Page 503 - Forensic Structural Engineering Handbook

13.48 MATERIAL-SPECIFIC FORENSIC ANALYSES

Color Variation
Comparison of masonry in place with a previously approved sample panel built at the job
site is the current method of determining color acceptance for brick. Slight deviations in the
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color of brick may not amount to failure to comply with a contract. “Brick Color Selection
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and Specification” and “The Color of Structure” 13 address brick color discrimination.
Masonry should be visually evaluated from a distance of 20 ft.

Cleaning
The multiplicity of stains, which occur on the several types of masonry, has generated a
bewildering array of cleaning agents and methods. At least 100 types of stains can occur on
14 different masonry materials. There are a dozen cleaning methods using at least 159 cleaning
agents containing 105 chemicals made by 87 manufacturers. There are at least 77 cleaning
operations using 27 types of equipment. Many cleaning methods, especially sandblasting, can
22
be very damaging to masonry. The cited literature presents specific recommendations for
cleaning virtually all types of stains from all types of masonry. 20

Demolished or Collapsed Masonry

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Spurling discusses specifications for demolition. Minor masonry demolition may be neces-
sary to replace defective flashing, in which case three or four courses of masonry are removed
immediately above the flashing. Grimm 28 discusses flashing specifications. Collapsed or
demolished masonry should be rebuilt to conform to Building Code Requirements for Masonry
5
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Structures and Specifications for Masonry Structures. The Masonry Designers’ Guide 46 is
based on those two standards.

CASE HISTORIES

Masonry failures have a lot in common, but all are different. Two examples of failures of
masonry are briefly described below.

A Low-Rise Hotel

Mold and mildew costs the U.S. hotel and motel industry approximately $68 million each
4
year in lost revenues and damage repair. Rooms cannot be rented that smell stale due to
odors emitted by mold and mildew. In one case, bathroom exhaust fans removed more air
than the air conditioning system supplied, creating a negative air pressure. In the warm,
moist climate, air infiltrating through exterior walls condensed behind wall covering, pro-
viding an ideal condition for mold growth.
In the case the hotel ordered demolition of all exterior walls and sued everyone involved,
including the masonry contractor who, it was alleged, had built a leaky brick masonry veneer
over steel studs. Worse yet, bricklayers, it was said, used chloride in the mortar. An engi-
neering firm’s report stated that chloride would “. . . greatly accelerate corrosion of wall ties,
resulting in premature failure of the wall.” That finding was based on a laboratory report,
which stated that three of seven mortar specimens tested contained a level of chloride which
exceeded 0.2 percent by weight of cement.