A chimney liner for a traditional fireplace must be parged in place with a mesh bottom plate and refractory cement above the smoke shelf where the existing clay flue is. Often times you have to remove the throat damper of the fireplace in order to give yourself enough room to work. The size of the liner for a traditional fireplace must be 1/10 the area of the face opening of the fireplace. Installing a liner that is too small for the fireplace will cause the fireplace to spill smoke out of the front. For instance, a fireplace that is 30" tall and 36" wide has an area of 1080 square inches. The flue size should be 1/10 the area of the face opening and shouldn't be less that 108" square inches which is the equivalent of a 12" diameter chimney liner. Typically, a 6" diameter liner is too small for a fireplace.