Heat proof screed is a dry cement-like material which provides a protective rendering to materials used in fireplace construction such as brick, stone, breeze block and concrete, which can be damaged by heat. DRY POWDER - add water and mix before use. 20kg will cover approx. 0.45 m² (4.8ft²) at 25 mm (1") thickness with a bulk density of 18.4 kg/m³ (115lb/ft³). Minimum recommended thickness 12.5 mm. Tested to 1300°C.