Term Description
Flat lock

A method of interlocking metal panels in which one panel edge is folded back on top of itself and the other panel is folded under, after which the two panels are hooked together.


A mat or felt composed of fibers, sometimes used as a membrane backer.

Flood (pour) coat

The surfacing layer of bitumen into which surfacing aggregate is embedded on an aggregate-surfaced built-up roof.

Flood test

A membrane-integrity test conducted by temporarily plugging or otherwise closing any drains and erecting temporary dams where required to retain water on the surface of a waterproofing membrane and then flooding the surface to a maximum depth of 2 inches at the high point and retaining the water for a minimum of 24 hours or as required by the manufacturer. See "water testing."

Flow properties

The ability of a coating to move freely as a liquid, allowing it to achieve a level surface.

Flowing-water test

A membrane integrity test conducted by applying continuously flowing water over a waterproofing membrane's surface without closing drains or erecting dams for a minimum of 24 hours or as required by the manufacturer. See "water testing."

Fluorocarbon films

Fluorine-substituted ethylene polymers, featuring outstanding formability, heat resistance, color retention, and resistance to solvents and chalking.


In metal decking, the space corresponding to the rib depth bound by the web sections.


A bituminous material used as feed stock for further processing and as a material to soften other bituminous materials.

FM Approvals

Commonly referred to as FM, a research and testing business unit of FM Global (a commercial and industrial property insurer) that classifies roofing components and assemblies for their fire, traffic, impact (hail), weathering and wind-uplift resistance.

Foam stop

The roof edge treatment upon which spray polyurethane foam is terminated.


A strength or energy exerted or brought to bear; cause of motion or change.


Forest Products Laboratory.

Freeze-thaw cycle

The freezing and subsequent thawing of material.

Freeze-thaw resistance

Resistance to cycles of freezing and thawing that could affect applications, appearance or performance.


The tendency of material or product to crumble or break into small pieces easily.

G-60 and G-90

Designations for galvanized metal sheet, indicating 0.60 ounces and 0.90 ounces of zinc per square foot, respectively; a combined measure of zinc coating on both sides.


The vertical triangular portion of the end of a building having a double-sloping roof from the level of the eaves to the ridge of the roof.


A BIEC International Inc.-trademarked name for a metal alloy coating that is composed of 55 percent aluminum, 43.4 percent zinc and 1.6 percent silicon. It is also known by various other trade names such as Zincalume,™ Zintro-Alum™ and Galval.™

Galvanic action

An electrochemical action that generates electrical current between two metals of dissimilar electrode potential.

Galvanic series

A list of metals and alloys arranged according to their relative electrolytic potentials in a given environment.


To coat steel or iron with zinc.

Galvanized steel

Steel coated with zinc for corrosion resistance.


(1) A roof that has two pitches on each side of a central ridge where the upper roof areas have less slope than the lower roof areas; (2) a roof with two inclines on each slope.


A metal thickness measurement; a smaller gauge number indicates a thicker metal.