Significant Changes in ANSI/AWC WFCM-2024

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Summary of the Presentation: Significant Changes in the 2024 Wood Frame Construction Manual (WFCM)​

This presentation, hosted by the American Wood Council (AWC), covers significant updates in the 2024 Wood Frame Construction Manual (WFCM), which replaces the 2018 edition and is referenced in the 2024 International Building Code (IBC) and International Residential Code (IRC). The updates primarily align with changes in ASCE 7-22, AWC’s 2021 Special Design Provisions for Wind and Seismic (SDPWS), and other relevant standards.

Key Updates in the 2024 WFCM​

1. Component and Cladding (C&C) Wind Uplift Provisions
   • Updates reflect changes in ASCE 7-22 wind load calculations, particularly for roof overhangs and uplift pressures.
   • Wind pressure coefficients were revised, slightly decreasing Zone 3 (high uplift zones) loads but increasing Zone 2 loads in some cases.
2. Snow Load Provisions
   • Snow loads now reference ASCE 7-22, with an increase in the thermal factor from 1.1 to 1.2 for ventilated attic insulation.
   • Unbalanced snow load provisions are updated, including how drift surcharge loads are determined.
3. Alignment with the 2021 SDPWS
   • Changes reflect updates in shear wall design, shear capacity adjustments, and connection detailing.
   • Perforated shear wall design calculations now use area-based methods rather than length-based methods.
   • Adjustments to wood structural panel sheathing, separating requirements for OSB and plywood.

Structural Design and Code Integration​

• The WFCM scope remains limited to one- and two-family dwellings but allows for small commercial buildings under specific limitations.
• The IBC Section 2309 allows WFCM provisions for Risk Category I and II buildings.
• The IRC recognizes the WFCM as an alternative design standard for structural provisions.

Key Technical Revisions​

• Roof Uplift Loads
  • Revised uplift values for rafter connections, ridge beams, and hip/valley beams based on new wind and snow load calculations.
• Sheathing and Fastener Requirements
  • Updated roof sheathing uplift loads require higher nail capacities in some cases.
  • Added differentiation between plywood and OSB sheathing requirements.
• Connection Detailing Adjustments
  • Revised strap and anchor bolt requirements based on updated seismic and wind provisions.
  • Changes to outlooker span requirements and rake overhang connections.

Conclusion​

The 2024 WFCM reflects significant updates in wind, snow, and seismic provisions, aligning with ASCE 7-22 and AWC’s 2021 SDPWS. These changes ensure more accurate load calculations, improved structural performance, and better code consistency for wood-frame construction.

For further details, professionals can refer to:

• 2024 WFCM Commentary
• 2021 SDPWS with Commentary
• ASCE 7-22 Design Guide

This concludes the summary of the presentation.