Structural clay tile

Structural clay tile describes a category of burned-clay building materials used to construct roofing, walls, and flooring for structural and non-structural purposes, especially in fireproofing applications. Also called building tile, structural terra cotta, hollow tile, saltillo tile, and clay block, the material is an extruded clay shape with substantial depth that allows it to be laid in the same manner as other clay or concrete masonry. In North America it was chiefly used during the late 19th and early 20th centuries, reaching peak popularity at the turn of the century and declining around the 1950s. Structural clay tile grew in popularity in the end of the nineteenth-century because it could be constructed faster, was lighter, and required simpler flat falsework than earlier brick vaulting construction.^[1]

Each unit is generally made of clay or terra-cotta with hollow cavities, or cells, inside it. The colors of terracotta transform from gray (raw, moist clay) to orange, red, yellow, and cream tones. This is due to an effect of the firing process which hardens the clay so it can be used for structural purposes.^[2] The material is commonly used in floor arches, fireproofing, partition walls, and furring.^[3] It continues to be used in Europe to build fire-resistant walls and partitions. In North America the material has largely been replaced by concrete masonry units.