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The Truth Behind Noncombustibility Claims of Magnesium Oxide Structural Panels

Fire safety is serious business. Structures in the built environment require extensive code compliance to protect the life safety of its inhabitants as well as the professional liability of the owner, designer, dealers, and more.

With so much at stake, it’s important to build with products you can trust to live up to their manufacturers’ claims of noncombustibility. Poured concrete floors offer fire performance, but their immense weight and prolonged setting times can cause roadblocks during the specification process. The rise of Magnesium Oxide (MgO) structural panels as a cost-effective replacement for poured concrete floors may seem too good to be true—and that is exactly the case.

The Test

Recent independent third-party research has verified that despite their manufacturers’ claims to the contrary, three of the leading MgO structural panels in the US market are, in fact, not noncombustible per ASTM E136.1  

The International Building Code (IBC) serves as the standard for modern building safety codes, helping to ensure the engineering of safe, sustainable, and resilient structures. The IBC requires Types I and II construction to incorporate building elements that contain noncombustible materials, including those in floor and roof elements, along with their associated secondary elements and members. By definition, structural subfloor and roof deck panels are considered secondary members per the IBC and must be noncombustible (i.e., tested in accordance with ASTM E136).

The IBC’s test for noncombustibility, published by ASTM International, is formally titled ASTM E136 Standard Test for Assessing Combustibility of Materials Using a Vertical Tube Furnace at 750°C. The test involves placing a sample product inside a furnace and monitoring the temperature increases at its surface and center.

If the sample can withstand a minimum of 30 minutes in the furnace without crossing a failure temperature threshold, the test will continue until temperature readings at the center of the sample rise by no more than 1°C over the previous 10 minutes. If the final temperature is less than 750°C, the sample passes the test. This procedure is then repeated with three identical samples, and at least three of the four samples must pass the test in order for the material to receive a passing grade.  Only then can the material be considered “noncombustible” per ASTM E136.

The Results

Per ASTM E136 “Commentary” Section X1.5.1.1, any building material that contains at least 3% combustible material has significantly increased odds of failing the noncombustibility test.  Since the Total Organic Carbon (TOC) content for the independently tested MgO structural panels ranged from a low of 3.61% to a high of 7.29% TOC, (levels far exceeding the 0.83% TOC of USG Structural Panels), the MgO panels were unlikely to pass before the test was even run. 

Consequently, it was no surprise that after five days of testing in May 2020, the final report from an independent lab showed that all four tested samples from each of the MgO structural panels—Megaboard, DragonBoard, and NOCOM—failed the ASTM E136 test for noncombustibility. Each of the samples tested recorded a maximum temperature substantially higher than the 780°C (1436°F) failure threshold of the ASTM E136 standard. The conclusion? None of these panels are noncombustible per ASTM E136.

The Takeaway

Those associated with the manufacture and sale of the three MgO structural panels may point to code reports and outdated test reports that supposedly support their claims of noncombustibility. However, those reports either relate to panels of different thicknesses or fail to provide adequate detail supporting their conclusions (see USG whitepaper for additional details, under the section entitled “The ‘Support’ Offered for Claims of Noncombustibility”).

In fact, since USG’s whitepaper was published, the International Code Council (ICC) has acted in respect to one of the MgO structural panels subjected to the tests referenced above. In May of 2021, the ICC withdrew Megaboard’s ICC ESL-1151 report (2018) and removed ESL-1151 from the ICC listing directory after its investigation into Megaboard’s claims of noncombustibility.

The results of USG-initiated testing in 2020, conducted by an independent, third-party laboratory, show that three leading MgO structural panels—Megaboard, DragonBoard, and NOCOM—cannot pass the ASTM E136 noncombustibility test, and therefore do not qualify as noncombustible structural building elements per ASTM E136. The use of combustible panels in settings that call for the use of noncombustible building elements can lead to noncompliant structures and pose a significant life safety issue. Designers, contractors, distributors, and owners should be aware that any claims of noncombustibility made by manufacturers of these 3/4" MgO structural panels simply are not accurate.

Additional information on study findings as well as details regarding the proven noncombustibility of USG Structural Panels can be found here.

 

1. After the publication of the USG White Paper on MgO noncombustibility, a fourth manufacturer, Huber Engineered Woods, no longer advertises or promotes EXACOR/extremegreen as noncombustible or suitable for use in noncombustible applications.