Abstract: A method for providing a polymer-modified fiber-cement composite by forming an aqueous composition including admixing an emulsion polymer having a glass transition temperature (Tg) of from ?25° C. to 150° C., cement, cellulosic fibers, siliceous material, and water; forming a composite precursor by removal of at least some of the water; and curing/drying the composite precursor at a temperature at least 10° C. higher than the Tg of the polymer is provided. In an alternative embodiment the emulsion polymer is applied to the composite precursor. Polymer-modified fiber-cement composites formed by the method of the invention are also provided.