The document discusses protective wall coatings for masonry buildings. It notes that while masonry is durable, buildings will inevitably leak due to construction defects. Protective coatings can serve as the first line of defense against moisture ingress. The document outlines best practices for selecting, applying, and installing protective coatings to properly repair masonry and prevent water damage. These include assessing damage, using vapor permeable coatings formulated for masonry, installing mock-ups, and applying the coating uniformly to form a continuous protective barrier.

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The First Line of Defense for Masonry Buildings
There are certain things in life that one may count on. The sun will rise in the east and set in the west; winter follows
summer; and you will be required to pay taxes. We can add one more certainty to the list: Buildings will leak.
Fall 2009
Technology The First Line of Defense for Masonry Buildings
Masonry buildings comprise a significant portion of the built environment; its design flexibility, durability and beauty have
made it the choice of design professionals.Protective coating’s role in stopping moisture infiltrationBy Christopher
PeregoThere are certain things in life that one may count on. The sun will rise in the east and set in the west; winter
follows summer; and you will be required to pay taxes. We can add one more certainty to the list: Buildings will leak.
The architecture of our buildings embodies our heritage and is a reflection of our values. As you tour the great cities of
the world, you can read their stories in the skylines. Masonry buildings comprise a significant portion of the built
environment; its design flexibility, durability and beauty have made it the choice of design professionals. Masonry is one
of the most durable methods of construction. The proof of this is evidenced on nearly every street corner around the
world.
A lifetime of experience in the construction industry can be summed up in a single statement: Buildings leak for a number
of reasons. While it is true that properly designed and constructed masonry buildings are effective in managing and
protecting a building from moisture, the reality is that few buildings are constructed without defect. Protective wall
coatings often are the first line of defense in correcting problems and preventing moisture ingress.
The benefits of masonry
The benefits of designing with masonry are numerous. Masonry offers versatility and beauty with an endless selection of
color, shape and texture. The Pyramids of Giza speak to masonry’s durability. These materials are fire resistant
and sound resistant. All of these benefits combined with a long lifecycle make masonry the material of choice for many
design professionals.
The challenges of masonry
While masonry provides many benefits, it is not without its issues. Most professionals agree that moisture is the biggest
challenge when building with masonry. Clip joints, missing flashing, obstructed cavities and missing design details are a
few of the factors that can contribute to moisture penetration. These issues can be compounded by settlement cracking,
leading to efflorescence, spalling face shells, corrosion of reinforcing and damage to the occupied spaces within the
building.
Protection starts with design
When it comes to protecting buildings from moisture, redundancy in design is a good thing. There are two primary types
of wall design utilized in masonry buildings today: cavity wall and single wythe construction. The goal of both designs is
to protect the building from moisture; however, the degree and method of protection differs with each approach.
Cavity Wall (rain screen)
Double layer of protection
Built in redundancy
Moisture management
More expensive
Single Wythe (barrier wall)
Single layer of protection
Relies on perfection
Moisture barrier
Less expensive
Both walls rely on good design and quality construction to perform well; however, a cavity wall has built-in redundancy
that can compensate for design or workmanship errors. A single wythe wall relies on the exterior of the masonry as the
primary line of defense against moisture. As a consequence, single wythe walls require perfection in design and
construction. With both types, protective wall coatings can be used to protect buildings from moisture infiltration,
preventing costly damage.
Protective wall coatings
Protective wall coatings are effective tools in the fight to protect buildings from moisture. Generally, wall coatings are
defined as high build coatings (10-20 dry mils) versus thin film paints (3-5 mils). The difference in film build is primarily
related to higher solids and polymer type, allowing for thicker film build without cracking of the coating. The benefits that
high build coatings provide over paints are numerous. These benefits include:
Properly applied high build coatings provide waterproof protection to masonry buildings.Properly applied high build
coatings provide protection from carbonation of mortar as well as chloride ion ingress.High build, elastomeric coatings
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have the ability to bridge moving cracks up to 1⁄16 inch.Thicker film build allows for the encapsulation of aggregate
for aesthetics and masking surface imperfections.Today’s high build coatings formulated for use on masonry
substrates can tolerate the naturally higher pH of masonry substrates better than most paints.High build coatings provide
equal or better aesthetic and color range compared to typical paints.High build coatings are more durable and will
physically last longer than thin film materials.When buildings leak, protective wall coatings can be part of a system
solution to correct the problem and to provide long-term protection for the building.
Coating repairs that last
Protective wall coatings provide many benefits to buildings; however, they are not a substitute for proper detailing and
good workmanship. Buildings leak for several reasons. A systems approach that provides redundancy in moisture
protection is often the best solution. Long lasting repairs begin with assessment to determine the cause of the problem.
Most masonry buildings, particularly older ones, require a combination of repairs.
A primary suspect in moisture infiltration is mortar – either because of cracking joints, settlement, or clip joints.
Regardless of the cause, damaged mortar should be repaired before the application of a wall coating. Cracks larger than
1⁄32 inch, signs of rust bleed, or efflorescence are indicators of problems. Additionally, mortar should be struck
concave and smooth. Raked or beaded joints should be avoided on exterior masonry. Damaged masonry units should
be repaired or replaced using compatible materials.
