What is the difference between Structural Glazed Tile (SGT) and Glazed Brick?
This is a question I am asked quite often during sales seminars given at distributors offices and at architectural and engineering firms. The units may look the same once installed in the wall, however, it is what’s behind that pretty face that determines the difference. I would like to briefly go into some of the similarities and differences between the two products.
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 are the differences between Glazed Brick and face brick installations?
Often we tell architects, contractors and our distributors that our glazed brick is installed generally “the same as regular face brick”. I would like to review some of the similarities and differences to be aware of when handling a glazed brick installation.
Glazed brick is generally installed in the same manner as face brick. Type N or S mortar is recommended for most installations following the guidelines in ASTM C-270. A 3/8″ joint size is typical with full head and bed joints (use a soft joint under the coping and shelf angles). Never use a sealer on the mortar joints.
Wall ties and expansion joints should be spaced in the same fashion as with face brick. Wall ties should be minimum 3/16″ dia. steel and placed at least every 24″ vertically and 36″ horizontally, or per local building codes. The current ACI530 states a minimum of one every 3-sq feet. Ties for veneer brick over steel stud back-up systems should be 2-piece adjustable, corrosion resistant spaced per every 1.67 sq. feet of wall area. Expansion joints should be located on each side of a corner at 4′ to 10′ from the corner. Use flexible anchors to connect to columns and beams.
Cavity wall construction is a basic BIA recommendation for all veneer brick construction. A minimum 2″ cavity wall works best for glazed brick walls. It is suggested that a vapor barrier be placed on the warm side of the interior wall to help control condensation. The glazed brick itself should be laid so that the coring is vertical. This allows gravity to drain any moisture through the wall to the flashing. Flashing should be placed at the foundation course, sills, steel lintels, and parapet walls under the coping material and at any design openings. Proper drainage is dependent on how easy water can escape from the walls. Weep holes or vents should be placed every 24″ on center (o.c.) at the foundation level and at every 32″ o.c. (staggered) at the lintels, sills, coping, etc.
A vented cavity drainage wall is the best system for a glazed brick veneer. Stagger vents placed in the head joints at 24″ o.c. at the top and bottom of any continuous expanse of glazed brick wall. This will help circulate the air within the cavity, drying the walls faster. The vents at the bottom of the wall sections take the place of weep holes as a way for water to escape from the cavity via the flashing. The rain screen wall system is a similar method to use with glazed brick walls. This method divides the walls into sections or compartments. Each compartment is still vented at the top and bottom using flashing. An air barrier over the interior wall within the cavity is also necessary to prevent airflow through the interior wythe. Besides allowing for air circulation, this method also equalizes the atmospheric pressure inside the cavity with the outside air pressure. Therefore, it does not draw moisture into the cavity wall through the mortar joints. For more information on vented walls read the BIA “Vented Wall” E & R Digest.
Weep holes/vents and flashing are critical to glazed brick walls, as the impervious finish does not permit the face of the brick to breathe. Make sure during construction that the cavity opening is kept clean to permit this system to work.
Regions of the country that have freeze/thaw cycles should not use glazed brick in places that have water being applied to or near the wall, such as planters, fountains and below grade applications. Designs that create areas that can pool water should also be avoided.
Some differences with glazed brick are in the handling of the material at the jobsite. Our material will arrive with the brick strapped and stretch wrapped to a wooden pallet. Do not double stack these pallets! Cover the glazed brick to keep it clean and dry prior to installation. When the brick is ready to use, leave them in the factory packaging. This means NO brick tongs and NO pitching the brick up to the scaffolding and NO stacking. Glazed brick should not be taken out of the factory packaging until the bricks are in the mason’s hand ready to be laid in the wall. This helps prevent chippage, as the units are fragile until installed in the wall.
Concave joints using a 1 ½” plastic jointer work best. Do not use metal tools on the glazed face. When cleaning off clumps of dried mortar, use wooden scrapers. The walls should be wiped down with a coarse rag (like burlap or a piece of carpet) 30-45 minutes after they are erected or when the joints are thumbprint hard. This regular maintenance will make the final clean-down go much faster. During the final clean-down, be sure to wet the wall with clean running water prior to applying any detergent. Do not use muriatic acid as it may etch or yellow the mortar joints. A final rinse with clean running water should be done immediately. If by chance there is still a milky looking film on the glazed brick, wash the area with a solution of vinegar and water, then rinse. This will remove the residue and leave a great looking wall!
