scope:

This Commercial Item Description covers four types of 1-part caulking compounds suitable for use as recommended by the manufacturers for sealing, caulking, filling, leveling and glazing in general exterior architectural service on buildings and structures

Unless otherwise specified, these requirements are predicated on caulking applied to maximum joints .375" wide by .375" deep, filled by either cartridge injection or hand spatula.

Type I- Oil Base Caulk is a traditional, slow-drying, elastomer-modified, vegetable oil based caulk. Oil base caulk gets firmer over years and may eventually become rock hard and brittle. Oil based caulk is not suitable for applications subject to expansion, contraction and settling. Type II- Siliconized Acrylic Latex Caulk is waterbased. Acrylic caulks have fair adhesion to most building materials and are available in a wide range of colors. Acrylic based caulks are not true elastomers and tend to loose flexibility after a few years of outdoor exposure. Acrylic caulks are paintable with oil and water base paints. Type III- Butyl Rubber is a true elastomeric caulk. Butyl rubber caulk is solvent based. Butyl rubber caulk has excellent adhesion to most building materials. Butyl rubber caulk is suitable for extreme outdoor exposures to water, sunlight, high and low temperatures and expansion joint movements due to wind-loading or settling. Butyl rubber caulk can be applied in more inclement weather and is paintable with either solvent base or latex paints. Type IV- 100% SILICONE caulk is a true elastomeric caulk. Silicone caulk adheres to most building materials, and has excellent adhesion to glass. Silicone caulk is suitable for extreme outdoor service exposure to water, sunlight, high and low temperatures and expansion joint movements. Silicone caulks generally require adhesion primers for paint to adhere..

Beneficial comments, recommendations, additions, deletions, clarification, etc., and any data which may improve this document, should be sent to: GSA, Paints and Chemicals Commodity Center, 400 15th Street. S.W„ Aubum, WA 98001.