Term Description

To make denser or more compact, as when a material (e.g., water vapor) changes from its gas phase to its liquid phase.


The storage of a material specimen under specified temperature, humidity, etc., for a specified time prior to testing.

Conductance, thermal (C)

See "a href="https://cottermanroofing.com/knowledgebase?field_category_value=All&fiel... conductance (C)">thermal conductance (C)."

Conductivity (electrical)

A measure of the ability of a material to conduct electrical current; the reciprocal of electric resistance.

Conductivity, thermal (k)

See "thermal conductivity (k)."


See "downspout."

Conductor head

An enlargement or catch basin at the top of a downspout or leader to receive rainwater from a gutter or scupper.

Construction joint

(1) A joint where two successive placements of concrete meet; (2) a separation provided in a building that allows its component parts to move with respect to each other.


The process of making a material or surface unclean or unsuited for its intended purpose, usually by the addition or attachment of undesirable foreign substances.


In the context of air retarder systems, an uninterrupted succession of air retarder materials, accessories and assemblies.

Control joint

A groove that is formed, sawed or tooled in a concrete or masonry structure to regulate the location and amount of cracking and separation resulting from the dimensional change of different parts of the structure, thereby avoiding the development of high stresses.

Cool roof

A roof system that uses products made of highly reflective and emissive materials for its top surface. Cool roof surfaces can remain at markedly lower temperatures when exposed to solar heat in service than surfaces of roofs constructed with traditional non-reflective roofing products.


The covering piece on top of a wall exposed to the weather, usually made of metal, masonry or stone and sloped to carry off water.


The product of polymerization of two or more substances (as two different isomers) together.

Copolymer alloy (CPA)

A type of thermoplastic compound used for manufacturing certain single-ply roof membrane materials. CPAs are produced by alloying polymeric plasticizers, stabilizers, biocides and antioxidants with PVC compounds.


A chemical reaction that results in the bonding of two or more dissimilar monomers to produce large, long-chain molecules that are copolymers.


A soft, malleable, naturally weathering metal used in metal roofing or flashing.

Core cut (core sample)

(1) A sample from a low-slope roof system taken for the purpose of obtaining primarily qualitative information about its construction. Typically, core cut analysis can verify or reveal the type of membrane surfacing; type of membrane; approximate number of plies; type, thickness and condition of the insulation (if any); an type of deck used as a substrate for the roof system; (2) for spray polyurethane foam-based roof systems, core cuts are used to obtain quantitative and qualitative information, such as thickness of the foam; thickness and adhesion of the coating; thickness of individual passes; and adhesion between passes and the adhesion of the foam to its substrate.


The decorative horizontal molding or projected roof overhang.


Vertical wood or metal strips installed on steep-slope roofs over which horizontal battens are secured. The primary roof covering is attached or secured to these horizontal battens.


Formed metal or elastomeric sheeting secured on or into a wall, curb, pipe, rooftop unit or other surface to cover and protect the upper edge of a base flashing and its associated fasteners.


(1) The term used for a row of roofing material that forms the roofing, waterproofing or flashing system; (2) one layer of a series of materials applied to a surface (e.g., a five-course wall flashing is composed of three applications of roof cement, with one ply of felt or fabric sandwiched between two layers of roof cement).

Cover board

An insulation board used over closed cell plastic foam insulation (e.g., polyisocyanurate) to prevent blistering when used in conjunction with hot bituminous membranes. Suitable cover-board insulations are glass-faced siliconized gypsum board, fiberglass board, perlite board, wood fiberboard or mineral fiberboard. Cover boards are also recommended between polyisocyanurate insulation and single-ply membranes to protect the polyisocyanurate.

Cover plate

A metal strip sometimes installed over the joint between formed metal pieces.


The surface area uniformly covered by a specific quantity of a particular material at a specific thickness.