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,

SCA-0170-1014

®

Snap to see more.

fectly flat floors, delivered.Perfectly flat floors, delivered.fectly flat floors, delivered.

SCA-0170-1014 ©2014 LAATICRETE InteTICRETE International, Inc. All trademarks shown are the intellectual properties of their respective owners.

®

national, Inc. All trademarks shown are the intellectual properties of their respective owners.

wwwSnap to see more.

.laticretesupercap.comwwwSnap to see more.

Rust stains and blistering along the ceiling cracks point to areas where stained and contaminated concretemust be chipped out and the steel underneath primed.

Click our Reader e-Card at durabilityanddesign.com/ric

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

there’s more beneath the surface.

Single-Ply

Self-Adhering Mod Bit

Living RoofsTM featuring GreenGrid®

Elastomeric Acrylic Coatings

mulehide@mulehide.com

Click our Reader e-Card at durabilityanddesign.com/ric

Click our Reader e-Card at www.durabilityanddesign.com/ric

WOC in Quark_Layout 1 10/27/14 7:54 AM Page 1