Building Code Council members debate IRC 'multiplex' appendix: stories, separations, sprinklers and shared spaces

Members of the state Building Code Council spent most of their Aug. 26 meeting detailing a proposed appendix to the International Residential Code (IRC) that would permit ‘‘multiplex’’ buildings — residential buildings of up to six dwelling units and up to three stories — and debating how those buildings should be defined and protected.

The council agreed on several baseline limits but left several major policy questions open, including whether to allow shared common areas or interior stairs that serve more than one unit, whether some projects could avoid automatic sprinklers if walls between units are built to higher fire-resistance ratings, and whether multiple multiplex buildings may be attached together. The group scheduled further work and assigned members to draft language on means of egress and separations for the next meetings on Sept. 9 and Sept. 23.

The matter matters because the appendix would let jurisdictions adopt a prescriptive alternative for small multifamily housing drawn into the IRC instead of the International Building Code (IBC). Proponents say that makes construction more affordable and easier to build on small infill lots; several council members and local officials warned that relaxing building-code requirements can raise life-safety risks and complicate water-supply and fire-access requirements.

Dustin (staff member) opened the discussion by reminding the group that the council had split its meetings to treat ‘‘single-exit’’ and ‘‘multiplex’’ topics separately. He walked members through a baseline draft and a separate proposal submitted by Marcus Johnson, who had asked the council to consider rules for attaching multiple multiplex buildings and for design flexibility.

The council settled a few basic limits: members expressed consensus that multiplex buildings in the appendix should be limited to three stories and 60 feet in height,…