The building code sorts the ways that buildings are used into separate "occupancy classifications". Every building is given an occupancy classification when it is built, and each occupancy classification has different building code requirements that go along with it. The requirements reflect the type of hazard or uses in the building.
A change of occupancy is when the proposed use would fall under a different occupancy classification than the building's existing permitted use. Changing a residential unit to commercial use, or changing a commercial unit to residential use, would be a change of occupancy. As would changing a unit approved for either commercial or residential use to a mixed use unit.
For a single unit to be used for mixed live/work, the city will review for the most restrictive requirement that applies to either a residential or a commercial use. For example, the unit's kitchen would have to meet the more strict commercial code requirements, and the room that could be used for sleeping would have smoke detector requirements that wouldn't apply to a normal commercial unit. Where live/work units have commercial space on one level and residential use on another, we approve plans that show the occupancy classifications of each level clearly identified.
Changing a residential unit to allow any commercial use is particularly difficult if the building is less than three years old. Building code requirements to do with accessibility improvements for disabled people don't only apply to new work. The code requires that improvements be made to the access based on the value of any alterations made to the building in the past three years. That means that, for a recently constructed building, the cost of the original construction would be included.
A residential unit that is served by stairs rather than an elevator will be especially difficult to alter for commercial use.
A Life Safety Reviewer can answer any questions that you have concerning a change of occupancy to live/work. Visit the Development Services Center or call (503) 823-1456.