Brick Masonry and Moisture

April 23rd, 2013 - Posted by Richard Shaffer under Technical

The function of the wall system (part of the building envelope) is to provide protection from the
elements such as wind, heat, cold, and rain (moisture). The design of the brick masonry wall
system should stop the intrusion of these elements into the interior space of the building and
prevent the weathering and deterioration of structural components in the building.
Some examples of moisture issues pertaining to brick masonry include efflorescence, spalling
and corrosion. Let’s take a brief look at each of these moisture-related issues.
Efflorescence is an indication that there may be a moisture management problem within the
brick masonry wall system; moisture is required for this to occur. As water reaches the surface
of the brick and evaporates, the salts which it transported are left behind as white crystal
deposits.
A second indication that there may be a moisture problem with brick masonry is spalling; which
is the fracturing/flaking of the brick surface and is typically the result of the freeze-thaw cycles
when excess moisture is present in the brick. Spalling may also be the result of deterioration of
structural components such as steel frame window systems, steel shelf angle, or use of inferior
materials in the brick which is less common.
The final indication that an issue with the brick masonry exists is corrosion; this is noted in
other wall materials used in construction and not the brick itself. For example, metal studs
exposed to moisture will corrode whether from infiltration of water through the brick or through
condensation between the interior wall and the brick masonry. There are other examples such as
the steel shelf angle and steel frame window systems which are not installed properly and allow
water infiltration into the building envelope.
Commonsense tells us that most water infiltration is the result of precipitation; however, air flow
and vapor diffusion may also result in moisture issues when there is no precipitation. Air flow
and vapor diffusion occur 24-7 all year; these will be discussed in a later article.
For now, we will look at moisture issues related to precipitation (water). There are a number of
forces that cause water to infiltrate brick and move into the interior of the structure, these
include: natural gravity, surface tension, wind/air currents, capillary action, and hydrostatic
pressure.
There are two (2) basic classifications for masonry walls based on the method of water
management utilized: the cavity wall and the solid barrier (or multi-wythe) wall.
The cavity wall provides a break (air barrier) between the exterior (masonry) and the interior
walls, preventing moisture from reaching the components of the interior wall. Provided that the
cavity wall is properly constructed, when moisture infiltrates the brick it will drain down the
cavity to the flashing and is reverted to the exterior through weep holes. In essence, the basics of
waterproofing is achieved, the moisture is moved away from the building envelope.
A solid barrier wall relies on the wall being of sufficient thickness (width) to prevent the
precipitation (moisture) from reaching the interior wall. In fact, the moisture is absorbed into the
masonry wall system with the intention that it will dry out during periods of non-inclement
weather. In our opinion, this is not the best type of barrier to be used.
There are three (3) conditions that must exist in order for leakage to occur: water has to be
present; the water has to be moved by a force (wind-driven, gravity, or capillary suction); and
there has to be a crack, penetration or breach of some type that the allows the water to infiltrate
the exterior wall (in this case, brick masonry).
The first place to look when dealing with moisture issues in brick masonry are the architectural
details. These details bring various components of the building’s facade together such as
overhangs, copings, window openings, and sills which are vital to preventing water infiltration into the interior of the structure. Unfortunately, this is where the majority of moisture issues occur – transitioning from one building component to another. The old adage, “Attention to Detail” is an absolute must to control moisture in brick masonry.

About the Author
Richard Shaffer, has four years’ experience in the construction industry, specializing in forensic investigations and remediation of residential, commercial and high-rise buildings. For more information, visit http://www.usbcinc.com or call the main office in Gainesville, Florida at (352) 505-6771.

This post was submitted by Richard Shaffer.

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