The building code requires that the construction separating residential and commercial uses resist the spread of fire. In existing houses it is usually not practical to meet the specific requirements of the code, and the building code appeal process can approve an arrangement that meets the intent of the code separations.
You should expect that an approved separation will mean applying several layers of gypsum board to the existing walls and/or ceilings between the residential and commercial uses. The separation would also have to be provided at the stairwells or any other place where the two different uses (residential and commercial) come together. For more information on Building Code requirements, talk to a Life Safety reviewer at 503 823-1456. Or, visit our Development Services Center.