Masonry Magazine August 1989 Page. 21
Moisture Penetration.
The use of quality materials and workmanship is essential in obtaining a satisfactory degree of water resistance. When water passes through brick masonry walls, it invariably does so through separations or cracks between the brick units and the mortar. It is virtually impossible for significant amounts of water to pass directly through a brick unit. Therefore, brick units which develop a complete bond with mortar offer the best moisture resistance. Brick and mortar properties should be compared to provide compatible materials which result in more watertight walls. Currently, there are no requirements for the degree of water resistance of a wall.
Temperature Variations.
Brick must withstand daily temperature cycles and seasonal extremes (-30°F to 120°F) depending on location, throughout its life. Thermal expansion and contraction of brick is not critical to the selection of brick, but it is important to designers and this movement should be provided for in design and construction. Brick also withstands temperature extremes in fires. Since brick is a fired material, it will not burn and acts as an excellent barrier to fire because it is non-combustible.
Structural Loads.
Ability to withstand either gravity or lateral loads relies heavily on brick strength, mortar strength and strength of the wall assembly. Compressive strength requirements found in the ASTM specifications for brick are based on durability performance. Structural analysis may require a higher compressive strength in order to resist the applied loads. It is common to use high strength units in loadbearing or reinforced brick masonry projects.
Cost
Material selection is often based on cost, usually initial cost only. Although initial cost is important, lifecycle cost is a better tool for making critical decisions. When deciding between different materials, all costs involved including labor and maintenance costs, future value and life expectancy should be considered. The selling price of brick is governed by many factors, including manufacturing methods and appearance of the unit. When considering different brick, one must take into account shipping costs. Since most prices quoted are plant prices, distance between the manufacturing plant and the jobsite is a major determinant of these shipping costs. Brick manufacturers and distributors can supply brick prices and shipping prices. Many of the Masonry Institutes throughout the country provide cost comparisons between different materials.
Availability
The availability of brick fluctuates with the time of the year and current construction trends and demands. On the average, brick production time runs about 5 days from pugging of the clay to the finished, fired product. This can change depending on many factors such as variations in raw materials, forming process, and kiln types. Many brick manufacturers have stockpiles of brick, but usually only a small quantity of each brick type. This may satisfy smaller jobs, but for large projects requiring large quantities of brick, a special production run must be made for the job. Most manufacturers have a set schedule as to when they produce a certain brick shade. It is at this time that the size of the run will be increased to accommodate the large order. It is wise to question the manufacturer as to a brick's availability.
It is best to purchase all brick from the same production run because there are typically slight color variations between runs. All manufacturers have quality controls to keep this at a minimum.
SUMMARY
This Technical Notes has described which characteristics of brick are important in selecting a particular unit. There is a wide selection of brick from which to choose. Selecting the appropriate material is important to the project's longevity and appearance.
The remainder of this Technical Notes is "Recommended Practices Relating to the Responsibilities and Relationships in Brick Construction". This document, developed jointly by the Brick Institute of America, National Association of Brick Distributors, and the Mason Contractors Association of America, explains some potential problems that may occur during and after the selection process, and how to avoid them.
The information and suggestions contained in this Technical Notes are based on the available data and the experience of the technical staff of the Brick Institute of America. The information and recommendations contained herein should be used along with good technical judgment and an understanding of the properties of brick masonry. Final decisions on the use of the information discussed in this Technical Notes are not within the purview of the Brick Institute of America and must rest with the project designer, owner or both.
REFERENCES
More detailed information on subjects discussed here can be found in the following publications:
1. Brick Institute of America Technical Notes 7 Series Water Resistance of Brick Masonry
2. ASTM Standard Specifications for Brick