How do I decipher the nomenclature of shape numbers in Structural Glazed Tile and Brick?
The first number times two always denotes the nominal length:
4W = 4″ x 2 = 8″ long
5J = 5″ x 2 = 10″ long
6T = 6″ x 2 = 12″ long
8W = 8″ x 2 = 16″ long
The first letter denotes the unit’s nominal height:
S = 2 5/8″
J = 3″
P = 4″
T = 5 1/3″
W = 8″
4S = 2 5/8″ x 8″
5J = 3″ x 10″
6P = 4″ x 12″
6T = 5 1/3″ x 12″
4W = 8″ x 8″
8W = 8″ x 16″
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.
What is an isolated base system?
The first course in any commercial project is often included as part of the entire wall system when actually it should be thought of as a complete system of its own. The first course running along the floor is an area of the wall that takes continual abuse when compared to the entire wall. The cause could be something as minor as the heels of children’s shoes rubbing against it to the harsh pounding of an electric floor scrubber or power spray cleaner. This first course needs special protection. The only material that I have ever seen successfully take all sorts of abuse year after year in all types of applications is Structural Glazed Tile (SGT). There is little, if any, maintenance to consider with SGT. The fired in ceramic glazed finish is part of the structural clay unit and it will never peel or flake off. It is also chemical, impact and fade resistant. It can be used in combination with most types of wall systems, not just masonry. Here are a few base options to consider:
This system is ideal for a cost-effective solution for the base course of your interior walls. Quik-Base is designed for structural use under lockers, corridors, kitchens of any high traffic areas. This system is very pleasing in appearance without rigid perfection for a significant cost savings. Nominal dimensions: Height 4″, Length 16″, Thickness 2″, 4″, 6″ and 8″ finished and/or 2-faces. Corner units also available. These units course out with other masonry units.
Recessed Cove Base
This type of base is typically used in wet areas or areas where there are sanitary requirement The recessed cove base is used with terrazzo or quarry tile flooring. It has a ½” lip at the bottom of each unit. This ½” lip allows for the finished floor to be placed after the walls are installed. The flooring material then fills up the ½” lip area, leaving a smooth and sanitary transition between the flooring and walls. Available in nominal face sizes of 5 1/3″ x 12″, 8″ x 8″ and 8″ x 16″, in thicknesses of 2″ and 4″.
Non-Recessed Cove Base
This type of base is typically used in wet areas or areas where there are sanitary requirements. The non-recessed or feather-edged unit is used with a concrete slab and a thin type of finished flooring material, such as vinyl, a painted surface, etc. Available in nominal face sizes of 5 1/3″ x 12″, 8″ x 8″ and 8″ x 16″, in thicknesses of 2″ and 4″.
This type of stretcher unit is typically used when cove base is not required. Available in nominal face sizes of 5 1/3″ x 12″, 8″ x 8″ and 8″ x 16″, in thicknesses of 2″, 4″, 6″ and 8″. Other face size units available.
All of the Elgin-Butler Brick Company’s base units
- Meet ASTM C-126, Grade S, sized for 3/8″ mortar joints (except for 6T Series sized for 5/16″ mortar joints), and the ceramic glazed finish shall be from the manufacturer’s standard color selection and shall meet ASTM C-126.
- Must meet UL requirements for zero flame spread and zero smoke developed.
- Nominal Face Dimensions: 6T Series ( 5 1/3″ high x 12″ long), 4W Series (8″ high x 8″ long) and 8W Series (8″ high x 16″ long).
- Bed Depth: Nominal thickness dimension of cove base units are 2″ and 4″, as required. Walls requiring vertical reinforcing must use 2″ veneer with CMU backup for reinforcing. The straight base units are available in 2″ veneer or 4″, 6″ and 8″ vertical cell for vertical reinforcing or horizontal cell.
- Shapes: Furnished as shown on the plans in accordance with current standard production of the manufacturer. All external corners shall be bullnosed unless otherwise noted. Internal corners shall be square unless otherwise noted.