Frequently Asked Questions
What is the difference between Structural Glazed Tile and Glazed Brick?
Both Glazed Brick and SGFT have a ceramic glazed face and a clay, fire clay or mixtures thereof, body which must meet the high quality standards as outlined in ASTM C-126 or ASTM C-1405.
Traditionally SGFT has been considered an interior unit. In the larger “tile” units, the cells or core holes run horizontally through the units and can be used in loadbearing and non-loadbearing applications. There is also a wide variety of shapes in the standard offering with SGFT.
Glazed Brick, on the other hand, has traditionally been considered an exterior veneer unit that comes in the smaller “brick” sizes. The core holes typically run vertically through these units. Brick also has a durability standard, which must be met with exterior use. In order to do this, we must specify for durability of the intended application of the glazed brick. In 1998, a new standard was developed to incorporate more stringent standards for ceramic glazed brick as compared to standard face brick use. The standard use for specifications should be used as follows: Ceramic Glazed Brick Units shall be Quality Ceramic Glazed Fire Clay Units as manufactured by the Elgin Butler Company or approved equal and conforming to the specifications of with ASTM C-1405, Grade S, Type I & II, Class Exterior (or Interior), Division as either: Solid (void area less than or equal to 25%), or H40V (void area greater than 25% but less than or equal to 40%), or H60V (void area greater than 40% but less than or equal to 60%). Sized for 3/8″ mortar joints. (Contact manufacturer for availability of Division specification available in each size.) The class in this standard considers the severe weather exposure in regard to water penetration of the finished assembly and also the freeze/thaw cycles, which are not considerations under the SGFT standard of ASTM C-126.
In today’s marketplace these traditional lines have been blurred. Glazed brick is now being used in interior walls and Elgin Butler’s Structural Glazed Facing Tile can be used as exterior walls. In any exterior glazed application, the design and installation is extremely important. Cavity wall construction and expansion joints are recommended, just as with facing brick, along with the installation of flashing, weep holes, and/or vents. The coring or cells must be laid vertically to allow for proper drainage. The properties of glazed brick allow it to be brought into the interior with little or no adjustments necessary for the installation.
Note: This article has been revised (10/03) from its original copy to incorporate the new then revised ASTM C-1405.
What specification do I use for Glazed Brick?
The American Society for Testing and Materials (ASTM) maintains a unit standard for Glazed Brick. Standard Speciation C1405 covers property requirements for glazed solid brick and glazed hollow brick. It was originally published in 1988 and combines property requirements for the unit body as well as the ceramic glaze. ASTM C1405 covers both interior and exterior applications and contains an appendix for design considerations when glazed brick is used in exterior wall systems.
How do ceramic glazes differ from prefaced glazed block?
Ceramic glazes are the result of maturing clays and other similar materials in a kiln at temperatures above 1500°F. The exposure to the high temperatures transforms the materials from their natural state to that of glass. The finish is impervious and is fused to the body of the masonry unit.
Prefaced concrete block has a finish made with resin which has been cured to provide color and a smooth texture to concrete block. It is not a ceramic finish.
What is a vented Cavity Wall?
A vented cavity wall is an exterior masonry wall system where air circulation between the masonry wythes is created through the use of vents and weepholes. The air circulation assists in drying the wall from the inside out. (link to Tech Note 13)
What is the history of Glazed Brick and Structural Glazed Tile?
Structural Glazed Brick and Tile were first used in the US in the early 20th century. Many of these first glazed units were manufactured as “salt glazed” brick and tile. This glazing process utilized the use of regular table salt, NaCl, and reduced oxygen during the burning of the units. The salt was shovelled through small openings at the burner locations onto the gas fuel. The salt then vaporized and chemically mixed with the silicates of the body to form the salt glaze finish. This type of glazing has been discontinued for environmental reasons. Many salt glazed brick and tile buildings can still be seen today. You can recognize them by their wide color range-from a buff to an orange-brown color. The finish is transparent, showing the body color, which adds to the color variation. It also has small bumps in the glaze finish. Even though a true salt glaze is no longer available, Elgin Butler Company does offer many ceramic glazes in an attempt to match these old type glazes. Due to today’s tighter color control, you may need to use more than one color to achieve a wall with wide color variation.
Today the quality control standards for the ceramic glazed finishes are much more stringent. ASTM C-126 outlines the minimum standards for imperviousness, glaze opacity, hardness and abrasion, fading and chemical resistance. Under ASTM C-126, units must also have ratings of 0 smoke density, 0 flame spread, and 0 fuel contribution and emit no toxic fumes. ASTM C-1405 can be used for glazed brick.
Since brick has been used for thousands of years, the nomenclature for the structural tile industry was developed with brick in mind; however, it had to denote the type of shape and which sides of the units were glazed:
The “S” Series is a “Standard” brick, 2 1/4″ high and 1 B.E. (Brick Equivalent)
The “D” Series is a “Double” brick, 5 1/16″ high and 2 B.E.
Naturally the “T” Series is a “Triple” brick (3 B.E.), but keeps the 5 1/16″ height and added the extra B.E. onto the length of the unit, making a 6T unit nominally 12″ long instead of the normal 8″ brick length. (Remember 3 units that are 5 1/3″ high equals 16″ for coursing.)
Sizes continued to get bigger as time went by:
The “W” Series is 8″ high and
The “Y” Series is 12″ high.