The accompanying article appeared in
the Summer 2010 issue of Life Safety Digest, the quarterly
magazine of FCIA - the Firestop Contractors International Association.
Fire-resistance-rated expansion joints help
keep fire in the
compartment of origin.
(Click to enlarge)
Non-invasive anchoring allows for ease of installation. This ensures for
proper installation which can be critical in life-safety applications.
(Click to enlarge)
A fire-rated expansion joint set in place
which maintains the performance properties of the interior wall system. The
watertight silicone outer seal of
the precompressed, impregnated foam joint is manufactured to color
coordinate with the tile and stone façade of the wall.
(Click to enlarge)
The composition of a UL-certified
fire-rated, preformed, precompressed, foam expansion joint is illustrated
here. The single-unit design features a front and rear bellowed silicone
facing which acts as a watertight seal and is available in a range of
colors. Behind this is an intumescent layer to provide initial
fire-proofing. These dual-sided layers surround fire-retardant impregnated
foam. The design of this single piece expansion joint provides all of the
features that can be installed with a multiple product system.
(Click to enlarge)
Today’s wall systems are being designed and constructed to perform a growing
number of functions. Beyond simply separating rooms or enclosing a
structure, they are expected to maintain thermal conditions, contain the
spread of fire and/or smoke, suppress the transmission of sound, and seal
out the intrusion of water and wind. But, as with any system, performance is
only as good as its weakest link.
Expansion joints historically represent one of the weakest links in wall
assemblies. Mandated to accommodate anticipated structural movement,
expansion joints are literally a gap or break through the entire system. The
ideal expansion joint filler would be one that will not only handle the
gap’s expansion and contraction, but also perform all other functions
expected of the adjacent wall system.
Why an Expansion Joint
Building materials comprising floors, walls and ceilings move due to thermal
expansion and contraction, structural shifts, and seismic activity. These
forces mandate the need for purpose-designed gaps which permit the building
materials to move independently of one another without damage. Smaller
planned crack locations are considered control joints while other locations
need to accommodate greater movement and therefore require larger gaps.
These larger gaps need to be fitted with structural expansion joint fillers.
It is important to fill these joints with a sealant or expansion joint
system which preserves the attributes of the wall. These attributes may
include a designated fire-resistance rating, smoke resistance, sound
attenuation, watertightness, wind resistance, or a thermal rating. Many
expansion joint systems on the market don’t take into consideration the
importance of these requirements and only function on an aesthetic level at
best. The ideal solution would match the attributes of the expansion joint
system to the requirements of the wall or, at the very least, ensure that
the expansion joint material does not degrade any aspect of the wall
Early in the design process, an assessment should be made of what is
required of the expansion joint system. The proper system should be
carefully engineered and selected to best match all of the wall’s properties
while handling the expected movement. The wrong choice in an expansion joint
can allow fire, smoke, moisture, heat and cold, sound, or other unwanted
elements to pass through the wall at the location of the expansion joint
gap. For example, metal-track-and-rubber-gland systems (“strip seal
systems”) which can fill the void and may handle the wall’s movement may not
effectively block the passage of sound or provide for watertightness,
fire-spread prevention, or thermal insulation. Or, as is often done,
fiberglass insulation is stuffed behind an expansion joint cover to help
meet the wall’s thermal rating. When movement occurs and the wall cycles at
the joint gap, the insulation (which may have little memory) can be crushed
and can no longer function as intended.
Precompressed Foam Solution
A solution to maintain the integrity of an interior or exterior wall system
is a preformed, precompressed foam expansion joint. This product is
constructed of fire-retardant-impregnated foam which is factory coated with
an exterior sealant specifically chosen to handle the wall’s environmental,
occupancy, and aesthetic requirements. These single-unit expansion joints
are manufactured and readily available in today’s market. The exciting
developments within this product design are advancements in composition of
the foam, impregnation and the sealant technology that are keeping pace with
the evolving performance expectations of the adjoining building assemblies.
