Occupancy Classification, Types of Construction, and Height/Area
This domain tests whether you can classify a space, assign a type of construction, and then apply the height and area limits that follow from that pairing. Most items give you a described building and ask for the occupancy group, the construction type, or which allowance lets an otherwise noncompliant building stand.
Core rules
- Occupancy groups are assigned by the purpose for which a space is used - assembly, business, educational, factory, high-hazard, institutional, mercantile, residential, storage, utility - and a building may hold more than one.
- Accessory occupancies that are ancillary to the main use and do not exceed roughly 10 percent of the story's floor area are classified with the main occupancy rather than separated from it.
- Types of construction run from Type I (most fire-resistive, noncombustible) through Type V (combustible), with A and B subtypes marking higher or lower fire-resistance for the structural frame.
- Height and area are limited by a table that cross-references occupancy group and construction type, and the limits can be increased for open frontage and for the presence of an automatic sprinkler system.
Worked example
A 100,000-square-foot warehouse includes an 8,000-square-foot office suite used solely by warehouse staff. The office is 8 percent of the story area and serves the main use, so it is an accessory occupancy and is classified as storage rather than as a separated Group B. That single step often preserves the building's allowable area. If the office grew past the accessory threshold, a rated separation or a mixed-occupancy calculation would be required.
Traps
- Classifying by building name or tenant label instead of by actual use.
- Stacking the frontage and sprinkler increases without checking each one's conditions.
- Treating an A/B subtype as interchangeable - the subtype changes structural frame, bearing wall, and shaft ratings.
- Forgetting that mixed occupancies can be handled either separated or nonseparated, and that the two routes have different requirements.