This paper is concerned with the workability, setting and strength characteristics of polymer-plaster composites. The discussions of the equations which are derived semi-empirically to describe the porosity dependence of mechanical properties (modulus of elasticity, flexural and compressive strength) of plaster are also included. The proposed equations appear to be in general agreement with the experimental data obtained for the unmodified plaster. The introduction of latexes such as polyvinyl acetate, styrene-butadiene rubber and polymethylmethacrylate onto plaster increases the setting time and decreases the values of flexural and compressive strength. The water requirement of the plaster is observed to decrease with increasing dose of latex. Methylmethacrylate impregnated plasters show a great improvement in compressive strength over that of the unimpregnated state. (c) 2005 Elsevier B.V. All rights reserved.