This glossary contains many useful terms and definitions that will help you understand much of the work we do at ROOFCORP.

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Hand-tabbing: method of spot applying asphalt-based adhesive to shingles for securement and wind resistance.

Headlap: the distance of overlap measured from the uppermost ply or course to the point where it laps over the undermost ply or course.

Heat flow: the quantity of heat transferred to or from a system in a unit of time.

Heat seaming: the process of joining thermoplastic films, membranes, or sheets by heating and then applying pressure to bring both materials in contact with each other. (see Heat welding.)

Heat transfer: the transmission of thermal energy from a location of higher temperature to a location of lower temperature. This can occur by conduction, convection or radiation.

Heat welding: method of melting and fusing together the overlapping edges of separate sheets or sections of polymer modified bitumen, thermoplastics or some uncured thermoset roofing membranes by the application of heat (in the form of hot air or open flame) and pressure. (see Heat seaming.)

Hem: the edge created by folding metal back on itself.

Hip: the inclined external angle formed by the intersection of two sloping roof planes.

Hip roof: a roof that rises by inclined planes to form one or more hips.

Hoist: a mechanical lifting device. Holiday: an area where a liquid-applied material is missing or absent.

Honeycomb: voids left in concrete resulting from failure of the mortar to effectively fill the spaces among coarse aggregate particles.

Hot or Hot stuff: a roofing worker’s term for hot bitumen.

Hue: the subjective perception of color such as red, yellow, green, blue, purple or some combination; white, black or gray possess no hue.

Humidity: the condition of the atmosphere with respect to water vapor. See relative humidity.

HVAC: heating, ventilating, and air conditioning equipment.

Hybrid roof covering: combination of two or more separate and distinct roof membranes; e.g., three ply smooth BUR and a modified bitumen cap.

Hydration: the chemical reaction by which a substance (such as Portland cement) combines with water, giving off heat to form a crystalline structure in its setting and hardening.

Hydrocarbon: an organic chemical compound primarily containing the elements carbon and hydrogen.

Hydrostatic pressure: the pressure equivalent to that exerted on a surface by a column of water of a given height.

Hydrostatic pressure relief system: a system of perimeter and/or under slab drains used to regulate the hydrostatic pressure in the earth surrounding a below-grade structure.

Hygroscopic: attracting, absorbing and retaining atmospheric moisture. Hypalon: a registered trademark of E.I. DuPont de Nemours & Co., for ”chlorosulfonated polyethylene” (CSPE). (see Chlorosulfonated polyethylene.)