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Patented Coatings Introduces New Technology to Snow Retention

May 15, 2011

Traditional snow retention systems
have existed nearly as long as smoothsurfaced
roofs have been discharging dangerous
and damaging snow slides (Photo 1).
All of these systems are basically the same
in that they secure some physical barrier
onto the roof surface in a position to stop
the sliding snowpack on its path to the discharge
edge of the roof (Photos 2 and 3).
While some are effective in stopping the
most damaging and dangerous discharges,
most if not all fail to eliminate discharge
The systems function most effectively
when their components are widely distributed
across the entire roof surface and
increase the points of contact with the
snowpack. This reduces the incremental
loading of the snowpack on each snow
retention component and the distance and
speed traveled by the snowpack before
being influenced by the resistive force of
each component. The most effective systems
are well designed to transfer the loading
to the roof and remain secure without
damaging the roof. The system’s structural
design and the design of the connection to
the roof are the easiest engineering parts of
the snow retention puzzle to solve.
The most difficult snow retention issue
is the reliable transfer of interactional forces
that occur within the snowpack
at, and upslope of, the
snow retention components.
Snow retention systems are
most effective in stopping a
snowpack that is well consolidated
in a solid mass and
least effective in stopping a
snowpack that has transformed
into a fluid flow such
as occurs during melting
When a thick snowpack
is being supported by a
retention component, the
roof area directly below the
retained snow and component
is usually bare and exposed. The component
contact point or edge of the snowpack
is also exposed. The contact point or
edge is one of the first areas of the snowpack
to start melting, reducing the ability of
the component to transfer resistive force
into the snowpack. Meltwater drains down
through the snowpack to saturate the bottom
of the snowpack against the roof,
reducing the bond between the roof and the
snowpack and creating a lubricating, floating
influence on the snowpack. Further –
more, the meltwater saturating the lower
edge of the snowpack causes additional
snowpack melting and softening that transforms
the previously solid-bearing condition
at each component into an unconsolidated
As a snowpack becomes fluid, even the
most structurally secure retention components
fail to transfer the required resistive
force into flow of an unconsolidated snowpack.
Portions of the snowpack flow around
or over well-secured components and slide
down the roof. Once larger portions begin to
accelerate down the slope, they are increasingly
difficult to stop. If there is a retention
component in the path of a large slide, it is
usually unable to stop and often unable to
sufficiently detour the sliding snow from
discharging from the roof.
Therefore, traditional retention systems
Photo 1 – Sliding snow discharge hazard. can, at best, reduce the potential for dam-
4 • IN T E R FA C E OC T O B E R 2011
OC T O B E R 2011 I N T E R FA C E • 5
age or injury caused by discharge.
Most, if not all, traditional snow retention
systems publish statements disclosing
that their systems are unable to
completely eliminate discharge.
The critical characteristics required
for any system to eliminate discharge
can be summarized as follows:
1) Uniformly distribute a vast num ber
of retention components across
the entire slope of the roof, thus
reducing the interactional force
at each component and preventing
any portion the snowpack
from beginning to slide.
2) The portions of the snowpack
that contact the retention components
must be protected from
melting conditions, remain fro –
zen, and maintain the ability to
maximize the transfer of force to the
retention components.
3) The base of the snowpack must
remain consolidated in one continuous,
frozen, monolithic mass across
the entire surface of the roof and
transfer interactional forces from
the frozen contact points to the
upper strata of the snowpack.
4) Systems must facilitate meltwater
drainage to the discharge edge of the
The best natural example of snow retention
on a sloping surface is an alpine glacier.
As the snow falls onto a mountainside, it
adheres to the rough irregular surface. Air
temperature, solar radiation, and gravitational
force cause moisture and meltwater
to flow down through the heavy, freshly fallen
snowpack. The meltwater settles at the
base of the snowpack, refreezes, and forms
a monolithic icy base layer directly over the
mountain surface. The underside of the icy
base layer is also exposed to melting temperatures
transmitting and radiating from
the earth. Because the dehydrated upper
portions of the snowpack insulate the icy
base layer from extreme weather conditions
above the glacier, the underside of the icy
base layer forms a continuous interface
between melting and freezing.
The icy base is supported and freezes to
the highest and most structurally sound
protrusions on the mountain surface. The
snowpack remains in place on the steep
mountain surface because of the frozen
bond between the monolithic icy base layer
Photo 2 – Bar retention system.
Photo 3 – Basic clip retention system.
and the multitude of structurally sound
rock protrusions. This is solid physical connection
between solid and structurally
sound objects. As conditions change and
the snowpack ages, the load at any one of
the multitude of bearing points may naturally,
gradually, and unperceivably
trans fer to other, more structurally
sound adjacent protrusions.
Melting conditions at the earth/
mountain surface cause meltwater to form
and drip from the underside of the icy base
layer. Meltwater falls to the sloped earth
surface and flows through naturally created
drainageways to the base of the mountain,
leaving the glacier in a flowing river.
Wes Fontecchio spent years making
repairs to installations damaged by sliding
ice and snow in the snow country of
Michigan’s Upper Peninsula and in northern
Wisconsin. He started applying various
elastomeric coatings onto old metal roofs.
The inventor established that a cured elastomeric
coating could hold a uniform matrix
of protruding aggregate and provide effective
snow retention upslope of items such
as chimneys, vents, and gutters that were
being damaged by snow slides.
His simple early systems showed immediate
success but also less-than-optimal
durability and appearance. Years of refinement
developed a highly effective, durable
snow retention coating system that became
the basis of a U.S. patent application filing
in late 2006. On July 20, 2010, the
Michigan Limited Liability Company–owned
by Fontecchio, Mark Blomquist (architect
and author of this article), and others –
obtained U.S. Patent #7,757,456 for the
Snowgrip system. The company also has a
patent pending in Canada.
Photo 4 – Clear base coat ready to use.
Photo 5 – Aggregate set in
energy-saving white
reflective base coat.
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6 • IN T E R FA C E OC T O B E R 2011
The new retention coating is described
as a two-part, monolithic, abrasive snow
retention coating for smooth-surfaced roofs
or other surfaces requiring snow retention.
Part one is an elastomeric base coat applied
to a clean, dry substrate (Photo 4); and part
two is a matrix of uniformly distributed
aggregate secured into the cured base coat
(Photo 5). The system is recommended to
coat the entire roof/substrate (from bottom
to top of slopes and all roof surfaces of a
building) to prevent any portion of the
snowpack from beginning to slide and to
eliminate destructive dynamic loading on
The system base coat (clear, reflective
white, or colored) has material properties of
solvent-based elastomeric coatings. The
base coat provides excellent adhesion, high
flexibility, and elongation properties. Basecoat
flexibility is critical to facilitate movement
of both the substrate and the aggregate,
while durably securing retention components.
The acrylic-based coatings tested have
not remained as flexible, don’t adhere to the
substrate, and don’t hold aggregate as well
as a polyurethane, hybrid, solvent-based
coating with stabilized, permanent elastomeric
properties (high tensile strength
and elongation greater than 500%). The
nonacrylic base coats used in the system
are not subject to freezing and can be
installed at colder temperatures, with the
clear coating having an installation temperature
as low as 0ºF.
While a thorough and deliberate installation
of the base coating as an elastomeric
leak repair/prevention coating could provide
substantial waterproofing benefits, the system
is primarily intended and prescribed as
a snow retention system. For example, an
effective snow retention system installation
may not necessarily need to coat the seams
or flashing. Only one base coat is required
for effective snow retention; but multiple
complete, edge-to-edge coats, including special
reinforcing and installation methods,
may be required to provide additional benefits
of waterproofing, enhanced aesthetics,
and extended durability.
The aggregate is a recycled material,
and the durable granules have relatively
sharp points and edges (though not cutting,
like glass or metal). The granules are the
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OC T O B E R 2011 I N T E R FA C E • 7
size of course sand, and it is recommended
that they be sparsely distributed at about
20 granules per sq in (Photo 6). Each granule
has a unique irregular shape that creates
firm embedment into the cured base
coat and frozen icy base layer of the aging
snowpack. The aggregate material is not
impacted by the freeze/thaw cycles, erosion,
or corrosion.
The liquid base coat can be brush-,
roller-, or spray-applied to any clean, dry
surface that needs snow retention treatment
(the clear base coat is too thick to be
sprayed). (See Photos 7, 8, 9, and 10.) While
the base coat is still wet, the aggregate
granules are uniformly broadcast onto
the surface so that the granules partially
sink into the liquid base coat. As the
base coat cures, it bonds to the substrate
and holds the granules protruding
from the base-coat surface.
Regardless of the snowpack thickness
or environmental conditions, the
snowpack retained by the coating system
will age like an alpine glacier as follows
(Figure 1):
1) The upper level of the snowpack
develops into a uniform lightweight
dehydrated insulating snow layer as
Photo 6 – SR coating on glass.
Photo 7 – Application on metal shingle prior
to installation. Photo 8 – Application on composite
shingle prior to installation.
8 • IN T E R FA C E OC T O B E R 2011
it reduces in density (snow load) as
gravity pulls meltwater down.
2) Meltwater refreezes and forms a
monolithic, structurally sound icy
base layer that freezes to the clustered
3) The securely supported icy base
layer is melted from below, and
meltwater drips onto the treated
4) Drainageways develop in the clearest
areas between the clusters of
aggregate. Meltwater drainage naturally
carves into the underside of the
icy base much like a river system
forms, with small tributaries on
upper slopes and large “river” channels
on lower slopes.
