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Genesis of a Waterproofing Flashing System for a Damp Climate

May 15, 2013

The answers to common construction problems are out there.
Tatley-Grund, Seattle, Washington, a contracting firm specializing
in whole-building repair of water-damaged multistory
structures, often sees failed peel-and-stick flashing membranes
on rough
During forensic investigations
of buildings suffering
water intrusion
problems in the Pacific
Northwest, principals
Stacey Grund and Ron
Tatley have documented
repeated cases of
adhesion failure that let
water into the building
envelope. See Figure 1.
“We’ve removed the
cladding and seen the
membranes peeled away
and curled up,” Grund
says. “We’ve seen where
contractors have had to
staple the membrane to
the sheathing because it
wouldn’t adhere to a wet
The majority of
the firm’s work is on
buildings less than five
years old; far too young,
1 8 • I n t e r f a c e A p r i l 2 0 1 3
Figure 2 – Only three years old, this Seattle apartment
complex had its cladding removed, windows replaced,
repairs made to rough openings and sheathing, and
cladding replaced at a cost of $14 million after its traditional
air-and-water barrier products failed. Tatley-Grund photo.
Figure 1 – This rotted plywood from a vaporimpermeable
peel-and-stick that trapped
moisture is typical of what repair contractor
Tatley-Grund, Seattle, finds in water-damaged
buildings. They found it counterproductive
to repair problems like this with the same
methods that they felt caused the damage to
begin with. Photo courtesy of BEI, LLC.
A p r i l 2 0 1 3 I n t e r f a c e • 1 9
Grund says, to need this kind of repair
(Figure 2). He has testified as an expert witness
in over 85 lawsuits concerning these
Part of the reason for the stream of
building envelope failures rests with the
unique climate of the Pacific Northwest,
Grund says. Though the area gets less rain
than is commonly believed, it has a high
percentage of cool, wet days. That means
not enough wet/dry cycles, which takes a
toll on building envelopes.
Current methods also must shoulder
some responsibility.
ASTM E2112 – 07, Standard Practice
for Installation of Exterior Windows, Doors,
and Skylights, requires 21 steps to properly
flash a rough opening, creating, by some
counts,1 74 interfaces between membrane
and sheathing. In a multistory building with
300 windows, for example, that’s 22,200
opportunities for air and water to leak
And in real-world circumstances—in
a repetitious 21-step procedure repeated
dozens of times a day—it’s possible for even
the most dedicated, competent installer to
miss a step. Unfortunately, that one missed
step can, and often does, compromise an
entire wall assembly when it permits water
It’s no wonder that the U.S Environmental
Protection Agency’s (EPA) Building
Assessment Survey and Evaluation (BASE)
study of 100 randomly selected U.S. office
buildings found 43% of the buildings had
current water leaks, and 85% had experienced
previous water leaks.2
In their own work in the late 1990s,
Tatley-Grund concluded it was counterproductive
to repair water-damaged buildings
using the same methods that appeared to
fail in the first place.
Being contractors, they wanted a
rough-opening flashing system that could
meet the needs of their clients and the
demands of the real world—especially the
extra-damp Pacific Northwest. They wanted
something simple to install that could tie
into existing air, water, and vapor barrier
systems, and that they could guarantee to
their clients would not delaminate, rip, or
otherwise fail for the designed life of the
building. Unfortunately, nothing like that
That didn’t stop them. They began with
a wish list. Tatley-Grund’s ideal flashing
system must:
• Bond to damp surfaces, since dampness
is a fact of life in the Pacific
• Be immediately waterproof in case of
• Be fluid-applied to avoid “buildup”
that could affect how well the window
fits into the rough opening
• Adhere permanently and without a
• Not shrink
• Be VOC-compliant, low-odor, and
environmentally friendly
• Be opaque when target thickness
is achieved so the installer knows
when the right amount is applied
• Withstand exposure to weather for
up to six months in case of construction
• Be compatible with most paints
• Be vapor-permeable
• Have few and easy application steps
• Be easily repaired
• Self-seal around fasteners
Tatley led the search. For four years he
tried and discarded urethanes, acrylics, and
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silicones. In 2004, after repeated unsuccessful
tries with existing products, a silicone
sealant manufacturer pointed to Tom
Schneider, an expert in polymer chemistry.
Schneider told the partners that with some
work, a modified silyl (MS) polymer resin
known as silyl-terminated polyether (STPE)
might work for their purpose. Guided by
the wish list, the Seattle contractors and
the chemist worked together to harness the
substance for flashing rough openings.
It turned out to be well-suited to the
task. The result, an STPE-based fluidapplied
flashing system meeting every
checkpoint of the Tatley-Grund wish list,
has been in continuous use, for both repair
and new construction, since 2005.
