Fire Penetration Rating Terms

F Rating, T Rating? What?

Fire rated assemblies are complicated enough but it is equally important to make sure that any penetrations of those assemblies are also put together well.

First some definitions:

F RATING. The time period that the through-penetration firestop system limits the spread of fire through the penetration when tested in accordance with ASTM E 814 or UL 1479.

T RATING. The time period that the penetration firestop system, including the penetrating item, limits the maximum temperature rise to 325°F (163°C) above its initial temperature through the penetration on the non-fire side when tested in accordance with ASTM E 814 or UL 1479.

MEMBRANE PENETRATION. An opening made through one side (wall, floor or ceiling membrane) of an assembly.

THROUGH PENETRATION. An opening that passes through an entire assembly.

Now onto the Code!

IBC 713 (2009) Covers the specifics of fire barrier penetrations.

713.3 Fire-resistance-rated walls.
Penetrations into or through fire walls, fire barriers, smoke barrier walls and fire partitions shall comply with Sections 713.3.1 through 713.3.3. Penetrations in smoke barrier walls shall also comply with Section 713.5.

713.3.1.2 Through-penetration firestop system.
Through penetrations shall be protected by an approved penetration firestop system installed as tested in accordance with ASTM E 814 or UL 1479, with a minimum positive pressure differential of 0.01 inch (2.49 Pa) of water and shall have an F rating of not less than the required fire-resistance rating of the wall penetrated.

Finally a summary of where F and T ratings are required:
(IBC 2009 Commentary)

A T rating is not required for wall penetrations, but a minimum of 1 hour is required where the through-penetration firestop system is installed in a floor assembly where the penetrating item is a pipe, tube or conduit that is in direct contact with a combustible material. This requirement is intended to minimize the potential for ignition of the combustible material on the unexposed side of the assembly due to elevated temperatures transmitted via the pipe, tube or conduit.

And where does the rubber meet the road on this?

I like to use the Hilti UL Firestop system selector.

It lets the user plug in their criteria and narrow down which product works for their assembly and penetration combination.

I know you’re excited!  Now go find some Firestop systems!


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