ASTM E136 vs E84: why a Class A fence is not noncombustible

ASTM E136 vs E84 is the difference between “does this fence material burn at all” and “how fast does flame run across its surface.” E136 is the test California’s Zone 0 rule uses to define noncombustible, so it decides what can go in the 5 feet next to the house. E84 produces the “Class A” ratings on vinyl, composite and coated fence brochures, and a Class A rating on its own does not make a fence noncombustible. Judge a fence bought for the house end by E136.

The two tests meet in one place that matters for metal fences: WUI Code Section 501.4.1 accepts a thin coating rated under E84 on a base that passes E136. Everywhere else they answer different questions, so a “Class A” line on a fence page tells you about E84 and nothing about E136.

What are the differences between E136 and E84?

The 2025 California Wildland-Urban Interface (WUI) Code cites E136-2024a in its Chapter 7 list of standards, and the 2025 California Building Code cites E136-2022. The E136 quotes here come from the E136-24a scope; the current E136-26 uses the same words. The E84 quotes come from the E84-26a scope. ASTM sells the full standards.

What does ASTM E136 measure?

Its scope says the method “covers the determination under specified laboratory conditions of the combustibility of building materials. Materials passing this test are typically classified as noncombustible materials.” The procedure: at least four samples, three of which must pass, each held at 750 C until it fails or 30 minutes pass. A sample passes if it loses 50% of its weight or less, raises the furnace temperature no more than 30 C (54 F) and shows no flaming after the first 30 seconds; or, if it loses more than half its weight, never raises the furnace temperature and never flames.

The scope also lists what the test does not do. Two limits affect fences:

• Coatings. “This test method does not apply to laminated or coated materials.” WUI Code 501.4.1 fills that gap with a separate route for coated materials, covered below.
• Melting. E136-24a, the edition the WUI Code cites, says the method is “not suitable or satisfactory for materials that flow, melt, or intumesce.” E136-22, the edition the 2025 California Building Code cites, uses longer wording: “soften, flow, melt, intumesce or otherwise separate from the measuring thermocouple.” Some version of that sentence has been in every edition since E136-09b.

The melt limit matters for aluminum, which melts at about 660 C, below the 750 C furnace. ASTM E2652 carries the same limit, and the claim that E136 has no such issue is wrong: E136-19, the edition used for the 2020 aluminum lab tests, carried the identical sentence. E2652 has also been listed inside E136 as Option B since at least E136-16a, so the two stand or fall together for aluminum.

Bare aluminum alloys do have reported passes. May 2020 lab reports on alloys 6061 and 6063 show no mass loss, no flaming and no temperature rise. Neither report mentions melting, and no regulator has said whether a pass on a material outside the method’s scope counts, so the question is open. Steel melts far above 750 C and is unaffected. If you are buying aluminum, ask for the E136 report on the uncoated alloy, check the edition, and get your local fire authority’s answer in writing.

What does ASTM E84 measure?

E84 calls itself a standard “for the comparative surface burning behavior of building materials,” written for “exposed surfaces such as walls and ceilings.” The sample is mounted in the ceiling position and burned for 10 minutes. Two numbers come out: a flame spread index and a smoke-developed index, and the scope warns “there is not necessarily a relationship between these two measurements.” The WUI Code accepts UL 723 as an alternative to E84 wherever it names E84.

Section 803.1.2 of the California Building Code sorts the flame spread index into classes:

Those classes come from the interior finish chapter; a fence maker quoting “Class A” is borrowing them. E84 presumes the material can burn in the first place.

How do the WUI Code and the Zone 0 rule use each test?

The Board of Forestry’s Zone 0 rule defines Noncombustible as “Materials that pass the American Society for Testing and Materials (ASTM) E136 test, thus meeting the standard for ‘noncombustible materials’ described in Section 501.4.1” of the WUI Code (14 CCR 1298.02(f); 1299.02(g)). Fences or gates attached to the house or within 1 foot of it need a 5 foot Noncombustible span (1298.04(b)(9)(A)).

The WUI Code uses the tests at three levels:

1. Noncombustible (501.4.1). Pass E136, or E2652 “using the acceptance criteria prescribed by ASTM E136.”
2. Noncombustible with a surface (501.4.1 exception). A noncombustible base with “a surfacing of not more than 0.125 inch (3.18 mm) in thickness having a flame spread index not greater than 50 when tested in accordance with ASTM E84 or UL 723.” This is the route for a painted or powder-coated metal fence. A Class A coating (25 or less) clears 50; a Class B coating clears it only if its actual index is 50 or under. More on powder coated aluminum.
3. Ignition-resistant (503.2.4). Tested on both faces in “the extended ASTM E84 or UL 723 test, for a total test period of 30 minutes, or with the ASTM E2768 test,” with a flame spread index of 25 or less and a flame front that never passes 10 feet 6 inches beyond the burner centerline. Fire-retardant-treated wood gets to ignition-resistant by a neighboring path (503.2.2, which points to California Building Code 2303.2 and its own extended E84 test). Neither path makes a material noncombustible, so both fall short of the Zone 0 definition; see fire retardant for wood fences.

Is a Class A fire rated fence noncombustible?

Not because of the rating. Some examples:

• Vinyl. Some vinyl fence, CertainTeed’s Bufftech among it, is sold with a Class A flame spread rating. Vinyl is still combustible, and the Wildfire Prepared Home designation does not permit fire-resistant materials such as vinyl, composite or fire-rated coatings within 5 feet of the home. Details on is vinyl fence fire resistant.
• Fiber cement. James Hardie siding has both: Class A with a flame spread index of 0 and a smoke-developed index under 5, and classified as noncombustible when tested to ASTM E136. For Zone 0 purposes the E136 line is what matters. Fence use is covered on masonry and fiber cement fences.
• Coated metal. A Class A result on the powder covers the powder. The metal underneath needs its own E136 basis, tested without the coating, since E136 does not apply to coated materials.

Which test do common fence materials have?

How do I read a fence maker’s fire data sheet?

1. Find the test number. “E136” or “E2652 with E136 criteria” speaks to noncombustibility. “E84,” “UL 723” or “Class A” speaks to surface flame spread only.
2. Check what was tested. The alloy, the powder, the board. A report on the coating says nothing about a foam core or a plastic insert.
3. Ask for the index number as well as the class. For a coating you need a flame spread index of 50 or less and a thickness of 0.125 inch or less.
4. Note the edition and lab. Every E136 edition since 09b, including E136-24a (cited by the WUI Code) and E136-22 (cited by the Building Code), says the method does not suit materials that melt. For an aluminum sample, ask the lab how it handled that. Also check the sample was uncoated.
5. Treat “fire rated,” “fire resistant” and “Zone 0 approved” as marketing until a test report backs them. The rule creates no product approval program.

The definition and the full material list are on what counts as noncombustible.