A fireplace hearth is the bottom section of the fireplace. The hearth was intended to be used as a heat proof resistant layer between the floor and the fireplace. If a hearth is to be used with a gas or electric fireplace, then the hearth does not need to be cut into sections or altered in any way. However, if the hearth will be used with solid fuel appliances, then the hearth should be cut into sections and rejoined. This allows for expansion and contraction created by the intense heat of solid fuel appliances (burning coal or logs) and would minimise or eliminate the risk of the hearth cracking. The hearth is often also filled with cement at the back to make it more dense and again limit the risk of any cracks developing.