What ceiling thickness is required for effective fire resistance?

An aluminum panel alone (0.7–1.0 mm) offers no rated barrier; fire resistance stems from the total assembly thickness. For a 1-hour rating, typical constructions use a single layer of 12.5 mm fire-rated gypsum or 25 mm mineral wool behind the panel, plus an intumescent coating of 0.2–0.4 mm. A 2-hour rating often doubles insulation thickness—25 mm gypsum or 50 mm mineral wool—and may increase the aluminum gauge to 1.0–1.2 mm. Joint sealants and grid accessories add a few millimeters but are crucial for continuity. Panel perforations or decorative facades require slightly more backing depth to compensate for openings. Always refer to manufacturer’s tested build-up diagrams, which specify minimum thicknesses of each layer to achieve the desired fire-resistance objective.