Watertight Expansion Joints and Construction Sealants by EMSEAL

DSM-DS System

Dual-sided silicone bellows seals from both sides of joint

DSM-DS is a highly resilient, double sided, silicone faced, precompressed sealant that has proved over the years the ability to solve difficult joint sealing problems where other systems have failed or are not suitable. It is ideal for new installations as well as expansion joint repair or retrofit jobs. It is especially useful in unique locations such as a topping slab seal in split slab assemblies, waste water facilities, tunnel walls and ceilings, planter walls, and interior side of foundation floors and walls which all benefit from its construction and performance*.

The dual-sided silicone facing allows DSM-DS to be installed from either the negative side or positive side. DSM-DS is adhered to the substrate walls with an epoxy adhesive which combines with the foam’s backpressure to be held in place. When accessible during installation, field-applied silicone sealant bands seal voids in the substrate and seal the edges of the bellows to the joint faces.

*NOTE: For structures with waterproofing, backfilled or blindside, EMSEAL suggests the use of BG system for most applications. The BG system is designed to tie into the waterproof system. The BG multi-cell gland and dual-level side flashing flanges provide for stress-free, redundant integration into the below-grade waterproofing membrane to form an integrated, secure watertight seal. 

DSM-DS System

Dual-sided silicone bellows seals from both sides of joint


  • Non-Invasive Anchoring
  • Continuity of Seal through changes in plane and direction
  • Ability to handle variations in joint size
  • Ideal for new and retrofit installations
  • ADA Compliant


1/2″ to 4″ (12 -100mm)
Larger sizes consult Emseal


Up to 100% Total (+50% and -50% of nominal supplied size.)




  • Slab on grade / foundation floors
  • Tunnel walls, ceilings and floors
  • Planter walls to seal inside planter and outer wall
  • Wastewater digester lids to seal out weather and reduce methane emissions
  • As containment for injected polyurethane grouts
  • Split slab as a topping seal when used in conjunction with a tied-in waterproof expansion joint at the structural slab
  • Below grade walls as a secondary seal

Watertight—the tensionless silicone bellows is installed just below the deck surface. This ensures watertightness is achieved at the deck surface.

Non-Invasive Anchoring—there are no hard metal-to-concrete connections in the system. This includes embedded pins, anchors, screws, bolts or tracks, trays or rails. The system is locked to the joint faces by means of the 1) backpressure of the foam, 2) the epoxy adhesive, and 3) the injected silicone sealant band at the joint face to foam and silicone bellows interface.

Continuity of Seal—as in all EMSEAL expansion joint systems, continuity of seal through changes in plane and direction is an essential performance differentiator. Details for watertight, field-fabricated transitions from deck to wall, at curbs, sidewalks, parapets, tees, and crosses are available with the DSM SYSTEM.

Aesthetics & Versatility—Standard color is gray (other colors available), uniform bellows appearance, double sealing, fuel resistance, and an enhanced ability to handle variations in joint size are among other system features.

Some examples of DSM-DS applications include:

  • Wastewater Digester Lids to Facilitate Methane Harvesting: DSM-DS has been used as a digester-lid perimeter joint sealant at wastewater treatment plants that harvest methane. Installed between the tank wall and the digester lid, DSM-DS keeps the weather out while reducing methane and other gas emissions. The product’s ability to resist gas pressure depends on the joint size and the expected pressure–consult EMSEAL. For more see Jamaica WWTP case study.
  • Tunnel Walls and Ceilings To Redirect Positive-Side Water Flow from the Negative Side: Existing tunnel structures often leak at expansion joints due to water draining through the surrounding ground and accumulating on the tunnel lining. Few options exist for addressing structural expansion joints in this situation.  DSM-DS  installed from inside the tunnel (the negative side) has proved its ability to redirect the positive side water around the tunnel lining where it can be manage to drains to filtered away in the surrounding drainage-coarse gravel.  The ability of the DSM-DS to effectively perform this role depends on there being active shedding of the water to prevent the accumulation of a head pressure–consult EMSEAL.  For more, see Wheeling Tunnel product case study.
  • Planter Walls:  Planters that are bisected by structural expansion joints present a unique sealing challenge.  The joint in the inside of the planter must be sealed to prevent irrigation water from leaking out of the planter into the structures below or adjacent.  The outside of the joint in the planter walls must be sealed to fill the joint aesthetically and to keep the weather out. DSM-DS, because it can be customized in depth to suit the thickness of the planter wall, and because the outer silicone bellows can be supplied in many industry standard colors, can be made to coordinate aesthetically with the finish of the outer face of the planter walls.  This means both the inside and outside of the planter can be sealed in a single installation step
  • Foundation Floors and Walls from the Negative Side:  It is not uncommon for existing foundations to leak at structural expansion joints.  The surest way to remediate this type of leakage is to excavate to expose the foundation to address the waterproofing from the positive side.  As this is seldom practical, a solution from the negative side is often sought.  This condition is very difficult to address especially where any sort of head pressure is likely to build up. DSM-DS alone has been successfully used in many cases to stem the flow of water into foundations where a perimeter drainage system on the outer side of the foundation wall and floor is functioning.  The perimeter drainage or some other active drainage system (ex. pumps) is necessary to keep the blocked water from building a head pressure against the back side of the DSM-DS.
  • Containment for Injected Polyurethane Grout:  In some more difficult cases where head pressure is likely to build and where active drainage is not present, DSM-DS has been installed to seal off the joint gap and to act as containment for polyurethane grout injected through the wall behind the DSM-DS.  The grout when subjected to water pressure is held in place by the resilience of the DSM-DS.
  • Produced by infusing a cellular foam base material with a hydrophobic, microsphere-modified acrylic impregnation, and coating the surface with a high-performance silicone to suit the application.
  • The external silicone facing is factory applied to the foam at a width greater than maximum joint extension and is cured before final compression.
  • Silicone application and curing takes place in a temperature and humidity-controlled factory environment. This ensures, in contrast to field applied liquid sealant and backer rod installations, that no movement takes place during curing that can cause deformation or stresses in the sealant material.
  • The material is precompressed to less than the joint size for easy insertion.
  • When compressed, a bellows is created in the coating. As joint movement occurs the bellows simply folds and unfolds free of tension on the bond line, and virtually free of tensile stresses in the silicone material.
  • The material is supplied in 6.56 LF (2m) shrink-wrapped lengths (sticks). After removal from the shrink-wrap and hard board restraining packaging, it expands gradually.
  • The foam provides a resilient backing to the silicone coating, making the system capable of resisting reasonable transient point loads.
  • Substrates must be parallel, plumb, have sufficient clear depth to receive the material specified, and be capable of resisting approx. 2.5 psi backpressure from the foam.
  • Fuel Resistance: Silicone sealant is not degraded by contact with fuel. Some swelling of the material will normally occur, but it will return to its original shape upon evaporation of the fuel.

(US Patent 9,200,437; 9,637,915)

  • Universal-90’s (or U-90’s) are factory-made 90-degree transition pieces that ensure continuity-of-seal where expansion joints change plane.
  • Use of U-90’s eliminates the field work needed to make plane changes making overall installation fast and efficient.
  • Watertightness through the plane change is guaranteed–leaving nothing to chance in field-fabricating inside and outside transitions.
  • U-90 transitions are symmetrically coated on both faces allowing them to be installed as an inside corner or as an outside corner.
  • Straight-run sticks are joined in the field to the U-90’s.
  • U-90’s have a 12-inch (305mm) long leg and a 6-inch (152mm) vertical piece on each side of the elbow.

(US Patent 10,570,611)

  • Custom-90’s, are factory-fabricated inside and outside 90-degree transition pieces coated on just the weather-facing faces.
  • Custom-90’s are available when field conditions and measurements are known up front.
  • Custom-90’s are widely used in applications where numerous inside and outside 90-degree transitions are required. Consult EMSEAL.
  • As with any construction product, the useful life of the material can be maximized with routine inspection and repair if required.
  • Clearing of surface debris and inspection will reveal any damage to the product or adjacent substrates that might affect building performance.
  • EMSEAL precompressed sealants are easily repaired–requiring only damaged sections to be removed and reinstalled–not the entire length of the joint as is typical of extruded-seal systems.
  • Available for shipment internationally.
  • Prices are available from local distributors or representatives. For more information, contact EMSEAL.
  • The product range is continually being updated, and accordingly EMSEAL® reserves the right to modify or withdraw any product without prior notice.