Window Frame Rating

Q: Can you verify what a window frame rating should be in a 1-hr load bearing wall? Does the frame need to maintain the 1-hr rating of the wall or can it be 45-minutes? This window is in a load bearing wall that separates a corridor from an office.

A: Since windows are openings in fire-rated barriers, I turn to NFPA 80-2010, section 17.1.3 on window frames. This section says fire window frame assemblies must be permanently labeled for such use. The Annex section of A.17.1.3 says the labeled assembly includes the frame and can include a ventilator, glazing material, retaining members, mullions, and hardware, if applicable.

The label reading ‘Fire Window Frame’ includes the design and construction of the frame, ventilator, glazing material retaining numbers, and hardware. Table of the 2012 Life Safety Code provides the minimum fire protection ratings for opening protectives in fire-rated barriers. According to “Exit Access Corridors” on this table, fire window assemblies in 1-hour corridor walls are permitted to be ¾ hour fire rated. So the frame would also be ¾ hour rated.