Sealants and Their Function
The prevention of moisture and air penetration begins with joint design that takes all conditions into consideration and joint preparation that is in accordance with recommended procedures. It is the sealant that is specified (and applied) and the workmanship on the job that oftendetermines how long the structure will be protected from the effects of weathering.
The primary function of a joint sealant is to maintain a positive seal between the sides of a joint, which may be subject to movement. Non-structural applications refer to applications where the sealant is not required to structurally support glass or panels, as in the case of structural silicone.
Such applications include expansion joints, weatherseals, end dams, screw heads, kerf seals, splice joints, etc. This type of sealant application does not contribute in any way to the structuralproperties of the building; rather, it helps to control the environment within the structure by resisting the passage of heat, light, sound, rain, snow, wind, odor, chemical and biological contaminants, and dust.
At the same time, the sealant must withstand the effects of thermal,moisture, and structural movement, including vibration and creep. It also provides sound insulation. In some cases, the sealant will be required to perform other functions, such as withstanding attack by insects, microorganisms, plants, or pollution.
The successful performance of a building exterior is frequently defined by its ability to keep rain and the elements outside, away from the building’s occupants. One of the critical links to ensuring a weatherproof building exterior is the joint sealant.
Selecting the Right Sealant
Generally, selecting the best sealant for any specific project is determined by the nature of the project performance requirements. Primarily, joint sealant should be selected around a few simple guidelines.
- Minimum contact required [by the sealant manufacture] with all bonding surfaces to
ensure adequate surface adhesion.
- Maximum movement potential necessary for the intended sealant to perform in a
structural or non-structural joint.
- Joint configurations and designs
Other considerations for key performance features of the intended sealant to be selected include: