There are many advantages of hardened polyurethane coving cornice over plaster coving cornice, excepting that is, traditional perceptions. Hardened polyurethane coving cornice, which comes under the family of plastic coving cornice, has come a long way since the original introduction of polystyrene coving cornice. It is fair to say if the plastic coving cornice had been developed before plaster coving cornice it would be difficult to explain why plaster coving cornice should be used.