United States
Hong KongFire-rated assemblies and gypsum
A fire rating belongs to a tested assembly, not to any component. Type X gypsum board is used in rated assemblies, usually at 0.625 inches, and every penetration needs a rated firestop system.
The single most consequential idea in the finishes category, and the one most often got wrong on real projects.
The rating is the assembly
A one-hour wall is a tested arrangement: specific board, specific thickness, specific framing, specific spacing, specific fasteners, specific joint treatment.
Change any of it and you no longer have the tested assembly, so you no longer have the rating.
Using Type X in an untested arrangement gives you a wall with expensive board in it. The listing is what carries the rating and the listing describes the whole system.
Type X
Gypsum board formulated for fire resistance, usually 0.625 inches thick. Type C is a further improved formulation used in some assemblies.
Thickness matters because it is part of the tested arrangement, not because thicker is generally better.
Penetrations
Every pipe, duct, cable and conduit through a rated assembly needs a firestop system rated for that penetration.
A hole with expanding foam in it is not a firestop. Firestop systems are tested and listed like the assemblies they protect. The listing is the rating.
Joints and edges
Head-of-wall joints, control joints and the perimeter all need treatment consistent with the listing. Fire follows gaps.
Why the general contractor cares
Because penetrations are made by every trade and firestopping is the coordination failure that fails inspections most often.
It is a general contractor problem even when no general contractor drilled the hole.
Common questions
What carries a fire rating?
The tested assembly as a whole, not any individual component.
What is Type X gypsum board?
Board formulated for fire resistance, usually 0.625 inches thick and used in rated assemblies.
Does rated board make a rated wall?
No. The listing describes the whole system, and substituting any part breaks it.
What is required at a penetration?
A firestop system tested and listed for that penetration. Expanding foam is not a firestop.
Why is this a general contractor issue?
Because every trade makes penetrations and firestopping is the coordination failure that most often fails inspection.