Calcium Silicate vs Vermiculite for Fire Door Cores -- Which Is Better?
Both calcium silicate board and vermiculite board are inorganic, non-combustible materials used as fire door cores. They meet the same fire rating requirements but differ in mechanical properties, manufacturing precision, weight, and cost. The choice depends on your door design and production priorities.
Detailed Comparison
| Property | Calcium Silicate Board | Vermiculite Board |
|---|---|---|
| Density (kg/m³) | 600 - 900 | 400 - 700 |
| Weight per m² at 40mm | 24 - 36 kg | 16 - 28 kg |
| Screw Retention (N) | 500 - 800 | 200 - 400 |
| Thickness Tolerance | +/- 0.5mm (CNC ground) | +/- 1.5mm (typical) |
| Compressive Strength (MPa) | 10 - 17 | 3 - 8 |
| Surface Hardness | Hard, smooth surface; minimal dusting | Softer; may produce dust during handling |
| Fire Rating (40mm) | 120 minutes (EN 1634-1) | 120 minutes (EN 1634-1) |
| Machinability | CNC routable; crisp edges | Machinable but edges less crisp |
| Material Cost per m² | Higher | Lower (20-30% less) |
When Calcium Silicate Is the Better Choice
Calcium silicate is preferred for high-end fire doors where screw retention is critical. Door hinges, locks, closers, and panic hardware must remain attached during a fire. Calcium silicate's 500-800 N screw pull-out strength provides a significant safety margin. The tight thickness tolerance (+/- 0.5mm CNC-ground) simplifies door assembly because the core fits precisely within the steel door frame without shimming or compression. The hard, smooth surface reduces dust during handling and cutting, which is valuable for high-volume door manufacturers operating clean production lines. Calcium silicate is also approximately 10-15% lighter than vermiculite at equivalent fire performance, reducing the door's total weight and making it easier to install.
When Vermiculite May Be Adequate
Vermiculite has a lower material cost per square meter -- approximately 20-30% less than calcium silicate at the same thickness. For cost-sensitive projects where the fire door has limited hardware that does not rely heavily on screw retention (or where screws are anchored to the steel frame rather than the core), vermiculite can meet the fire rating requirement at a lower core cost. The broader thickness tolerance means manufacturers may need to adjust assembly processes to accommodate variation.
For a more detailed comparison including test data and application examples, see our full calcium silicate vs vermiculite comparison page.