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Engineers, product groups urge SBCC to retain model CLT provisions and not relax lumber-grade or thickness requirements
Summary
Stakeholders including APA, PRG committee members and structural engineers told SBCC that proposed Washington-specific relaxations to CLT lumber-grade or thickness could reduce airtightness and fire-life-safety margins; they urged adopting current 2024 IBC language and NCAPA PRD 3 20 (2025) provisions.
Several technical witnesses raised concerns about proposed state amendments affecting cross-laminated timber (CLT) specifications.
Eric Gu (APA Technical Services) said a proposed relaxation of minimum lumber grade in longitudinal layers effectively creates a state-specific deviation from the consensus NCAPA PRD 3 20 standard and could compromise CLT airtightness and fire containment. Hans Scribe Bomgren, a registered structural engineer and PRG 3 20 committee member, said the 2024 IBC corrected a prior error by specifying actual, not nominal, CLT thicknesses and urged the SBCC to carry the model-code language forward rather than retain an amendment that could undersize roofs, floors and walls by about 0.5 inch.
