A core material for a composite light weight building panel formed from a settable mixture, said mixture including an acrylic, polymer-based resin comprising: 85% by volume water based copolymer emulsion of polyvinyl acetate with versatate and/or acrylic copolymers in a water emulsion; 10% water soluble colloid protector; 5% additives; such that the resin obtains a specific gravity in the range of 1000.+-.50 g/l and an 8 Ford viscosity at 20.degree. C. of 7.+-.1: and the mixture having the following ratios: from 1 to 3 liters of cement; more than 2 liters of resin; from 10 to 100 liters of light weight filler material; less than 6 kilograms of water, and such that the volume of cement is more than half the volume of resin.