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Building Envelope Science 101 Missing Paint and Escargot

May 15, 2014

The property was a large, multibuilding
apartment complex
in central Florida,
only six years old; and the
owner wanted a new paint
job to freshen up the buildings.
It was a typical painting/sealants
job to clean, prime, seal, and paint—a minimum
one-primer and one-finish coat
using a high-build, water-based elastomeric
paint system. A consultant was hired to
develop the specifications and provide quality
assurance. Bids were solicited, and a
qualified painting contractor was selected.
After a few months, the buildings were
painted and ready for turnover and final
payment. All was fine until damage began
to appear!
Within a few months of completion,
the property management noticed areas
where paint was deteriorated or missing in
areas of the wall surfaces. Spots about a
half dollar in size were scattered about the
wall surface in random locations. The spots
indicated that the tan-colored topcoat was
largely gone, leaving only the white primer
exposed. It was isolated and primarily in the
lower five to six feet of the exterior wall. Very
minor areas of the damage occurred higher
up, but always below the second-floor
accent band. It was a peculiar phenomenon.
The most puzzling aspect of this case
was that there were no paint chips on the
ground below the damaged areas.
Where we saw paint spots were deteriorated
or missing, we always noticed
something extra. Small, dark, tube-shaped
objects stuck to the surface of the wall—at
times, as many as 10 to 15 of these objects
within a square-foot area. They were stuck
to the painted wall over perfectly painted
surfaces. Many were curiously pigmented
the same color as the paint. They were very
small, so we pulled out our pocket microscopes
and loops to get a closer look. Now,
hold your breath.
What were we looking at? It turns out
that the objects were the excrement of some
small animals, colored with paint pigment.
But how could this be? Could the painting
contractor actually have painted over this
much debris? Not according to the consultant’s
records. These walls were thoroughly
cleaned prior to any painting work being
started. This residue problem had to have
come after the painting was complete. There
No v e m b e r 2 0 1 4 I n t e r f a c e • 1 7
Figure 1 – Conventional wisdom says that you can set out a small dish of beer to catch and
rid your garden of snails. Unfortunately, you may attract local varmints as well. What does
this have to do with building envelope science? Read on.
is only one practical way we know of to get
paint pigment inside the stomach of an
animal: It has to eat it. Then the undigested
remains are excreted in the animal’s waste
product. This might explain what had happened
and exactly what we were seeing.
Armed with this information, we hunted
the wall surfaces, the soil below, and the
bushes adjacent to find the culprit animals.
Bingo, we found some small snail shells!
Could these be the miscreants?
Could snails be depositing pigmentladen
waste on the walls adjacent to the
damaged areas? This stuff was full of undigested
paint pigment. It was completely
embedded within the excrement of snails
that had traveled across these walls, stopping
only for a meal and to relieve themselves
along the way. The hunt continues.
We continued to hunt for some actual
living snails, as the shells alone could not
have done the damage. Then we spotted
the first snail on the lower portion of a column.
He was a small snail, observed in his
not-so-natural habitat, actually during his
feeding time. We caught him red-handed,1
munching away on that nice new elastomeric
paint, soon joined by a few more of the
culprits. These guys really seemed to like
the paint. It became clear that the hungry
snails were causing all of this mischief. At
this point we didn’t know what kind of snail
they were or why they were methodically
devouring the paint on these buildings.
Come to think of it, we basically knew
very little about snails. So we gathered
some specimens and enlisted
our colleagues in academia to help
identify these shelled vandals.
With the help of two talented
biologists and snail experts in
North Florida,2 we now know our
paint-eating friends as the Asian
tramp snail, a.k.a. Bradybaena similaris.
Terrorizing backyard gardens in
America since 1939, this invasive species
comes all the way from Asia and
has since traveled into Florida. Now,
these guys typically feed on soil and
foliage—not paint. Something was
afoul here. It wasn’t time to break out
the garlic and butter just yet. What
did these guys like so much about the
paint? A little more research would
soon answer the question.
Something about this paint was
attracting the snails, so we began
to research the composition to see
what secrets it held. What was the delicious
ingredient that this paint contained? It
turned out to be calcium carbonate (CaCO3).
The paint from the bucket contained 33%
CaCO3 by wet weight measurement; and
upon drying, up to 54% CaCO3 by dry
weight measurement. This simple compound,
CaCO3, an essential ingredient in so
many things on our planet (from pearls to
eggshells and agricultural lime to antacid)
is also the building block for these guys’
shells—their homes. Snails typically eat soil
and vegetation to get the calcium carbonate
they need, but in this case, the paint was
much more tasty!
Our friends had atypical appetites.
These guys were like kids in a candy store
with grandma’s coin purse. They could
get everything they needed to build their
home—without leaving home—simply by
devouring the new paint on the walls. Time
to issue an eviction notice!