Since then, the company has found the
STPE resin versatile enough to be the base
for a gun-and-spread joint and seam filler
and a roller-applied primary air- and waterproof
Architectural Record magazine recognized
the STPE-based flashing system in
the publication’s list of top waterproofing
products of 2010.3
STPE Chemistr y
STPE-based products are the leading
construction sealants in Europe and Asia—
including Japan, where STPE was developed
in 1978.
In their raw state, STPEs are clear resins.
At the molecular level, STPE consists
of a polyether “backbone” with methoxysilyl
chains on either end. With moisture and
the proper catalyst, those chains condense
together, creating weather-repellent, durable
silyl bonds to hold the high-performance
membrane together, Schneider explained.
This results in several of the properties
Grund and Tatley sought for their wet locale,
such as being instantly waterproof on application;
being usable on damp substrates;
and at the same time, curing even faster in
case of contact with water, such as rain.
Those weren’t the only reasons
Schneider thought STPEs were good candidates
for Tatley and Grund’s flashing
Edward M. Petrie, author of McGraw-
Hill’s Handbook of Adhesives and Sealants,
wrote a paper4 on silyl-modified polymer
technology for The Adhesives and Sealant
Council. In it, he compared MS polymers
such as STPEs with urethane and silicone
sealants. He used a table to show how MS
polymers outperform the others across a
range of factors (Table 1).
Petrie noted a major MS polymer drawback:
strength loss over long periods of
UV exposure. STPE-based rough-opening
flashing and primary air and water barriers
could be compromised in case of lengthy
exposure during construction delays. That
was one of several issues Schneider knew
he would have to address.
Fro m Resin to Realit y
The hardest part about going from
the raw material to the finished product,
Schneider said, was that there was no one
to ask when he had questions. The overseas
manufacturer of the raw material was
tight-lipped, and few in the U.S. had heard
of STPEs.
2 0 • I n t e r f a c e A p r i l 2 0 1 3
Table 1 – Edward M. Petrie compared STPE, urethane, and silicone on a 1-10, worst-to-best
scale. From The Handbook of Adhesives and Sealants, McGraw-Hill.
Property S TPE U rethane Silicone
Environmental friendliness 10 5 9
Nonbubbling 10 6 10
Low-temperature gunnability 10 8 10
Slump resistance 10 10 10
Quick cure 10 7 10
Storage stability 10 7 9
Body (tooling) 8 10 8
Weather resistance 8 6 10
Adhesion to various substrates 10 5 8
Mechanical properties 10 10 10
Heat resistance, mechanical stability 9 8 10
Nondirt pickup 10 10 5
Stain resistance 8 8 5
Paintability with water-based paint 10 10 3
Totals 133 110 117
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He started with what the resins already
had that corresponded to the wish list: They
were flexible; durable; and resistant to heat,
cold, water, and chemicals. They were solvent-
free. They could self-seal around and
to fasteners. They had excellent adhesion
on a wide range of substrates. They were
vapor-permeable and had a suitable cure
Unfortunately, the available STPE resins
all varied in viscosity, flexibility, and
strength, Schneider said. None was exactly
right. He mixed and matched until he had a
blend the contractors liked.
Alone in the laboratory, Schneider
worked to create from the STPE resin a
product with all the properties called for
by Tatley and Grund’s wish list. He experimented
with UV inhibitors; treated pigments
for impact-resistance; and increased
vapor-permeability, flow characteristics,
antimicrobials, and plasticizers.
Again and again he took his latest batch
to Seattle for the crews to try out, and over
and over he returned to the lab to try again.
It was only a matter of time. That time
turned out to be 2005.
Flas hin g Rough Openin gs
In its 2005 debut, here’s how that first
alternative to peel-and-stick membranes
worked (Figure 3):
1. The waterproof flashing membrane,
which they named Wet-Flash PM
7000, is gunned out of a cartridge and
over the entire inside surface of the
rough opening, 12 mils thick and 4
to 6 inches out onto the sheathing or
CMU wall around the rough opening.
2. A precreased textile counterflashing
is adhered to the bottom of the rough
opening, folded over the sill, and
pressed into the flashing material.
3. After a 15- to 30-minute cure time,
the window goes in.
For flanged windows, the PM 7000
applies over the flanges except for drainage
weeps left in the sill area.
That’s simpler than the 21-step ASTM
E2112 – 07 method.
Tatley-Grund’s method also solved
“buildup.” In splicing and wrapping corners
of rough openings with peel-and-stick,
Grund said, installers sometimes find
they’ve built up the surface an extra quarter
to three-eighths of an inch. In those cases,
windows have to be jammed in, which can
damage the peel-and-stick and compromise
the rough opening’s watertight integrity.
“That’s one reason we wanted a fluidapplied
solution,” he said.
