This practice covers the minimum requirements for installing clay flue lining for residential concrete or masonry chimneys. Footings shall be constructed of concrete or solid masonry and the foundation shall be placed with respect to adjacent structures to minimize the possibility of damage. Both the concrete footings and foundations shall conform to local building codes. Flue liners shall be installed using refractory mortar in such a manner as to minimize ledges or steps within the flue passageway and shall be surrounded by masonry on all sides with a separation not exceeding the flue liner wall thickness. Materials used for chimney construction shall comprise of the following: flue linings, refractory mortar, concrete block, brick, mortar, firebrick, and natural stone. Chimney connection shall be made by either a metal or clay thimble while the chimney caps shall be made of precast or cast-in-place concrete, metal, or stone caps. Combustible materials shall be permitted to abut the masonry chimney sidewalls; wherein, the minimum air space clearance between the interior or exterior masonry chimneys and the combustible materials shall be met.