Page 551 - Forensic Structural Engineering Handbook

BUILDING FACADES 15.3

standards for design and construction. Among the entities responsible for developing stan-
dards for construction and testing of building facades are membership organizations, such as
ASTM International, which generate consensus documents through the work of committees
and task groups. These task groups represent different areas of practice and include architects,
engineers, conservators, scientists, contractors, and others. The documents published by
ASTM include standard test methods, standard practices, and standard guides. While a test
method or practice provides recommendations for a definite course of action, a guide may
propose a series of suggested options and does not establish a specific course of action.
Other organizations that develop standards for the construction industry are specifically
devoted to work in one area of the field or to the applications of one material. Examples of
such organizations include the American Concrete Institute (ACI) and the Brick Industry
Association (BIA), which provide a series of technical publications as well as standards;
the Indiana Limestone Institute, which publishes a handbook to assist designers; the
National Building Granite Quarriers Association (NBGQA); the National Concrete Masonry
Association (NCMA); and the Sheet Metal and Air Conditioning Contractors’ National
Association (SMACNA), which publishes a notebook of recommended details for sheet
metal and flashing; among many others. The American Architectural Manufacturers
Association (AAMA) and the Window & Door Manufacturers Association (WDMA) publish
test procedures and standards specific to windows, doors, and curtain walls, as does the
American National Standards Institute (ANSI). In determining what standard is appropriate
for a specific investigative task, the latest version of appropriate standards should be carefully
reviewed, since standards and other publications are constantly changing. The newest version
of a standard may be either more or less stringent than the previous version. In addition, for
investigation and repair of an existing building or structure, it may be important to review the
codes and standards that were in effect at the time of construction. Codes or standards may
not have been in place to address specific issues of building construction or performance in
the area of concern. In that case, the investigator needs to decide whether existing construc-
tion should be, or even can be, held to the requirements of present-day standards. The require-
ments of the specific test, material, or repair need to be considered to determine what standard
is appropriate and applicable for a given task. Also, the requirements of that standard may
affect the criteria selected for the building element or system.
Several cities in the United States have enacted facade ordinances in response to facade
failures that have heightened awareness of this public safety concern. Ordinances are cur-
rently in effect in Chicago; New York; Boston; Detroit; and Columbus, Ohio. Most ordi-
nances require periodic physical inspections by a qualified professional of facades on
buildings over a certain height, usually five or six stories. A critical examination report is
filed periodically with the governing authority, such as the municipal building department.
The report identifies and documents unsafe conditions for correction.

BUILDING WALLS

Mass and Cavity Walls

Traditional load-bearing building walls were constructed of brick, stone, or concrete and
were often several feet thick. This mass wall construction was very tolerant of environ-
mental exposure and resistant to the effects of water penetration. Water that migrated
beyond the surface of these walls was absorbed and simply evaporated over time. In the last
century, traditional walls evolved from solid masonry several layers (wythes) thick to thin-
ner layers of masonry separated by a cavity. The cavity, which is a continuous space behind
the exterior cladding, serves to convey water that penetrates the exposed facade to through-
wall flashings and weep holes, back to the building exterior.