The board is made from wood pulp fibre, cement and lime as the calcium source, quartz sand and fly ash as the silica source, formed and then cured under high-pressure saturated steam to build a tobermorite crystal structure. The result is inorganic, dimensionally stable and non-combustible.
The published figures are what a specifier should check. Thickness 8, 10 and 12 mm, sheet size 1220 × 2440 mm, apparent density 1.05 ± 0.05 g/cm3, screw holding at the face not less than 800 N, fire class A1, smoke toxicity AQ1, moisture expansion below 0.12 %, drying shrinkage no more than 0.06 %, bending strength at least 10 MPa and impact resistance at least 2.2 kJ/m2.
The two numbers that decide whether a painted finish cracks are the moisture expansion and the drying shrinkage. A board that moves 0.12 % on wetting and 0.06 % on drying moves about 1.4 mm across a 1.2 m sheet. That movement has to be absorbed at the joints — which is exactly what the flexible seal and the taped joint are for — rather than resisted by a rigid joint that cracks.
Screw holding of 800 N is what makes the board usable as a service interface: sockets, small cabinets and hand-sanitary brackets can be fixed to it without a separate backing, provided the fixing is not within a cut edge. Where the load is heavier, the reinforcement module takes it into the stud grid, as it would on any other board.