 30m, new provision 4.1.8.23 applies even though it is not high importance.
  • 4.1.3.4: New load combinations for service loads – this affects P-delta for wind.

 

Key Changes in Structural Commentaries

  1. Importance Categories, including post-disaster buildings.
  2. Loads and load combinations for serviceability limit states.
  3. Tributary areas and live load reduction factors for slabs.
  4. 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 been comprehensively updated to align with the changes to NBC 2020’s seismic design provisions. Key updates include:

  1. Canada’s 6th Generation Seismic Hazard Model (CanadaSHM6).
  2. The new approach to seismic hazard calculation, including the use of site designation.
  3. The use of the NBC 2020 Seismic Hazard Tool.
  4. The application of the new Seismic Categories.
  5. The application of provisions for sloped column irregularity and for buildings with gravity-induced lateral demand.

Additionally, this edition introduces Commentary M, which addresses large farm buildings, including bins and silos.

 

Key Changes in CSA A23.3-19 Compared to A23.3-14

  • Flexural Ductility (Clause 10):
    • The limit for the ratio of the neutral axis depth to the effective depth (c/d) for flexural ductility has been reduced in Clause 10.5.2.
    • This change results in a lower maximum tension reinforcement limit, ensuring the steel yields before the concrete reaches its ultimate strain, thus providing higher flexural ductility. While this is a fundamental change, studies suggest the impact on the required longitudinal reinforcement in typical designs might be less than 5%.
  • Slenderness Effects (Clause 10):
    • For non-sway frames, the M1/M2 ratio (ratio of the smaller to the larger end moment) is now taken as 1.0 if M2 is less than the minimum moment (M2,min).
    • This change makes column designs more conservative in certain cases by potentially classifying more columns as slender.
  • Effective Flexural Stiffness (EI)eff (Clause 10):
    • New selection criteria have been added for determining the effective flexural stiffness used in slenderness calculations. CSA A23.3-14 allowed using either of two equations. The 2019 edition provides more specific guidance for selecting (EI)eff.
  • Two-Way Shear around Circular Columns (Clause 13):
    • A new provision defines the critical section for two-way shear (punching shear) around circular columns. This provides a more precise approach for this geometry. Studies indicate that for circular columns, the punching shear ratio might remain similar between the two code versions when using the exact perimeter.
  • Curtailment of Reinforcement (Clause 12):
    •  A new provision has been added for the curtailment of reinforcement within the band width bb of slabs.
  • Cover for Fire Resistance (Clauses 7 & 8):
    • Additional information regarding concrete cover requirements for fire resistance has been included in these clauses.
  • Strong Axis Bending in Bearing Walls and Flexural Shear Walls (Clause 14):
    • New requirements have been added to account for strong axis bending in bearing walls.
    • New wall thickness and slenderness requirements are introduced for flexural shear walls.
  • Compressive Stress Limit at Transfer in Prestressed Concrete (Clause 18):
    • Clause 18.3.1 now permits a higher compressive stress limit in the concrete at the ends of simply supported prestressed members at the time of prestress transfer.
  • Seismic Shear Walls (Clause 21):
    • The requirements for moderately ductile shear walls have been detailed more extensively.
    • Due to significant overlap, the requirements for moderately ductile and ductile shear walls are now presented together in Clause 21.5.
    • Redundant shear wall design requirements that were already covered in Clause 14 have been removed from Clause 21, directing designers to Clause 14 for dimensional limitations, transfer of forces, and other general requirements.
  • Annex D (Anchorage):
    • Crucially, Annex D, which covers the design, installation, and quality assurance of cast-in and post-installed mechanical and adhesive anchors, became normative (mandatory) in the 2019 edition. In A23.3-14, Annex D was informative (non-mandatory). This is a significant change impacting the design and execution of anchorages in concrete. The 2019 edition also references ACI 355.4 for proof loading requirements when specified.

 

Key Changes in CSA S16:19 Compared to S16-14

  • Gerber Girders: Explicit design rules have been added for Gerber systems (cantilever beams with suspended spans).
  • Single Angles as Beams: New provisions are included for the design of single angles used as flexural members.
  • HSS Members as Beam-Columns: Updated design rules for hollow structural sections (HSS) subjected to combined axial load and bending moments.
  • Moderately Ductile Plate Walls and Truss Moment-Resisting Frames: These new seismic force-resisting systems have been introduced into the standard.
  • Inelastic Analysis: The standard now includes guidelines and considerations for using inelastic analysis methods in structural steel design.
  • Third-Party Inspection: A new informative Annex (Annex P) provides guidance for specifying third-party inspection of steel structures. While informative (non-mandatory), it highlights important considerations for quality assurance.
  • Updates and Revisions to Existing Provisions:
    • Lateral Torsional Buckling (LTB): Modifications and clarifications have been made to the design provisions for lateral torsional buckling of beams.
    • Compression Members: The provisions for doubly-symmetric compression members have been restructured and condensed, with a greater emphasis on considering torsional buckling.
    • Width-to-Thickness Limits: The standard includes updated criteria for width-to-thickness limits for multi-sided hollow sections and singly-symmetric I-sections. There are also clarifications in the tables related to these limits.
    • Bolt Hole Diameters: Updated bolt hole diameters are specified for net section calculations in shear connections.
    • Fillet Weld Resistance: The factored shear resistance of fillet welds has been revised. Notably, the strength enhancement factor is clarified as not applying to single-sided welds, and the reduction factor for multi-orientation welds has been simplified.
    • Effective Area Method for Compression Members: Tables for factored axial compression resistances are now solely based on the effective area method.
    • Combined Shear and Moment in Beams: The beam selection and beam load tables now consider the reduction in shear resistance due to the presence of bending moment.

 

Disclaimer

The information provided in this article is intended for general educational and informational purposes only. SBSA make no representations or warranties regarding the completeness, reliability, or applicability of the information for specific engineering projects. Readers are advised to consult applicable codes, standards, and qualified professionals before making any design or construction decisions. SBSA disclaim any liability for errors, omissions, or outcomes resulting from the use of this information.