Watertight Expansion Joints and Construction Sealants by EMSEAL

SJS System – Why Use It?

In consideration of the specification of SJS-Seismic Joint System from EMSEAL

Thanks for consideration of the adoption of our SJS System for use on your project.

You will find that the SJS System is an evolution of proven existing technologies applied innovatively to large joints.  SJS already has an impressive 14-year track record of performance and adoption. And, with the development of SJS-FR you now have the option for a built-in fire rating; with SJS-FP you can integrate SJS into plaza deck and split slab construction, and with SJS-FP-FR, you guessed it, you can waterproof and fire rate plaza deck construction with a single product.

SJS is a system that so effectively employs the performance characteristics of its components as to appear disarmingly uncomplicated.  Yet, it is a system that was launched following a methodical, iterative, and thorough development, testing, prototyping, and field testing process.

It’s performance was modeled using Finite Element Analysis (FEA) and subsequent customization such as plate specification for extraordinary loading on specific projects have been modeled again using FEA to prove to the specifier and owner the suitability of the system.  We have even gone so far for one owner to provide independent lab certification of the stainless steel grade supplied in order to confirm the mill certifications provided by our suppliers.

We are pleased to demonstrate to you the type of evidence you are requesting is available in abundance from EMSEAL. We would challenge you to compile a similarly complete validation of performance claims for the manufacturers of the self-centering bar systems, their components, or any other technology type you are considering specifying.

Innovation is the basis of our entrepreneurial spirit and our economy.  Without embracing evolving technologies from the standpoint of good, sound engineering common sense, thorough vetting through testing, modeling and field trials, and with a modicum of risk, we would not be flying through the sky, walking on the moon, or even improving the lifespan of our parking decks by tensioning cables through curing concrete to increase the final density of the deck.

For 15 years since 1990 our sales team pleaded for a comparative ‘seismic joint’.

“Just give us what everybody else has–a self-centering bar, plate and gutter system–so we can have a shot at this work.”   Our response was consistently the same:

Just because everyone else has one, when what they have does not adequately address the purpose, doesn’t mean we should copy it.

“Innovate, don’t imitate,” is the slogan that drives our product development philosophy and we are arguably the only expansion joint manufacturer that is consistently challenging existing paradigms, including our own, to bring improvements and innovations to the field.

Our invention of a breakthrough microsphere-modified acrylic impregnation in 2005 provided the platform for the development and release of evolutions of our previous technologies in subsequent years that include:

  • DSM System for decks;
  • Double-Sided Colorseal for walls;
  • SJS System for seismic and large deck joints;
  • DFR2-the first ever trafficable, watertight, 2-hour fire-rated all-in-one deck joint;
  • WFR2-the first ever watertight, 2-hour rated, STC 56+, all-in-one joint system for concrete and gypsum walls;
  • DSF System for NSF-61 compliant applications;
  • Chemseal for chemical resistant applications;
  • Universal 90’s for factory fabrication of terminations and transitions.

These innovations join our long list of other industry-standard products: Seismic Colorseal; Backerseal; Thermaflex, Migutan, Migutrans, and our ground breaking line of Emshield fire and water resistant expansion joint products, in establishing EMSEAL as the leader expansion joint innovation.

The Need for a Better Seismic Expansion Joint

Our research, observation, and conversations with owners who have failed and leaking joints including cover plates or self-centering bar systems installed and were pleading for a better replacement, were:

“They are so noisy we can’t rent the retail space below these joints in our garage” (Providence Place Mall);

“They leak onto the lower levels of the garage forming ice sheets in the winter” (Morris Crossroads Corporate Center and U of Tennessee);

“The screws keep backing out and the plates clatter drawing complaints from the library, preschool and hotel adjacent to the deck” (U of Tennessee);

“The “gutter” leaks at all joins, has become clogged with dirt, grit, food, and syrup, and has become a tunnel and haven for rodents” (Oakland Raiders);

“The plates are cupping under wheel loads, the screws have come loose and the joint leaks” (U of Georgia);

“The plates have come loose, are a trip hazard, and the joint leaks into the concession area below” (Philadelphia Eagles);

“We don’t care if it leaks at this point please get rid of the noise, it sounds like someone firing a gun” (Home Depot World HQ Parking Deck, Atlanta, GA);


The Goal

The R&D project goals for the SJS System were:

These goals were based on the shortcomings of the self-centering bar and cover plate systems.  All of these criteria were met, are embodied in the SJS System, validated by independent testing, and have been proved in nearly 14-years of in-field service.

Fundamentally, as it relates to the sealing of large joints in any concrete deck and particularly in post-tensioned concrete the SJS System is unique.

