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Fire Endurance Ratings of Clay Brick Masonry
One of the most frequently asked questions of the designer is "How do I achieve a 1, 2, 3 or 4-hour fire rating using various clay brick masonry assemblies?"
Intuitively, we are comfortable with clay bricks as a fire resistant material because of their use as a liner in fireplaces and kilns where temperatures exceed those expected in most construction fires. In addition, we have observed the effect of fires on buildings where the only thing to remain standing is the brick. Most designers do not question that brick is non-combustible, or resistant to fire, what they question is the fire resistance of each of the brick wall configurations in hours as it relates to building code requirements.
For many wall assemblies, the information is available from Brick Institute of America (BIA) technical Notes 16 and the International Building Code Table 720.1. For some assemblies, the designer is allowed to use methods of calculating fire resistance. Until recently, designers had to rely on ICBO Evaluation Report #5058 to obtain 1 and 2-hour fire ratings for Adhered and Anchored Veneers. Today this information is found in Chapter 7 of the International Building Code, Table 720.1.
Adhered brick veneer is defined as brick veneer secured and supported through adhesion to an approved bonding material applied over an approved backing. The most common wall assembly is defined by a facing of thin brick between �" to 1�" in thickness applied over a plaster backing. If this combined masonry layer is 1�", the masonry side of the assembly qualifies for a 1-hour fire rating. If the masonry layer is 2: or more, the masonry side of the assembly qualifies for a 2-hour fire rating. In this assembly, the plaster is applied to metal lath, which in turn is applied to wood or steel framing. Anchored Brick Veneer
Anchored brick veneer is defined as brick veneer secured to an approved backing by mechanical fasteners. The most common wall assembly is defined by a facing of brick between 2" and 5" in width anchored through mechanical connectors to wood or steel framing.
Structural Load Bearing Brick
Structural load bearing brick is defined as a masonry assembly of brick, mortar, grout and reinforcing that is designed to support all gravity and lateral loads. These masonry elements are generally part of the lateral load resisting system. Greater fire endurance performance and economics can be achieved through the use of reinforced masonry. Fire rating of 3 and 4 hours can be achieved through the use of up to 8" of hollow clay brick as shown.
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