This specification covers structural clay loading-bearing wall tiles of the following grades: Grade LBX, suitable for general use in masonry construction and adapted for use in masonry exposed to weathering; and Grade LB, suitable for general use in masonry where not exposed to frost action, or for use in exposed masonry where protected with a facing of stone, brick, terra cotta, or other masonry. Tile covered by this specification are manufactured from clay, shale, or similar naturally occurring substances and subjected to heat treatment at elevated temperatures (firing), which must develop sufficient fired bond between the particulate constituents to provide the strength and durability requirements. Tiles shall adhere to water absorption, compressive strength, and dimensional (nominal thickness and mass) requirements specified for individual grades.