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34 D+D NOVEMBER 2014
Clues to a Coating Failure
n our business, we see many coating
failures caused by the missteps of those
of us directly involved in the painting
trade: specifier, GC, painting contractor,
owner, even the well-meaning paint
consultant/inspector.
Some of the most common causes in-
clude: wrong coating/system was specified
for that substrate or exposure environment;
surface preparation was inadequate; or the
coating was applied during improper envi-
ronmental conditions.
Sometimes, however, we see problems
where the “paint people” did the job right, but
the actual design of the structure — the
bones, if you will — is damning the coating
work to failure. When it comes to paint,
beauty truly is only skin deep (generally 3-5
mils, or roughly the thickness of a dollar bill);
paint cannot fix structural issues that are in-
tegrated into the building design.
But when the structure in question is a
gorgeous new complex in the Pacific North-
west whose highly lauded modern urban
design is contributing to the problem, paint
may be required to go above and beyond the
call of duty.
That’s what I found when called to inspect
an uber-modern new mall complex designed
to minimize its footprint on the landscape.
Instead of the typical design of building a sea
of parking spaces around an island of stores,
the entire complex is built in multiple stories,
with the vast parking lot on the (pedestrian)
ground level, and the chic “main street” style
shopping complex on the second level.
I
By Dave Lick, Paint Quality Assurance Inspector
THE CASE OF THE PAINT-DRIPPING PARKING GARAGE CEILING
Clues to a Coating Failure35
Wet Paint after Six Months?I was called in because this massive first-
level parking garage had an equally massive
concrete ceiling that was experiencing fairly
dramatic coating failure. Customers were
complaining that paint from the ceiling was
dripping onto their cars.
The GC called the painting contractor and
said “you better get down here, we have wet
paint dripping on cars from the concrete ceiling
you painted.” Painting contractors don’t gener-
ally get calls like this six months after complet-
ing a job, so after a quick look at the situation,
the painting contractor brought me in.
The initial inspection of the ceiling revealed the
first clue: the areas with the failing coating were
visibly damp with moisture. Where was it coming
from?
Temperature Variation Means Water CondensationRemember that the second floor retail area is
not one giant continuous fully enclosed building,
but instead features a “Main Street” design
where the stores are separated and pedestrians
travel from store to store via asphalt walkways.
There are also open driving areas and a sub-
stantial second-level open parking lot. And the
parking garage ceiling in question is not in a sub-
terranean parking garage, but rather at pedes-
trian/ground level with sides open to ambient air.
Now, consider that in the Pacific Northwest
there is a lot of moisture, and the ambient air
temperature can fluctuate greatly. So when the
exposed blacktop on the second level gets cold,
moisture condenses directly below on the con-
crete garage ceiling and the massive concrete
beams that hold it up, manifesting itself as either
shining water droplets or ice crystals.
I noted a wide variation in paint performance
across the garage ceiling. Where there was a
building directly above, the ceiling surface below
was essentially insulated from weather, so there
was no condensation and the coating was gener-
ally intact. But in the areas where there was only
exposed blacktop above the ceiling, substantial
moisture was present along with widespread
coating failure.
CAN COATINGS COMPENSATE FOR A FAILURE IN DESIGN?
(Below) This vertical white line on the floor isnot an intentional stripe of paint but points tothe problem with the ceiling coating.
(Facing page) Despite being in a new mall com-plex, this parking structure revealed a dramaticcoating failure after just six months of the paintjob’s completion. Photos courtesy of MasterPainters and Decorators Association.
Moisture Times 2 So now I had the answer. It’s bad enough to
have moisture from one side, but this ill-fated
latex film was being riddled with moisture on
both sides: water coming in through cracks on
the underside, and frequent condensation on
the outside.
The initial coating system was a product ap-
proved under MPI (Master Painters Institute)
#3 Alkali Resistant Primer followed by two
coats of an MPI #10 Exterior Flat Latex. This is
a reasonable system for exterior concrete
(typical flat latex is pigmented enough to resist
some water exposure), but it’s not designed to
accommodate immersion in heavy condensa-
tion every time there’s a temperature varia-
tion. Standing water plus thermal shock from
freeze/thaw will soften a conventional flat
latex over time.
And the hydrostatic pressure behind the
paint film will always eventually break the ap-
plied coating away from the surface, especially
around the cracks.
So what appeared to be wet white paint
splattering the pavement and the cars of
shoppers was in fact the softened and soaked
paint film disbonding from the surface. The
water/paint mixture then dripped onto the sur-
face below. The resulting white paint drips on
the pavement were well adhering and could
easily be mistaken for drips of fresh, wet
paint.
But Wait, There’s More
To further complicate matters, discoloration in
the efflorescence powder and telltale rust-
colored streaks and spots on the white paint
indicated that the water seeping through the
cracks was passing through steel on its way
through the slab.
One might suspect the cause to be rusting
rebar or reinforcing wire, but when that’s the
case, the rust spots are generally present in
some kind of pattern. Instead, these appeared
to be random, so I surmised that the source
was some other form of embedded steel close
to or at the ceiling surface.
36 D+D NOVEMBER 2014
Cracks in the PictureMore than one factor was contributing to the
“dripping paint” problem, however. A closer
look revealed hairline cracks in the ceiling;
that’s an unexpected find in a slab that’s
barely one year old.
Where there are cracks, and where there
is precipitation, there will be water ingress.
