AEC definitions
A fire-resistance rating is the period, in hours, that a building assembly is shown by test or listed design to withstand fire and transfer of heat. A 1-hour wall meets that test only if it is built as the listed assembly, including the fasteners, the joints, and the penetrations. Writing '1-HR' on a wall type without an assembly is not a rating.
Definition
Ratings apply to walls, floors, roofs, doors, and dampers as the code requires for construction type, occupancy separation, shafts, and corridors. Fire-resistance rating is not the same as flame spread on a finish. A door in a rated wall has to have a compatible rating and closer. Penetrations need a listed firestop. The plans should key each rated element to a listed assembly or a prescriptive code detail. The inspector looks for that assembly in the field, not for the note.
In depth
A UL or similar design number states stud spacing, layers, and screws. Substituting a board because it is 'also gypsum' can void the rating. The submittal should include the design number the drawings name.
If the project uses a prescriptive code table instead of a listing, cite the table. Do not invent a hybrid.
A 1-hour wall with an unrated door is not a 1-hour separation. Door, frame, glazing, and closer come from the door schedule and the listing. Dampers protect duct openings. Firestopping protects the rest.
Sidelights and borrowed lites are openings. They need a rating when the wall does.
A rated floor that stops at a curtain wall without the joint detail is a gap. Shafts must run through the roofs or floors the code names. The section is where continuity is drawn. The plan tag alone does not show it.
Penetrations above the ceiling are still penetrations. The rating does not stop at the tile.
Changing a tag from 1-hour to 2-hour in a revision requires the assembly, the doors, and the supports to change with it.
The structural ability to carry the extra layers is part of the change.
Examples
Partition type A1 cites a listed 1-hour design. The door schedule gives those openings a 45 or 60 minute door as the code requires for that wall.
A duct penetration includes a fire damper and an access panel. The rating note alone would not have been enough.
The wall section shows the shaft wall continuing to the underside of the deck, with the joint firestopped.
FAQ
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