The snails had clearly overstayed their
welcome. So what was the solution? Simple
enough: Iron phosphate, a nontoxic snail
bait recommended by the local Extension
Office to “evict” the unwanted guests. This
material would be applied around the perimeters
of the buildings as often as needed,
essentially acting as both a barrier and a
poison to the creatures. That was the first
1 8 • I n t e r f a c e N o v e m b e r 2 0 1 4
Figure 2 – The Asian Tramp Snail, a.k.a. Bradybaena similaris, terrorizing backyard gardens in
America since 1939.
Figure 3 – A horrifying conveyor belt of
thousands of tiny teeth. The paint had no
step. Then, time to repaint.
Only the lower portions of the
buildings needed repainting. (The
horizontal accent band was heroically
acting to deter the snails
from climbing any higher up the
wall.) And maybe we should try a
not-so-delicious paint this time.
With the known track record, we
selected something that contained
none of the goodies responsible for
this mess—no calcium compounds
to tempt any stubborn snails that
might remain after our iron phosphate
In building science, we sometimes
need to dig deeper and to
think outside the box. One of the
most important lessons we have
learned in our field is to always
ask questions. Why were these little
black objects stuck to the wall
where we were seeing the paint
“failures?” How did the paint pigment
get into them? Was this an
No v e m b e r 2 0 1 4 I n t e r f a c e • 1 9
Figures 4 and 5 – The calling card our friends left us with. Inset: Snail excrement at 60x magnification.
There is only one way we know of to get paint pigment inside the stomach of an animal.
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isolated incident, or could it be responsible
for other paint failure cases?
Should the coatings industry now take
note and look at alternate formulations for
their exterior paints? Further investigation
is needed, but at least for our particular
client, we answered their pressing question:
“What is causing the paint deterioration on
our freshly painted walls?”
1. Or whatever the equivalents of
hands are for a snail.
2. Thanks to Dr. Henry Lee and Bill
Frank of the Jacksonville Shell
3. Since iron phosphate is very lethal
to snails, we would assume any
remaining strongholds to be evolutionary
super snails.
2 0 • I n t e r f a c e N o v e m b e r 2 0 1 4
Robert J. Bitterli,
LEED GA, is the
president and
CEO of Ivy Group
Consultants, a
St. Petersburg,
F l o r i d a – b a s e d
forensic architecture
and building
sciences firm working
the Southeastern
United States. He has practiced architecture
for 35 years and forensic architecture for the
past 25 years. He can be reached at rbitterli@
Robert J. Bitterli, AIA,
Mitchell Wright,
RWC, IACT, is a
principal of Ivy
Group Consultants
and has been
engaged in the
field of building
science and forensic
for the past 12
years, specializing
in many aspects
of the building
envelope, including analysis and design of
exterior walls, windows, doors, skylights,
and roofing, as well as numerical analyses
of thermal and moisture transport
through building materials and structures.
Wright is an RCI Registered Waterproofing
Mitchell Wright,
Many women who earn engineering degrees are
not being retained in the engineering workforce, studies
show. Women comprise almost 20% of engineering
school graduates, but only 11% of practicing engineers.
The multiyear Project on Women Engineers’
Retention (POWER) study was funded by the National
Science Foundation and conducted by Dr. Nadya Fouad
and Dr. Romila Singh of the Center for the Study of the
Workplace at the University of Wisconsin at Milwaukee.
Over 3,700 women who had earned an engineering
degree responded to the survey and indicated that
“workplace climate was a strong factor in their decisions
to not enter engineering after college or to leave the profession
of engineering,” Fouad stated. Nearly 40% had
quit the profession or never entered it. Yet for those who
entered the industry and remained, “workplace climate”
was also cited as explaining their current satisfaction.
“[Work] climate issues and lack of advancement lie
at the heart of women opting out and/or not leaning in,”
according to analyst Nadya Fouad. Women’s decisions
to stay in engineering “can be influenced by key supportive
people in the organization, such as supervisors
and coworkers. Current women engineers who worked
in companies that valued and recognized their contributions and invested substantially in their training and professional
development expressed greatest levels of satisfaction with their jobs and careers.”
A similar study on male engineers is currently in the works.
Though RCI has no firm data on the gender of its members (there is no such indicator on the membership application),
RCI’s Director of Membership Programs, Alec Jeffries, estimates RCI’s female membership at around 5%, with the majority
of those women members in the Industry category. Approximately 10% of RCI members (280) are self-reported professional
engineers. (RCI does not independently verify this information.)
This graph, provided by the American Society for Engineering
Education (ASEE), represents the percentage of women by discipline
for engineering bachelor’s degrees earned in U.S. universities in
2010-11. Women account for 18.4% of the engineering degrees
conferred. Women represent 22.6% of those receiving master’s
degrees in engineering.
Why Women Engineers Leave the Field