Fi eld perfor manc e
The first field trials of the fluid-applied
STPE flashing system took place on several
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• Can be applied to wet or dry surfaces.
• Repels rain from the instant it goes on.
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Figure 3 – An applicator demonstrates the relative simplicity of waterproofing a rough
opening with the STPE-based flashing system. Photo, courtesy BEI, LLC.
A p r i l 2 0 1 3 I n t e r f a c e • 2 1
window-replacement projects in early 2005.
While the formulation lived up to most
expectations, Schneider said it required
adjustments for viscosity (it needed to be
thinner), cure-time (it was drying too fast),
and color. Applicator feedback indicated
changing the color from gray to red would
make it easier to inspect the flashing for correct
thickness. A further refinement added
fiber to the resin to reduce “drippiness.”
One of those early projects took place
in 2005 at Renaissance Condominiums in
Seattle. In 2009, Tatley-Grund returned to
the Renaissance Condominiums with independent
inspectors from OAC, Seattle, a
full-service architecture, construction support,
and forensic engineering firm. The visit’s
purpose was to inspect a representative
sample of the building to gauge how well
the STPE-based flashing had protected the
rough opening and surrounding sheathing
over the years.
With the owner’s permission, the investigators
removed about 50 sq. ft. of Hardy
Board siding and weather-resistive barrier
on the building’s exterior to reveal the
sheathing and rough opening. From inside
the building, they cut an opening beneath
the window so they could inspect the wall
cavity. The inspection addressed the south
and west corners of the building, since
those are the elevations most exposed to
Seattle’s wind and rain patterns, according
to OAC’s report.
The report states the inspectors found
Tatley-Grund’s flashing system in good
repair and functioning as intended, and
all inspected surfaces dry and in good condition.
Tatley-Grund plans to reinspect in
Since Schneider’s first successful batch
of STPE flashing material was applied on
rough openings in 2005, he has helped
Tatley-Grund pioneer other STPE-based
products and procedures to make their
repairs to water-damaged buildings more
effective. They include a joint and seam filler
and a roller-applied primary air barrier.
Testin g
Tatley-Grund’s STPE system passed
ASTM E2357-05, Standard Test Method
for Determining Air Leakage of Air Barrier
Assemblies. In this test, the joint and seam
filler, original flashing, and primary air
barrier products—all derived from the STPE
base resins—were tested at 75 pascals of
pressure, corresponding to a 25-mph wind.
The system also passed the International
Code Council Evaluation Service’s Acceptance
Criteria 212 for water-resistive barriers.
The water-resistive test requires the
coating to perform at least as well as
asphalt-impregnated building paper. Since
climatic conditions in the Pacific Northwest
routinely exceed the preceding test requirements,
Tatley and Grund built their own
test chamber in which they could subject
mock-ups to more stringent weather simulations
(Figure 4).
Testing assemblies rather than single
products is important, they reasoned, since
it doesn’t matter if an individual component
can pass a test if the assembly fails.
Tatley built what was basically a giant
metal box about 10 ft. high, 30 ft. around,
and weighing around 12,000 pounds. See
Figure 5.
Wall assembly mock-ups fit airtight into
the open side of the box. The exterior side of
the mock-up faces into the box, where there
2 2 • I n t e r f a c e A p r i l 2 0 1 3
Figure 4 – Ron Tatley makes some adjustments to the Design Verification Test Chamber he
developed to test the air- and watertight integrity of wall assembly mock-ups. PROSOCO photo.
2 4 • I n t e r f a c e A p r i l 2 0 1 3
are nozzles to simulate rain
and fans to build air pressure.
The interior side of the mockup
faces out, so inspectors
can see where water is forced
Water almost always comes
through, Grund says, because
they usually test to failure.
It’s good to know exactly how
much stress an assembly can
take, he says. See Figure 6.
The Design Verification
Test Chamber also features
sensors and gauges to accurately
measure that stress,
which, Grund says, can be
ratcheted up to Category 5
hurricane levels.
They’ve used the chamber
to demonstrate the STPE
system’s ability to withstand
hours of water spray driven
at 2,880 pascals of pressure
and racking movement corresponding
to the 155-mph
wind-driven rain of a Category
5 hurricane.
Air leakage testin g
In chamber tests similar to ASTM E2357
air barrier assembly testing, but using
a smaller mock-up, Tatley, Grund, and
Schneider found their STPE system limited
air leakage to 0.17 air changes per
hour (ACH). That exceeds the 0.6-ACH
passive house air leakage standard. It far
exceeds the 5.0-ACH Energy Star standard
for Climate Zones 3 and 4. See Figure 7.
