Adaptive Reuse of Clay-Tile Arched Floors
by D. Matthew Stuart
This article about antiquated structural systems is the second in a series aimed at structural engineers involved in the repair, restoration, or adaptive reuse of older buildings for which no drawings exist. —Editor
Concrete and steel-framed floors constructed in the late 1800s and early 1900s often included hollow clay-tile arches that spanned between beams and girders. The arches were typically covered with a concrete topping and often had plaster applied directly to the soffit of the exposed tiles.
These types of floor systems were often stronger and stiffer than was calculated by the simple conventional methods of analysis used at the time. In addition, the clay tiles served two purposes: transferring loads to the supporting beams, and providing fire protection for the structural steel.
There are two basic types of clay-tile arched floor systems: segmental and flat. Both systems were constructed using hollow clay tiles of varying sizes and shapes, with internal open cells similar to today's hollow masonry blocks. The typical web and face shell thickness was one-half inch, and all four sides of the closed faces of the tile were also typically scored.
The "blocks" were manufactured by a number of different companies, including National Fireproofing Corporation, Pittsburgh; Henry Maurer & Sons, New York; Whitacre-Greer Fireproofing Co., Waynesboro, Ohio; and Fraser Brick Co., Dallas, Texas.
Flat arch tile units typically varied in depth from six to 16 inches. The average dead weight of these units varied from 25 to 58 pounds per square foot. Segmental arch tile units were provided with radial sides so that each tile acted as a voussoir component of the arch. Segmental tiles typically came in six- and eight-inch depths.
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This article is reprinted from the December 2007 issue of STRUCTURE magazine, with permission of the publisher, the National Council of Structural Engineers Associations (NCSEA).