Building Envelope - the outer elements of a building, both above and below ground, that divide the
external from the internal environments.
Built-Up Roofing - a roof covering made up of alternating layers of tar and asphaltic materials.
Butt Joint - a joint having the edge or end of one member matching the edge, end, or face of
another member without overlap.
Butyl Rubber - a copolymer of essentially isobutene with small amounts of isoprene. As a sealant it
has low recovery and slow cure.
Capillary Migration - movement of water induced by the force of molecular attraction (surface
tension) between the water and the material it contacts.
Caulk (noun) - a material with a relatively low movement capability, usually
less than + 10%. Generally refers to oil-based caulks, and sometimes to butyl and acrylic latex
Caulk (verb) - to install or apply a sealant across or into a joint, crack, or crevice in order to prevent
the passage of air or water.
Closed-cell Foam - A foam that will not absorb water because all the cells have complete walls.
Closed Cell - a cell totally enclosed by its walls and hence not interconnecting with other cells.
Cohesion - the molecular attraction that holds the body of a sealant or adhesive together. The
internal strength of an adhesive or sealant.
Cohesive Failure - failure characterized by rupture within the sealant, adhesive, or coating.
Compatibility - the capability of two or more materials to be placed in contact or close proximity with
one another and each material maintaining its usual physical or chemical properties, or both.
Compression gasket - a gasket designed to be used under compression.
Compression Seal - a preformed seal that is installed by being compressed and inserted into the
Compression Set - the amount of permanent set that remains in a specimen after removal of a
Condensation - the change of state of a vapor into a liquid by extracting heat from the vapor.
Construction Joint - in the construction of members intended to be continuous, a predetermined,
intentionally created discontinuity between or within constructions and having the ends of the
discontinuous members fastened to each other to provide structural continuity.
Control Joint - a formed, sawed, tooled or assembled joint acting to regulate the location and
degree of cracking and separation resulting from the dimensional change of different elements of a