Class C Fire Rating for FRP Panels: What It Means for Your Building

What the Fire Rating Actually Measures

The fire rating on an FRP panel is not a measure of whether the panel burns. It is a measure of two specific things: how fast flame spreads across its surface, and how much smoke it generates while doing so. Both values come from a single test — the Steiner Tunnel — run under either ASTM E84 (the U.S. standard) or CAN/ULC-S102 (the Canadian equivalent). The two test methods are functionally identical and the results are interchangeable for Ontario Building Code purposes.

In the test, a 24′-long sample of the material is mounted in the ceiling of an enclosed tunnel and exposed to a calibrated gas flame for 10 minutes. Instruments measure how far the flame travels along the surface and how much light a smoke beam can still pass through the exhaust. The two numbers that come out are the Flame Spread Index (FSI) and the Smoke Developed Index (SDI), each scored against red oak (FSI 100) and inorganic reinforced cement board (FSI 0).

Class A, B, C — What Each One Means

Notice that the smoke developed limit (≤450) is the same for all three classes. The difference between Class A, B, and C is entirely about how quickly flame can travel across the surface — not about how much smoke is produced or whether the material is “safe.”

What These Numbers Mean in a Real Fire

Plain English: in a building fire, the wall finish is rarely the source of ignition. The contents — cooking oils, packaging, paper goods, plastics — are what start and sustain fires. The wall finish matters because if flame reaches it, the question is how fast it spreads to the next room.

• Class A surfaces burn slowly enough that they buy occupants extra evacuation time even in spaces with high occupancy or long egress paths. Required where the consequences of trapped occupants are highest — exit corridors, assembly halls, schools.
• Class B surfaces are an intermediate tier — acceptable in many commercial occupancies under the OBC where Class A is not specifically required.
• Class C surfaces contribute to flame spread more than Class A, but in occupancies where contents and equipment are the dominant fire load (a commercial kitchen has cooking oils everywhere; a food plant has packaging stacks), the wall finish is not the controlling factor. Class C is the correct rating for the use.

How to Read an FRP Panel's Test Report

Any reputable FRP manufacturer publishes a test report (sometimes called a “classification report” or “test certificate”) for each product. Ask for it before you spec. The report will state:

• The test method (ASTM E84 or CAN/ULC-S102).
• The laboratory that conducted the test (Intertek, UL, QAI, etc.).
• The exact panel composition and thickness tested.
• The Flame Spread Index value and the Smoke Developed Index value.
• The classification: Class A, B, or C.
• The date of the test (most jurisdictions accept reports within 10 years).

If a supplier cannot produce a current test report for the exact panel they are quoting you, do not spec the product. The OBC, CFIA, and Public Health inspectors can all request the report.

Ontario Building Code §3.1.13 — Where Class C Is Accepted

OBC §3.1.13 governs the flame spread and smoke developed ratings of interior finishes. The detailed table in the Code maps each occupancy classification to a required maximum FSI. The simplified version that covers most commercial FRP applications:

This table is a starting point — always verify the specific requirement with the Authority Having Jurisdiction (the local building department) for your occupancy classification, sprinkler status, and building height/area. A sprinklered building often gets a one-class reduction allowance under the OBC; an unsprinklered high-occupancy space may need a higher class than the table suggests.

Is Class C “Less Safe” Than Class A?

This is the most common question we get from facility managers, and the honest answer is no — for the right occupancy. The fire-rating classes are a building-code tool for matching surface flame-spread performance to the consequences of failure in a given space. A Class C panel in a kitchen is not “less safe” than a Class A panel in an exit corridor; they are correctly rated for different jobs. Specifying a Class A panel in a commercial kitchen does not make the kitchen safer — it just costs more money for a margin the code does not require.

Where Class C is wrong is when the OBC requires Class A or B for the space — exit paths, assembly, certain school and care occupancies — and someone substitutes Class C anyway. That is a code violation and a real safety issue, but the failure is the substitution, not the panel itself.

How Class C Relates to CFIA Compliance

CFIA cares about the wall surface being smooth, non-absorbent, durable, and cleanable. It does not specify the fire rating — that is the OBC's job. But the CFIA-acceptable system spec we use for food facility installs is built on Class C FRP because it is the right OBC rating for almost every food-facility occupancy. Both reviews — CFIA wall surface and OBC §3.1.13 — pass with the same Class C panel installed to the system spec. Detail in our CFIA install requirements guide.

Specifying the Right Rating for Your Project

If you are building or refitting in the GTA and not sure whether your space requires Class A, B, or C, the safest path is a 10-minute call with your architect or local building department before you spec the wall finish. Corevance regularly works alongside designers and AHJs to confirm the correct rating, supply the matching panel test reports, and install to the OBC and CFIA spec. Call 437-849-3781 for a free spec review.