The results are supported by recent project
testing at the Karuna5 Passive House,
under construction in Yamhill County,
Oregon, where a partially installed STPE air
barrier system achieved 0.42 ACH in blowerdoor
Compatibi lit y
Adhesion to a wide range of surfaces,
including damp ones, was important,
Grund said, since repairs require the flashing
to tie into existing air, water, and vapor
barrier systems. However, Grund noted that
adhesion alone is not sufficient for longterm
“For example, we’ve seen sealants
with excellent adhesion on peel-andsticks
over the short term,” he said. “In
the long term, some sealants block offgassing
from peel-and-sticks, resulting in
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Figure 5 – Ron Tatley (right) and assistant Matt Travis test a wall assembly mock-up in the Design
Verification Test Chamber. Photo courtesy of PROSOCO.
discoloration and damage. If you don’t know from experience and/or
prior testing whether two products will be compatible, it’s best to test,”
he said. “We’ve found heat testing and accelerated weathering testing
are good predictors of long-term compatibility,” Grund added.
Environ menta l
As sealants and adhesives, STPEs have long been known for environmental
friendliness, another item on the Tatley-Grund wish list.
They contain no solvents or isocyanates6 common to many sealants.
An STPE-based air and water barrier system derived from Schneider’s
formula was recently installed on the under-construction Bullitt Center
in Seattle. The Bullitt Center is being constructed according to the
requirements of the Living Building Challenge.7 When completed, it will
stake a claim to being the greenest office building in the world.8 See
Figure 8.
Builders chose the STPE system first for its demonstrated ability
to hold air leakage to passive house and net-zero levels. They also
chose it because it didn’t have any ingredients from the Living Building
Challenge’s “red list” of environmentally harmful substances.
A p r i l 2 0 1 3 I n t e r f a c e • 2 5
Figure 6 – An inspector points to where air pressure, simulating winddriven
rain, has forced a leak in a wall assembly mock-up during
testing in the Design Verification Test Chamber. Photo courtesy of
2 6 • I n t e r f a c e A p r i l 2 0 1 3
Conc lusions
In the end, this is not the story of a
“miracle product” but simply that of existing
chemistry being applied to and solving
known problems.
“Although daunting to consider and
potentially expensive on the front end, longterm
solutions to difficult problems are
achievable,” Grund says. “As was the case
with Tatley-Grund over 10 years ago, the
existing materials the market offered were
insufficient. We took it upon ourselves to
develop and make our own material/system.
That resulted in a much better finished
product for our customers and reduced
risk and higher profitability for the company.”
1. David W. Boyer, “Rethinking the
Way We Build,” SWRI Applicator
Magazine, Summer 2011, pp. 6-11.
2. “Baseline Information on 100
Randomly Selected Office Buildings
in the United States (BASE):
Gross Building Characteristics,”
Proceedings of Healthy Buildings
2000, Vol. 1, pp. 151-156, www.epa.
3. “Product Reports – Thermal &
Moisture Protection,” Architectural
Record, December 2010.
4. Edward M. Petrie, MS Polymers in
“Hybrid” Sealants, The Adhesives
and Sealant Council.
5. Field Notes blog post, August 3,
2012,; and
Green Journey blog post, August 15,
6. Isocyanates are the raw materials
that make up all polyurethane products.
They include compounds classified
as potential human carcinogens.
7. More information on the Living
Building Challenge, arguably one
of the world’s most stringent environmental
standards, can be found
online at
8. “The Greenest Commercial Building in
the World,”
Paul Grahovac works for PROSOCO, Lawrence, Kansas, as
the company’s Building Envelope Group technical director
with 17 years of experience in the building products industry.
The company manufacturers products that clean and protect
brick and stone architecture, including air and waterproof
barriers. Grahovac’s professional activities include: LEED
AP; International Code Council; Air Barrier Association of
America’s Technical, Flashing, and Whole-Building Testing
Committees; National Concrete Masonry Association’s Air
Barrier Task Force; ASTM Committees on building performance,
vapor permeability, and window installation; RCI; ASHRAE; and the following
National Institute of Building Sciences Councils: Building Enclosure Technology;
Environmental Council (BETEC Building Enclosure Integration Committee); and the
Council on Finance, Insurance, and Real Estate.
Paul Grahovac
Figure 7 – An installer seals a rough opening with
an STPE-based flashing at an under-construction
passive house in Yamhill County, OR. The builders
chose the fluid-applied flashing because of
demonstrated performance in stopping air leaks
through the building envelope. Photo courtesy of
Hammer and Hand.
Figure 8 – This architectural rendering
shows the under-construction net-zero Bullitt
Center, Seattle, WA. The Bullitt Center has
an environmentally friendly STPE-based
air- and waterproof flashing system to help
it meet the stringent energy conservation
standards required to be certified as a
“Living Building.” Rendering courtesy of
Miller-Hull Partnership.