--- title: "FRP Grating ASTM E84 Class 1 Fire Rating: Test Results" description: "ASTM E84 fiberglass grating fire rating: Class 1 means a flame spread index of 25 or less. See FSI and SDI results for six Strongrate models on DNV TAF0000191." url: https://www.strongrate.us/resources/astm-e84-class-1-fire-rating/ markdown: https://www.strongrate.us/resources/astm-e84-class-1-fire-rating.md published: 2026-10-16 updated: 2026-10-17 --- [Home](https://www.strongrate.us/) › [Resources](https://www.strongrate.us/resources/) › [ASTM E84 fire rating](https://www.strongrate.us/resources/astm-e84-class-1-fire-rating/) # What Does ASTM E84 Class 1 Mean for FRP Grating? _Updated Oct 17, 2026_ In ASTM E84 testing of fiberglass grating, Class 1 (also called Class A) means a flame spread index of 25 or less; building-code Class A also caps the smoke-developed index at 450. Six Strongrate models on DNV Type Approval TAF0000191 Rev. 1 test at flame spread 5–20 and smoke-developed 15–400. For other models, ask for the report on the finished grating. ## What are Strongrate’s ASTM E84 results for fiberglass grating? DNV lists an ASTM E84-19a flame spread index (FSI) and smoke-developed index (SDI) for each of the six models on Type Approval TAF0000191 Rev. 1, issued Feb 11, 2022 and valid until Feb 10, 2027. Each result applies to its own model and resin only. **ASTM E84 fiberglass grating results: six Strongrate models as listed on DNV Type Approval TAF0000191 Rev. 1 (ASTM E84-19a)** | DNV designation | Type and mesh or profile, in (mm) | Depth, in (mm) | Resin | FSI | SDI | Product page | | --- | --- | --- | --- | ---: | ---: | --- | | 38×38×25 mm [note 1] | Molded, 1-1/2" × 1-1/2" (38 × 38 mm) square [note 1] | 1" (25 mm) [note 1] | Isophthalic polyester [note 1] | 10 [note 2] | 55 [note 2] | [1" molded grating](https://www.strongrate.us/molded-fiberglass-grating/1-inch-square-mesh/) | | 38×38×32 mm [note 1] | Molded, 1-1/2" × 1-1/2" (38 × 38 mm) square [note 1] | 1-1/4" (32 mm) [note 1] | Fire-retardant orthophthalic polyester [note 1] | 5 [note 2] | 250 [note 2] | [Molded fiberglass grating](https://www.strongrate.us/molded-fiberglass-grating/) | | 38×38×38 mm [note 1] | Molded, 1-1/2" × 1-1/2" (38 × 38 mm) square [note 1] | 1-1/2" (38 mm) [note 1] | Isophthalic polyester [note 1] | 15 [note 2] | 30 [note 2] | [1-1/2" molded grating](https://www.strongrate.us/molded-fiberglass-grating/1-5-inch-square-mesh/) | | 25.4×152.4×38 mm [note 1] | Molded, 1" × 6" (25 × 152 mm) rectangular [note 1] | 1-1/2" (38 mm) [note 1] | Vinyl ester [note 1] | 10 [note 3] | 15 [note 3] | [Rectangular mesh](https://www.strongrate.us/molded-fiberglass-grating/1x4-rectangular-mesh/) | | I 6015 [note 4] | Pultruded I-bar [note 4] | 1-1/2" (38 mm) [note 5] | Isophthalic polyester [note 4] | 20 [note 2] | 400 [note 2] | [I-bar grating](https://www.strongrate.us/pultruded-fiberglass-grating/i-bar-1-5-inch/) | | T5020 [note 4] | Pultruded T-bar [note 4] | 2" (50 mm) [note 5] | Vinyl ester [note 4] | 20 [note 2] | 300 [note 2] | [T-bar grating](https://www.strongrate.us/pultruded-fiberglass-grating/t-bar-2-inch/) | _DNV designations read as mesh × mesh × depth. The certificate does not state the pultruded depths; they are from Strongrate’s 2023 catalog (types I-6015 and T-5020)._ Notes: 1. Inch sizes are North American nominals of the metric certificate designation. 2. Result as listed on DNV certificate TAF0000191 Rev. 1 (ASTM E84-19a); applies to this model only. 3. Result as listed on DNV certificate TAF0000191 Rev. 1 (ASTM E84-19a); applies to the 1" × 6" model only, not to a 1" × 4" product. 4. Bar depth and open area are not stated on the certificate. 