Flooring (C-15) · Lesson 5 of 7

Floor Finish Fire Class: Radiant Flux Classes and Where They Apply

"Floor Finish Fire Class: Radiant Flux Classes and Where They Apply" is lesson 5 of 7 in the Flooring (C-15) Learning Hub. It opens with "What Section 804 Covers" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. What Section 804 Covers
  2. Class I and Class II
  3. Where a Minimum Class Is Required (804.4.2)
  4. The Sprinkler Exception
  5. Testing, Hang Tags, and Carpet Over Underlayment

The worked example in the course applies this lesson to a realistic job in 5 steps, from "Classify each product" through "Paperwork".

What you'll be able to do

  • Explain the main idea of "Floor Finish Fire Class: Radiant Flux Classes and Where They Apply" in plain language you can use on the exam.
  • Apply this step with confidence: "Where a Minimum Class Is Required (804.4.2)".
  • Apply this step with confidence: "The Sprinkler Exception".
  • Apply this step with confidence: "Testing, Hang Tags, and Carpet Over Underlayment".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Floor Finish Fire Class: Radiant Flux Classes I and IICRITICAL RADIANT FLUX, W/cm²no classClass IIClass I00.220.450.60P 0.52Q 0.31R 0.40Class I: 0.45 W/cm² or greaterClass II: 0.22 W/cm² or greaterHang tag: maker, style, and class (804.3).Carpet is tested with its underlayment.CLASS NEEDED BY SPACECorridor inNeedsPQRGroup BClass IIOKOKOKI-2, no sprinklersClass IOKNONOI-2, sprinkleredClass IIOKOKOKI-2 = areas where restraint is not used.Sprinklered = throughout, per 903.3.1.1or 903.3.1.2 (exception to 804.4.2).Under 0.22 W/cm² is neither class.P is Class I; Q and R are Class II. Class I rooms need P unless sprinklered.Tag the product, test carpet with its underlayment, and keep the test report for the building officialSource: 2025 CBC 804.1 to 804.4.2 (Chapter 8, p. 5). Groups B and I-2 per 804.4.2.CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: What Section 804 Covers

2025 CBC Section 804.1 makes interior floor finish and floor covering materials comply with Sections 804.2 through 804.4.2. Its exception exempts floor finishes and coverings of a traditional type, such as wood, vinyl, linoleum or terrazzo, and resilient floor covering materials that are not composed of fibers, in areas other than Groups I-2 with detention and I-3. In practice the section bites hardest on carpet and other fiber floor coverings.

Step 2: Class I and Class II

2025 CBC Section 804.2 classifies floor materials by critical radiant flux, tested under ASTM E648 or NFPA 253: Class I is 0.45 watts per square centimeter or greater, and Class II is 0.22 watts per square centimeter or greater. Section 804.4.1 requires all occupancies to meet ASTM E648 with a specific optical density smoke rating not exceeding 450 per ASTM E662. A reading below 0.22 W/cm² is in neither class.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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