Make Your Move
As Architectural Designs Evolve, Structural Glazing
by Ellen Rogers
Glass is getting thinner, bigger and clearer. It twists, it curves,
it morphs into unique geometric shapes. Without question, architectural
facades are very different today than they were 30, 20 even 10 years ago.
As technology has evolved, architectural designs have become increasingly
cutting edge. But reality check: those thin, big, curvy walls aren’t for
every project—nor does every project have the budget necessary to use
them. Structural glazing, however, still provides plenty of opportunities
to design and construct a unique façade—and the possibilities to do so
continue to evolve.
Techniques such as two- and four-sided structural silicone glazing (SSG),
for example, have been around for decades—and continue to draw a strong
interest from architects. According to Joe Marks, chief strategy officer
with Architectural Glass & Aluminum in Livermore, Calif., SSG projects
are even more popular now in some ways when compared to years past.
“It’s a mature practice,” he says. “[SSG] may not be a novelty, but it’s
a part of their [architects] pallet.” He says he’s seen a shift toward
designing the external component of curtainwall as a design feature rather
than just a necessary part of the glazing system. “A SSG curtainwall becomes
the canvas and the external expressed components are the design feature,”
he explains. “Architects are not moving away; they are embracing it even
Still, facades today are different than those of 30 years ago. Marks says
some things to consider when looking at the changes in façade designs
are the increase in both the complexity of the project and the size of
the glass panels.
“The typical glass size [early on] was around 35 square feet. Now it’s
not unusual to see glass that’s 50 square feet and above which increases
the load requirements of the silicone,” says Marks. “The larger the glass
the more silicone you need and the architect needs to understand there
is a relationship to the site line of the silicone joint and those larger
spans of glass.” He adds that suppliers are stepping up their products
to accommodate the increasing loads to accommodate larger lites.
Larry Carbary, an industry scientist with Dow Corning based in Midland,
Mich., says there’s a shift in that products today are more robust when
compared to years past. Products are being designed for higher windloads;
there are also more silicone gaskets and more unitized shop applications
compared to stick systems. And, he stresses, there’s a greater appreciation
of the quality control process.
four decades + in the field without full-scale failure
L.A. Confidential While structural silicone glazing has continued
to thrive, it is not universally accepted. Joe Marks, chief strategy
officer with Architectural Glass & Aluminum in Livermore, Calif.,
says, for example, Los Angeles County is adverse to it.
“There’s a high concern for public safety and in the case of L.A.
if you go back to the 1980s there have been incidences of building
failure in one form or another (not related to SSG) that were very
public and there was a lot of public scrutiny,” he says. “As a result,
the county became very conservative.”
He’s quick to point out there has been no direct evidence of a specific
problem or high probability of SSG failure, “it’s just to them there’s
still this [perspective] that it’s a newer technology, when in fact
it’s been around since the 1970s—that’s four decades or more in the
field without full-scale failure.”
He says it’s not that SSG projects or even others such as point-supported
glass walls have not been built in Los Angeles. “They have had variances
… but it requires a lot of due diligence, test reports, etc. [The
county] wants a lab research report, etc. for all components that
go into the application, so you have to be extremely diligent to make
sure everything going into the building has met approval through the
“You have a lot more attention paid to quality control,” says Carbary.
“Within the specifications they are taking serious what has to be specified
of the installation contractors.”
Speaking of the system’s performance, Carbary adds that when the sealant
is placed around all four sides, it provides a thermal, air and water
barrier and allows movement in glass and aluminum. “We’ve seen very few
callbacks related to air, water and structural performance,” says Carbary.
While structural glazing may have started with silicone, today there are
other options available for achieving a similar two- or four-sided aesthetic.
3M, for example, offers acrylic foam tapes, which can also be used in
structural glazing applications. According to Steve Austin, global technical
service specialist, 3M™ VHB™ Tapes - Architectural Markets, the structural
glazing tape essentially replaces structural silicone to attach the glass
“Structural glazing goes back to 1990 for 3M,” says Austin. “It seems
relatively new to some people in the U.S., but we have been doing this
for 24 years now. Our first structural glazing project in the U.S. was
No Room for
Structural glazing projects have been deemed high-risk applications
by some owners, architects and others in the past. Still, after
four decades there’s never been a catastrophic failure—and this
is certainly the path on which everyone wants to continue. So,
what steps and precautions should be taken to ensure a safe and
Joe Marks, chief strategy officer with Architectural Glass & Aluminum
in Livermore, Calif., explains two likely causes for a failure.
“One could be inadequate design of the size of the SSG joint,
another could be the sealant’s incompatibility with materials
being adhered,” he says. “The other might be a contaminate, whether
onsite or in shop, that prevented the adhesion.”
And the fix for such a failure doesn’t come easy. “It can be elaborate
if there’s a failure throughout the building or one that is characteristic
of the project. Even, if it’s a small aspect of the project, it
will still be enough to raise red flags so that the entire installation
is suspect,” says Marks. “The remedy is extensive and that means
cutting the glass out completely, cleaning and starting over on
both the glass and metal substrate to which you’re adhering. It’s
very involved and very expensive. There is no simple fix for a
structural silicone failure.”