5. Values as printed in the factory catalog (2023); confirmed in your quote and submittal drawings. All six flame spread indexes are at or below the 25 that US guide specifications call Class 1 or Class A, and all six smoke-developed indexes are at or below the 450 that building-code Class A allows. The lowest FSI, 5, belongs to the fire-retardant orthophthalic model (38×38×32 mm); the highest SDI, 400, belongs to pultruded I-bar model I 6015. ## Is every Strongrate resin rated Class 1? Strongrate’s 2023 catalog says so. It lists four fire-retardant resin systems, vinyl ester (VEFR), isophthalic polyester (IFR), food-grade isophthalic polyester (FG) and orthophthalic polyester (OFR), and rates each one ASTM E84 Class 1, a flame spread index of 25 or less. Test results apply to the model and resin tested, so for any size, mesh or resin other than the six above, ask for the E84 report on the finished grating before you specify it as Class 1. ## What does Class 1 mean under ASTM E84? ASTM E84 is a tunnel fire test, and grating results are reported as a flame spread index and a smoke-developed index. US guide specifications for fiberglass grating require a flame spread index of 25 or less, the rating the industry calls Class 1 or Class A. The building-code Class A for interior finish pairs that limit with a smoke-developed index of 450 or less. **Fire-rating limits that FRP grating specifications cite** | Rating | Flame spread index (FSI) | Smoke-developed index (SDI) | Where it is used | | --- | ---: | ---: | --- | | Class 1 / Class A (grating guide specifications) | 25 or less [note 1] | — | US guide specifications for molded and pultruded grating | | Class A interior finish (building code) | 25 or less | 450 or less | IBC interior-finish classification (Chapter 8) | | Food-grade grating exception | up to 30 | — | Strongwell’s molded guide specification, for food-grade resin | _Check the code edition your jurisdiction has adopted. Only thresholds confirmed in our sources are shown._ Notes: 1. A specification threshold, not a test result. The International Building Code covers fiber-reinforced polymer in Chapter 26 (Section 2612) and interior-finish flame spread classes in Chapter 8; confirm the section numbers in the edition adopted locally. ## Why does the smoke-developed index matter? Flame spread alone does not describe smoke. Across Strongrate’s six models the SDI ranges from 15 to 400 even though every FSI is 25 or less: the 1" × 6" rectangular vinyl ester model is at 15, while pultruded models T5020 and I 6015 are at 300 and 400. Compare SDI as well as FSI, and check the smoke limit in your code or specification. ## Which other fire tests appear in FRP grating specifications? Guide specifications may also ask for self-extinguishing behavior under ASTM D635 and a UL 94 V-0 rating; list these in your quote request if your specification requires them. For vessels and offshore installations, ASTM F3059 rates fire integrity: the DNV certificate gives the six listed models L0 per ASTM F3059-15. L0 is a lower fire-integrity level than the Level 2 some phenolic gratings carry, so where a fire-integrity level is required, get DNV or project approval before using Strongrate grating. ## What does the DNV type approval say about fire? DNV issued Type Approval TAF0000191 Rev. 1 in Hamburg on Feb 11, 2022 to Nantong Strongrate Co., Ltd., and it is valid until Feb 10, 2027. It is a fire-technical evaluation of the six listed models only: it does not approve structural strength, it excludes hydrocarbon and jet fires, and acceptance for a given location is case by case. DNV requires a periodic assessment at least every second year, and each grating must be marked with the brand and its fire rating. The DNV-listed models use isophthalic polyester, vinyl ester and fire-retardant orthophthalic polyester resin; the catalog lists no phenolic resin. See [certifications and test reports](https://www.strongrate.us/about/certifications-and-test-reports/). ## How should you specify fire performance for FRP grating? State the ASTM E84 flame spread limit (25 or less is the usual guide-spec value), add a smoke-developed limit where your code requires one, and require the test report on the finished grating in the specified resin. Clause text is in our [fiberglass grating guide specification](https://www.strongrate.us/resources/fiberglass-grating-specifications/), and resin choices by family are on [molded fiberglass grating](https://www.strongrate.us/molded-fiberglass-grating/) and [pultruded fiberglass grating](https://www.strongrate.us/pultruded-fiberglass-grating/). ## Frequently asked questions ### Do I need a