Successfully sealing joints, such as control joints and around door jambs and window frames, in concrete masonry walls depends on the overall design and construction of the entire building envelope. Movement joints (also called control joints) are needed in some concrete masonry walls to accommodate drying shrinkage, thermal movements, and movements between different building components. Movement joints, joints around fenestration, doors and penetrations, and isolation joints (joints at dissimilar material interfaces) rely on joint sealants to help preserve the overall weather-tightness of the building envelope. In addition, properly sealed joints may be required to meet a specified fire resistance rating or sound transmission class.

The sealant’s primary role is to deform as the joint moves, maintaining the seal across the joint. Most joint sealants are field-applied (as opposed to preformed). For instance, a raked-out mortar joint or open movement joint may receive sealant from a gun-squeezed cartridge, typically applied over a backup material.

This TEK provides a basic overview of joint sealants, installation guidelines to help ensure longevity, and recommended maintenance procedures, based primarily on ASTM C1193, Standard Guide for Use of Joint Sealants (ref. 1) and ASTM C1472, Standard Guide for Calculating Movement and Other Effects When Establishing Sealant Joint Width (ref. 2). This TEK does not address adhesives.

For optimum performance, the sealant must be properly applied to a well-constructed joint. For example, joints that are too thick relative to the width may cause failure of even the best sealant. Detailed information on control joint design and construction is available in CMU-TEC-009-23 (ref. 3).