Fire Rated Plasterboard Calculator — 30 to 120 Minute Systems

For a 60-minute (EI60) fire resistance, you typically need two layers of 12.5mm Gyproc Fireline plasterboard on each side of a steel or timber stud partition. This gives a total board thickness of 25mm per side. Some systems achieve 60 minutes with a single 15mm Fireline board, but the double-layer 12.5mm system is more common in UK commercial fit-outs. The rating is a property of the whole tested system, so always work to a specific British Gypsum White Book partition spec.

For fire-rated systems, you must use the correct length drywall screws. For a single 12.5mm layer, use 25mm screws. For double layers, the first layer uses 25mm screws and the second layer uses 42mm or 45mm screws to penetrate through both boards into the stud. Per the British Gypsum White Book, fix at 300mm centres in the field of the board, reducing to 200mm only at external corners and openings. On two-layer systems the inner board is perimeter-fixed at 300mm and the outer board is fixed at the perimeter plus intermediate stud positions at 300mm. Always confirm against the specific tested system.

Standard paper joint tape is acceptable for most fire-rated plasterboard systems. The joints should be taped and filled with appropriate jointing compound (not self-adhesive mesh tape, which is not suitable for fire-rated joints). The key is ensuring all joints are properly sealed with no gaps, as the tape and compound help maintain the fire barrier at the board joints.

Gyproc Fireline (a Type F board to BS EN 520) contains glass fibre reinforcement that improves fire resistance. A single 12.5mm Fireline board achieves 30 minutes fire resistance within a tested system, compared to approximately 20 minutes for standard wallboard. For rated fire partitions (EI30 and above), you must use Fireline or an equivalent fire-rated board — standard plasterboard alone will not achieve the required rating.

Yes — for a fire partition to achieve its rated performance, both sides must be boarded to the tested specification. An EI60 partition typically needs 2 × 12.5mm Fireline on each side (4 layers total). Our calculator covers one side — double the quantities if you are boarding both sides of a new partition.