Water percolating through concrete will pick
up concrete salts and deposit them on the
coated surface; the water then evaporates
but the salts remain behind and build up over
time. This is what we call efflorescence. The
inspector observed bubbled paint and, be-
neath it, the telltale damp white powder
indicative of efflorescence. Large blisters
filled with water and efflorescence were also
present.
(Top) The shiny surface of the ceiling provides one indication of the presence of condensation moisture. (Left) Ceiling cracks, paint blisters and efflorescence deposits pointed to additional water entry beyond the condensation issue.(Right) Large blisters loaded with water, including this one at more than one foot long, and efflorescencewere also present.
Clues to a Coating Failure37
So my report noted no evidence of paint
failure caused by the choice of the initial paint
system, a flaw in the manufacturer’s product
or improper application. Instead, the list of
causes were:
• Heavy continuous condensation on the
painted surface.
• Cracks in the concrete leading to water
build-up behind the film.
• Efflorescence on the paint film caused by
water ingress through the cracks.
• Rust staining from an unknown source in or
above the ceiling slab.
So what to do? No conventional latex is
meant to withstand constant freeze/thaw and
condensation coming and going all times of the
year. Also, paint or coatings cannot stop the
development of efflorescence and blistering
because the hydrostatic pressure of the water
behind the paint film will always break the ap-
plied coating away from the surface, especially
around the cracks. The only way to stop the
efflorescence and the rust staining is to fix
the cracking in the concrete and the subse-
quent water infiltration.
Using Paint to Solve Non-Paint Problems I offered this solution: power wash the blis-
tered and failing areas at 1500-2500 psi to
remove all the loose paint. Then, when there’s
a hiatus in the condensation cycle and the sur-
face is known to be dry, apply an exterior high
performance water-based coating, such as a
product approved under MPI #163 Light Indus-
trial Coating, Exterior, Water Based, Semi-
Gloss, over the entire ceiling surface.
The higher resin content of these products
should offer the maximum resistance to im-
mersion in water condensation in an architec-
tural coating.
I further recommended that in the areas
prone to heavy condensation, the water re-
sistance and adhesion of the new topcoat
could be maximized by first applying one of the
concrete conditioner products now on the
market. These products are available in either
pigmented or clear formulations. The clear
What appears to be paint drips was evident on the pavement beneath the blistered ceiling area, butinspection revealed that it was the softened, soaked paint film disbonding from the ceiling surface.
Random rust staining could also be seen on the painted ceiling, indicating the presence of someform of embedded steel.
38 D+D NOVEMBER 2014
product I selected penetrates equally well into
both painted and bare concrete surfaces.
In hindsight, that concrete ceiling could have
been treated like an industrial surface, with a
waterborne epoxy system or, better, applied
over a chemically etched or sweep blasted
surface.
However, for parking garages, the builder’s
and owner’s goal is understandably simply to
“make it white” for aesthetic purposes, and the
budget isn’t available for a high-performance
system.
Also, while an industrial coating may have
better resistance to condensation, it can’t
solve the problem of water infiltration from
cracks in the concrete.
Dealing with the Rust Stains To solve the rust stain issues, I recommended
that the affected areas be chipped out to
remove all stained and contaminated concrete,
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Rust stains and blistering along the ceiling cracks point to areas where stained and contaminated concretemust be chipped out and the steel underneath primed.
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Clues to a Coating Failure39
and any exposed steel found underneath be
primed with a high-grade epoxy primer such as
a product approved under MPI #101 Primer,
Epoxy, Anti-Corrosive, for Metal.
An epoxy filler product would be used to re-
pair the depressions and chipped sections of
concrete, and the primed surfaces would re-
ceive two coats of the specified topcoat, either
MPI #10 Exterior Flat Latex or the same MPI
#163 described earlier.
I am well aware of the limitations of this pro-
cedure: it should prevent the bottom portion of
the steel bits just inside the ceiling slab from
rusting due to condensation moisture. But it’s
not possible to prime the top side that’s deeply
embedded in the slab. So if water seeps through
the cracks and reaches those unprimed steel
tops, they will rust and new stains will appear.
Breaking the Cardinal Rule of Repainting So the moral of this story is:
• We can’t change the environment that’s
causing constant condensation.
• We can’t fix the cracks that go right through
the parking ceiling slab and enable ground
water to seep in.
• We can’t fix the fact that there are steel
particles rusting in the concrete.
Yet we’re going ahead and repainting in hopes
that the new system stays intact for as long as
possible. This line of thinking defies a funda-
mental rule of painting over an untimely failure:
don’t do it until you’ve identified and solved
whatever problem caused the failure, or you can
expect to get it all over again.
At times like these, the inspector, painting
contractor and paint supplier are tempted to
tell the GC and owner, “Hey, this isn’t a paint
problem...” But when faced with the challenge,
you try to mitigate or solve it with the knowl-
edge or tools at your disposal. And we hope that
the architect community will learn from these
“unintended consequences” of a laudable new
design concept, so these problems can be
avoided in the future.
Reprinted with permission from the MPI (Mas-
ter Painters Institute). MPI content describes
best practices for com-
mercial, institutional and
light industrial painting.
About the AuthorDave Lick is a paint quality
assurance inspector for
the Master Painters and Decorators Association.
In addition to performing inspections, writing
specifications, and providing failure analysis and
consultations for contractors, architects and
property management companies, Dave is also a
key contributor in the development of the Master
Painter’s Institute’s Training Programs. D+D
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