Expansion Joints and Pre-Compressed Sealants


Tech Data

Install Data


Guide Spec





• Dual-faced, silicone coated, primary seal

• Easy installation, non-invasive anchoring

• Below grade negative-side installation

• Below grade walls

• 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 contain methane for harvesting

• As containment for injected polyurethane grouts

Joint Sizes:
to 6"
(12 -150mm)*

*for floor joints larger than 4" (100mm) and larger, where an integral coverplate is desired, consider SJS System

Movement Capability:
up to 100% Total (+50% and -50% of nominal supplied size.)

is a unique, highly resilient, double silicone faced precompressed sealant that has proved over the years to be able to solve difficult joint sealing problems where other systems have failed or are not suitable. As such, it is ideal for new installations as well as expansion joint repair or retrofit jobs. 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 keeping the methane and other gases in.  The products ability to resist gas pressure depends on the joint size and the expected pressure--consult EMSEAL.  See Jamaica WWTP Project Summary.

 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.  See Wheeling Tunnel Project Summary.

 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 any of 26 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 conditions 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.

Click here to see who else is using DSM and DSM_DS?


Product Description
DSM-DS is a watertight, precompressed primary seal with dual factory-applied opposing-face silicone bellows. It is constructed from acrylic-impregnated hydrophobic foam containing no waxes or asphalt.  

Negative-Side Water Management: DSM-DS in the Wheeling (WV) Tunnel

Methane Harvesting Containment: DSM-DS in the Jamaica (NY) Waste Water Treatment Facility

 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) from injected silicone sealant bands 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 walls, floors, tees (etc.) are available with the DSM-DS SYSTEM.

 Movement Capability
+50% and -50% (Total 100%) of nominal material size (see "Performance").

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

• Capable of movements of +50%, -50% (100% total) of nominal material size.
*for floor joints larger than 4" (100mm) and larger, where an integral coverplate is desired, consider SJS System.

• Substrates must be parallel, plumb and capable of resisting approx. 2.5 psi backpressure from the foam.

• Standard sizes from 1/2" (12mm) to 6" (150mm).

• DSM-DS is produced by coating an impregnated cellular foam with silicone on opposing outside faces.

• The expanding foam is cellular polyurethane foam impregnated with a water-based acrylic containing a high performance micro-cellular additive.

• The silicone external 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 factory-controlled environment. In contrast to field applied liquid sealant and backer rod installations, no movement takes place during curing that can cause deformation or stresses in the material.

• 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 foam provides a resilient backing to the silicone coating, making the system capable of withstanding external pressure.

• DSM-DS is supplied in 6.56 LF (2m) shrink-wrapped lengths (sticks). It is precompressed to less than the joint size for easy insertion. After removal from the shrink-wrap and hard board restraining packaging, it expands gradually.

EMSEAL JOINT SYSTEMS LTD. 25 Bridle Lane, Westborough, MA 01581
EMSEAL LLC. 120 Carrier Drive, Toronto, ON M9W 5R1



1-800-526-8365 -- 508-836-0280 --  techinfo@emseal.com -- Fax: 508-836-0281

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