Glazed architectural terra-cotta has many material properties similar
to brick or stone. It also has many material properties radically
different from those traditional masonry materials. It is those
differences which must be considered for a better understanding
of some of the material characteristics of glazed architectural
terra-cotta when it is used as a building material.
Difficult to identify: Glazed architectural terra-cotta probably
comprises one of the largest if not the largest constituent material
in some of our urban environments today. However, the infinite
varieties of glazing have hidden this fact from the casual observer.
One of the attractive features of glazed architectural terra-cotta
in its time was that it could be finished (glazed) in exact imitation
of stone. In fact, many building owners and architects alike are
often surprised to discover that what they presumed to be a granite
or limestone building is glazed architectural terra-cotta instead.
 Typical construction detail of glazed architectural terra-cotta ornament. Drawing: Detail, Architectural Terra Cotta, Charles E. White, Jr., 1920. |
Two separate systems: Historically, glazed architectural terra-cotta
has been used in association with two specific and very different
types of building systems: as part of a traditional load-bearing
masonry wall in buildings of modest height, and as a cladding
material in High Rise construction. As cladding, glazed architectural
terra-cotta often utilized an extensive metal anchoring system
to attach it or to "hang it" onto a wall framing system
or superstructure. In the first instance the anchoring
was limited; in the second, the anchoring was often extensive
and complex. Likewise, in the first instance, deterioration has
generally been limited. However, where glazed architectural terra-cotta
was used as cladding, particularly in high rise construction,
present-day deterioration and failure are often severe.
Complexity of deterioration: Deterioration is, by nature of the
design, infinitely complex--particularly when glazed architectural
terra-cotta has been used as a cladding material.
Deterioration creates a "domino"like breakdown of the
whole system: glazed units, mortar, metal anchors, and masonry
backfill. In no other masonry system is material failure potentially
so complicated.
Poor original design: The root of deterioration in glazed architectural
terra-cotta systems often lies in a misapplication of the material.
Historically, glazed architectural terra-cotta was viewed as a
highly waterproof system needing neither flashing, weep holes
nor drips. This supposition, however, has proved to be untrue,
as serious water-related failure was evident early in the life
of many glazed architectural terra-cotta clad or detailed buildings.
"The Preservation of Historic Glazed Architectural Terra-Cotta" an Historic Preservation Brief