With both cavity walls and single wythe walls, drainage is an important element of a properly functioning wall. Even with
the best design and workmanship, moisture can find its way into the wall section. Flashing and weeps are a critical
component of any wall system. Damaged and missing flashing should be replaced. Care should be taken to ensure that
weeps are not coated over or obstructed.
Other areas that can contribute to moisture ingress are sealant joints, penetrations, window perimeters and parapet caps.
Selecting the right material
Not all materials are appropriate for all substrates or applications. Masonry and concrete masonry are unique substrates
with unique requirements. Efforts to save money often go unrewarded when projects need to be recoated because an
inexpensive paint was used in place of a protective coating (and subsequently fails).
When selecting a material, it is important to choose one that is formulated for use on concrete, masonry and concrete
masonry. Masonry substrates can be high in pH, which can cause certain types of materials to fail prematurely. Using a
material that was not formulated for use on masonry can lead to premature color fade, chalking and delamination of the
coating.
Vapor permeability also is an important attribute of a wall coating. While preventing moisture from getting into the
substrate, a protective wall coating also must allow moisture within the substrate to escape. A coating functions much in
the same way our skin functions, it is waterproof while still allowing our bodies to perspire. When selecting a material, it is
important to evaluate the test data provided by manufacturers and verify that the mil thickness used to report permeability
is the same mil thickness that is recommended for the application of the coating. Reporting a high permeability value is
meaningless if the recommended coating application is significantly thicker.
Once a material has been selected, it is a good idea to have a mock-up installed on the building. Mock-ups provide
validation of the compatibility of the coating with the substrate and provide an example of workmanship. It is important
that the mock-up be installed in an area that is representative of the substrates to be coated and be allowed to remain
until the end of the project. The same crew that will be working on that particular project should install it. The mock-up
allows the owner to evaluate color and texture, and becomes the standard of performance for the project. Mock-ups
protect the owner, the contractor, the design professional and the manufacturer. Memories quickly fade, but mock-ups
are the ultimate arbiters.
Successful installation
As with most construction materials, preparation is 90 percent of the battle when it comes to successful wall coating
applications.
During the assessment phase, a thorough inspection of expansion joints, penetration and window perimeters should be
conducted. Damaged sealant should be removed and replaced. Care should be taken to ensure compatibility of the
sealant with the wall coating to be applied. Parapet caps and walls should be inspected and repaired as necessary.
Parapet caps should extend three inches down the face of the masonry and should be caulked to prevent wind-driven
rain from being blown up the wall beneath the cap.
Wall coatings are generally defined as high build coatings (10-20 dry mils) versus thin film paints (3-5 mils).All
efflorescence, mold, mildew and rust stains should be removed before application of a coating. Cleaning methods will
vary based upon the nature and age of the substrate. For best results, consult with a cleaning products manufacturer for
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recommendations appropriate for the specific project. As a general rule of thumb it is best to use the gentlest method of
cleaning possible, taking care not to damage the substrate. Once clean, allow the wall sufficient time to dry before the
application of a wall coating.
The application method will vary based upon job site conditions. Wall coatings may be applied by brush, roller, or airless
sprayer. Regardless of the application method, it is important that the material be installed in a uniform manner. The most
common application issue related to high build coatings is uniformity. When properly applied, a high build coating
provides a continuous layer of protection over the exterior of the building. Pinholes, holidays and skips are tantamount to
having holes in the bottom of a boat. These voids can allow moisture to penetrate the wall system, leading to the
formation of efflorescence and eventually delamination of the coating, exposing more of the substrate.
Uniform film thickness also has an impact on aesthetics. Uneven application of a wall coating can lead to variance in
sheen and color. A common problem in the application of a wall coating is lap marks. For a uniform appearance, it is
important that the coating be back rolled in one direction. Failure to do so can result in a texture effect commonly called
“zebra striping.” This is similar to the effect created when grass is mowed in two different directions.
Finally, one of the most important factors in a successful coating application is the applicator. It is important to select a
qualified contractor who has experience installing high build coatings and is familiar with the nuances of masonry
buildings. Good communication between the contractor, design professional and coating manufacturer will contribute to a
successful installation.
Pulling it all together
The benefits of designing with masonry are numerous. The enduring beauty of masonry buildings can be found on nearly
every street corner around the world. While it is true that properly designed and constructed masonry buildings are
effective in managing and protecting a building from moisture, the reality is that few buildings are constructed without
defect.
Success begins with preparation: repairing damaged mortar, masonry units, flashing and sealant. Material compatibility
and vapor permeability are important performance attributes. Mock-ups provide assurance to the owner and protection to
all parties involved on the project. Finally, uniform application is critical to the proper performance of a wall coating.
Together with proper repairs, protective wall coatings can provide the first line of defense in correcting problems and
preventing moisture in masonry buildings. MD
Christopher Perego is the market segment manager (Building Restoration) for BASF Construction Chemicals –
Building Systems.
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