Here are some points worth noting to aid your decision when contemplating different cornice products, as well as to help eliminate paying for a poorly-made product:
· Traditional cornices were cast using three materials; Plaster of Paris, hessian and wooden laths.
· Modern cornices are now made from polystyrene, plasterboard or glass-reinforced plaster (GRP) commonly.
· Many companies still make cornice traditionally, particularly in England.
· There are many different quality plasters available for manufacture; varying from approximately £5 per 25kg bag, up to £40+ per 25kg.
· There are different lath thicknesses. Naturally, you will want to use the thickest lath possible, which will benefit the strength and fixing of the cornice.
· Traditionally made plaster cornices adhere to most fire regulations rules, if made correctly.
· Every cornice should have a bracket (lath or hessian) on the back to increase strength.
· Hessian allows the cornice to be flexible. This is a great advantage when working in a building where the walls and ceilings aren’t straight or level.
· There should be no hessian visible on the finished face of the cornice once dry.
· The cornice should be around 7-10mm thick in all places – to avoid weak points.
· If there is cracking visible on the face of your cornice, it is likely because the laths were dry in the process of manufacturing the cornice.