Non-invasive anchoring and the fact that our cover plate is not in any way attached into the concrete should be the driver of performance criteria on which a specification  is based.

The essential differentiators of the SJS System over any other are:

  • no metal embedments
  • no drilling
  • no cutting
  • no hard connections to the concrete whatsoever
  • watertight
  • quiet

Our evolutionary based innovations eliminate the shortcomings that come with self-centering bar systems and cover plates, in post-tensioned or any other concrete for that matter, and further eliminate the need to lower yours and your clients performance expectations on this critical element of the structure.

We offer the following documentation in support of our claims and in addition answers to the sometimes-asked questions below:

FEA 1—2006-04-03_EMSEAL_SJS_FEA-Analysis.PDF

FEA 2–2007-02-09SJSMedatechFEAPlateThickness.pdf

FEA 3–2007-06-29_EMSEAL_SJS_ForkliftAnalysis.pdf

FEA 4–2008-11-13ROI_SJS_Fatigue_Analysis15-inch.pdf

FEA 5–2009-04-28EMSeal-Summary-Detroit-Report.pdf

SCOF Tests (Standard Coefficient of Friction)–2008-09-19SCOF-SJS_SYSTEMCoverplate.pdf

UL 2079 Cycling Videos


Embracing a new or evolved technology does not equate to an admission that previously employed technology didn’t perform within its limitations.  On the contrary it is the consultant’s responsibility to inform and advise owner/clients of the latest treatment options.

With going on four years of experience and over 22,800 feet of material installed on more than 45 projects, in 18 states, and four countries, the SJS SYSTEM has been widely adopted and is functioning well.

What testing has been done to verify the adhesion of the foam to the concrete during a seismic event?

UL 2079 contains a cycling component that puts joints through an aggressive rapid-cycling cycle.  UL 2079 has been the basis of cycling certification of our other breakthrough innovations in fire-rated expansion joint sealants for decks and walls DFR2 and WFR2.  The early vetting of these product concepts ran in parallel with the development of the SJS System.  We contracted with UL to perform the cycling test as part of our “proof of concept” stage of the R&D process.  The favorable cycling result caused us to continue to pursue development of both the SJS System and the fire-rated products.  EMSEAL foam, bonded to concrete with epoxy in the standard manner prescribed by our installation instructions has subsequently repeatedly passed this testing as part of the UL Certification process, proving the bond and the ability of the foam to follow rapid joint cycling. Please watch the UL 2079 video and observe the foam product being cycled and while you’re there take a look a the SJS System installation at Mets CitiField: UL 2079 Cycling Videos.

How sensitive is the adhesive to foam bond to variations in tolerance of the sides of the formed joint?

Within reason not at all.   Because the non-sag epoxy paste is applied to the face of the formed joint, as long as the face has been cleaned well, the epoxy can be used to fill voids that inevitably exist.  In addition the flexibility of the foam under its own 2.2 lbs/sq.in of backpressure will press into the voids to form a secure bond.  If there are massive deficiencies such as voids left by poor concrete consolidation, or protrusions left by poorly aligned formwork, etc., these of course must be rectified before installation.

What testing and/or analysis has been done on the plate for vertical and lateral traffic loading? What loads used?

Extensive independent-lab-run Finite Element Analysis (FEA ) was employed in proving the SJS System concept and has been subsequently conducted to simulate some extremely severe conditions of both vertical and lateral loading.  The first FEA simulated a 4000 lb SUV, brakes locked, skidding across the joint.  The subsequent stresses are enormous and safety factors are very impressive (more typical of life-safety factory for elevators for example) than for deck joints.  The total lateral displacement of the plates under these conditions was less than 3/4 of an inch (19mm).  Do you have similar studies of the self-centering bar systems–I would be curious to know how they compare?  The FEA and other tests done by independent engineering firms in validating the SJS System performance claims contain all of the load and assumption data used for your perusal and can be accessed at the previously listed links.

Any fatigue analysis or testing?

The next independent FEA we conducted was to simulate fork-lift loads over various plates for some isolated conditions on Atlanta’s CONRAC deck.  All of our recommendations for coverplate thickness are based on what FEA terms “infinite life”.  Please see above list of FEA and other testing.

What is an acceptable deflection criteria for the plate at design maximum opening?

We specify plate thickness based on material type (aluminum or stainless) based on the vehicle type, loading and joint gap widths expected and communicated to us by the designer of the project.  Deflection of the plates of our system vs. any other system will be roughly equivalent for similar cover plate materials and thickness if similar calculations are done.

