Workgroup asks staff to refine IRC vs IBC comparisons for multiplex appendix

SBCC staff presented a draft multiplex housing appendix targeted for the International Residential Code (IRC), allowing more than two units to be placed vertically under a residential code pathway rather than the International Building Code (IBC). The staff member framed the appendix as a way to enable multiplex typologies under a more residential design approach and as part of the 2024 code package.

Roger Heeringa and other members pointed out inaccuracies in the staff’s single‑stair comparisons and urged a recheck of code tables; Heeringa said the principal cost difference stems from shifting design and engineering from an IBC commercial approach to an IRC residential approach. “The low end for an IRC building is $200 a square foot; the low end for an IBC is $300 a square foot,” Heeringa said as a rough comparison, and urged staff to explicitly call out engineering and review‑time savings in the analysis.

Angela Haupt said plan‑review time may not change substantially in large jurisdictions with dedicated senior reviewers but could reduce time for smaller jurisdictions. Staff agreed to revisit the IRC vs IBC comparisons, incorporate engineering cost considerations, and clarify which multiplex sizes and configurations the appendix would permit.

No formal motion was taken on the multiplex appendix at this meeting; staff will revise the draft analyses and return them for workgroup and Council consideration.