Abstract: A method is provided for manufacturing molded simulated stone and wood architectural articles for buildings and homes. The method incorporates a unique mold assembly including a resilient silicone rubber mold supported within a rigid mold cradle/foundation, and a vented lid having a High-Density Polyethylene (HDPE) interior surface. The silicone rubber mold is initially treated with a liquid polyester gel coating that is cured and then coated with an acrylic/vinyl ester back coating. Once the back coating is cured, a predetermined volume of a modified high-density, natural mineral fiber-reinforced, 2-component hybrid polyurethane liquid expanding composition is dispensed therein and the mold is covered with the vented lid. The system is pressurized and heated to produce a molecularly-fused, lightweight rigid article having the desired architectural shape.