A fiber cement sheet comprising: a cementitious matrix wherein the cementitious matrix comprises 36% by weight of a portland cement, 39.75% by weight of a silica aggregate, 10% by weight of a low density additive in the form of microspheres, 3% by weight of further additives and 11.25% by weight reinforcing cellulose fibers wherein the microspheres and reinforcing cellulose fibers are distributed throughout the cementitious matrix, wherein the fibre cement sheet comprises tongue and groove connectors (45, 47) defined on opposite longitudinal edges of the fiber cement sheet, wherein the groove connector contains an adhesive filled membrane situated therein, wherein the fiber cement sheet has a dry density less than 1.25 g/cm 3, a thickness less than 1.9cm (0.7500 inches), and is (a) able to withstand uniform loads of 9.57KPa (200 psf) or greater according to test method of Section 6.4.2.4 of PS2 and with an average deflection of less than 0.17cm (0.067 inches) at 2.87KPa (60 psf); (b) able to withstand impact loads of 0.1 KJ (75 ft/lbs) and a proof load of 181.4Kg (400 pounds) or greater following impact according to ASTM E 661 Procedure A with a deflection of less than 0.27cm (0.108 inches) under a 90.7Kg (200 pound) load after impact; and (c) able to withstand concentrated static loads of 249.5Kg (550 pounds) or greater according to ASTM E 661 with a deflection of less than 0.27cm (0.108 inches) under a 90.7Kg (200 pound) load, when spaced on a span of 60.96cm (24 inches) or less on center. a cementitious matrix wherein the cementitious matrix comprises 36% by weight of a portland cement, 39.75% by weight of a silica aggregate, 10% by weight of a low density additive in the form of microspheres, 3% by weight of further additives and 11.25% by weight reinforcing cellulose fibers wherein the microspheres and reinforcing cellulose fibers are distributed throughout the cementitious matrix, wherein the fibre cement sheet comprises tongue and groove connectors (45, 47) defined on opposite longitudinal edges of the fiber cement sheet, wherein the groove connector contains an adhesive filled membrane situated therein, wherein the fiber cement sheet has a dry density less than 1.25 g/cm 3, a thickness less than 1.9cm (0.7500 inches), and is (a) able to withstand uniform loads of 9.57KPa (200 psf) or greater according to test method of Section 6.4.2.4 of PS2 and with an average deflection of less than 0.17cm (0.067 inches) at 2.87KPa (60 psf); (b) able to withstand impact loads of 0.1 KJ (75 ft/lbs) and a proof load of 181.4Kg (400 pounds) or greater following impact according to ASTM E 661 Procedure A with a deflection of less than 0.27cm (0.108 inches) under a 90.7Kg (200 pound) load after impact; and (c) able to withstand concentrated static loads of 249.5Kg (550 pounds) or greater according to ASTM E 661 with a deflection of less than 0.27cm (0.108 inches) under a 90.7Kg (200 pound) load, when spaced on a span of 60.96cm (24 inches) or less on center. (a) able to withstand uniform loads of 9.57KPa (200 psf) or greater according to test method of Section 6.4.2.4 of PS2 and with an average deflection of less than 0.17cm (0.067 inches) at 2.87KPa (60 psf); (b) able to withstand impact loads of 0.1 KJ (75 ft/lbs) and a proof load of 181.4Kg (400 pounds) or greater following impact according to ASTM E 661 Procedure A with a deflection of less than 0.27cm (0.108 inches) under a 90.7Kg (200 pound) load after impact; and (c) able to withstand concentrated static loads of 249.5Kg (550 pounds) or greater according to ASTM E 661 with a deflection of less than 0.27cm (0.108 inches) under a 90.7Kg (200 pound) load, when spaced on a span of 60.96cm (24 inches) or less on center.