Firestopping

Definition

The tested system sealing a hole through a rated wall, to the wall's own rating.

Why It Matters

A fire-rated assembly is the recipe and this is what happens when somebody puts a hole in it. The code requires a through penetration to be protected by an approved firestop system installed as tested, rated not less than the assembly it passes through. Two ratings come with it: an F rating for how long the system holds the fire, and a T rating for how long it holds the temperature rise on the far side. The systems are proprietary and listed by number, and an installation has to reproduce the tested configuration, which is why inspection of the finished work is destructive and cuts it open. So a crew filling the gap with whatever was on the truck builds a defect that surfaces at somebody else's inspection years later. It runs the other way too. A shop in a qualified firestop contractor program can bid work its competitors cannot, but UL's version requires it to employ at least one designated responsible individual and keep a management system audited every year, so ask whether that person is staying.