I know that the Brick Industry Association does not typically recommend using brick from older buildings in new masonry walls. For repairs to many older buildings, however, it is impossible to match the original brick. What problems do you see in reusing brick to perform isolated repairs?
BIA Technical Notes on Brick Construction, No. 15, discusses the use of salvaged brick in new buildings for its appearance or low initial cost. In many cases, these walls made from salvaged brick will not be durable because of the questionable bond of the new mortar to the salvaged units and because of the questionable quality of the units themselves. There are, however, many cases when it may be appropriate to remove brick from one part of a building for use in repairing existing masonry walls in another part of the building. Sometimes these units are taken from a portion of the wall in an area being remodeled or from a relatively concealed area so that the units can be used to make repairs in a highly visible area. Crack repairs or brick removed for lintel replacements in older buildings can be very noticeable if the color or texture of the brick units does not match that of the surrounding units. This can be very detrimental to the overall appearance of a building, so the costs associated with taking brick from one area to use in another can be justified.
Some problems can occur if proper care is not exercised. These units must be taken from the veneer wythe. Units in the veneer wythe are typically face brick units that have been fired properly. In many cases, bricks in the center portion of the wall were under-fired units from the outer portions of the kiln. These units are less durable and therefore are not suitable for exterior exposure.
Before using these units in a repair, they must be cleaned properly. If the old mortar is not completely removed from the bond surfaces, bond can be negatively impacted. The pores of the brick units may be filled with old mortar, lime particles, dirt, or other deleterious materials. Even with careful cleaning, the bond of new mortar to these units will be reduced because these materials cannot be completely removed. For repairs in small areas, using these salvaged bricks should not present a problem.
Bond in these areas will generally be needed only for developing a reasonably watertight exterior surface. When large areas of masonry will be rebuilt using salvaged bricks, it may be desirable to build prisms and perform bond-wrench tests in accordance with ASTM C 1072. If the bond strengths of these prisms are similar to that of the new mortar, there should not be any significant problems.