Fire-rated plasterboard comes in two thicknesses; 12.5mm and 15mm. Either thickness can be used depending on what is specified for your application, although it is worth noting that 15mm fire-resistant plasterboard will give superior fire protection than 12.5mm fire-resistant plasterboard.In terms of size, all the sheets sold here at Materials Market are 2400mm x 1200mm, although 2700mm and 3000mm length sheets are available on request. The 12.5mm is available both in tapered edge and square edge, with tapered edge being more popular than square edge.