Add 5th Apartment Without Sprinkler System?

There is a seemingly willful gap in information in scoping code (IBC) for small group R structures: those on the threshold of IRC/IBC: I am working on an existing 4 unit building where we do not have verified assembly information so the construction is assumed to be V-B.

The owner would like to renovate the existing basement, which is ~50% above grade, into an apartment with a new exterior exit. Three of the units share a common interior exit stairway & the upper ones are served by a fire escape. The 4th unit is built like a townhouse on the rear of the building and does not share any exit components.

If an existing 4-unit residential building (currently not sprinkler protected) adds a 5th unit in the basement — and that unit does not share exit components — is there a code path that allows the project to proceed without installing sprinklers throughout the entire building?

Or, a way to construct the new unit in an existing fire area in a way that does not increase risk (ie: 2-hour separation)?

While the group is a trigger for requiring a system, looking at Chapter 5 as a scoping reference, the total fire area is below the threshold for a sprinkler system in group R-2 with V-B construction.

Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe