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Keeping a useful doorway in an attached ADU fire separation
A doorway between an attached ADU and the main dwelling could be convenient, but I’m unsure how much it changes the required fire separation. Do local code and the ADU’s layout determine whether an interior connection is allowed and what protection it needs?
I’d also like to understand how doors and other openings differ from pipes, wiring, or ducts passing through the shared wall or ceiling. Existing framing and concealed conditions could limit the options, so this seems worth discussing with the building department and a qualified designer early. What choices have you found are most affected by the specific layout, rather than a generic wall-rating assumption?
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2 replies
“Attached ADU” doesn’t by itself settle whether a doorway can connect it to the main dwelling. The answer can depend on how the local code classifies the ADU and which code and amendments the jurisdiction has adopted. I’d identify those rules first; only then can a designer or building official say whether the opening is permitted and what protection it needs.
- Concealed framing can make the practical choice less obvious: a door is a large, operable opening, while pipes and wiring usually pass through smaller, localized penetrations. Ducts are a separate concern because they can carry smoke and may need specific protection.
- So even if a connecting door is permitted, that doesn’t settle how services can cross the separation. Each opening and penetration needs its own compliant detail, and the existing layout may mean routing services elsewhere is simpler than altering the shared wall or ceiling.