If you are building a new fireplace or opening a chimney breast to create one, you can line the opening with fire bricks set in place with heatproof mortar or use fireplace board. The mortar joints should be thin: 3 to 5 mm. Generally speaking, 10 kg of heatproof mortar can be used to place 100 standard sized fire bricks. Alternately, you can render over the existing brickwork with Fireplace Render to a thickness of approximately one inch. Heatproof Screed can also be used to create a base for the fire area. Free standing stoves can be lined with Fireplace Render as well.