A 1-hour fire resistance rating means a wall, floor, beam or column assembly withstood 60 minutes of a standardized furnace fire, under ASTM E119 or UL 263, without failing structurally or letting fire and heat through.
Ratings are earned by testing a specific assembly, or by calculation methods the code allows, and are documented in listings such as those from UL. Change the assembly, for example by adding an unsealed penetration, and the rating no longer applies.
Where garages meet ratings
- Construction type. Type IIA requires a 1-hour frame and floors; Type IIB requires none. See Type II construction and Type I construction.
- Separations. Walls and floors between a garage and other uses often need a rating, set by the occupancies involved and whether the building is sprinklered.
- Exits and shafts. Stair and elevator enclosures commonly need rated construction. See vertical circulation.
- Penetrations. Pipes, conduits and ducts passing through a rated assembly need tested firestop systems.
What a rating does not mean
- It is not a promise that a real fire will last an hour or that the building will survive one; it is a comparison against a standard test.
- It covers the assembly as tested. Field changes, damage and missing firestopping erode it.
The Parkonomics view
A rating is a chain, and the weak link is usually a hole someone drilled later. When chargers, conduits or new tenants arrive, put firestopping on the punch list with the same priority as the wiring.
Related terms: Type II Construction, Type I Construction, Smoke Barrier, Fire Wall, International Building Code, NFPA