Preparation and Application Instructions for Tremco Spec 3 Sealant

Joint Design

Tremco Spec 3 silicone sealant can be utilized in any joint designed in accordance with accepted architectural/engineering practices. The joint width should be 4 times the expected movement but not less than 1/4" in width.

Joint Dimensions

For joints 1/4" to 1/2" in wide, the width-to-depth ratio should be even. Joints that are 1/2" wide or greater should have a depth of at least 1/2". The minimum joint size should be 1/4" by 1/4".

Surface Preparation

For the best adhesion, the joint interface needs to be sound, clean and dry. Depending on the targeted substrate, the joint surface may require a vigorous wire brushing, grinding, sand blasting, solvent washing and/or use of primer.

Tooling & Cleaning

Tooling is highly suggested immediately after application of this silicone sealant to ensure a firm, tight contact with the joint interface. Dry tooling is the preferred method of application.


Cleaning can be performed with solvents such as Xylene, Toluene, IPA or MEK while sealant is in an uncured state. Handle these chemicals with caution as they are hazardous materials.

Joint Backing - Using Bond Breaking Tape

Closed cell polyethylene backer rods are preferred as joint backing to control the depth of the sealant bead. Where the depth of the joint interface will prevent the use of joint backing, an adhesive backed, polyethylene tape should be applied to prevent three-sided adhesion. Joint backing must be clean and dry at time the sealant is applied.


Tremco Spec 3 silicone sealant is easy to apply using your common caulking devices. Fill the joint completely and tool immediately afterward, as previously mentioned. At 75°F, 50% R.H., a sturdy skin will begin to form within 10 to 30 minutes. For more information, check out for complete application instructions. Limitations

  • Do not apply this silicone sealant to damp or surfaces that are dirty.
  • Always handle this product with adequate ventilation.
  • Not intended for continuous water immersion.

DISCLAIMER: These instructions are from the product manufacturer. PK Supplies Inc. makes every effort to ensure that these instructions are accurate. By following these instructions you agree that PK Supplies Inc. is not liable for any damages or losses caused by these instructions.

Instructions can be used for...