Abstract: A structural panel for use in building construction and the like wherein side skin sheets of fiber-reinforced polyester are spaced to form a mold cavity to receive a foamable resin composition which, upon curing, is integrally secured to the skin sheets so as to prevent delamination of the skin sheets from the core. The methods of making the side skin sheets and introducing the foamable core composition therebetween provide a structural panel of high strength and durability independent of the size of the panel, with increased core integrity over panels heretofore available.