Suppliers, however, also take extreme cautions and measures to
ensure a quality procedure. Steve Austin, global technical service
specialist, 3M™ VHB™ Tapes - Architectural Markets, says his company
takes precautions to control who uses the product and for what
projects and restricts the sale of its tapes to only approved
“We have a strict approval process,” he explains. This includes
a review of drawings/design criteria. “We explain this to the
customer and then they send in the substrates for adhesion testing
… we can’t predict adhesion; you just have to do the test, which
only takes three days for acrylic foam tapes,” says Austin. “We
then issue a test report to the customer that explains the results,
etc.” He adds that before the contract glazier begins the project
they also undergo training with a 3M representative, who issues
a standard operating procedure as a step-by-step guide; this is
followed with production audits to make sure the operators who
are working on it are the ones who were trained, etc. A warranty
can be issued after all process steps and the project are completed.
Structural silicone suppliers follow similar procedures as well.
Larry Carbary, an industry scientist with Midland, Mich.-based
Dow Corning, says his company asks specifiers to include in their
contract documents to the contract glaziers submissions from the
structural silicone supplier that include the following criteria:
• Product data sheets;
• Blueprint review of the project so that the design can be confirmed
as meeting industry and project requirements;
• Adhesion test reports on actual surfaces that come in contact
with the structural silicone;
• Compatibility test report on accessory materials that come in
contact with the structural silicone; and
• Application and quality control instructions for the use of
“Dow Corning will then provide the services
that allow the contract glazier to fulfill his contractual obligations,”
says Carbary, explaining that his company offers the application
and quality control training, blueprint review service, adhesion
testing and compatibility testing.
“Communication of these reviews and results will include application
and quality control instructions. If the contract glazier is
unclear of any of this or is uncomfortable in any way, Dow Corning
will provide training on the application and quality control of
structural silicone in person. Knowledgeable service and support
is critical to ensuring installers are comfortable installing
and quality controlling structural silicone applications.”
Still, the applications are not without questions and even concern, in
some cases. Marks says something he has faced in working with architects
is a conflict of design intent verses what can actually be done cost effectively.
“The architect might want a large opening module done with one 75-square-foot
insulating glass unit. You have to look at how it will perform from a
loading perspective, how it pencils out from a cost perspective, find
a fabricator who can effectively make units that large, etc. … it’s not
always the most practical,” he explains. “While architects may be pushing
the envelope, there are often constraints that bring them back down a
little bit. They have a vision, but sometimes there’s the reality of what
can be done.”
Carbary adds it’s also important to keep in mind attention to detail and
“One of my worries is the younger professional will take [this] for granted.
I hope quality control never becomes lax. I remember 30 years ago people
were afraid of [SSG]; it was a fear factor and today nearly every major
iconic high rise is specified with SSG.”
“It comes down to managing risk,” agrees Austin. “The industry can’t afford
to have a failure; no one wants panels falling off a building.”
But how do these projects hold up and what do these buildings look like
after 30-plus years? They still look good, experts agree. Marks points
out that’s a testimony to the industry.
Carbary points out that the first four-sided SSG project was the SHG Inc.
building built in 1971 in Detroit. He says it has held up well and is
still performing today.
Marks agrees, “If you look at the amount of SSG square footage installed
it’s remarkable. The performance has been very good and it’s a resilient
product. If it’s cleaned and maintained properly it will look as good
[decades later] as it did when it was installed.”
Structural glazing applications have become well established in many markets.
But what’s next? As architects continue to search for the next big thing
in facades, where will structural glazing applications fit in? Marks says
he sees a challenge to keep designs cutting edge mixed with increasing
code restrictions/parameters related to building loads and energy performance.
“… I think eventually we’ll see double cavity IG and [triple glazing]
becoming common to get thermal requirements down to where architects can
continue to design with glass [given increasingly] stringent energy code
restrictions,” says Marks.
Carbary adds, “The use for SSG is stronger than ever because of its proven
performance with each passing natural event such as hurricanes, earthquakes,
rain events, extreme temperatures and UV exposure. Structural silicone
is the key to performance for seismic-, impact-resistance and blast mitigation.
The continuous flexible rubber anchor allows the glazing to remain in
the opening after the event. This is critical for human safety during
Speaking of structural glazing tapes, Austin says he’s also seen increasing
opportunities for applications in which the products can be used. For
example, he says his company’s products have grown to be used in hybrid
stick-wall, storefront and skylight/canopy applications when early on
they were most commonly used in unitized and door/window applications.
“The industry has evolved and has seen the value in its use in hybrid-stick
wall systems,” he says, explaining these jobs are still a stick wall system,
but the glass is bonded to the frame in the shop and then sent to the
job site and installed with mechanical fasteners that lock the frame into
Austin adds that these tapes have also provided new opportunities for
contract glaziers who might not otherwise take on a structural glazing
“Glass shops can do these four-sided jobs where they might not have entered
the market before. Because acrylic foam structural glazing tapes are fully
cured, the units can be moved immediately after bonding. This allows glaziers
to do these types of jobs as they don’t need expensive silicone dispensing
equipment nor large shop space for curing glazed units.”
Looking at the growth and possibilities that surround the future of structural
glazing, Carbary says, “There is always interest in newer developments,
but nobody wants to be first. Our industry really resists new technologies.”
He points out that even after 40-plus years there are still some design
professionals who think of it as “so new and unproven that they refuse
to acknowledge the history. There was actually one design professional
who publicly declared that structural silicone was ‘Krazy Glue’ and refused
to consider it.”
The challenge for the industry will be to continue to educate and inform
architects and others the benefits that these products can provide—design
flexibility and design freedom. And its performance is proven.
Ellen Rogers is the editor of USGlass magazine. Follow her on
Twitter @USGlass and like USGlass on Facebook to receive updates.
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