When International Building Code (Section 714.4.1.1.2, 2012 ed.) says a firestop “shall have an F rating/T rating”, what does the slash line mean?
F rating divided by T rating
F rating OR T rating
F rating AND T rating
Or “you are just F…ing out of luck”?
They are two separate ratings. The particular section you cited is for horizontal assemblies, which requires firestopping to have both an F rating AND a T rating. Firestopping in other fire-resistance-rated assemblies (i.e., walls) are only required to have an F rating.
The F rating is for resistance to the passage of flame (hence the “F”) to the nonexposed side.
Because heat rises, horizontal assemblies are subject to extreme temperatures compared to vertical fire-resistance-rated assemblies, so they must resist the conductance of temperature (hence the “T”) through the firestop system to limit the temperature rise on the nonexposed side to 325 deg. F above its initial temperature.
If a firestop system does not have a T rating, then it cannot be used in a horizontal assembly.
I haven’t kept up for several years now, but it seems to me there was a W rating for firestopping on floors that had to do with water-tightness of the assembly. Is that still in effect?
You can get assemblies with a W rating, but it is not a requirement in the IBC. As far as I know, it never has been … unless it was a local amendment.
There is a W rating, but the IBC does not currently require that rating and there were no proposals to include that rating for the 2018 IBC. Thus, it is an owner/designer decision to require the W rating.
There is also an “L” rating that measures passage of smoke. At one time I believe NFPA 101 required “L” ratings for some assemblies. I don’t believe that IBC has every required “L” ratings. IBC requirements regarding smoke barriers do not appear to “quantitative”.
Does anyone know if “L” ratings are being require by any codes?
IBC 714.5 Penetrations in smoke barriers and 715.6 Fire-resistant joint systems in smoke barriers have requirements for L ratings
I understand
T is for Temperature Rise
F is for Flame penetration
What are L & W (besides the name of a gyp board distributor)?
I’m sure there is probably a better (more direct) source, but I’m liberally copying the following from this website: https://www.uniquefirestop.com/ul-systems/
Flame: The F rating is expressed in hours. This number indicates the specific length of time a barrier can withstand fire before being consumed or before permitting the passage of flame through an opening.
Temperature: The T rating is expressed in hours and indicates the length of time the temperature on the side of the penetration without fire does not exceed 325 F above the ambient temperature. This ensures the temperature on the side of the wall away from the flame does not reach the flash point of any materials on that side of the wall.
Smoke: The L rating is the amount of air (smoke) that can leak through a penetration, measured in cubic feet per minute. The test is administered at ambient temperature and at 400 F to determine the actual performance of fire-stopping materials at different temperatures.
Water: The W rating, established in 2004, indicates the fire-stopping material has passed the UL test for water tightness. The Class One requirements for water tightness include subjecting the material to a 3-foot water column for 72 hours, followed by a fire and hose stream test, conducted in accordance with ANSI/UL 1479. A Class Two listing requires the material to be resistant to a 20-foot water pressure head. Finally, a Class Three listing requires the material to be resistant to 57.54-foot water pressure head. According to one of its spokesmen, UL developed the new W rating to prevent water damage and mold-friendly moisture associated with through penetrations.