Silicone Seal

Preformed silicone seal for weatherproofing applications

Features & Benefits
  • Economical, high-performance alternative to cutting-out and recaulking existing failed weatherproofing sealants
  • Extremely low-modulus alternative to wet sealants  High-movement seal capable of +200/-75 percent joint movement
  • High-shear movement seal capable of handling specified live loads, wind sway and seismic movements in a properly designed joint 
  • SWRI-validated performance
  • Ability to provide a complete weatherseal system when used with Dow Corning® AllGuard Silicone Elastomeric Coating
  • Available in custom designs to allow easier application and smoother transitions.
  • Available in matte and textured finish (similar to EIFS)

Preformed silicone elastomer extrusion.


Dow Corning® 123 Silicone Seal is specifically designed for use in repair of failed construction joints and glazing details due to design error, field failure or when the life span of sealants and gaskets has expired. It can be used in a variety of applications such as:

  • An economical, high-performance alternative to cutting-out and recaulking existing failed weatherproofing sealants
  • A restoration joint on EIFS at both the EIFS-to-EIFS joints and window perimeter joints
  • An aluminum splice in high-performance window and curtainwall applications
  • A high-performance flexible flashing material ideal for maintenance crews
  • A uniform-looking parapet or coping joint
  • A leak-free transition seal
  • A seal for leaking skylights
Typical Properties

Specification Writers: These values are not intended for use in preparing specifications. Please contact your local Dow Corning sales office or your Global Dow Corning Connection before writing specifications on this product.



abe-Construction-Chemicals---Dow-Corning-123-Sealants-ValidationDow Corning 123 Silicone Seal is a preformed, ultra-low modulus silicone extrusion that is bonded to substrates using Dow Corning® 791 Silicone Perimeter Sealant or Dow Corning 795 Silicone Building Sealant.1 Easy to- install Dow Corning 123 Silicone Seal can be used in both new and remedial construction applications.

Dow Corning 123 Silicone Seal is available in the following standard colors: black, white, grey, bronze, limestone and sandstone. This product is also available in custom colors (1000 linear feet [305 m] minimum).

The same color of Dow Corning 791 or 795 Silicone Sealant should be used to bond the seal to the substrate.

In addition to standard and custom colors, Dow Corning 123 Silicone Seal is also available in a textured finish. The color or texture can also be altered at the job site using Dow Corning AllGuard Silicone Elastomeric Coating.

In addition to custom colors, Dow Corning 123 Silicone Seal is also available in custom extrusions with grooves to facilitate bending and dimensional shapes. These shapes may be custom designed to fit mullion and window systems and to work with the flat strips to provide improved aesthetics as well as maximum weatherproofing protection. Contact your Dow Corning Sales Application Engineer to discuss your design concepts and learn how they can be captured in long-lasting silicone materials.

How to use

abe-Construction-Chemicals---Application-of-dow-corning-123-tapeDow Corning 123 Silicone Seal must be bonded to clean, dry, frost-free, dustfree substrates using Dow Corning 791 or 795 Silicone Sealant. Field adhesion testing should be done to determine if primer is required for proper adhesion of Dow Corning 791 or 795 Silicone Sealant to the substrate.1

Preparation Work

Porous surfaces should be cleaned with abrasion cleaning followed by blasts of oil-free compressed air. If highpressure water cleaning is necessary, use caution to prevent water from entering the structure through the existing failed joint. Exterior surfaces must be visibly dry before installing Dow Corning 123 Silicone Seal.

abe-Construction-Chemicals---Dow-Corning-123-Custom-DesignsNonporous surfaces should be cleaned using the two-cloth solvent wipe as outlined in Dow Corning’s sealant application guidelines. Masking Apply masking tape in areas of high visibility to ensure good aesthetics (see Figure 2).

Dow Corning 123 Custom Designs are available to meet aesthetic and weathersealing needs with a single product.


Apply a bead of Dow Corning 791 or 795 Silicone Sealant to each side of the joint according to the following schedule:

Handling Precautions

Product safety information required for safe use is not included. Before handling, read product and safety data sheets and container labels for safe use, physical and health hazard information. The material safety data sheet is available on the Dow Corning website at You can also obtain a copy from your local Dow Corning sales representative or Distributor or by calling your local Dow Corning Global Connection.

Packaging Information

Dow Corning 123 Silicone Seal is available in 100-foot rolls. Standard stocked sizes include widths of 1″, 11/2″, 2″, 21/2″, 3″, 4″, 5″ and 6″ (25, 38, 51, 64, 76, 102, 127 and152 mm) in black, white, grey, bronze, limestone and sandstone colors. Standard, but non-stock sizes, include widths of 31/2″, 41/2″ and 51/2″ (89, 114 and 140 mm) in all colors. All sizes of blue spruce, dusty rose, adobe tan, charcoal and rustic brick are non-stock items. Custom sizes are available in 1 to 6″ (25 to 152 mm) in 0.5″ (13 mm) increments, and 7 to 12″ (178 to 305 mm) in 1″ (25 mm) increments.


Dow Corning 123 Silicone Seal is not intended for use:

  • With Dow Corning® 790 Silicone Building Sealant as an adhesive.
  • With non-Dow Corning® sealants or acetoxy cure silicone sealants as the bonding sealant.
  • In below-grade applications.

This product is neither tested nor represented as suitable for medical or pharmaceutical uses.

Health & Environmental Information

To support Customers in their product safety needs, Dow Corning has an extensive Product Stewardship organization and a team of Product Safety and Regulatory Compliance (PS&RC) specialists available in each area.

For further information, please see our website, or consult your local Dow Corning representative.

Limited Warranty Information – Please Read Carefully

The information contained herein is offered in good faith and is believed to be accurate. However, because conditions and methods of use of our products are beyond our control, this information should not be used in substitution for customer’s tests to ensure that Dow Corning’s products are safe, effective, and fully satisfactory for the intended end use. Suggestions of use shall not be taken as inducements to infringe any patent.

Dow Corning’s sole warranty is that our products will meet the sales specifications in effect at the time of shipment.

Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted.


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