Connections that change direction cut down the flow of air. A general rule is not to use more than two ninety degree turns, and it is better to use forty-five degree turns. This helps to improve the flow of flue gases and thus cut down on a creosote buildup. Most chimneys in new and existing homes are constructed of a noncombustible material. This may be brick, concrete block, or some other type of stone.
Brick held by mortar is the preferred type.
Since these chimneys are heavy, it is necessary that the chimney be placed on good footings. Concrete footings on one story houses should be at least 8 inches thick, rest on compacted soil, and extend out at least 6 inches from the outside edges of the chimney. Two story houses should have footings at least 12 inches thick. Flue tiles are connected together with cement mortar joints struck smooth on the inside. There should be an inch of space between the outside of the hue tile and the surrounding masonry to reduce heat loss.