The SJS System cover plates are designed to achieve “infinite life” under design loading conditions. Under this loading, the deflection of the system is minimal, and the safety factors on yield are quite large. For example, our FEA analysis shows, on a typical deflection scenario for a fully loaded SJS System for normal automobile traffic over even a 15-inch wide gap (10-inch wide nominal joint at max (+50%) opening) and using a 3/8” Type 304 stainless steel coverplate, is less than 1/32”.

In addition to designing the system to achieve “infinite life” under design loads, a further FEA was conducted to simulate 3 times normal design loading. This simulation resulted in no permanent yielding of the cover plate, and no permanent deflection.

Other manufacturers whose systems are not designed around “infinite life” may reduce cover plate thickness in an effort to reduce overall cost. While simple calculations will show that the design is safe under static loading, they do not take into account the dynamic, and repetitive nature of the actual situation. Long term repetitive cycling will induce stress concentrations, localized yielding, cracking, and cupping of materials with reduced safety factors. These behaviors can lead to rapid failure of the system itself, and potentially of the deck materials as well.

In the case of a bus drive lane at a major airport where the joint is located at a turning lane and where bus loads as well as substantial tire torque on the plates is occurring, we ran a further independent FEA to simulate a 45,000 lb bus, torqueing its tires at a dead stop.  From the results we designed, SJS-HD with increased spline and foam assembly depth, a coverplate thickness and bolt-hole spacing to provide “infinite life”  according to the FEA under this heavy-duty scenario.

Is Emseal truly watertight? Is there a testing criteria?

Yes.  The criteria is that no water passes through the joint and that no water is evident from the underside leaking through the joint, and that no water presents itself on the decks below.  This can be observed as the result of observation after rain storms over time or as the result of deliberate water testing by damming an inch of water over the joint.  The reason this can be observed is that the system is watertight at the deck surface and does not employ gutters either as a component of the system or attached below the joint as a fail safe.

Gutters attached below expansion joint systems hide the symptoms of leaking joints and are, in our opinion, not a good idea.  De-icing salt or low-pH water that leaks through non-watertight joints into gutters must first contaminate the joint system components and the concrete over which it flows.  This precipitates corrosion and structural damage of concrete in beams, columns, and decks.

The University of Tennessee Knoxville, Morris Crossroads Executive Park, the owners of the new stadiums for the New York Yankees, Mets, Jets/Giants, and Twins and Atlanta CONRAC; Providence Place Mall, Green Bay Packers; U of Georgia; San Francisco 49ers and dozens of other parking and stadium owners have all entrusted watertightness of their buildings to EMSEAL and the SJS System either in new or retrofit conditions. If they leak–we hear about it. Where we have had problems they have been minor, traceable to installation oversight and immediately rectified.

10 years of experience and hundreds of thousands of feet of material on projects worldwide is a more than adequate a sample from which to gauge our claim that the SJS System is watertight. (Who’s using SJS System?)

It must be made clear that EMSEAL endeavors to provide WATERTIGHT expansion joints and not weather tight products.  The distinction here, is as stated above.  Keep the water at the surface or exterior of a structure.  Do not allow the water to enter the building.  Once the water is in the building, the owner has been given a water management system.  If a manufacturer submits a gutter as a component of their solution, they have admitted that the primary system will leak.  The gutter will trap moisture in the joint gap and will rapidly contribute to concrete damage.  The gutter approach negates inspection for the building owner leaving deterioration most likely unobserved for an extended period of time.

What criteria is used to define noise mitigation/dampening?

When you want a loud noise to accentuate an orchestral piece, you bang two pieces of metal together. Or you strike pieces of loosely attached metal laid across an opening in a frame with rubber mallets.  A cover plate with any play under it riding over a hard surface or another piece of metal is the same idea.  Make the plate’s riding surface a hollow box of metal and you’ve added a resonance chamber to further amplify the sound.  Bolt down, or embed a metal box to high PSI concrete with metal pins or anchors, cantilever it even slightly off a beam into air and then strike it hard, and repeatedly, with the enormous force of air-filled rubber mallets and you’ve designed pretty much a perfect noise making machine.

Remove any one of the elements above and you will make less noise.  The criteria to define the SJS Systems noise mitigation/dampening claim is ultimately the absence of cacophony unpleasant to the human ear (click this link to see and hear the difference in this video).  Here are  the elements that go into the SJS System being arguably the quietest coverplate system available:

A) The reason coverplates bang is they either don’t lie flat as the result of camber or undulations in the concrete, cups in the plates, or loosened fastenings.  If you can level the concrete you can eliminate undulations.  By using our self-leveling, flexible, low-aggregate, resin nosing material (Emcrete) in a blockout as a leveling medium–we level the plates and in addition, the medium on which the plate rides becomes a sound attenuating material that is softer than metal or concrete or metal boxes.

