Understanding UL Nomenclature for Firestop-Through Penetrations: Part 1

(#3 in a Series)

The UL firestop nomenclature, as you saw in Understanding UL Nomenclature for Firestop-Rated Joints  is a series of letters and numbers. It is a sort of ABC’s and 123’s of firestop installation systems. The joints are very much straight forward. The through penetrations are slightly more involved because you are dealing with the various MEPS (Mechanical, Electrical, Plumbing, Fire-Sprinkler) trades and subsequently, a lot more variability than is found with joints. The good news is that the first letter and the first number are the most important things to focus on. This makes it a little easier to understand.

The first letter will be one of 3 letters W, F or C. W stands for wall (I told you it was easy) F stands for floor and C stands for combination. This means that the assembly can be either a floor or a wall. However, if you want to remember that it stands for concrete you will be very close because concrete is the only construction material typically used for both floors and walls and the UL listed details that start with C can be used both for floor applications as well as wall applications. The other letters give you more information about the assembly. For example WL is a framed gypsum wall WJ is a concrete or block wall, FC is for stick built construction and FA would be a concrete floor 8” thick or less.

A, B, C, J and L are the key ones you will deal with. If you want more specifics here is the actual break-down:

A = Concrete floors less than or equal to 5 inches thick
B = Concrete floors greater than 5 inches thick
C = Framed Floors
D = Steel Decks

E = Floor Ceiling assemblies consisting of concrete with membrane penetrations (update 3/2/2019)

F-I = Not Used
J = Concrete or Masonry Wall less than or equal to 8 inches thick
K = Concrete or Masonry Wall less greater than 8 inches thick
L = Framed Walls
M = Bulkheads Marine
N-Z = Not Used

The numbers get a little more in-depth and we will get into that in Part 2.

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