Modulus is the stress needed to stretch a sealant a set amount, often 100 percent. Low-modulus sealants stretch easily and put less stress on weak or friable substrates such as EIFS, stone and old masonry, and generally have higher movement capability. High-modulus sealants resist deformation and suit structural glazing and areas exposed to traffic or vandalism.
EIFS needs a low-modulus silicone, the stiff stuff will pull the lamina right off the foam.
Also heard as
- secant modulus
Related terms
Movement capability
How far a sealant can stretch and compress, as a percentage of joint width, while keeping its seal.
Silicone
A sealant with a silicon-oxygen backbone, prized for UV resistance and high movement capability.
Substrate failure
The joint face itself breaking, so sealant comes away with a skin of concrete, coating or EIFS still attached.
STPE
Silyl-terminated polyether, a moisture-curing hybrid sealant that is paintable, weather-resistant and free of isocyanates.