Expansion Joints and Pre-Compressed Sealants

Below-Grade Wall Expansion Joint

Tech Data

Install Data


Guide Spec


Sample Request



High density 20H SYSTEM impregnated expanding foam sealant for below-grade wall applications.

***Note:  The 20H SYSTEM has been largely replaced for deck joint applications by the DSM SYSTEM

With its introduction in 2006 the DSM SYSTEM supersedes it's predecessors, 20H SYSTEM and DSH SYSTEM, in most applications. The DSM SYSTEM builds on a track record of over 30 years of sealing horizontal plane joints with impregnated foam sealants and is an evolution of EMSEAL’s earlier technologies.   The DSM SYSTEM features greater movement capability, dual sealing, a fuel resistant silicone bellows coating, better low temperature flexibility, and improved high temperature stability.  It achieves these improvements through EMSEAL’s new microsphere-modified-acrylic impregnation technology and is free of any asphalt compounds.  Additionally, the DSM SYSTEM is totally free of wax or wax compounds. Consequently the suitability of the DSM SYSTEM is extended geographically as well as to applications such as in metal-angles, and top-decks previously not recommended for joint-face-adhered systems.

The 20H SYSTEM continues to be well-suited for installations in below-grade, positive-side wall joints***



Sealing Below-Grade Walls using the 20H SYSTEM:
The 20H SYSTEM is installed from the positive side of the retaining wall into a pre-formed joint opening in cured concrete.  The joint opening would be formed with extruded polystyrene that is stripped out from between the cured joint faces deep enough to receive the 20H foam (3-inches for 2-inch nominal 20H for example).

The 20H SYSTEM is installed flush to the face of the positive side of the wall. The below-grade waterproofing membrane and drainage board are installed over the 20H SYSTEM using the membrane manufacturers standard inverted, slip-sheet, detail.

While it is not necessary from a waterproofing standpoint to fill the joint on the interior (negative) side of the wall it is wise to seal this joint to keep vermin out.   The 20H SYSTEM is fine for this purpose however, if the aesthetic of a black joint filler is a concern, use COLORSEAL on the interior.

As far as ensuring watertightness is concerned, it is very important to thoroughly detail and specify the termination of the waterproofing membrane AND the 20H SYSTEM at the wall footing.  It is best to carry both the membrane and the 20H SYSTEM below the elevation of the interior floor or slab and into a well-designed drainage perimeter (gravel, tile, etc.).  This will ensure that water running down the wall in the drainage board and/or on the membrane and 20H SYSTEM is properly drained away does not back up against the wall.

The 20H SYSTEM consists of 20H foam, epoxy adhesive and topcoat.

Permanently elastic, high-density, cellular polyurethane foam, impregnated with water-based, polymer-modified asphalt, compressed to approximately 20% of its uncompressed dimension.

Supplied pre-compressed to smaller than mean joint size; installed flush with, or near to surface into wet epoxy adhesive, the material expands to seal the joint.

Exposed top surface is treated with Topcoat flexible coating to enhance sealing and durability.


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

Copyright © 1998-2015 by EMSEAL Joint Systems, Ltd. All rights reserved.
This document may not be reproduced in whole or in part without permission.