fire-retardant resin to get Class 1 grating? Not on Strongrate’s DNV-listed results: its isophthalic polyester and vinyl ester models have flame spread indexes of 10 to 20, within the 25 that US guide specifications call Class 1. Each result applies only to the model and resin tested, so check the result for the model you will buy. ### Which Strongrate model has the lowest flame spread index? The 1-1/4" (32 mm) deep, 1-1/2" square-mesh molded model in fire-retardant orthophthalic resin (38×38×32 mm), at FSI 5. Its smoke-developed index is 250. ### Does Strongrate offer phenolic fiberglass grating? Strongrate’s catalog lists four resin systems, vinyl ester (VEFR), isophthalic polyester (IFR), food-grade isophthalic polyester (FG) and orthophthalic polyester (OFR), and no phenolic grating. If a project needs phenolic grating, say so in your [quote request](https://www.strongrate.us/request-quote/). ## Related pages - [Fiberglass grating technical resources](https://www.strongrate.us/resources/): Index of fiberglass grating technical resources (load tables, sizes and weights, specifications, fire ratings, how-to guides, comparisons) and the standards they cite. - [Fiberglass grating certifications and test reports](https://www.strongrate.us/about/certifications-and-test-reports/): Strongrate’s fiberglass grating certification, DNV Type Approval TAF0000191 Rev. 1, what it covers, and the ASTM E84-19a results for its six listed models. - [Fiberglass grating specifications](https://www.strongrate.us/resources/fiberglass-grating-specifications/): An editable three-part CSI MasterFormat 06 74 13 guide specification for molded and pultruded fiberglass grating, with specifier’s notes, origin and warranty options, Strongrate catalog material data and a compliance table. - [Molded fiberglass grating](https://www.strongrate.us/molded-fiberglass-grating/): Molded fiberglass (FRP) grating from Strongrate’s Nantong factory by depth and mesh: square, rectangular and mini meshes, the four DNV-listed models with their ASTM E84 results, panel sizes, resins, surfaces and how to get factory pricing. - [Fiberglass grating price per sq ft](https://www.strongrate.us/pricing/fiberglass-grating-price/): Fiberglass grating prices per square foot and per panel: dated US market benchmarks, what moves the price, and how Strongrate quotes factory-direct prices per project. - [Fiberglass grating clips](https://www.strongrate.us/accessories/fiberglass-grating-clips/): Hold-down clips for molded and pultruded fiberglass grating: the STRONGFIX types in Strongrate’s catalog, common US clip types, the Type 316 stainless and 4 ft spacing rules in US guide specifications, and how to order clips with grating. **Request a quote:** https://www.strongrate.us/request-quote/ · Order a sample: https://www.strongrate.us/samples/ — Ask for the DNV certificate and the fire data for the model and resin you plan to order. Quotes within 1 business day (US Central time). ## Sources - Strongrate product catalog “Your Best FRP Solution” (image PDF, Sep 2023), supplied by the site owner (accessed Oct 17, 2026) - [Fibergrate molded grating guide specification (Section 06610); Strongwell Section 06 74 13 molded grating specification](https://www.fibergrate.com/media/180193/fibergrate-frp-molded-grating-specs.pdf) (accessed Oct 15, 2026) - [Fiberglass-AFI, Fire-retardant FRP and the FRP fire code (secondary summary of the IBC)](https://www.fiberglass-afi.com/specifications/fire-retardant-frp-and-the-frp-fire-code/) (accessed Oct 15, 2026) - [DNV Type Approval Certificate TAF0000191 Rev. 1 (PDF hosted on Strongrate’s ShipServ supplier profile 261792)](https://www.shipserv.com/Shipserv/pages/profiles/261792/certifications/20241010142426209-DNV-GL-Certificate-GRATINGS-Strongrate.pdf) (accessed Oct 15, 2026) - [Strongwell Section 06 74 13, FRP Molded Grating and Stair Treads specification](https://www.strongwell.com/wp-content/uploads/2013/03/StrongwellSpecs-Molded-Grating-and-Treads.pdf) (accessed Oct 15, 2026) --- Fiberglass (FRP) grating made by NANTONG STRONGRATE CO.,LTD in Nantong, China. Products ship from China. Made in Nantong, China · Ships from China · HTS 3925.90.