5) The snowpack recedes from the
edges and safely and gradually
melts away, one drop at a time
(Photo 11).
Unlike other SRSs, Snowgrip provides
the following:
1) The new coating system promotes
uniform roof loading (minimal loading
at a maximum number of points)
of roof structures and membrane
substrates rather than the much
more concentrated loading (imposed
at considerably fewer multiple
points or lines) provided by other
2) The coating system promotes free
Photo 9 – SR coating sample on brick.
Photo 10 – Snow retention
coating on limestone sill.
Figure 1 – How the snow retention coating works.
OC T O B E R 2011 I N T E R FA C E • 9
flow of meltwater. It creates an air space/drainageway
below a well-supported insulating snowpack rather than
the meltwater-damming condition at clip/fence points or
lines of other SRSs.
3) Retention points are protected from melting conditions.
The multiple points of frozen physical connection
between the icy base of the snowpack and retention
components are well insulated and protected from melting
conditions above the snowpack. Because the connection
points between the snowpack and retention
components of other SRSs are extremely exposed to
melting air temperatures and solar exposure, they have
the inherent inability to prevent the failure of the snowpack
structure to transfer loading to their relatively few
and isolated retention points. The melting of the snowpack
destroys the ability to transfer load to other SRSs
as the snowpack melts and transforms from a relatively
solid mass to an increasingly heavy and fluid flow.
The inventor’s trial-and-error method of development was
initially not well received by members of the architectural and
engineering community. Design professionals wanted quantitative
and qualitative design criteria and not just the display of a
system sample holding a block of ice on a 60º to 70º incline
(Photo 12).
Photo 11 – Meltwater (dyed here for clarity)
flows under the block without moving the
Photo 12 – 100 psf load on snow
retention coating surface.
10 • I N T E R FA C E OC T O B E R 2011
In an effort to give engineers
some requested design criteria,
developers determined that each
granule could easily support a load
of five pounds before dislodging
from the base coat. At 20 granules
per sq in and 144 sq in per sq ft, the
Snowgrip could potentially support
14,400 lbs per sq ft. Thus, further
evaluation indicates Snow grip is
only likely to be loaded to a level of
well under 10% of its capacity.
So far, developers are not aware
of any sliding snow discharge from
roofs treated with the coating system
that have followed 100% coverage
recommendations. In some isolated
cases where the recommended
full coverage was not installed,
sliding discharge has been prevented,
though some creeping of the
snowpack was observed and re –
quired maintenance to remove
small portions of the snowpack that
extended beyond the roof edge.
Current installations have performed
100% effectively in preventing
sliding discharge on slopes up
Photo 13 – Demonstration of aged ice block on sample in nearly vertical position.
OC T O B E R 2011 I N T E R FA C E • 1 1
to a 12/12 pitch,
but theoretically
would perform on
steep pitches (Pho to
13). How ever, it is
anticipated that
snow on snow
slides and windinfluenced
beyond the
control of the snow
retention coat ing system
be comes more
likely on steepersloped
The developers introduced a Public
Code Change Proposal to the International
Code Council during the 2007/2008 Code
Development Cycle. The submittal proposed
requirements for snow retention or other
design features that would greatly reduce
the likelihood of injury caused by sliding ice
or snow discharge from buildings. Like
most first-time code-change proposals, the
proposal was opposed by several established
industry representatives and was
rejected by the code council. Nevertheless,
there was a significant level of support that
may provide the basis for a similar code
change request in the future when the performance
of the new coating system can be
more reliably documented by successful
installations (Photos 14 and 15).
The best way to become familiar with this
new, first-of-its-kind snow retention coating
is to view the 8-minute video available at and videos at,, and
Photo 14 – Green snow retention
coating on 10/12 pitch. A snow slide
in a prior winter tore the railing off
the deck.
Mark Blomquist, co-owner/developer of Snowgrip, is a secondgeneration
architect practicing in the upper Midwest based
out of Iron Mountain, Michigan, for the last 30 years. Over
the last ten years, Mark has been a principal architect on
building projects totaling over $250 million. Contact Mark at or 906-396-7000.
Mark Blomquist
12 • I N T E R FA C E OC T O B E R 2011
Photo 15A and 15B –
The top photo shows a
residence coated with
Snowgrip in early
winter, while the bottom
residence shows it in
the late winter.
Almost seven months after a snowstorm destroyed the roof of the Metrodome, the Minnesota Vikings’ home was restored on July
13, 2011. Workers reinflated the bubble roof in about 45 minutes (see time-lapsed video at
A dozen 100-horsepower fans pushed the new Teflon-coated fiberglass into place on the Minneapolis skyline following a $20 million
repair job. To watch the original collapse on December 11, 2010, view the film at