Fire Rating and Life Safety
Building codes and concerns for life safety mandate that designated walls in
buildings be fire-resistance rated forming compartments in buildings to
contain the spread of fire. Without a fire-resistance-rated wall system,
fire can travel outside the building compartments (floors and rooms) or
through an outside wall where it can “leapfrog” back into a building a floor
above. A joint gap, like an open door, is an ideal passage for flame and
smoke. Any product being considered for specification in expansion joints
should be tested using UL 2079, “Tests for Fire Resistance of Building Joint
Systems” before accepted for use in fire and life safety situations. UL 2079
and ASTM E 1966, “Standard Test for Fire Resistive Joint Systems” are the
test standards that are the suitability for use statements for expansion
joint systems in fireresistance- rated assemblies in buildings.
Preformed, precompressed expansion joints are now available with a
fire-retardant impregnated foam and intumescent coating as well as with an
additional watertight weathering surface.
Versions of these materials have
successfully endured the normal and seismic joint cycling, fire testing, and
hose stream components of the UL 2079 testing, they are listed for up to a
2-hour fire ratings in walls and up to 3-hours in floor and deck
The obvious benefit is having a single product with the ability to work as a
firestop system, while still performing all of the thermal, sound, smoke,
moisture and insulation functions normally expected of the entire wall
assembly including the expansion joint.
Interior and exterior walls are expected to block out sound transmissions
from between rooms or from the outdoors to the inside of a building. An
appropriate expansion joint should basically be able to
maintain the sound
suppression level of the wall. ASTM E413 (Classification for Rating Sound
Insulation) and ASTM E90 (Test Method for Laboratory Measurement of Airborne
Sound Transmission Loss of Building Partitions and Elements) tests are used
to determine the rating for interior noise transmission (STC – Sound
Transmission Class) and exterior noise transmission (OITC – Outdoor-Indoor
Transmission Class). Superior wall sound attenuation (STC 50 or higher and
OITC 40 or higher) should be approximated or met by the expansion joint
installed in the joint gap. If the joint rating falls much below the wall
rating, then the sound suppression of the entire wall is compromised.
Current precompressed foam sealant technology has proven successful in
meeting these sound attenuation requirements due to its unique cellular
composition which has the ability to baffle and suppress sound. The STC and
OITC performance of an expansion joint should always be determined and
matched to the wall as a principle criterion of selection.
Expansion joints should do more than handle structural movement. They must
also act as a seal to maintain the environmental conditions on both sides of
the wall. Wind and water are often the downfall of expansion joints. There
are several ways that the uncontrolled passage of air and/or water through
wall assemblies can dramatically impact a buildings performance. Managing
the comfort of the interior environment of a building hinges on the
compartmentalization of HVAC air movement. Energy efficiency can be
substantially enhanced by controlling of the infiltration and exfiltration
of air through exterior walls as prescribed in air-barrier assembly design.
Additionally, all structures are subjected at some time or another to high
winds and wind-driven water from micro-bursts, tornados, or hurricanes.
ASTM (American Society of Testing Materials) prescribes several tests
designed to prove the ability of a wall assembly to withstand the effects of
air, wind and water from these various sources. Ironically, these tests can
be performed and passed without the presence of an expansion joint within
the wall assembly. Furthermore, seldom are these standards required in
specifications of expansion joint sealants alone. It also may be good
practice to specify materials that meet these standards and to require in
the submittal package independent laboratory certification of testing and
passage of ASTM E-330 (Structural Performance of Curtain Walls by Uniform
Static Air Pressure Difference – Gust Loads), E-331 (Water Penetration of
Curtain Walls by Uniform Static Air Pressure Difference), and E-283 (Rate of
Air Leakage Through Curtain Walls).
Commonly specified expansion joint fillers like strip seals, extruded-rubber
compression seals, and cover plates may not by design pass these tests
without extra products used in the configuration.
Gaps in joints of the aluminum rails and plates, non-airtight interfaces
between product components, as well as the undulations of typical substrates
may prevent these technologies from sealing adequately under wind and
wind-driven water conditions. A lack of resilience in the rubber glands of
strip seals prevents this technology from resisting pressure loads.