B) By eliminating any metal anchors or embeds into the concrete deck we sever a hard, resonance inducing connection to the concrete.  We replace this with two highly resilient foam springs.  The foam has been independently tested to have a STC of 54.  It is an exceptional sound noise reducing medium.  Consequently the vibrations of any noise induced at the plate is further absorbed and dissipated into the foam. Self-centering bar systems would be essentially transparent to noise. An STC of 20 is not unreasonable to suppose for a cover plate and gutter system. With each 10 db increase, a normal person perceives a “doubling” of the subjective amount of noise. This means that the self-centering bar systems could be perceived to be 8X louder (3 doublings). And, that’s not even taking into account the fact that these systems can actually generate noise, in addition to not damping it.

C) The coverplate screws are self-tapped into the spline which is flanked by the foam.  This means vibration that normally works to loosen screws is virtually eliminated.  Screws that stay tight, keep the plates down snug and they do not bang.

The bottom line, is when you drive over SJS System installed as recommended over our resin-rich nosing material you might hear a gentle, low-frequency, thud but not a harsh, penetrating, high-frequency, metallic clang.

(Click this link to see and hear the difference in this video)

What are the benefits to the owner?

No metal embedments, no drilling, no cutting and no hard connections to the post-tensioned concrete whatsoever are the essential differentiators of our system over any other.  Add watertightness and sound dampening and it is clear why this technology is in the best interest of owner/clients.   Eliminate screws loosening, eliminate gutters and eliminate water management to downspouts, and it is clear why the use of SJS System is in the owner’s long-term maintenance and total cost of ownership interests.  With the elimination of the gutter system and the decrease in labor costs to install the SJS system relative to the self centering technology, we would additionally submit that the SJS System‘s installed cost is LESS expensive at NEW CONSTRUCTION as well.

At the end of the day, the self-centering bar technology was a beefing up of an interior joint design in the hopes it would be suitable to parking deck and other open-air uses.  It has worked adequately in some cases where meticulous installation has been assured but the basis of its design for the application demands into which it has been marketed is flawed.  The “gutter” component in the predecessor interior joints was referred to as a “moisture barrier” and was intended to catch the few drips of cleaning water that got through the joint.  This water would evaporate in the “moisture barrier”  The fundamental roots of these systems in interiors puts their principle of operation in contradiction with the requirements of a parking structure.

By contrast, the SJS System  was developed to meet the rigorous requirements of performance of open air structures free of the constraints of the interior joint paradigm.  Trafficable, watertight, sound attenuated, durable under vehicle loads.  Engineered, independent lab tested, field proven.


In 1990 EMSEAL received a letter from a major national design and engineering firm.  In every one of the thousands of luncheon seminars since, our specification development engineering team have opened our presentations with a paraphrase from that letter:

“[We have come to realize that our] projects show more problems with expansion joint seals than all other product categories combined.  Yet, expansion joint seals are a miniscule part of most of our projects in terms of construction costs.  …How can we work together to produce trouble-free expansion joint seals?”

Working with engineers, architects, general contractors and subcontractors in the shared goal of providing owners with trouble free joint seals, EMSEAL has made the realities and wisdom of this quote the de-facto mission of the entire company.

Through espousing an approach based on:

  • ownership of responsibility for our respective aspects of the work;
  • communicating early, often and in 3-D;
  • development of 3-dimensional joint layouts that have been adopted as a new page in the bid documents by numerous firms nationally;
  • emphasis on continuity of seal and thinking, designing, detailing, bidding, constructing, manufacturing, and installing in three dimensions;
  • working with designers to have the courage to advocate for better technologies and to justify to owners these recommendations as in their economic interest;
  • the invention of shear pockets to handle perpendicular movement in extruded glands;
  • warranting transitions in similar and dissimilar technologies to be watertight;
  • and through the R&D process previously described, EMSEAL is working together with like-minded firms all over the world to produce projects with trouble-free joint seals.

Thanks again for your consideration. The evolution of the building sciences is inevitable and evident all around us.  EMSEAL is working continuously to bring evolution to the tiny portion of building science that is structural movement joints.

EMSEAL’s 20+ year mission to elevate structural expansion joint technology and practice has been deliberate, conservative, and dogged in its single-minded pursuit and ask that you will acknowledge this effort through the adoption of our joint systems in your base spec and on future projects.  From the SJS System product page, you can access a guide specification for use in making SJS basis of design for your seismic and wide joints.  And, cross reference your spec in the drawings with details from the SJS System CAD library.