In high-occupancy interiors, surface selection is part of life-safety coordination. Hospitality lobbies, healthcare corridors, institutional circulation routes, elevator lobbies, and other public spaces must support substantial occupant movement while meeting requirements for interior finishes, means of egress, and wall assemblies.
For thin-profile architectural stone, appearance and thickness are only the starting points. The project team must review the available fire-performance documentation, the specimen and configuration tested, the proposed substrate and adhesive, and the requirements of the applicable code and authority having jurisdiction.
Flexible Natural Stone by Angkop Corp is produced using ECO-FLEXI MCM, a Modified Clay Material technology. Product profiles are approximately 2–5 mm, depending on the selected profile. In code-sensitive applications, each finish should be assessed against its documented test scope and proposed installation assembly.
Understanding ASTM E84 surface-burning results
ASTM E84, commonly called the Steiner tunnel test, evaluates the surface-burning characteristics of a material specimen under controlled laboratory conditions. It reports two primary indices:
- Flame Spread Index (FSI): the relative extent of flame travel across the exposed surface.
- Smoke Developed Index (SDI): the amount of smoke developed during the test.
The numerical FSI ranges commonly associated with interior-finish classifications are Class A at 0–25, Class B at 26–75, and Class C at 76–200. The commonly referenced SDI limit for these classifications is 450 or less.
FSI and SDI must be read together. These values describe surface-burning behaviour under the test method. They do not establish the fire-resistance rating of a wall, partition, shaft enclosure, floor-ceiling assembly, or other complete building assembly.
Documented result for the tested specimen
The available 2025 SGS report documents a 2.5 mm Modified Clay Material specimen tested in accordance with ASTM E84-24, with the following reported results:
- FSI 0
- SDI 5
These values fall within the numerical thresholds commonly associated with Class A surface-burning performance for the tested specimen.
This statement is specimen-specific. The result applies to the thickness, substrate, and configuration documented by the laboratory. It should not be presented as a universal result for every product profile, thickness, substrate, adhesive, or installed condition.
For a project submittal, compare the proposed finish and installation assembly with the tested specimen. Where the project differs, the design team should determine whether additional documentation or review is required.
Current supporting documents are available through the Angkop Resource Hub. Project-specific questions can be directed to Angkop specification support.
Fire performance depends on the complete assembly
A surface-burning result is not a fire-resistance rating for a complete wall. Project-level performance depends on the relationship between the finish and the construction behind it.
The review should include:
- The exposed surface and documented test specimen
- The adhesive or bonding method
- The receiving substrate
- Joint, edge, and transition conditions
- Penetrations and adjacent materials
- The underlying wall, partition, corridor, or enclosure assembly
- Any required fire-resistance, separation, or smoke-control function
The finish does not replace framing, sheathing, fire barriers, fire partitions, smoke barriers, or other required construction. This distinction is especially important in corridors, exit passageways, and exit enclosures, where the code may regulate both the surface finish and the wall assembly.
Code context for high-occupancy interiors
IBC Chapter 8 addresses interior wall and ceiling finishes, including classification by surface-burning characteristics. The applicable requirement depends on the occupancy group, location within the means of egress, sprinkler protection, adopted code edition, local amendments, and authority-having-jurisdiction interpretations.
NFPA 101 also addresses interior finishes and means of egress. Requirements should be reviewed for the applicable occupancy chapter, building conditions, and adopted edition.
A documented FSI and SDI result is therefore one part of the compliance review. The registered design professional, code consultant, contractor, and authority having jurisdiction must determine how the test information applies to the proposed location and assembly.
Substrate and installation coordination
Thin-profile stone is applied over a receiving substrate rather than functioning as an independent wall system. Potential interior substrates identified in the source specification include properly prepared gypsum board, cement board, fibre-cement board, masonry, and concrete.
Before installation, coordinate:
- Substrate type and existing wall construction
- Surface preparation, flatness, and cleanliness
- Moisture and site conditions affecting adhesion
- Adhesive compatibility and application method
- Corners, openings, trims, joints, and penetrations
- Transitions to adjacent finishes
- Compatibility with the underlying wall assembly
The material’s thin profile can support stone expression where a deeper finish would affect detailing, clearances, or circulation. It does not remove the need to verify the complete wall build-up or dimensional requirements.
Practical specification checklist
Code and location
- Confirm the occupancy group and adopted code edition.
- Identify whether the finish is in a corridor, exit access route, exit passageway, interior exit stairway, lobby, or another regulated location.
- Confirm the required interior-finish classification with the code consultant and authority having jurisdiction.
Assembly and installation
- Identify the complete wall or ceiling assembly receiving the finish.
- Confirm any required fire-resistance, separation, or smoke-control function.
- Coordinate the substrate, adhesive, joints, penetrations, edges, and transitions.
- Include the applicable test report, product data, and installation documentation in the submittal.
Resolve fire-performance questions before installation
For high-occupancy interiors, fire performance should be resolved during specification and submittal review, not after material arrives on site. The 2025 SGS report provides surface-burning information for a defined 2.5 mm Modified Clay Material specimen tested in accordance with ASTM E84-24, with reported results of FSI 0 and SDI 5. Appropriate use of that information depends on respecting the test limits and coordinating the complete project assembly.
Review the interior wall system collection, access the technical resource hub, or request samples and specification support before installation.
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