Precompressed, preformed foam sealants with a factory-coated facing provide
a primary seal capable of far exceeding the pass criteria of these ASTM
tests. They possess the ability to move with structural or thermal shifts
while maintaining a wind and watertight seal. The latest evolution of this
time-tested technology is comprised of cellular polyurethane foam which is
infused, or impregnated, with an acrylic-based polymer which is free of
older wax or asphalt compounds. These older compounds can compromise
movement and cause compression set. In the summer, when thermal expansion of
walls causes expansion joints to close down in size, high heat conditions
and compression occur that can result in these compounds bleeding onto or
into substrates. Requiring independent lab certification through Fourier
transform infrared (FTIR) spectroscopy and differential scanning calorimetry
(DSC) analysis can ensure that the materials being submitted are free of wax
or asphalt compounds.
Independent laboratory certification to ASTM E-330, E-331 and E-283 will
provide assurance that the products being submitted have displayed no water
leakage at pressures equal to winds above hurricane force and wind loading
that shows essentially no deflection at positive or negative pressures of up
to 4950 Pascals (equal to 200mph wind loads). It is not unreasonable to
expect an expansion joint sealant to perform to these standards as the
technology exists to do so. It is reasonable to demand certification through
independent testing that the product being tested has been proven to perform
at the level expected of the wall assembly.
When an expansion joint or joint system is installed, it has to be held in
place in the expansion gap. Traditionally, mechanical or plated systems were
anchored in place through intrusion of the substrate by screws or drilling
which both could have damaged the wall and often compromised the seal.
Precompressed, impregnated expansion joints offer a simpler solution -- they
are held in place by the backpressure of the foam’s compression and the
pressure-sensitive adhesive nature of the impregnation. This
anchoring eliminates any damage to the joint surfaces or the adjacent walls.
This method also permits the joints to be installed in corners and at turns
that are impossible to seal with screw-anchored strip-seals where drill
access is obstructed. It is also the easiest and most logical solution for
retrofit applications where failed joints need to be removed and replaced.
Of added importance is the quicker and cleaner installation which a foam
product provides -- this dramatically reduces installation time and is
ultimately more cost-effective.
Choosing the right expansion joint in today’s design and building
environment has evolved from demanding a traditional single-purpose product
to a multi-purpose product.
Today’s expansion joint seals are expected to eliminate the passage of air
through wall assemblies, thereby minimizing energy use and loss and
maintaining HVAC balance, while sealing interior space from exterior
temperature conditions, wind and moisture. This seal should remain in place
throughout a full range of environmental conditions such as driving rain,
hurricane-force winds, and extreme hot and cold thermal conditions. Because
sound attenuation is a key purpose of a wall system, the correct expansion
joint should meet or exceed the sound transmission classes (STC and OITC) of
the adjoining walls. There can be no compromise on the life-safety issue of
compartmentalization to ensure fire containment and minimization of fire and
smoke spread. Expansion joints are manufactured to stop the spread of fire
and should be UL 2079 tested and listed, to prove their ability to do so
while also being able to accommodate joint movement. UL certification
additionally provides an annual (at least) audit of the manufacturer and
their production process to ensure that the materials being sold meet the
standards of manufacture and composition of the materials
submitted for testing. In this way, and in contrast to testing by non-UL
labs to UL standards, certification by Underwriters Laboratories provides a
further level of assurance to the Specifier, building owner and manager, as
well as building occupant, that life safety is being properly addressed.
Precompressed sealant expansion joint technology has evolved to keep pace
with advances in building science and design. It is possible today to get
all of building assembly performance criteria in the single installation of
a single technology and structures around the world are now benefiting from
this advancement. As single-unit systems, this technology removes the need
for separate materials and installation costs as well as eliminates
substrate configuration compromises needed to accommodate multiple
materials. They are even manufactured to color coordinate with the aesthetic
aspect of modern wall systems. Specifiers can be assured that the final
choice of an independent laboratory tested, precompressed, impregnated-foam
expansion joint will allow you to “fill the gap” without sacrificing the
structural, thermal, sound and life safety attributes expected of today’s
modern walls, floors and ceilings.
EMSEAL Joint Systems, Ltd.
Located in Westborough, Mass. and Toronto, Ontario, EMSEAL has been
and supplying innovative and high quality expansion joint systems to the
architectural and construction industries since 1979. Its current line of
precompressed preformed sealants are engineered to today’s changing
structural and aesthetic requirements as seen in the EMSHIELD line of
fire-rated products including WFR2, DFR2, SecuritySeal and SJS-FR1.
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