Fire resistance rating
A fire resistance rating states how long a building element can contain fire or keep its function in a standard test, usually given in hours.
A fire resistance rating states how long a building element can contain fire or keep its function in a standard test, usually given in hours.
Definition
A fire resistance rating is a classification, expressed as a period of time, for how a wall, floor, door or other element performs when exposed to a standard fire test. It is a result for a tested assembly, not a general quality.
A plain example
A designer may call for a wall assembly rated for a certain number of hours. The contractor then builds exactly the listed assembly: specified studs, boards, fasteners, joint treatment and firestopping, since changing parts can void the listing.
Why it matters
Ratings drive layout and materials in corridors, shafts, party walls and exits. They are tied to code, and approval rests with the authority having jurisdiction, so the assembly chosen must match a recognised listing.
Common confusion
The rating belongs to an assembly, not to a single board or stud. Fire resistance is also not the same as reaction to fire or flame spread, which describe how a surface burns. Never assume a product is rated alone.
On a project
Find the listing number or design number cited in the specification and make sure the contractor submits the same assembly. Check firestopping at penetrations and joints, since the rating relies on them.
Quick answers
- Is the rating a property of one material? No. It applies to the tested assembly with all of its parts.
- Is fire resistance the same as flame spread? No. Flame spread and reaction to fire describe surface burning, not how long an assembly holds.
- Who approves a rated assembly? The authority having jurisdiction. Confirm with the engineer of record and the local authority.
Related terms
Always check the project drawings and specification, and confirm requirements with the engineer of record and the local authority.
Questions people ask
Is the rating a property of one material?
No. It applies to the tested assembly with all of its parts.
Is fire resistance the same as flame spread?
No. Flame spread and reaction to fire describe surface burning, not how long an assembly holds.
Who approves a rated assembly?
The authority having jurisdiction. Confirm with the engineer of record and the local authority.
Sources and further reading
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