Building Code Council tags four alternative-construction appendices for revision after technical questions

The Building Code Council tag reviewed a package of proposals to adopt four International Residential Code appendices nationwide in Washington — covering straw bale, cob, hemp-lime and light straw/clay wall systems — but stopped short of recommendation after members requested targeted edits and a follow-up meeting.

Proponents and technical witnesses told the tag the appendices provide a prescriptive, consistent permitting pathway that will reduce the need for one-off alternative submissions and unpermitted construction. "I see these appendices as offering options, right, to conventional wood-frame construction," architect Martin Hammer said, arguing the documents are backed by structural, fire and durability testing. Verdon Structural Engineers principal Anthony Dente, who said he led engineering on several appendices, added the appendices are "robust, conservative documents" with guardrails that limit use where engineered design is required.

The tag's technical members raised a set of recurring concerns. Several members, including Quinn Tai, asked whether the appendices' references to ASTM tables and IRC energy chapters conflict with the Washington State Energy Code. "We do have our own energy code that's much more robust," Micah Chappell of Seattle Department of Construction and Inspections said, urging the proposals be tailored to Washington. Engineers and authors acknowledged the concern and said the appendix thermal values or U-value pathways can be used to comply with state energy requirements, but agreed the cross-references should be corrected.

Members also pressed on inspection and enforcement language. Tag members asked for explicit appendix language giving local building officials authority to require third-party or special inspections where needed; proponents pointed to existing appendix inspection sections for cob and straw-bale but agreed to add clarifying text that jurisdictions may require special inspections.

Seismic scope proved another sticking point. Several members recommended excluding prescriptive paths for the highest seismic zones (seismic design category E) and specifying that engineered designs or IBC alternative-submission paths are required there. "The conservative thing to say would be to exclude seismic design category E," Hammer said; engineers agreed that engineer-led alternative submissions remain viable for high-seismic areas.

Council staff said they will draft revisions addressing energy-code citations, inspection authority, scoping limits and the option to include recently approved fire-tested hemp-lime assemblies; the revised proposal will be circulated to proponents for review. The tag set a tentative follow-up meeting two weeks out to review edits and advance the package toward the state public-comment and rulemaking process.

Votes at a glance: The tag unanimously approved the meeting agenda and the minutes from the Sept. 2 meeting after brief clarification; at the end of the session members moved and voted to table remaining agenda items to the next meeting. No final action was taken on the appendices themselves.

The tag's next procedural step is for staff to publish redlined language and for proponents to return with targeted edits. The group scheduled a follow-up meeting to resume consideration and prepare the package for public comment and council deliberation.