A structural fiber cement sheet containing cementitious matrix and reinforcing cellulose fibers distributed throughout the matrix having a dry density less than 1.25 g/cm.sup.3, a thickness less than 0.7500 in, and able to withstand uniform loads of 200 psf or greater according to test method of Section 6.4.2.4 of PS2 and with a deflection of less than 0.067 inches at 60 psf when spaced on a span of 24 inches or less on center.