SBCC committee issues interpretation: ADU/duplex cannot egress through another unit; protected shared egress allowed under specified conditions

The BFRW voted Feb. 13 to approve a draft opinion answering whether an accessory dwelling unit (ADU) or duplex may egress through another unit and whether attached dwelling units may use a shared egress area.

Dustin reviewed the code language and the committee's reading of the 2021 IRC: "Based on these sections, R311.1 and R311.2, it would be my interpretation that you are not allowed to egress through a separate dwelling unit to get to the public way," he said. That formed the committee's answer to question one.

On question two—whether attached dwelling units may have a shared protected egress area—the committee concluded that Washington's code amendments allowing "shared accessory rooms" (R302.3/R302.35 as applied to two‑family dwellings) permit a protected common space provided it meets the protective opening and separation criteria. Micah and Angela noted that practice varies by jurisdiction and that some jurisdictions accept rated vestibules or alternate methods.

The committee approved the interpretation draft by motion and will issue the opinion as the BFRW position on the 2021 IRC. The chair emphasized that an opinion is advisory and jurisdictions retain authority to apply alternate methods or local interpretations.

Next steps: SBCC staff will finalize the opinion text for distribution as the committee's response to the request.